New carbs need some help.

[jerryXR]

I have an 89 that was not used much in the past few years the bike never had good throttle response
so i pickup up a brand new set. Before i put them on i wanted to see what was in them and compare to
my old ones. The old carbs had 114 mains larger in dia. compared to the new ones along with adj. needles
and 37 pilot jets. The old carbs seemed to be on the rich side plugs and pipe were always black. Now with
about 50 miles with the new carbs you have to choke the crap out of it and throttle sucks bad idle and
pulled the plugs and look brand new no color at all. And even seem to be running hotter. The new carbs
have 117 mains small dia. 37 pilot and stock needles. The bike has k&n pods and a stainless supertrapp
pipe. Need some help where do i start? Jet kit? or just buy what i need?
thanks jerry

[SlowOldGuy]

Swap the adjustable needles over to the new set of carbs and tune them in.  With the equipment you've got, you're lean on the needle position.  Try the needle clip in the 2nd groove from the top.  You might also want to bump the idle jets to 40s if you take them back off.  Good thing about needle tuning is you don't have to remove the carbs.

DavidR.

[andyb]

Old carbs are dirty, and have worn through the needle jets.
New carbs need bigger mains and pilots.  Needle may need tweaking after that.

Probably fastest solution is to buy a factory pro kit, and replace the emulsion tubes.  That'll put you back into the ballpark right away, as it sounds like there's a couple problems that can't be tuned around.  It'll be a bit expensive, though.  What's the mileage on the bike, how long has it sat, how many discs are in the muffler, and what's your elevation?  

[jerryXR]

The adjustable needles can i use them with the new carb jets they are smaller in dia. and the inside
taper does not look the same. Should i start with pilot jets and get the idle and off idle set first? The
bike has 29000 miles on it but valve job and 1mm over pistons were done about 4000 miles ago. I have
11 disc's on the pipe not sure of the elevation.

[WS]

Hi Jerry,

It is always hard to work on the carbs when you do not have the right equipment. Do you have the tool to balance the carbs. Did you adjust the mixture screws to see how the engine responds on each cylinder? That can tell you a lot about the lean/rich status of the carbs at low idle to 1/4 throttle position. The adjustment should be also the same on each zylinder. I do not know out of my head what the original main jet size is. But with open filters you should go up 15 with the main from original size. That means original main 117 you should install 132 main. But this is the last step.

Good luck Werner

[andyb]

6 sizes for just pods?  Pods/pipe I usually start at 4 and go from there..



Take whichever set you're going to use, and clean them really well.  If they're not clean, it frankly doesn't make any difference what you do for the rest of the steps.

You've got an 89 with a pipe and pods.  Assuming that's a full pipe system rather than a slipon, and that you've got a larger number of discs in it (makes it louder, less restrictive), here.

Start by pulling all 8 of the emulsion tubes you've got from the carbs.  You're inspecting to make certain that their inner opening (where the needle fits into) is round.  On high mile machines, they get worn and you end up fat in the midrange.  Get four of those together, and stick em in.

For the mains, it's going to depend on your needles a bit.  If you know where the needles came from (factory pro or dynojet or non-US model), it'll help.  FP needles want a 132 main jet to start.  Otherwise, I'd suggest a 122 as a good starting point, a 120 if you're over 3500' in the mountains or the like.

Needles are easy to move around, stick em near the middle, usually 2-3 clicks from the top.

Pilots will again depend on a number of things, but a 37 is too small.  What was in the old carbs?  I'd start with a 40, but be aware that you may well need a 42. 

Air jets, what do you have there?  Stock works in most situations, though some of the kits swapped sizes around a bit.

Then take a quick look at the float height/fuel level, and see that that they're remotely close to right.

Carb specs are listed here someplace, to give you an idea... but that's for a stock machine, not a modded one.

Once you've done all that lot, take it for a spin after throwing a synch at it and tweaking the mix screws, and see how it feels.  Then you can begin seeing where the problems are and tuning appropriately.

It's a fair amount of work to get remotely right.  Loads quicker and easier to just get a jet kit to get you in the ballpark, possibly emulsion tubes if worn, and go from there.  Depends on how much you like an excuse to tear into a set of carbs a few times, really.

[fj1289]

Only thing to add -- double check the pilot air jets.  If the adjustable needles are from a dynojet kit - then it probably has smaller pilot air jets installed to richen the bottem end with the 37.5 pilot jets.  IF you have the smaller pilot air jets (144's I think) - then either continue to use them or install stock 155 pilot air jets when going to the 40 or 42.5 pilot jets.  IF you have the 144 pilot air jets, AND you are going to use the existing needles, I'd keep the 37.5 pilot and 144 pilot air jet combo since they would be a "matched set" from the dynojet kit. 

I'm guessing it is a dynojet kit from the description of the mains from the original post - "The old carbs had 114 mains larger in dia. compared to the new ones..."  If I remember right, 114's are a dynojet main included in their jet kit.  Are there any other markings on the mainjets?  Or just the size?

Chris

[rlucas]

I've been told, although I can't verify this, that the Factory Pro jet kits are genuine Mikuni jets, and the Dyno/Cobra kits use proprietary sizing. IOW, they don't correspond as to size. I vaguely recall seeing a conversion chart somewhere, but I can't find the link. I've always had a great deal of luck with the Factory Pro kits, on several bikes including the FJ.

I could also be completely wrong. 

Rossi

[racerrad8]

Here it is; http://www.fjowners.com/index.php?topic=1973.0

Randy - RPM