Hi All,
I have spent the last 4 months restoring my 4CC Japanese Import FJ 1200. It had been stood out in the Irish weather for a few years so there was a load of corrosion all over it she ran when I bought it but the brakes were seized so I didn't drive it.
I now have it back to roadworthy condition with YZF600 front forks, fender and front and back wheels.
She starts and idles perfectly and pulls as she should up to 4.5-5k rpm but then starts misfiring as if its running out of fuel..
I've stripped the carbs and blown out all the jets and circuits (3 times), swapped out the fuel pump and fuel lines, changed the plugs, HT caps and coil leads and fitted a relay to the coils, all to no avail.
Also, I've fitted a new stock air filter, air box and ignitor box from an unrestricted 3CV model.
Can anyone offer any advice as to where the problem might be?
Thanks in advance.
The JDM (Japanese Domestic Market) FJ's were both power restricted and speed restricted as a condition of their sale in Japan. I have no experience with these models but I recall something about a restriction in the carb boots (smaller diameter) and a restrictive rev limiter in the tachometer.
Perhaps someone will chime in here.
I know the FJ guys over in the UK have come across this issue before. You may want to check in with them.
http://www.fjclub.co.uk/ (http://www.fjclub.co.uk/)
Good for you on getting that FJ back on the road. :good: Cheers Pat
Quote from: Pat Conlon on August 12, 2018, 12:10:42 PM
The JDM (Japanese Domestic Market) FJ's were both power restricted and speed restricted as a condition of their sale in Japan. I have no experience with these models but I recall something about a restriction in the carb boots (smaller diameter) and a restrictive rev limiter in the tachometer.
Perhaps someone will chime in here.
I know the FJ guys over in the UK have come across this issue before. You may want to check in with them.
http://www.fjclub.co.uk/ (http://www.fjclub.co.uk/)
Good for you on getting that FJ back on the road. :good: Cheers Pat
Correct Pat...... yes my JDM '91 would not go past 180KPH as there is a circuit inside the back of the speedo that somehow cuts ignition, and yes the intake manifolds have a smaller diameter.
Cheers
Harvy
Read this article
https://forum.thinkbike.co.za/archive/index.php/t-21969.html
Info on the 4CC engine is at the bottom of the page.
Hannes
Thanks for the replies everyone but I didn't mention that my engine won't rev past 5k rpm even in neutral.
It sounds like a rev limiter or fuel starvation to me but I've replaced the fuel pipes and paid attention to their routing so there are no kinks and checked fuel flow to the pump and to the carbs and it's all good.
I can't see how the restriction in the speedometer can affect engine rpm if the bike is standing still..
Anyone any other ideas?
Hmmmm....
Maybe your fuel pump is not flowing enough fuel?
Try bypassing the fuel pump and run a gravity fed line with an overhead suspended fuel container to feed the carbs directly.
If it were an ignition interrupt you could hear a pop when the ignition cuts out then refires the plugs.
The pop would come from the flash off of the unburned fuel in the cylinders.
what do the plugs look like? do they carbon up after it misfires? maybe one of the ignition coils is failing
Quote from: aj52 on August 13, 2018, 04:12:01 AM
Read this article
https://forum.thinkbike.co.za/archive/index.php/t-21969.html
Info on the 4CC engine is at the bottom of the page.
Hannes
Thanks Hannes for this link :good2:
Holy crap, did you guys see the jet sizes in the JDM 4cc model? It's no wonder it won't rev past 5k
87.5 for a main jet? (normal 110) That's gotta be a misprint
WTF?
For the Japanese domestic market:
Engine type: 4CC
Carb type: BS36 (manifold diameter 32.5 mm)
Main jet: #87.5
Main air jet: #45
Pilot jet: #42.5
Pilot air jet: #135
Full-powered models:
Engine type: 3XW
Carb type: BS36 (manifold diameter 36 mm)
Main jet: #110
Main air jet: fixed
Pilot jet: #42.5
Pilot air jet: #155
Quote from: Pat Conlon on August 13, 2018, 11:34:43 PM
Quote from: aj52 on August 13, 2018, 04:12:01 AM
Read this article
https://forum.thinkbike.co.za/archive/index.php/t-21969.html
Info on the 4CC engine is at the bottom of the page.
