All Tuning Options (what can I mess with)

[crackerkorean]

Ok I am hoping over the next few days to really get the bike dialed in.

Right now I have a really big dead spot from 4-5k. It bucks and bogs. The wife really likes the ride other than this part.
If I really twist the throttle itl eventually get out of it and just take off.

Here is a list of things that I know to use to tweak the bike.
1. Air Fuel Mixture Screws
2. Check YICS for leaks
3. Carb Syncing (they are pretty even at idle but when I rev the front pulls more, is that ok??)
4. Jet Sizes
5. Nickle trick ?? Is this only for non modded air boxen?

Any other things to look at?
Also should I do anything with jetting when I change to the MAC exhaust?

[Lucky]

assuming the carbs are clean, the YICS doesn't leak (and there are no other vacuume leaks) then it is all in the synq & pilot screw settings.

for Mac pipes jetting should remain stock, but on 82 carbs change the pilot air jets (top of the carbs) to 135.

the nickle trick is for non modded airboxes (no vacuume flapers)

if you've done all of the above & still have the stumble, then the carbs are not as clean as you think (dipped) or the pilots (usually) need to be turned out more, or both.  properly cleaned & tuned, the bike should only stumble slightly when cold.

make sure the choke plunger seals are in good shape (not torn or cracked)

hth, --Lucky

[crackerkorean]

That was something else that I noticed. I can start it now without the choke.
From how I understand it if I add choke it would raise the RPMs right?
Mine kills the bike.

[Superfly]

Yes, the choke will raise the rpms.  If your choke is killing it, there is a problem there....   Might need to throughly clean it one more time, or your pilots are way out of wack.

[crackerkorean]

The carbs are clean. I would really hate to clean them again but......

What is the proper way to set the pilots?

[Superfly]

On my 82 carbs, I would always start off with 2.5 turns (from lightley seated) for the front, and 4.5 for the back.

[VisionaryDan]

Superfly, you set the pilots different between the front and the back? Both my bikes are set the same front and back. My original is set to 4.5 and my second V is runs best at 3 turns. It never occurred to me to set these at different positions between the two carbs. Is there a reason for this? If I change the settings on the pilots wouldn't it effect the carb sync?

Dan 

[h2olawyer]

The reason for different settings is to compensate for the different front & rear length & back pressure of the exhaust system.  The settings will have some effect on synch.  That's why it takes so long to get everything dialed in to eliminate the stumble.  That's also why the main jet sizes are different front & rear.

H₂O

[VisionaryDan]

H2, I kwew that the main jets were different but this was the first I heard that the pilot screws were setup different. Ironicly, I had both bikes sync by a Yamaha dealer and I don't think they touched the pilot screws when they did either bike. My original V - I won't touch because it has no stumble to speak of but my second V has just enough to make it a pain when crusing around 4000-4500 RPM. I guess it can't hurt to try to set it up to Superfly's recomendations to see if it helps the stumble.

Learn something new everytime I read through postings here.
Dan

[motoracer8]

I have a 83, whitch had the air box mod as std. But I messed around with the carbs some to get them right. What I ended up with is #130 main jets, #50 pilots, #132.5 pilot air jets, and #180 air correction jets. The air correction jets I made from Webber carb parts from a car. Set the float level 35-37mm, Look at the accelerator pump nozzles, they should aim rite at the butterfly near the body rite where it opens. Pump shot 0.25cc. That is one turn of the throttle, closed to wide open.
Before you start any carburetor work you should check valve clearence and make shure you have no vacuum leaks. The rubber manifolds crack and leak, vacuum hoses fall off, And the YICS can leak. The manifolds are still available from Yamaha. I get 45/50 mpg, with good color on the plugs.
Also I have seen loose throttle shafts, whitch make them run lean. If you have access to a exhaust gas analizer set the idle C.O. between 2.5 & 3.0%.

Ken---

[crackerkorean]

I am going to see if I can get it dialed in this weekend.

I was wondering though......when I have the manometer set on the carbs and they are level at idle. Should I rev the bike to see if the vacuume is the same?
I did just to see what it would do before and the front one had more vacuume than the rear. Or is this a non issue.

[Night Vision]

......when I have the manometer set on the carbs and they are level at idle. Should I rev the bike to see if the vacuume is the same?
I did just to see what it would do before and the front one had more vacuume than the rear. Or is this a non issue.

I noticed the same thing. when I rev'd the bike off idle, they became uneven. That's one of the reasons I put the bike on the center stand, turned the idle knob so the bike was at 3500 rpm and adjusted my carbs. I was able to tune the "bup" out of the "bap bap bap bup" with the mixture screws and sync'd my carbs at that rpm.

I realize that this is probably against conventional wisdom, and I'm sure others will say to sync at idle.....

but in my mind... I figured that 3500 rpm is around half the rpm range I ride.... so why not have the carbs tuned and sync'd halfway in between??

besides, I have never openly claimed to have any wisdom ( on this forum anyway)  :D