Guess I needed some bigger pilots! Even though all advised against?

[ironsheik]

Hey y'all. I thought I would post my experience with some first time carb tuning on my stock 83 gs1100 with a Yosh race pipe and stock intake with K&N filter. It can be a PITA! I have a Dynojet stage 1 kit and could only get the bike to accept throttle once I went back to stock 112 mains and moving the needles up a clip to the 4th position. But it still ran really badly below 4k. After a ton of trial and error and months neglected off the road I am now at a reasonably running bike with 47.5 pilots, needles still at 4 (3rd position caused 3-4k hesitation), mixture screws about 3 turns out, 120 mains and the cover off the box.

The plugs always looked pretty decent/slightly lean with 45 pilots, needles at 4 and using 117.5s or 120 mains which was really confusing considering I could hardly get the bike to idle with the needles at the recommended 3rd position. All advice on all the threads I could find says that no one ever really needs to up the pilot. Seems a little weird being that there's no way this bike could run right without bigger pilots. Can my experience be so different from most others?

Anyway, even if you've got the right larger main, you might have to up your pilot jet and might have to play with needle heights. Hopefully this can help get some other folks on the right track. I've still got some decel popping and very very minor hesitation so I'm going to play with the mixture screws and possibly put the airbox cover back on. Plugs finally look a bit richer at low-midrange. Yay!

 

[Kaiser Sosei]

Just went through this with my '80. Same issue with the stock pilot, had to bump it up to 47.5 and raise the needle one notch from what Dynojet recommended. 120 mains as well, not sure where the mixture screws ended up, but adjusted for highest idle. Before the larger pilot I was getting a lot of poping from the exhaust during deceleration and hesitation as well during the transition to the needle jet. This is with a Vance and Hines 4-1 and K+N in the stock airbox with the lid off. Now it runs like a champ.

 

[TheCafeKid]

Do not change the pilot. Stage one is too small for a KN box filter and a yosh.
At least you'd need the larger of stage one jets (stage two I guess) or the smaller of stage three.

Changing the pilots will only make it sloppy and fat down low.

Go with stage two or smaller stage three jets (DJ132 iirc) and clip in the 2.5 slot from the point. You'll need extra small washers to shim a half clip step. Washer goes on top of the current one. Clip in the second slot iirc.

The pilot on BS34 (and all GS BS series carbs) is fed through the main. If it's too small, a bigger pilot isn't going to help.
You need to work these carbs from the main jet back. Not from the pilot up.

I spent well over a season fine tuning my GS1100ES with pods and a full yosh race system, a DJ stageIII kit is all you need but you need to pay attention to what the bike is telling you.
I ended up very similar to what I just told you but obviously running a full stage three kit. I even had 1150 36mm carbs on it and merely needed to move the clip. Before I sold it, that bike would pull your arms out of socket where ever you snapped the throttle.

Mind you, while the current temps won't have such a big effect on your set up since you're running a box, come summer you may have to lean the screws a bit and maybe back off the needle a half step. Shell run like a scalded dog with the cool dense charge autumn air, but may be a bit wet once the temps and humidity rise in the summer.
It may not be noticeable, but I notice. The perils of squeezing every last ounce out of an otherwise un-modified motor...

 

[Guest]

she still pulls purty good, josh....smiley

 

[koolaid_kid]

Josh, I thought that info was in the Miikuni tuning doc (on BassCliff's site?) that you tune from the main down. Or did I miss something?
You know how I did mine, so it was a bit different.

 

[TheCafeKid]

Josh, I thought that info was in the Miikuni tuning doc (on BassCliff's site?) that you tune from the main down. Or did I miss something?
You know how I did mine, so it was a bit different.

Isn't that what I just said? Tune from the main, back.

Btw Greg, glad to hear I miss her sometimes man, she was mostly always good to me. We had a fight or two here and there but it happens

 

[koolaid_kid]

Isn't that what I just said? Tune from the main, back.

Btw Greg, glad to hear I miss her sometimes man, she was mostly always good to me. We had a fight or two here and there but it happens

I was speaking of the actual Mikuni tuning document. One exists, I read it, and it goes into much greater detail than just main down. It was very helpful for me because it explained a lot of stuff. I went to BassCliff's site and did not find it. I guess I'll try to find it, but perhaps not tonight. (Yawn)
I guess I'll ask BassCliff to put it on his site if I can find it again. It might mitigate some of the questions you have to answer again and again.

 

[koolaid_kid]

Link to carb tuning information

Link to carb tuning information

Here is a link, it is fairly complete: http://www.factorypro.com/tech_tuning_procedures/tuning_carbtune,CV,high_rpm_engines.html

 

[TheCafeKid]

I have that laminated in the garage. Yes quite useful, but it's not mikuni's guide. It's factory pros guide. But, it is quite useful. Assuming of course that you understand what the difference between slightly lean and slightly rich feels and sounds like. That was a bit of a hurdle for me when I was tuning.
I don't remember if the guide suggests it or not, but the biggest help for me was marking off my throttle with tape so I could see roughly which circuit I was having the problems in. Not just guessing, well that feels like the pilot, or the needles, etc.

 

[ironsheik]

Thanks for that reminder. I've certainly read those a bunch but a lot of that I'd forgotten. I'm going to do a lot of riding tomorrow and see how far I can get based on these ideas and some plug chops now that I've got a bike that rides decently.

Cafe: I couldn't get the bike to run right with 112s, 117.5s, 120s, DJ 132 and 138s! Changing the pilots got me there with the 120s so now I'm going to make sure the 120s are right on. Wish me luck! I'm getting tired of removing and draining the carbs but that's to be expected.

 

[koolaid_kid]

I have that laminated in the garage. Yes quite useful, but it's not mikuni's guide. It's factory pros guide. But, it is quite useful. Assuming of course that you understand what the difference between slightly lean and slightly rich feels and sounds like. That was a bit of a hurdle for me when I was tuning.
I don't remember if the guide suggests it or not, but the biggest help for me was marking off my throttle with tape so I could see roughly which circuit I was having the problems in. Not just guessing, well that feels like the pilot, or the needles, etc.

Picky, picky. It is an excellent guide for tuning our Mikuni carbs, none the less.
Yes, the marking of the throttle can be useful. They use engine speed instead.

 

[TheCafeKid]

Well, your clip needs moved for sure...

And engine speed has little to do with it...you can spin 5000rpm and be at minimal throttle openings...

Just saying

 

[ironsheik]

How do you mean? I had it on 3 and the bike stuttered through 3-4k half throttle. Moving it to 4 solved that. I did a WOT plug chop in 2nd from 4k to 9k and the plugs certainly don't look rich, a tad lean even so maybe I'll try 122.5s and see where that gets me. Hopefully that's enough time to get a good reading on the plugs? WOT chops are a bit scary on this thing!

It still gurgles/pops a tiny bit and feels buzzier than I think it should. Getting there at least!

 

[Katarat]

http://www.jockeyjournal.com/forum/showthread.php?t=64769 using DJ jets you arent all that rich compared to Mikunis