Mystery, No-name Jets - Need Guidance on Correct Size for Slight-mod Application

[FJ1100mjk]

Hello:

I'm rebuilding a set of carbs from an '87, and when I got them apart, I noticed that the main jets do not have any numbers stamped on them. The needles have six notches on them with the clip set at the second notch from the top. I haven't gotten the pilot jets out yet to see if they are the standard size or not, but I found the air bleed jets to be 155's.

The bike currently has K&N pods on it with a K&H exhaust (non-SST) system, and a Dyna 2000 ignition with Dyna coils, that the PO installed. And I bought the bike in non-running condition, so I haven't ridden it - yet.

I plan on going back to a stock airbox arrangement with either a Uni filter or a K&N (I have both laying around) in it when I put everything back together again, so I'm thinking that the main jets will require replacement, and maybe the pilots and air bleed jets too.

Can anyone provide guidance on the sizes for the main, pilot, and air bleed jets, and in addition to what notch that the clip has to be on the needles? I try to run non-oxygenated fuel that I can get around town, but I may have to run ethanol mixed gas when out on the road if on a trip.

I live in the St. Paul area, and if it matters, the elevation is around 500 - 1000 feet above sea level.

Thanks.
Marty

[Pat Conlon]

Hey Marty, sorry for the late reply. You saw this in the Carb Files section? http://www.fjowners.com/index.php?topic=1974.0

My recommendation: Jets are cheap. Randy @RPM has all you need. Throw away all the unmarked jets. Install known sizes. They are cheap.

[FJ1100mjk]

Pat:

Thanks for the reply.

Yes, I had previously reviewed the post that you sent the link for. However, all of the riders' listings of their settings dealt with their respective bikes having pod filters on them, and I'm going back to a stock airbox, so I was fishing for info on jets' and needles' sizes and settings for the stock airbox mounted with the V&H exhaust system.

I did find your post "Why* aftermarket air filters (UniPods) affect fuel mixtures in CV carbs" very informing, and see that you are "running stock exhaust, airbox with UNI replacement filter and a DJ kit with 110 mains, 144 air pilot, and needle on groove 1.5".

My Clymer manual states that my '87 should have 112.5 mains in the carbs, and 37.5 pilots. I'll check my pilot sizes when I remove them and get those sizes if they are different, but I'm wondering if the 112.5 mains are correct for having a V&H exhaust system on my bike. And it looks like I may want to change the needle groove to the first position, but I'm a little vague on the direction for that setting too.

I'm building a list of items that I will be buying from Randy, and it goes beyond just carb parts, such as inner bushings on the forks that I first need to remove and inspect to be certain that they're needed.

Marty

[Pat Conlon]

.... I see that you are "running stock exhaust, airbox with UNI replacement filter and a DJ kit with 110 mains, 144 air pilot, and needle on groove 1.5".

No, before Randy rebuilt my engine on my '84 my jetting (all Mikuni jets)  was 42.5 pilots, needle clip at #3 and 122.5 mains, oem air pilots.
I ran Unipods and oem exhaust with Cobra F1R slipons. 5 degree advance rotor on the ignition. I am at sea level and suffer very hot summer temps.
The 42.5 pilots were a tiny bit rich, no problems at sea level but when I rode up in the mountain's thin air, the low end would be on the rich side.
If I had to do it over I think #40 pilot jets would be better.

Now that my engine is 1349cc all the jets have changed.    Cheers. Pat 
 

[Flynt]

"Now that my engine is 1349cc all the jets have changed" - Pat



To what?  I took the plunge and Randy gets my engine Thursday.  

I have a month or so to learn from the experienced, then I'm tuning again.  Knowledge appreciated.  

Frank

[Klavdy]

Mate, that is going to be pretty close to the ultimate FJ.
"Bout the only things left after the monster engine would be light weight wheels,,,

[racerman_27410]

"Now that my engine is 1349cc all the jets have changed" - Pat


To what?  I took the plunge and Randy gets my engine Thursday.  

I have a month or so to learn from the experienced, then I'm tuning again.  Knowledge appreciated.  

Frank

You are going to love it..... it's quite addictive KOokaloo! 

[fj1289]

Also,  don't forget that which jet kit was already installed in your carbs will make a big difference in your jetting.  The needle design has a large effect on what main jet you need to run.  Dynojet needles are narrow at the tip compared to the factory pro needles - the factory pro needles require much larger main jets. 

See here for a comparism -- http://www.fjowners.com/index.php?topic=1974.0

Good luck and post your results!

