Help me with Carb tuning!!!

[akreider]

Setup -

Mukuni BS34SS carburators with K&N pods, Dynojet stage 3 jet kit, replaced fuel air mixture screws, aftermarket performance header (not sure what it is previous owner put it on), and Yoshimura R3 race pipe.


What I did -

When I installed the jets I screwed them all in until they were snug not torqued in hard. Used a digital caliper to set the floats at the proper height of 24.6 I think (I set it according to the suzuki shop manual). Checked for vaccum leaks by misting starter fluid around the boots to see if idle increased and I found none. Set the air screws by screwing them in till they were snug marked their position then set them at 2.5 turns (1 turn = screw turning 360&#176. Petcock was checked and everything was fine.

Problem -

From what I understand for the suzuki manual is that the air screw is used only for the slow system (with throttle closed or engine at idle).
The bike will start up only with the choke on and after it is running I can push in the choke only partially and still keep the engine running. And when I twist the throttle when the bike is idling with the choke on it will bog down and die if I keep the throttle open. But if I keep twisting the throttle and let off the rpms will increase then once the engine's rpms are over 6000 the engine responds right away to throttle without any hesitation. I assume that this is because at that point the engine is not using the "slow system" therefore not using the air screw.

Question -

How can I solve this problem? Did I properly install all the jets by just setting them snug? Also when I read the settings for the carbs, it said 1.2 for the air jet, does the mean the size or how many turns I should set it at? And finally what is the bypass and pilot outlet and what do their settings of 0.8 and 0.9 respectively mean?

Thanks for all your help

[chef1366]

On mine with a very similar setup went up to 47.5 pilot jets and 170 pilot air jets. Screw the jets until snug.

[Billy Ricks]

If you set the floats at 24.6 you are most likely starving the carbs. Most models call for the floats to be set at 22.4.

[akreider]

Thats what I set them at I just couldnt remember the number when I was posting this thread.

Why did you change your jets? To correct what problem?

[chef1366]

I went up on the pilot jet because I couldn't get a good idle to 1/4 throttle. It didn't matter how I adjusted the idle adjustment screws. I went up to 170 air jet because of the jump in the main jet size. If you're messing with a Dynojet try setting the needle on the second notch up or the fifth down. Dynojets setting suggestions are usually lean. I'm also using the 132 dynojet main. My bike runs absolutely kick &ss with this set up. Did you have your cams degreed in?

[akreider]

No I havent had my cams degreed in. How is that done?

[chef1366]

You need adjustable cam sprockets and a buddy who knows what he's doing.

[GS850_Coug]

Air Screws

If I'm not mistaken, you may have tweaked your air screws/jets. They are not supposed to be snugged when adjusting, as this can damage the jets. They should be threaded in until just making contact, then set at proper number of turns. If I'm wrong, somebody please correct me.

[akreider]

That is one thing I made sure not to do is to tighten them in, I only set them right when they touched.

Ok I have to admit my major lapse in thought while installing the jet kit, I didnt read the fine print that says to only change the air screws if it is running to rich. So I reinstalled the stock one earlier today and that solved the problem of the engine dying when twisting the throttle. The bike was just getting to much air. But I still have the problem of having to use the choke to keep the engine running. It will only run around 2000 rpm, I cannot back the choke off enough to get it to normal idle speed. I currently have the e-clips in the 2nd groove up or 5th from the top on the needle. I also have the 138 main jet installed.

[GS850_Coug]

This is by far the best tuning info for this carb: http://www.factorypro.com/tech_tunin...m_engines.html

[chef1366]

You are adding fuel with the choke on during the pilot circuit. Try going up to the 47.5 pilot jets like I suggested earlier. If your running strong and not rich on your main leave it alone. Your idle adjustment screws should be 1.5 to 2.0 turns out. When I was referring to snug it was with the jets not the screws. My setup on an 80 1100. Dynojet stage 3. 132 main jet. 47.5 pilot jet. 170 pilot air jet. Needle two notches up or 5 down. Idle adjustment set to highest rpm method. Mercury stick synchronized. Took me alot of trial and error to get this right.

[akreider]

Time to get back to work on the bike... just got back from vacation.

When the mixture screw is turned in or (tighter) does that lean the mixture out for the idle circuit? Or is it just the opposite?

[chef1366]

On CV carbs like ours tightening is lean and loosening is rich.

[akreider]

I must have shut my brain entirely off, even with every one telling me to change the pilot jet. I never thought to do it. I must of been thinking that the stock jets would be good enough for some crazy reason.

I figured I would just swap in the kit and fuel mixture screws and I would go. (KN really should put pilot jets into their kits) Then it hit me like a ton of bricks (reason to change it) with the kn pods 4into1 header and yoshi can my bike is running crazy lean at idle with the stock pilot jets and no matter how many times I turn the mixture screw it would never deliver enough fuel to the engine.

I feel like the biggest moron for total neglecting the pilot jets and assuming the stock ones would suffice.

Now when I bump up the pilot jets to 47.5s will the 160 pilot air jets from dynojet work?

Adam

[chef1366]

I use Mikuni 170 pilot air jets. I don't know the difference between the mikuni and dynojet pilot air jets. I assume it's bigger since your stock jet is mikuni 160.