Hannes
Thanks Hannes for this link :good2:
Holy crap, did you guys see the jet sizes in the JDM 4cc model? It's no wonder it won't rev past 5k
87.5 for a main jet? (normal 110) That's gotta be a misprint
WTF?
For the Japanese domestic market:
Engine type: 4CC
Carb type: BS36 (manifold diameter 32.5 mm)
Main jet: #87.5
Main air jet: #45
Pilot jet: #42.5
Pilot air jet: #135
Full-powered models:
Engine type: 3XW
Carb type: BS36 (manifold diameter 36 mm)
Main jet: #110
Main air jet: fixed
Pilot jet: #42.5
Pilot air jet: #155
Pat
While I am waiting for carb kits,I've put my ABS's carbs with standard exhaust system on the other FJ.
What I can confirm is that the jets on the intake boots side,is 135.
I wll open di carbs up when other carbs are sorted to put back on the bike.
What I also can confirm is that bike is nowhere near as lively with the ABS's carbs than with the other set and aftermarket exhaust.
Hannes
For US models with stock components;
The Main Air Jet is fixed and not replaceable.
The Air Pilot Jet is #155
Pilot (idle) Jets are either #37.5 or #40
Main Jets are either #110 or #112.5
Thanks David! I made the corrections on the pilot air jets.
I know the USA models had smaller pilot jets (37.5/40) than the European models (42.5).
What do you think of that main jet size on the JDM (87.5) Is that a typo?
I have a hard time believing that a FJ would run with a main jet that small.
I know the XJR1300 we worked on that came from Japan had a 95 main jet in it. Whether that was stock for those years or not I do not know. I do know the stock main jet needle on the XJR1300 has very little taper making it very lean. The slides also have a smaller hole next to the main jet needle compared to the US FJ.
Well I've torn down my carbs (yet again) only to discover that the main jets are in fact #875's ..
I rigged up a gravity fed fuel tank and tried it that way before I stripped the carbs and there was no improvement.
So could the small size of the main jets really cause this issue?
And if I replace them, what size should I go for?
To start with, I would stay with stock sizes: 112.5 main jets and 155 pilot air jets. All available from RPM
Later on if you add an aftermarket header, Unipods and ignition advance, you could go to 115 or 117.5 mains and shim the needles 1/2 step.
Thanks Pat, I've ordered the jets and I'll keep you posted on how she goes when I've fitted them.
Good deal.
While you wait on the jets, why not take your coils off and bench test them (primary and secondary) to rule out a dodgy coil.
I just thought of something....
Re:Jetting, a DavidR pointed out the main air jets are fixed on our USA carbs, yet the JDM specs show the main air jet to be a #45 size jet...so the 3 questions are:
1) Even though the USA main air jets are fixed, does anyone know the size?
2) Does the OP need to take out the JDM #45 main air jets and install the size used in our USA bikes?
3) In lieu of buying new main air jets, perhaps just drilling out the JDM jets to the correct size used on our bikes?
If the bike won't rev past 5K then it's either a rev limiter built into the ignition or an air flow limit.
Adding more fuel via changing jets will not solve your problem.
Just for reference, drilling an AIR jet larger will allow more air into the circuit and thus make it leaner.
The DJ kit includes a #144 air pilot jet which is smaller than the stock #155 to richen up the idle mixture.
David, do you think the OP will be ok with the JDM #45 main air jet and the 112.5 and 155 jets?
I was curious how the JDM #45 jet compared to our fixed main air jets.
The idea was to get his carbs back to the un restricted jetting.
Of course there is still the issue with the smaller JDM 32mm intake boots choking down the air flow.
A set of new 36mm boots should solve that issue:
http://rpmracingca.com/proddetail.asp?prod=36Y-13586-00-00%2C36Y-13596-00-00&cat=39 (http://rpmracingca.com/proddetail.asp?prod=36Y-13586-00-00%2C36Y-13596-00-00&cat=39)
Does anyone have a wiring diagram on the JDM '91 FJ? I wonder if there is a sensor wire running from the ignition box to the speedometer or Tachometer the OP could cut.
