Easiest way for more power on your '82

[jasonm.]

I have put both my '83 and '82 on the dyno. And done a lot of tests to find the reasons for the jetting differences. First, with the flapper installed, your '82 is probably running rich from 5000 to 7000rpm and maybe to redline. In the update the dealer put a #135 air jet in the rear carb. But not the front. Well, I remember people saying how fast they went and how much room they needed before they were going "fast enough". My '82 now goes nearly as fast as my '83. I did one little thing that made a big difference. I put a #135 air jet in the front also. I set the low speed screw an extra 1/2 turn CCW and checked the carb sync. I gained a lot on acceleration and top end. The middle is crisp...no flat spot. The flat spot is the damn flapper taking it's time opening. The dyno does not lie. Lets just say the "one ton" mark is easy in a 5th gear roll on. And takes little distance or time to get there. Plus I have a big Vetter fairing I am pushing through the air. My carbs have been dipped and are clean as can be.  Put the #135 air jet in front. It'll take 15 minutes or less. And you'll be happy.

[Lucky]

You hit this one on the head Jason!  I had to put my carbs back on after setting testing a set I rebuilt,(I've R&R'd my carbs so many times, I oughta use Velcro...)

anyway, I took the 135 in my spare set and put it in the rear and wow what a difference!  first thing I noticed was the bike started in 1/2 crank instead of the usual 1 & 1/2 cranks, but that might be a lot of things...

the other thing I felt was that the power band was much longer by at least 1600 rpm!
I havent adjusted the pilot screws yet, and it ran a bit hotter than usual, but i'll do that later.
 --Lucky

[QQBS]

Luckey:  Whatever was the outcome of your replacement/alternative exhaust system creation project?

[Dave T.]

Good find man. I was deducing the same thing. That damn flat spot is from the transition of that flapper from closed to open. I figured out it only takes 1" of vacuum to open the flapper all the way, but the size of the venturi will determine how the flappers stabilizes, and engine load is a factor.

I was thinking the Vision was too lean between 0 and 4000 rpm, and then it was too rich over 5000 rpm's. I haven't tried experimenting with the pilot air jets yet, but now I might have to get a #135 air jet (I think they are the same as the main jets). The one thing that helped me was going leaner on the mains. I went to a #120 front and a #122.5 rear. I was thinking of going to a 117.5 front, 120 rear. But I noticed the V can run like a raped ape at high rpm's with stock jetting and removing the airbox cover all together. But, then there is that stumble x 10 when you have no flapper (air velocity increaser??).

One thing I have noticed since I have started reading this fourn is that the people are really getting smarter and more skilled at fixing this motorcycle. Pretty soon I think that there is going to be a special setup that will make this Vision run like a champ at any rpm's. I know we all have real jobs and families, also that we aren't funded by the government with millions for R & D for this bike. But bits and pieces filter in here and there.

I will try it soon... ? :P

[Lucky]

QBS, between work, pee-wee football, and rebuilding carbs, I haven't even had time to do anything with it.  maybe in the winter, lol.
eventualy I will, and i'll let you know when I do.
--Lucky

[dogg]

Hey Jason!

I am looking at a blow up of my '82 carbs.  I see a Main jet that goes in from the side and a Main jet that is accessible from the top of the carb.  Which jets did you change to  #135's?  I need some speed!

                        thanks, dogg

[Lucky]

it's the one right on the top of the carb.  don't drop it into the throat of the carb! you don't want it to get past the throttle plates and into the cylinders, other than that, it's about as simple as it gets, just be sure to use a well fitting screwdriver to remove it, because it's brass, it's soft and will strip out easily.
--Lucky

[dogg]

Later.

       dogg

[Dave T.]

I had a 132.5 jet and I put it in the front carb (air jet). Then I took the 120 and put it into the rear main spot. I had to turn the front air screw out 1 turn and re-sync'd the carbs.

The only difference I noticed was the mid-range was a little stronger, but that's it. It will still stumble around 4k once in a while, but not often. I didn't notice any change in top end. This may be because I have lean main jets in (120F, 120R). But I had more burbling problems when I had 122.5, 127.5 main jets in. This is still the best my V has ever run since I got it though. My V seems to pull the hardest from 4000-6000 rpm's.

One thing I did figure out is that if you have starting problems, your V probably needs to have the pilot air screws adjusted (and/or cleaned) and the carbs sync'd. If they are set right, your V will start by hand. If not, who knows. It would also be nice if the V's flapper had an adjustment rod so you could make minor adjustments in it's position. I'm sure someone will (or already has) done this.

[Lucky]

Hey DT you hit it on the nose. any of the carb's i have rebuilt, where the owner say's it is hard to start the bike, have needed both carb syncing and pilot adjustment.  of course their usually pretty dirty too.

the hard part is when i get a carb that has sat without running for a few years, and will not start after i rebuild it.. that's when i have to guess at the sync and pilot settings.  If I was smart i would have recorded the sync rod lengths and pilot screw adjustments, but i haven't... plus the sync rod lengths would be done with a micrometer, in hundreds of an inch, and really, how many of you have those laying around?

