Can you please look at these plugs and let me know how you think the bike is running? I would say it's running lean based on the plugs but I'm a newbie. Also, I have the fuel mixture screw at 3 1/8 turns out and it still has a slight bog right off idle which I think means it's running lean.
Current setup is below:
1986
Stock headers & collector. F1R slip-ons.
Unipod Air Filters
Carbs not sync'd (yet)
Plugs have about 50 miles on them.
40.0 Pilot Jet
155 Air Bleed
115 Main
Needle shimmed with one spacer
Air fuel mixture screw is 3 1/8 turns out.
Thoughts?
Regarding the oil level, on these bikes does the engine oil sometimes not fully drain back into the pan? I just changed the oil few weeks ago with 20w-50 VR1 (conventional) and I know it was to the top of the line on the oil sight. After a few small rides totaling about 10-15 miles after the bike was cold I noticed it was slightly less than half way up the oil sight. So I topped it back up to the top line. Then I went for a 10 mile ride and after letting the bike sit for 30 mins the oil was well above the line basically to the top of the glass. So I drained some of the oil out while it was hot and got the oil back to the top line. So that makes me think when I saw the glass about half full that the oil was somewhere else? When I topped it off I only put in a little at a time until it was at the top line. The oil was cold at that time.
Then went for 20 mile ride and afterwards oil was right at the top line, so that's good.
Then just did a 5 mile ride and now the oil is about 1/8" below the top line.
I'm pretty sure my bike is burning some oil just because of age and probably bad valve seals from it sitting 15 years but so far the oil in the glass sight doesn't seem to follow a logical pattern. I'm hoping there is a logical reason that not all the oil drains back into the pan sometimes?
Also for the spark plugs I know I torqued them in well to spec and when I went to take them out the were not tight I needed basically no pressure to loosen them which I thought was odd, do I need to use blue thread locker on the spark plug threads?
hopefully these photos post larger so you can see better
Forgot to mention I do get popping on deceleration when laying off throttle at higher RPM's, sounds good but that may also speak to a lean mixture?
Here she is
It's difficult to gauge fuel mixture from the FJ plugs (they run a wasted spark system, so they fire every stroke, not just every other stroke), but at 50 miles, at least we can say it doesn't look like the bike is burning oil - the plugs are still very clean.
Definitely DO NOT use thread lock on the spark plugs - they have crush/spring type washers on them. If they're a bit loose after torque'ing them and riding it a bit, just give them a little "nip up" by hand, but be careful not to overtighten them or strip the threads in the head - a lot of the bikes I work on, come into the shop with very loose spark plugs, lots are only finger tight but amazingly, it hasn't yet caused a discernable running problem on any of them (I guess I've developed a "feel" for tightening them after the first torque'ing :biggrin:) . At least on a FJ, you can get the plugs out in a couple of minutes to check them all.
With air pod filters and the F1R pipes, the bike likely is running lean, but the popping you mention could also be due to leaks at the exhaust joints/headers. I've no idea if your jet sizes are stock or not unfortunately (ours in the UK were jetted completely differently to the USA), but hopefully Randy/Robert, or someone else here can confirm that for you.
Along with wasted spark that Dean mentioned, US market FJ's have a closed throttle vacuum advance on the ignition timing which flash burns and left over hydrocarbons (gas) from the combustion cycle.
This is not used for performance (happens at closed throttle) but it's part of the US EPA smog system.
It is this vacuum advance that turns your plugs white. (and clean)
You look at this and think OMG you're running lean. Not true.
Discussed here: https://fjowners.com/index.php?topic=11690.0
If you want to get an accurate plug color, disconnect the advance vacuum line off your #2 intake manifold. Don't forget to cap off the vacuum inlet port on the manifold.
Cheers. Pat
I checked vacuum leaks at the intake by spraying starting fluid around it when running and no spike in RPM. How can I check for leaks in the exhaust? Everything looks flush and tight IMO.
I was thinking to go up to 42.5 Pilot since I'm at 3 1/8 turns out and I was also thinking to try 117.5 main.
Pat, when I disconnect that vacuum line and cap the intake do I need to also cap the vacuum line or do anything else?
Quote from: 86FJNJ on June 09, 2025, 06:59:17 AMI checked vacuum leaks at the intake by spraying starting fluid around it when running and no spike in RPM. How can I check for leaks in the exhaust? Everything looks flush and tight IMO.
I was thinking to go up to 42.5 Pilot since I'm at 3 1/8 turns out and I was also thinking to try 117.5 main.
Pat, when I disconnect that vacuum line and cap the intake do I need to also cap the vacuum line or do anything else?