I know of a sensor wire which sends a tach signal (or is it from the coil?) to activate the fuel pump, and deactivate the fuel pump when no tach signal is present (safety shut off)
Quote from: Pat Conlon on August 15, 2018, 02:21:17 AM
David, do you think the OP will be ok with the JDM #45 main air jet and the 112.5 and 155 jets?
I was curious how the JDM #45 jet compared to our fixed main air jets.
The idea was to get his carbs back to the un restricted jetting.
Pat, I have no data on that, only a guess.
If the air jet and main jet are somehow a "matched" pair, then that would probably mean the #45 air jet is smaller than the fixed "unrestricted" air jet that is used with the 110 - 112.5 main jets.
The #45 air jet being smaller should tend to richen up the a/f mixture in the emulsion tube even more if larger main jets are installed.
The main question is, is the air jet a significant source of air for the overall needle jet circuit or is it more a source of bleed air to help promote atomization of the fuel as it's pulled up the emulsion tube and into the carb throat? I know on other bikes DynoJet included glue-in inserts to change the size of the main air jet. I would think this has an effect on the idle quality and throttle response at small throttle openings but that effect would diminish as more throttle was applied.
The JDM carbs are intentionally jetted lean. I can believe the factory would also limit RPM to a safe range to prevent that leanness from overheating the engine at higher revs. But, that also brings up another option where if they are going to restrict the red line, why not just leave the carbs the same as unrestricted models?
If there is no 5000RPM rev limiter on a JDM, then do the smaller diameter intake manifolds provide enough restriction to limit the achievable RPM? Doing a little math shows the 32mm intakes have a flow area that is ~80% of the 36mm manifolds. Is that significant enough to restrict the engine to a red line that is almost half of an unrestricted model?
I do have a somewhat related data point based on experience with my FZ1. Hoffman was visiting me and we were out riding. He was on the FZ and at an intersection he pulled up to me and said the FZ would NOT rev past6000 RPM. Since it was my commuter bike I never rode it with much aggression and never revved it that high. We swapped bikes and sure enough at about 6K the motor would just stop accelerating. If I continued to twist the throttle more the bike would actually start to slow down.
When we got back home the first thing I did was change the original fuel filter thinking it might be clogged after ~50 Kmiles. I couldn't shake any debris out of the old filter, and it looked fine. A road test showed the bike still nosing over at 6K. I pulled the seat to look at the air box. That's when I noticed about 4 inches of an old tank bag strap had been sucked into the airbox intake port. I had changed from a strapped tank bag to a magnetic bag a few months earlier and hadn't bothered to remove the strap from under the seat. That strap is about 1 inch wide. So at high air flow it was getting sucked up against the air filter and blocking approximately 4 square inches of the intake area. I have no idea what the actual intake area is, but the loss of 4 in^2 was significant enough to essentially limit the bike to a 6K redline.
And that's how I know that lack of revs is an airflow issue rather than a fuel issue. Once I removed that strap, the bike freely accelerated past 6K up to red line.
I probably should avoid such absolute conclusions.
If the fuel mixture is off bad enough it will affect an engine's ability to rev also. So it's not just airflow.
Hi all, from my research I have discovered that the Japanese Domestic Market 4CC FJ 1200 is restricted to 180kph (112mph) and around 90bhp by
1. Airbox restriction in the horn by about 50%
2. Electronic limiter in the CDI igniter box
3. Restriction in the speedometer.
4. Reduced diameter of carb rubbers.
To counter these limitations I have fitted an ECU, instrument cluster and the airbox from a 3CV model.
So It came as a surprise to me to find out that there are restrictions in the carb jetting too.
She starts, idles and pulls well up to around the 5k mark and that is where the main jet takes over from the slow running jets.
So I can only assume after removing the restrictions the smaller main jets must be at fault.
Unless the coils are faulty.. but then how is it she idles sweetly and runs lovely up to 5k?
My head is about to fall off...
Are you still using the 32mm intake manifolds?
Make sure that the main jet washers are in place. I just had an experience, fixing a problem with an FJ, that would not rev past 6,000rpm.