I have found that there is a pretty wide range for "initial" pilot settings on the 82's, anywhere from 2.5f & 4.0r to 4.5f to 6+ rear.  I haven't seen any differences as far as jet-wise, etc, between the carbs, the only consistant difference i have noticed is that the emultion tubes bottoms have 2 or 3 different shapes to them.  some have a lip, some are tapered, and some are straight.  but i don't think this really makes any differance.

the other thing i wanted to mention is that the flapper vacume pot holes, according to Jason, are indeed slotted and he has found that by sliding it back (?) he could get the flapper to open a little bit sooner, taking up the 'lag' time used in opening the flapper.  i haven't looked at mine, but it is worth a checkout.

--Lucky

[Rick G]

Hi Lucky,  I eyeball the butterfly sync. then set the low speed screws at two turns, to get it started. It will run well enough to adjust things.

[VK]

I am planning on installing the #135 jet as Jason recommends and would of course also like to optimize the pilot screw settings as well.  I recall messing with these back in the mid 80's, but do not at all recall how far I moved them.  For that matter, I do not even recall if they threaded normal (clockwise turns them in) or backwards (clockwise turns out).  Am I correct in assuming that if I turn clockwise until I meet resistance, then turn counter clockwise somewhere between 2.5 and 4.5 turns for the front and 4 to 6 turns for the rear I will reach a typical initial setting?  My goal is to improve starting and fuel economy, with improved starting the most important.  (I assume I will have to resynch my carbs after any such changes.)  By the way, do counterclockwise turns make the mixture richer or leaner?  Also, any recommendations on what setting to pick initially and how do I tell I've picked the "best" setting beyond just having the bike startup reliably?

Thanks for your help, this is a great forum!  VK

[jasonm.]

CCW makes it richer. It is a mixture screw, not just air. But you are varying the gas flow the most. Put a #135 front and rear in the air jets. A 132.5 won't make much difference. I also tried smaller mains. But it was not the best overall. I also have my flapper adjusted part way open. And the pilot screws open about 4.5 turns each. I have a digital tach that reads changes in 10rpm increments. So I have mine "spot on". I say if the the carbs are clean. Start at 4 full turns out. I worked with another guy who clean his carbs also. And his ran best at about the same setting(4 out). And that YICS makes it difficult to notice if your adjustment has changed the idle. I did my adjustments with it "plugged". You'll know right away when you have gone too far with the screws.

[jasonm.]

OH D.T., Try a 120F and 125 rear main. Or go to the stock sizes and open the flapper like me and set the screws 4 to 4.5 CCW. I checked all 3 of my flappers they all fully open at about 5 inches Hg.

[VK]

Jason,

Thanks for the additional tips!  

VK

[Mark]

If  ichange the rear one to 135 do I have todo anything with the mixture screws?  Iam slow with the carbs, so  Iam not sure how to do it if  Ido. Also where do I get one from and how much do they run?  Oh yea I got my stator replaced and I am cranking on the miles just need to replace the exhaust, finish the carbs  ( Lucky will be getting them this winter ) and find some extra parts like 1/4 faring and passenger back rest, crank case guards stuff like that. Then I will be REAL FLIPPIN HAPPY   :D  Thanks for all the help I have read on this page, you guy's are great.  Mark

[jasonm.]

You should already have a #135 air jet in the rear and a #130 air in front. This is assuming you have the flapper update assembly. Just make sure both have a #135. Yes the mixture screw may need a slight tweek. Probably no more than half a turn. Usually out. Total between 4 and 4.5 out(CCW).

[VK]

Just thought I'd post my success story on this modification.  I had a #135 jet in front and a #120 jet in the rear.  I don't know if it came that way from the factory or if they got switched when I had the carbs cleaned after taking the bike out of 11 years of storage.  (I am embarrassed to admit that I brought the bike to a shop for that job, just didn't have time myself.)  In any case, I replaced the #120 and now have #135's all the way around.  While resynching the carbs, I noticed a collapsed hose to my YICS.  I checked the YICS when replacing the hose and found that my repair with a gasket and sealer didn't take.  I redid the repair using a fuel resistant epoxy this time.  I also adjusted the low mix screws doing my best to center the setting around the drop off.  (Turn one way until rpms drop, turn the other way till rpms drop and try to hit center.)  Both front and rear seem to be centered somewhere in the range of 4 to 4.5.  (I don't have a digital tach so it is kind of hard to tell with certainty.)

The end result of these changes is that the bike now runs great and seems more eager to start than when it was new.  Needless to say I find riding immensely more enjoyable being able to stop somewhere and not have to worry about whether a hill is near by that I could use as a jump in a pinch.

[jasonm.]

I also had a #120 jet in one set of carbs. I think it was the front main. But No jets in these carbs were a #120 stock. A #120 air jet will really make it too rich. The air jets and mains are the same type. If you live at a high altitude. Then reducing the main jets makes sense.

[Cdnlouie]

I am in the final stages of Vision tweeking.  Appreciate your jetting discussion as it helped me solve the fact that someone had totally botched my carbs with wrong jetting.

I got a handful of jets today at the dealer and there is a lot of selection available for the Mikuni lineup.  I am going back to stock mains (122.5 front & 127.5 rear) and will give the 135 a go in both air jets.  Is this the combo you found to work most successfully for your bike?

I am going to try the 135 air jets with the current 120 F & R mains just to see what I get for performance.

Do you know why the stock jetting included a larger rear main jet (127.t)?

If anyone needs jets I have a dealer with a box full of them.  If I was buying another vision, I think I would check the jetting sizes right away.  They are really easy to change and that means people mess with them a little too easily.

louie