You can leave the vacuum hose open, just cap the manifold port.
Thanks Pat! I will cap the port.
What are your thoughts on me changing from 40 to 42.5 pilot and 115 to 117.5 main?
Unipods and F1r slip one. Needles already shimmed.
Quote from: 86FJNJ on June 09, 2025, 09:34:16 AMThanks Pat! I will cap the port.
What are your thoughts on me changing from 40 to 42.5 pilot and 115 to 117.5 main?
Unipods and F1r slip one. Needles already shimmed.
I don't think you need to change. #40 pilots and #115 mains should be fine with your current engine mods. Just some fine tuning and you'll be there.
thanks Pat, any thoughts on the oil level issue? Does oil sometimes not fully return to the pan? Why am I seeing varying oil levels on the sight glass?
I always have the bike on center stand when checking oil level. After 50 miles plugs don't seem to be caked with oil which I would think they would be if I were burning that much oil so quickly.
Yes, it takes time for the top end oil to drain back, don't worry about it.
Check your oil level cold on the center stand like the owners manual states.
Get some miles on your bike. It's common to have the valve seals shrink harden when the bike is stored, they tend to soften and expand after some fresh miles are put on the engine.
Cheers
After all of my consultations with FJ experts and online searching I think I have either a vacuum leak by the intake ports or dirty pilot circuit or both. Although I did spray starting fluid and carb cleaner around the intake while idling and no noticeable change in RPMs. New intake gaskets from RPM shipped out today just to be safe and I'll take the carbs off and blow some carb cleaner and compressed air through the pilot circuit and go for a ride.
It seems to run really well in the midrange, I've not gone past 6k rpm and not sure I want to very much except just for testing/tuning purposes...but if I have a clogged pilot circuit that really only effects things up to 1/4 throttle correct?
Would there be any harm in me "living with" that dirty pilot circuit for a couple hundred miles in the mid range of RPM's to confirm the bike isn't burning a crazy amount of oil? Once I confirm the bike is not burning an excessive amount of oil I plan to order new tuned carbs from RPM but that's a bit of an investment so don't want to do that until I know engine doesn't need major overhaul.
Also I'm sure you all already know this, but this has been a game changer for me while working on the FJ.
To reverse the tank, keeping it hooked up and secured into the same tank brackets so it doesn't move. Way easier than taking it on and off and using one of those small auxiliary gas cans. I put a bungie cord around it through the rear grab handles as an extra safety measure but locked into those two frame mounts it's not going anywhere.
Why has nobody mentioned this to me yet, this should be FJ 101 when joining the group.
That's yet another advantage the fuel pump brings to the table.
Pat, if I can't get the pilot circut clean on my own to have a good idle with the current 40.0 pilot is there any harm in me just living with it like that and riding it for a couple hundred miles as long as the majority of that time I'm past 1/4 throttle and not operating the bike in the pilot circut? I just want to get some miles on it to confirm bike is good with no major issues before dropping big $ on new tuned carbs from RPM. I cant imagine that causing any harm.
It depends on how bad....In my opinion, riding a 100+ hp motorcycle on the street with no or poor low speed manners (meaning you have to keep the rpm's high to avoid stalling) is not the best idea for a safe ride.
If I had to...I would want to run it on the freeway and avoid stop and go situations.
Safest thing for you would be to pull the carbs, drain them, box them up and send them to Robert @ RPM. He will work his magic on them, guaranteed.
Just be careful. Does the reward outweigh the risk?
Cheers
It's not that bad the bike actually runs really well it's just a slight bog off idle and I have screws 3 1/8 turns which I know is a lot, enough I know it's not right but I've comfortably rode around without issue and even on backroads I'm always in the middle of the rpm range like 2500-4500 so as long as it's not hurting the bike I'll do another cleaning on my own and try to rack some miles up and see how it is
Ok, that's not too bad. It's a good idea to run some gas (with Seafoam cleaner) thru those carbs and get some miles on that engine. Perhaps that's all that's needed?
I have a hunch that your bike will run better the more miles you ride.
Also...If you use a little oil, so be it, don't worry. Our air cooled engines have loose piston ring tolerances to account for the latent heat build up we get.
Cheers
Put some seafoam in gas and will report back after a while.
What about a little seafoam in engine before oil change?
I have never used Seafoam in my FJ crankcase.