The main jet washers were missing and the main jets were above the fuel level in the float bowls. Just a thought.
Regards, Pete.
Quote from: FJ12IRL on August 15, 2018, 01:40:58 PM
......My head is about to fall off...
Stay with it Nigel.
What you're going thru is going to help the next guy.
I fully intend to save all your information and findings in the Files for easy future reference.
As you can tell, we don't see JDM FJ's very often.
David, thanks for taking your time in sharing your knowledge with us. I learn something every time you post.
Hey Randy or Robert, can you do us a favor? Can you grab a carb and see what drill bit size fits the fixed main air jet in our USA carbs. Again, I wonder how that size compares to Nigel's #45 JDM air jets.
Nigel, can you see if your JDM main air jets are removable?
Cheers
I have no problems with both the FJ's to go to the red line.
It is only cutting out at 180,when the limiter kicks in.
I don't think there is a rev limiter.
The one with the aftermarket exhaust is more lively than the ABS one.
It is jetted differently than the ABS.
Hannes
Quote from: aj52 on August 16, 2018, 02:03:09 AM
It is only cutting out at 180,when the limiter kicks in.
I don't think there is a rev limiter.
Please explain these two statements.
There's a limiter but it's not a rev limiter? Then what kind of "limiter" is it?
Quote from: FJ_Hooligan on August 16, 2018, 07:57:55 AM
Quote from: aj52 on August 16, 2018, 02:03:09 AM
It is only cutting out at 180,when the limiter kicks in.
I don't think there is a rev limiter.
Please explain these two statements.
There's a limiter but it's not a rev limiter? Then what kind of "limiter" is it?
Both of them goes to the red line in 1st and 2nd gear,in 3rd when you hit 180 on the speedo,something interrupts that the bike doesn't want to pick up speed. Feels like the bike is surging,at about 175 the bike pulls again till 180 and start surging again.
When the ABS is finished,I am busy with upside down forks,I will then be able to see if it is the speedo that has something to do with it.
Hannes
Quote from: FJ_Hooligan on August 15, 2018, 02:48:02 PM
Are you still using the 32mm intake manifolds?
Yes, I am.. but I think I'll mod them out to 36mm
FYI I ping'ed Randy....
He will be able to get an answer for us next week on the size of the USA unrestricted main air jets.
Fractional drill bits won't work, he needs his dad's numbered drill bits.
Stay tuned.
Quote from: Pat Conlon on August 16, 2018, 07:31:43 PM
FYI I ping'ed Randy....
He will be able to get an answer for us next week on the size of the USA unrestricted main air jets.
Fractional drill bits won't work, he needs his dad's numbered drill bits.
Stay tuned.
Pat,
A #48 (0.076 inch dia) is too big and a #49 (0.073 inch dia) is slightly loose, it will wiggle just a tad.
That is if you trust a set of number drill bits from Harbor Freight...... :-)
Thanks David.
Pardon the stupid question: On the #'s used for the Mikuni jet sizes, are those jet #'s equivalent to the #'s used on the drill bit sizes, or are they different?
Never mind, I think I've answered my question:
The larger the Mikuni jet # the larger the jet diameter.
However, it appears with your above information on the drill bit #'s the larger the drill bit # the smaller the diameter. (#48=0.076 and #49=0.073)
Quote from: Pat Conlon on August 17, 2018, 03:21:27 AM
Thanks David.
Pardon the stupid question: On the #'s used for the Mikuni jet sizes, are those jet #'s equivalent to the #'s used on the drill bit sizes, or are they different?
Never mind, I think I've answered my question:
The larger the Mikuni jet # the larger the jet diameter.
However, it appears with your above information on the drill bit #'s the larger the drill bit # the smaller the diameter. (#48=0.076 and #49=0.073)
Pat, the Mikuni jet size is the actual size in millimetres (hole diameter) i.e. jet size 112.5 = 1.125mm diameter.
Thanks Peter. I used to know that........ :wacko3:
So, if the JDM carbs have a #45 main air jet, (0.45mm) that has has an opening of 0.018" diameter
In our unrestricted carbs, David can get a loose fit in the main air jets with a 0.073" drill bit which is ~ 1.85mm, this tells me that Nigel (OP) needs to open up his JDM main air jets if he wants to run our larger main jets.