[andyb]

Chris speaks the truth.

Starting from the beginning, you've got adjustable needles.  I don't have the spec in front of me, but if they're tapered strongly to the tip, they're <random aftermarket>, OEM for non-US market, or DynoJet.  The jets being unmarked though, that's an interesting quandry.  I'm guessing (guessing!) that what you have is a set of carbs that someone guessed at the jetting by buying a generic jet kit from a less than reputable dealer, such as chinese ebay stuff or a DJ knockoff of some sort.  That may not be a bad thing, honestly!  With adjustable needles, if the taper is reasonably close, you can put them fairly precisely where you want them, and short of dynotesting, I'd wager that you'd never know if you have a mild weak spot in the half-throttle midrange pulls.  Testing against another bike with a known set of comparable mods would be guesswork as to who weighed more, bearing/brake friction, and who opened the throttle just a little farther.  The jets are a larger concern.

I'd suggest to start by simply getting it in running condition.  It's damned tricky to adjust jetting when there's no fire!

If you want a known starting point rather than a questionable one, you could post a picture of the needles (there's enough of us that we could compare, take a measurement or two mayhaps) and someone could compare them to a known quantity.  From there, it'd just be a question of getting things pretty close with known jets from various kits--always cheaper to just buy the sizes you need, even if you miss here or there--and the fine tuning, as usual, will be up to your personal taste, right wrist, individual machine, fuel type and quality, air quality, riding conditions, and what the plugs say.

Is the exhaust a full system, or does it appear to be slipon type?  K&H isn't one that I've heard of, did you mean V&H?  If the headpipes are a single welded 4-1 unit, painted black (and probably rusted?) with a round cannister, that's the V&H SS exhaust.  From stock, I'd go up 1-2 sizes on the mains for that with a stock airbox.  Air jets are fine at 155, most likely.  Pilots will depend on how it runs, but 37's or 40's will be right (likely 37's).  Needle position will take some trial and error to make it specifically right for you.

I'd suggest using a few methods to determine needle position.  One involves a video camera mounted in such a way that you can record rpm vs time in a given gear with the throttle held steady at half throttle or thereabouts (masking tape and a pen makes it easy to be repeatable), doing plug chops, dynotesting, or even just watching your mileage.  For example, my daily ride (not the FJ) gets 44-46mpg in normal mixed riding, but when I am out "playing" that improves to 50-52mpg.  Most of my "playing" miles happen in the midrange, and I know that my mains are oversized (intentionally as it happens, long story), which tells me that my needles are definitely down too far, and they'll be moving up a clip the next time I get into the carbs this winter/spring. 

With a true 4-1 pipe, you can expect a mild flat spot right around 6krpm or thereabouts; it's usually felt as a smooth spot on top gear pulls where everything sounds good but shortly after (~7k) the bike seems to really come on cam and pull harder.

[FJ1100mjk]

Everyone:

Thanks for all of the feedback and tips on my previous post. Below, is a pic of one of the mystery carb needles with an overall length provided. Maybe someone can identify what manufacturer made the needle, and then I can work backwards and determine what the no-name jet sizes are.

After a few doses of PB Blaster and application of a heat gun on the carb bodies, I was able to extract the pilot jets and the emulsion tubes. I don't know who provided the tip on loosening these things, but thanks. With an aided-eye (cheaters and a magnifying glass), I cannot see any numbers on the pilot jets.

I'm a fellow aspiring King of Cheap, but may have to throw the towel in and buy the real Mikuni jets in the aforementioned sizes.

Based upon input, I determined that I have the V&H SS full exhaust on my bike.

Thanks.
Marty

[Harvy]

Marty, I'm not entirely certain, but I believe that is a Dynojet needle. Factory Pro needles have only 5 grooves from memory.


Harvy

[racerrad8]

I, as well, do not know what brand of needle you have. I can tell you, based on the photo, the plastic needle holder is installed upside down and the indicator tab has been removed. The removal of that tab allows the needle to "float" 360* in the emulsion tube leading to varying fuel distribution amongst each individual carb.

The needle was designed, with the indicator tab and the raised block (in photo, top of plastic holder) were designed to keep all of the needles in the same position.

Lastly, that plastic part is not a serviceable part without buying the complete new O.E. Yamaha needle set.

The carb rebuild kits I sell do have the stock designed needle in brass and are adjustable. The kits also have all of the jets needed to get you back to square one, but they do not have the plastic needle holder.

Randy - RPM