I do remember a long time ago when I used a crankcase cleaner in an old high mileage Ford 292 Y block. (TBird)
I guess it worked too well in removing carbon because that engine started using oil much more than it was originally using before the treatment.
fair point maybe there is such a thing as too good, I am mainly hoping it cleans the carb pilot circuit out a little and the exhaust ports have a bunch of crud in them from what I'm guessing is oil leaking past the valve seals...nearly at 100 miles on the FJ so I'll try to keep racking up miles.
Weird thing happened yesterday, rode the bike to work and all was fine, then leaving work I could not get dash lights to turn on to start the bike...thought the battery was dead but after a bunch of tries eventually they did turn on and neutral light was clearly on but when I tried to start the bike it lunged forward which means it was actually in gear, so that was a first. It was very hot out so not sure if the FJ's get quirky when it gets hot out?
I had that happen with me, it was my key ignition switch that was acting up so I bought another one...
http://www.rpmracingca.com/proddetail.asp?prod=M%2FC%3Aflatkeyswitch
If your neutral light shines, you should be in neutral.
If not, look at your neutral switch and circuit.
http://www.rpmracingca.com/proddetail.asp?prod=1L9-82540-00%2B93210-29196
Sometimes a scuffed grounded, burnt or pinched signal wire will cause a false neutral light.
Sometimes I get a pesky clutch plate that sticks, so while I'm in neutral my bike will creep forward like it's in gear...when it isn't. As the clutch pack gets some hours and miles on it, the sticking plate disappears.
Cheers....keep riding your bike, I'll bet you a jelly donut any hardened leaking valve seals will soften up and seal after some miles.
Report back on your oil usage. Smoking on start up?
Ride well. Pat
thanks Pat, yes on start up smokes like it's on fire for about 30 seconds, then goes down to a light smoke and after about a minute it's gone.
It's 39yo so I can live with some smoke on start up. So far after 35 miles yesterday in 85 degree NJ weather no reduction in oil level on the sight glass so I'll keep watching it
Try parking on the center stand, see if that reduces start up smoke.
Parking on the side stand allows all the top end oil to shift over to the left side (low side) and bunch up on the #1 and #2 cylinders.
Same thing happens to the carbs with crap gas. It always seems like the first carbs to get plugged up are the left side #1 and #2 carbs.
Cheers
Thanks pat, I've actually been using the center stand and still does it. Another 50 miles done today with half of that two-up and no drop in oil level so that's good. I'll keep and eye on it.. I think the seafoam is helping the idea is slightly increasing from what it was so that's would mean pilot circuit is getting more fuel now right?
Yes, the low speed manners are improving...good...
Sometimes it takes multiple tanks of Seafoam to get those little passages opened up.
Ok so def have a weird issue with the oil level. I changed my oil and filled it to the top line. After a little running at idle afterwards I went out all day and the oil is only halfway up the sigh glass between the bottom and top lines. Yes bike is on center stand.
This is happening intermittently, sometimes all the oil returns to the pan, sometimes it doesn't.
Any reason for this to happen?
To clarify I didn't change the oil filter so whatever oil was in the filter was not affected by my oil change.
So it's not like I changed the filter and disconnected the oil filter to get the engine completely dry. I just drained the pan. The oil I drained only has like 100 miles on it.
In addition to the top end, the clutch pack and transmission gear clusters holds a slight bit of oil...
Like your tire air pressures, Check your oil in the morning before your ride, top it off, then ride.
Absent an obvious oil leak, don't worry about it durning the day, you will drive yourself crazy...
as usual thanks Pat. This was driving me crazy, I just wanted to make sure I didn't have an oil issue. I know I didn't have a leak and there is no way the bike could burn that much oil that quickly. I'll just keep an eye on the oil level and gradually top it off to the top line...just really weird to me that it was at the top line (cold) when I drained it, I filled it with cold oil and let it idle for a few mins and then half the oil in the sight glass is gone which I would estimate to be worth about half a quart of oil or so. Only thing I could think of is maybe when draining the pan it pulls some oil from the oil cooler lines which then gets pumped backed into the oil cooler lines upon start up causing the oil level to be lower?
Is checking valve shim clearance a task a regular person (me) can do while the engine is in the bike or does it need to be done by somebody with some decent knowledge/experience and does engine need to come out? I hear a slight tap from the right intake area under the valve cover that I assume may be a valve or something...it's faint but there. There is 20,000 miles on the bike and I don't know the history if valves were ever serviced before. Am I at risk to keep riding the bike this season if I take it easy for another 500 miles or so? Anyone know of any shops in the New Jersey area that work on FJ's / Legends if it's not a task I feel confident in taking on?
Checking the valve clearances is an easy job on the FJ.