...or if his JDM main air jets are removable, he's looking for a #185 or 190 air jet? (if my math is correct)
Going from the JDM #45 main air jet to a #185 air jet sounds a bit much, however, on the fuel side, going from the JDM #87.5 main jets to our 112.5 jets is also a big jump.
Makes sense, the logic being: More fuel flowing thru the carbs needs more air to make it work.
Nigel might as well replace his JDM #135 pilot air jets with some #155's which we run.
Quote from: Pat Conlon on August 17, 2018, 12:31:54 PM
Thanks Peter. I used to know that........ :wacko3:
So, if the JDM carbs have a #45 main air jet, (0.45mm) that has has an opening of 0.018" diameter
In our unrestricted carbs, David can get a loose fit in the main air jets with a 0.073" drill bit which is ~ 1.85mm, this tells me that Nigel (OP) needs to open up his JDM main air jets if he wants to run our larger main jets.
...or if his JDM main air jets are removable, he's looking for a #185 or 190 air jet? (if my math is correct)
Going from the JDM #45 main air jet to a #185 air jet sounds a bit much, however, on the fuel side, going from the JDM #87.5 main jets to our 112.5 jets is also a big jump.
Makes sense, the logic being: More fuel flowing thru the carbs needs more air to make it work.
Nigel might as well replace his JDM #135 pilot air jets with some #155's which we run.
Hi Pat
The set of carbs with the aftermarket exhaust has 112.5 main jet and 157.5 air pilot jet. The other jet,think it is called pilot jet is 42.5.
I don't know where main jet sits to check that. Is like I said,the bike ran very well with that setup and fuel consumption was also way better than the JDM set with OEM exhaust.
Hannes
Were these JDM carbs you converted?
And the other thing was when I put the ABS's carbs with the aftermarket exhaust,from about 4500rpm,it blew fire out of exhaust.
Quote from: Pat Conlon on August 17, 2018, 01:05:16 PM
Were these JDM carbs you converted?
Both my bikes are JDM. I bought the one with the aftermarket exhaust in March. Don't know if you will recall it,but it is the carbs that some idiot used thread seal tape at the valve seats.
That is why I put the ABS's carbs and exhaust onto it. ABS is work in progress.
Where are the main air jet located,then I can check tomorrow what size it is
Main air at 9 o'clock.
Pilot air (removable) at 1 o'clock
(http://fjowners.com/gallery/2/medium_10_18_05_11_2_04_01_7.jpeg)
Quote from: Pat Conlon on August 17, 2018, 01:29:39 PM
Main air at 9 o'clock.
Pilot air (removable) at 1 o'clock
(http://fjowners.com/gallery/2/medium_10_18_05_11_2_04_01_7.jpeg)
Thanks Pat,will check tomorrow.
I didn't know there is also a jet in that hole.
The ones at 1 o'clock are 157.5
Hannes
Quote from: aj52 on August 17, 2018, 01:07:13 PM
And the other thing was when I put the ABS's carbs with the aftermarket exhaust,from about 4500rpm,it blew fire out of exhaust.
If you put larger fuel main jets in and are still running the small (#45) JDM main air jets, I could see this happening.
As DavidR posted above ^^^ more air is needed to be introduced into the carb to properly atomize the extra fuel (from the larger jets).
Sounds like you have a lot of raw fuel running through your engine.
That was what I thought after I saw the flames coming out Pat
Can't use the standard JDM carbs with aftermarket exhaust,it needs to be jetted
FJ12IRL you also need to know what main jet needle and emulsion tube is in your carbs. If they are different that what we have in the unrestricted models, just changing jet sizes might not resolve the issue.
The needle and emulsion tube are both numbered and need to be identified
Quote from: Pat Conlon on August 17, 2018, 01:47:00 PM
Quote from: aj52 on August 17, 2018, 01:07:13 PM
And the other thing was when I put the ABS's carbs with the aftermarket exhaust,from about 4500rpm,it blew fire out of exhaust.
If you put larger fuel main jets in and are still running the small (#45) JDM main air jets, I could see this happening.
As DavidR posted above ^^^ more air is needed to be introduced into the carb to properly atomize the extra fuel (from the larger jets).
Sounds like you have a lot of raw fuel running through your engine.
BIG CAVEAT here. The main jet doesn't really determine the fuel flow until the needle is pulled most of the way out of the needle jet (emulsion tube) probably beginning somewhere around 3/4 throttle. At anything less than that and the needle position and shape are controlling the fuel delivery in the main circuit.
If you never get to 3/4 throttle, you could run without a main jet and possibly not even notice. Except that the main jet holds the needle jet in place. :-)
Which carb circuit/jet has the most influence/control on fuel delivery is determined by throttle position, NOT RPM.
I can cruise on the freeway at 80 MPH with less than 1/8th throttle. The size of the main jet has ZERO influence at that throttle position. On the otherhand, attempting to accelerate from, say, 50 to 100 MPH using WOT means the main jet has LOTS of influence.
And the carb circuits have a lot of overlap.
(http://cdn.shopify.com/s/files/1/1415/0180/articles/carb_tuning_1024x1024.jpg)
I hear ya David.
The goal of my exercise is to get the jetting in FJ12IRL (Nigel's) JDM carbs close to what we have.
He still has air flow to address along the that mystery ignition interrupt.
Besides, I've been taught that getting the main jet correct is the first step in the tuning process.
http://www.factorypro.com/tech_tuning_procedures/tuning_carbtune,CV,high_rpm_engines.html (http://www.factorypro.com/tech_tuning_procedures/tuning_carbtune,CV,high_rpm_engines.html)
.
I hate carbs!
{rant on} . . .The only thing I hate worse than carbs would be trying to get the air/fuel mix right with carbs,
without having an Exhaust Gas Analyzer (rich/lean), and maybe a dynomometer. . . . {/rant off}
Quote from: Pat Conlon on August 16, 2018, 07:31:43 PM
FYI I ping'ed Randy....
He will be able to get an answer for us next week
Looks like David already did it.
As Robert already mentioned, as well as David, the needle and emulsion tube need to be identified before recommending jetting changes.
Randy - RPM
Luckily I have Pete nearby..... :sarcastic:
Quote from: racerrad8 on August 18, 2018, 09:33:20 PM
As Robert already mentioned, as well as David, the needle and emulsion tube need to be identified before recommending jetting changes.
Randy - RPM
Yep, according to the Yamaha GFSM for the '91, the needles and the needle jets (aka:emulsion tubes) are different.
JDM needles = 5FZ74-2
Usa needles = 5FZ74-3
Needle jets:
JDM = Y-0
USA = Y-2 Do these USA specs sound right Randy?
Quote from: Pat Conlon on August 19, 2018, 04:15:03 PM
Quote from: racerrad8 on August 18, 2018, 09:33:20 PM
As Robert already mentioned, as well as David, the needle and emulsion tube need to be identified before recommending jetting changes.
Randy - RPM
Yep, according to the Yamaha GFSM for the '91, the needles and the needle jets (aka:emulsion tubes) are different.
JDM needles = 5FZ74-2
Usa needles = 5FZ74-3
Needle jets:
JDM = Y-0
USA = Y-2 Do these USA specs sound right Randy?
The stock, non adjustable needle we see in USA carbs is 5FZ72
The emulsion tube is 378 Y-2
So, if the JDM carbs use different needle and emulsion tubes, the jetting we use in the US will probably not work correctly. I have never seen a set of JDM carbs, so I do not know what the difference is to be able to offer advice.
FJ12IRL, it might be worth snapping a couple of photos and verifying the part number you have on your parts.
Randy - RPM
I see a set of FJ1200 carburetors on e-bay for $195.00
Hi all, the new jets arrived today and I installed them. The bike now will rev out to the red line with no load, it wouldn't do that previously.
I'll take her out for a spin tomorrow to see how she's performing.
Hi All, Just been out for a test drive and I'm proud to say that my JDM FJ is able to access ALL the ponies!
She pulls well all the way to the redline in every gear now, no flat spots, idle is a little off but I will balance the carbs later.