Once you've got the petrol tank off (or turned around on the rear subframe) you can take the rocker cover off easily (and take the spark plugs out) and following the instructions in the manual for ensuring the appropriate TDC's (rotate the crank to line up the timing marks) you can check (and record) the actual clearances with a set of feeler gauges.
Putting in different shims to correct any out of tolerance valve clearances that you find, can be a difficult task for someone not experienced/confident in working on bike engines and you'll need the little adjusting tool to remove the old shims and put the new ones in.
The thing is, my FJ has only ever had clearances that I felt I needed to change/rectify by being too tight. I've not found any yet where the clearances were too large.
With these shim valve clearance adjusted engines, since people say "a ticky valve is a happy valve" - and then again, FJ engines are naturally a little tickier than modern liquid cooled engines.
Thanks for the advice! If it's not a concern maybe I'll wait until this winter to take on that effort.
It's not a bad idea to check valve clearances. Loose valves, no problem, but look for the tight valves.
While you have the valve cover off, replace the grommets that seal the valve cover bolts.
(http://www.rpmracingca.com/prodimages/large/2GH-1111G-00-00-1.jpg)
http://www.rpmracingca.com/proddetail.asp?prod=2GH-1111G-00-00&cat=39
Those little fuckers always seem to dry out and leak. Be very careful in torquing on those valve cover bolts. They have a stepped shoulder, so if you over tighten them you will break them off.
Cheers
Thanks pat yes I did already replace the valve cover gasket and grommets with new from RPM.
What size feeler gauge should I be able to get under the came to ensure it's not too tight? Also does the cam/valve need to be in a certain rotation to check that gap? I'm guessing the valve needs to be fully closed when checking?
Rotate the crank so the cam lobes are pointing up (180° away from the valves)
Exhaust minimum clearance: 0.16
Exhaust maximum clearance: 0.20
Intake minimum clearance: 0.11
Intake maximum clearance: 0.15
Get a .16 and .10 for your quick go/no go measurements. Only worry about the tight no go valves.
Measure on a stone cold engine, like overnight cold.
If you become a contributing member of the forum you will be eligible to rent the RPM shim kit which has all the shims (and tool) you need for this service work.
https://fjowners.com/index.php?topic=8968.0
Carb question: bikes runs good at mid range and top end. Having starting trouble and hanging idle. Won't start unless I crack the throttle 1/8 turn, even with choke fully on. Once warmed up if I blip throttle at idle it sometimes hangs at 1,500rpm for 3-5 seconds before going back down to idle. Only noticeable when idling, runs fine otherwise.
Previously I was running 40.0 pilots, 155 air bleed and fuel mixture screws were 3.5 turns out. I changed to 42.5 pilots and kept the 155 air bleed to try and fix the issue. Fuel mixture screws are 3 turns out now. I would think I can be a half turn less on the fuel mixture which the increase in pilot size.
Any ideas what's going on? I already replaced intake boot o-rings and vacuum caps as a precaution. Sprayed fluid all around intake boots and no reason to think there is a vacuum leak.
Unipod filters and F1R slip-ons.
I do use a small amount of fuel stabilizer in my fuel to help prevent the gas from going bad. But I cut the dose in half to 1/3 of directions so I don't think that's it but mention it just in case. I haven't pulled plugs yet but they were just put in 500 miles ago so probably unlikely to be a spark issue.
Good info: https://www.youtube.com/watch?v=q9A2TL9RvwQ&pp=ygUGI21kenJ4
I watched it thanks. Maybe the air in NJ is different or maybe my bike is a unicorn...but I just see all you guys talking about fuel screws being 2.5 turns out etc and I'm at 3 turns out with 42.5 pilots and 155 air bleeds and I still have lean idle symptoms so I can't help but think there is something I'm missing. But at this point I'll just keep backing the screws out until it's good.
This exercise assumes you have clean carbs and balanced air flow.
If your carb linkage returns correctly, and you have a hanging idle, it's a lean condition. Plain and simple.
Turn your mixture screws out 1 turn (from 3.0 to 4.0 turns)
If that doesn't work, try one more 1/2 turn out.
See if that helps your hanging idle. It should, if not you have plugged fuel passages in the carbs. You've already checked for vacuum leaks. If it's not unmetered air causing your lean condition, then it's lack of fuel.
At 4.5 turns out, if you get an idle dip, then it's too rich, turn the screws in 1/4 turn increments leaner until the dip goes away.
Your hard start condition indicates dirty choke circuit or idle circuit.
Don't overheat your engine. Get a box fan (or two) to keep air blowing thru the engine or you will cook your exhaust valves and seats.