I can say without doubt that the main cause of my troubles were the main jets sizes.
Thanks to all of you who helped me out with this, I can finally enjoy riding my beautiful FJ :yahoo:
Quote from: FJ12IRL on August 22, 2018, 09:18:01 AM
Hi All, Just been out for a test drive and I'm proud to say that my JDM FJ is able to access ALL the ponies!
She pulls well all the way to the redline in every gear now, no flat spots, idle is a little off but I will balance the carbs later.
I can say without doubt that the main cause of my troubles were the main jets sizes.
Thanks to all of you who helped me out with this, I can finally enjoy riding my beautiful FJ :yahoo:
Good for you.
What jets did you put in.
Is it still OEM exhaust system.
Hannes
Quote from: aj52 on August 22, 2018, 09:35:50 AM
Quote from: FJ12IRL on August 22, 2018, 09:18:01 AM
Hi All, Just been out for a test drive and I'm proud to say that my JDM FJ is able to access ALL the ponies!
She pulls well all the way to the redline in every gear now, no flat spots, idle is a little off but I will balance the carbs later.
I can say without doubt that the main cause of my troubles were the main jets sizes.
Thanks to all of you who helped me out with this, I can finally enjoy riding my beautiful FJ :yahoo:
Good for you.
What jets did you put in.
Is it still OEM exhaust system.
Hannes
I replaced the 87.5's with 112.5's..
stock exhaust system.
Quote from: FJ12IRL on August 22, 2018, 09:18:01 AMHi All, Just been out for a test drive and I'm proud to say that my JDM FJ is able to access ALL the ponies!
She pulls well all the way to the redline in every gear now, no flat spots, idle is a little off but I will balance the carbs later. I can say without doubt that the main cause of my troubles were the main jets sizes. I replaced the 87.5's with 112.5's.. stock exhaust system.
FJ12IRL,
Sound good, man. I'd keep the stock exhaust, unless you want to re-do the jetting again. An aftermarket exhaust system
may get you a few extra ponies (if even that much), but I've
never seen results that justify the money and trouble of an aftermarket exhaust.
My $.02 worth . . .
Quote from: FJ12IRL on August 22, 2018, 09:47:59 AM
Quote from: aj52 on August 22, 2018, 09:35:50 AM
Quote from: FJ12IRL on August 22, 2018, 09:18:01 AM
Hi All, Just been out for a test drive and I'm proud to say that my JDM FJ is able to access ALL the ponies!
She pulls well all the way to the redline in every gear now, no flat spots, idle is a little off but I will balance the carbs later.
I can say without doubt that the main cause of my troubles were the main jets sizes.
Thanks to all of you who helped me out with this, I can finally enjoy riding my beautiful FJ :yahoo:
Good for you.
What jets did you put in.
Is it still OEM exhaust system.
Hannes
I replaced the 87.5's with 112.5's..
stock exhaust system.
Thanks a lot.
The ABS one also had stock exhaust,going to open it up when the other carbs are finished and back on the non ABS one.
If it still have the 87's in,I am going to swap them out with the 112,5's then.
Hannes
Quote from: aj52 on August 17, 2018, 01:38:48 PM
Quote from: Pat Conlon on August 17, 2018, 01:29:39 PM
Main air at 9 o'clock.
Pilot air (removable) at 1 o'clock
(http://fjowners.com/gallery/2/medium_10_18_05_11_2_04_01_7.jpeg)
Thanks Pat,will check tomorrow.
I didn't know there is also a jet in that hole.
The ones at 1 o'clock are 157.5
Hannes
Ok,got a chance today to look at the main air jet.
It is also a fixed jet,can not remove it.
I measured it with nozzle cleaner set and use a micrometer.
It is 0.60mm. It goes in quite stiffly with that tip.
Hannes
Mikuni Jet sizing...? (http://www.fjowners.com/index.php?topic=18078.msg181849#msg181849)
As far as the fixed main air jet, my Hanson number drills fit the #49 (.073") almost perfectly in the fixed air bleed jet. 48 won't even try and 50 is sloppy.
Based on my other post above, the .073" converts to 1.8542mm and that is no where close to the listed size of 45 for the US market as well as the JDM. That would make it a 185 jet size if it was based on the holes size.
If I'm way off base please let me know...
Randy - RPM
Quote from: racerrad8 on August 23, 2018, 07:25:48 PM
...and that is no where close to the listed size of 45 for the US market as well as the JDM.
I didn't know that the GFSM lists the USA carbs as having a #45 main air jet.
The listing of a #45 for the JDM sounds logical with the goofy #85 main jets.
This Mikuni jet numbering is getting weird. Could the numbering on air jets be different than fuel jets?
Randy, do the 155 pilot air jets actually measure 1.55mm? (0.060")
Quote from: Pat Conlon on August 24, 2018, 01:42:51 AM
Randy, do the 155 pilot air jets actually measure 1.55mm? (0.060")
No, the 155 fits a #51 (.067") pretty nicely, but a #50 (.070") will not fit.
I pulled a 160 jet and it too fits the #51 which is sloppy and the #50 will not fit.
The #53 (.059") drill bit which is as close to .060" I have is really sloppy in both the 155 & 160 jet.
Randy - RPM
Quote from: racerrad8 on August 24, 2018, 10:28:11 AM
Quote from: Pat Conlon on August 24, 2018, 01:42:51 AM
Randy, do the 155 pilot air jets actually measure 1.55mm? (0.060")
No, the 155 fits a #51 (.067") pretty nicely,
Ok, so the #155 pilot air jet is actually 1.70mm in size (0.067")
Sounds like there is no correlation between the Mikuni jet numbers and the diameter (other than larger is bigger)
Hi All,
Just an update on how she's running post re-jet.
I took her out for a long spin and an "Italian Tune Up" (revving the nuts off it) and she is pulling cleanly all the way from idle all the way up to 6.5k then pulls hard all the way to the redline in all the gears just like my old FZR1000 Genesis.
I have re-installed the JDM clocks and it was great to see the needle go past 180km/h and keep going strong until I ran out of road!!
Carbs have all stock jets installed bar the 112.5 mains, so I can say with extreme satisfaction my FJ is fully de-restricted!
Once again thank you all for your help getting my ponies back. :good2:
Congrats Nigel!
See? It all worked out and you helped us learn something to boot!!
Quote from: Pat Conlon on August 24, 2018, 01:03:59 PM
Congrats Nigel!
See? It all worked out and you helped us learn something to boot!!
I have a lot of experience with older (80's & 90's) Japanese motorcycles but I have to say the JDM model FJ with all those restrictions really tested me..
When I posted originally, I was at the end of my tether, about to call it a day and sell her back to the Breakers I'd bought her from and now, having learned from the members here and resolved the issues I had with my FJ, I'm really glad I asked for help.
I hope to help some of you out in the future if I can.
Cheers
Nigel.
Quote from: FJ12IRL on August 24, 2018, 12:56:24 PM
Hi All,
Just an update on how she's running post re-jet.
I took her out for a long spin and an "Italian Tune Up" (revving the nuts off it) and she is pulling cleanly all the way from idle all the way up to 6.5k then pulls hard all the way to the redline in all the gears just like my old FZR1000 Genesis.
I have re-installed the JDM clocks and it was great to see the needle go past 180km/h and keep going strong until I ran out of road!!
Carbs have all stock jets installed bar the 112.5 mains, so I can say with extreme satisfaction my FJ is fully de-restricted!
Once again thank you all for your help getting my ponies back. :good2:
Hi there
So the speedo has no effect then on the restriction?
From previous posts you mentioned that you changed the ECU and airbox as well.
Could you see the difference between the JDM airbox and the 'new' airbox?
I want do derestrict both of mine too,now that we have an idea where the restriction lay.
Thanks
Hannes
Hi Hannes, The restriction in the airbox is in the horn of the cover. You could remove the plastic and that would do the trick. I needed the carb rubbers so i bought the whole lot from a breaker.
The rev limiter is in the CDI igniter box, when you replace it with any other non-JDM box the speed limiter in the clock is disabled.
Thanks a lot for the pics.
I need to open that other block off piece then.
So now the search starts for the ECU here in RSA
Hannes
There's loads of them on ebay Hannes.