Anything Ignition Related that shows up around 6000 RPM???

[Guest]

Hi Guys,

After changing jets up and down, and not seeing any real appreciable difference in my right around 6,000 RPM rev-limiter style stutter/flutter/miss, I am beginning to doubt that this is a carb issue. I haven't double-checked the valve adjustement or cam timing yet, but this bike starts and runs PERFECTLY and pulls very well right up to the 6000 RPM mark, at which time it falls off a bit and then, around 6500, just flutters/stutters or otherwise falls down, as if it had an electronic rev-limiter.

I've tried two sizes larger jets, 175s, and then dropped them down to 160's, and neither of these changes really affected the overall problem that occurs right at around 6000-6500 RPM.

SO, I'm turning to testing the ignition, so as I read through all the ignition testing bits available in the resources here, I'm mostly seeing testing for bike not running problems. My bike RUNS fine (put 30-miles on her today)... It just doesn't run fine over 6000...

Are there ANY ignition related issues with the GS850 that I should be checking for that would fit the problems I'm encountering? Any thoughts on what to test and check??

Thanks,

[TheCafeKid]

Uhh. Yeah. Your main jets are wayyyyyyyy to big. Its drowning. 6K (really not rpm related but I'm guessing that's where you wind it up to when you start to come on the mains in whatever lower gear you're in) even with pods and a pipe you're way too big. I'm trying to recall but I think your stock main was 112.5? Something like that. Even with pods an a pipe the largest you're probably looking at is 130 MAYBE 132.5. I think you'd prolly be ok with 127.5 or 130. But, if you ARE running pods and a pipe, the jets aren't the only problem. The needle is the bigger issue. Right now you're not noticing any problems in the midrange because the main is soooooooo freaking huge it's let enough fuel by to feed the midrange circuit. But as you see, you've traded midrange function for a top end that falls on it's face.

If you're running pods and a pipe, and I'm assuming you are or you wouldn't be fiddling with these MASSIVE main jets, you need a dynojet kit. The stock needles WILL NOT work. Period. I don't care what you heard someone say or read on some thread on here. They cannot be made to work in all circuits correctly with the stock needles.

Hope this helps.

[salty_monk]

I agree with Josh's comments above but I did have an igniter issue on an 80 1000G that only surfaced at 6k RPM.

The fix was to rip it out & fit a DYNA S for $120.

[Steve]

I am thinking that he is talking about the pilot air jets, thinking they are the mains.

The stock pilot air jets are 180, and that is the ballpark he's playing in.

Darin, the main jets are down at the very bottom of the carb, sitting in the float bowl. The jets that I think you are playing with are the pilot air jets, in the intake throat. Leave those at the stock 180.

What is your situation with air filter and exhaust? Are you running stock on both, or pod filters and/or a header? Knowing what you have will help us greatly with your situation, but TheCafeKid is right, a DynoJet kit is your best bet. The only unknown would be whether you need a Stage 1 or a Stage 3.

.

[TheCafeKid]

I am thinking that he is talking about the pilot air jets, thinking they are the mains.

The stock pilot air jets are 180, and that is the ballpark he's playing in.

Darin, the main jets are down at the very bottom of the carb, sitting in the float bowl. The jets that I think you are playing with are the pilot air jets, in the intake throat. Leave those at the stock 180.

What is your situation with air filter and exhaust? Are you running stock on both, or pod filters and/or a header? Knowing what you have will help us greatly with your situation, but TheCafeKid is right, a DynoJet kit is your best bet. The only unknown would be whether you need a Stage 1 or a Stage 3.

.

I don't know bout that. Nearest Ive seen, pilot airs only come in tens. 160 170 180. Etc. Don't think I've ever seen a ##5 pilot air jet. Could be wrong though.

[Darin Jordan]

Guys... Sorry, I should have clarified... It has K&N Pods with a 4-1 header, and a DynoJet Stage III jet kit... recommended Jets are the DJ165's... and I've tried them, DJ 175s, and DJ160s. You guys are thinking Mikuni Jet sizes, which don't directly correlate.

At this point, I've done everything carb related that has been suggested here, and by the DynoJet technicians, to troubleshoot a carb issue, and nothing has cured the problem. The carbs are setup exactly like DynoJet recommends. As of right now, it has the DJ160s installed, and everything else is exactly as the Stage III kit specifies.

One would think that I'd have seen SOME difference in the issue by ranging the jet sizes, but it appears about the same regardless, so I'm not convinced it's a jetting issue and am starting to think ignition problem.

Like I said before, it starts right up, idles great, and runs really well right up to that 6K point... then it acts like an ignition/cylinder cut-out style rev-limiter...

Any suggestions would be appreciated.

[TheCafeKid]

Check your ignitor like Salty Monk said. It's prolly hurting. Really the only way I can think to test it would be to replace it and see if it goes away. Hard to test things at that RPM. Not where I'd want to run a motor up to with no load on it and leave it for any length of time.
You could fish around the boards here for another uses ignitor box. Or you you could spend $120 on a dyna S ignition and be done with it for ever.

[Darin Jordan]

Check your ignitor like Salty Monk said. It's prolly hurting. Really the only way I can think to test it would be to replace it and see if it goes away. Hard to test things at that RPM. Not where I'd want to run a motor up to with no load on it and leave it for any length of time.
You could fish around the boards here for another uses ignitor box. Or you you could spend $120 on a dyna S ignition and be done with it for ever.

OK, I'll check the ignitor and test the voltage to the coils...

This Dyna-S ignition... is that something that is recommended even if you don't have points? My 1980 has electronic ignition already (stock)... Is the Dyna-S recommended to replace that as well?

[TheCafeKid]

OK, I'll check the ignitor and test the voltage to the coils...

This Dyna-S ignition... is that something that is recommended even if you don't have points? My 1980 has electronic ignition already (stock)... Is the Dyna-S recommended to replace that as well?

Only if you're ignitor goes south. A NEW OEM fresh from Suzuki ignitor box will run you about $400 or so... Worse if it was a later model with electronic advance. A dyna S gets rid of the ignitor box altogether for $120. You might find a used and suspect ignitor box on eBay or the board here for less. But why risk a used part unless we are just being cheap. Let us know what ya find

[Darin Jordan]

Only if you're ignitor goes south. A NEW OEM fresh from Suzuki ignitor box will run you about $400 or so... Worse if it was a later model with electronic advance. A dyna S gets rid of the ignitor box altogether for $120. You might find a used and suspect ignitor box on eBay or the board here for less. But why risk a used part unless we are just being cheap. Let us know what ya find

I see... sounds like the Dyna-S is the way to go either way then... even if just "guessing and checking"... Would eliminate one possibility anyhow.

I think I'll check the standard parameters tonight, and if all checks out, go ahead and order the Dyna-S and see if that helps.

[Steve]

I just looked on the comparison chart, the DJ165 is equivalent to the Mikuni 155.

Stock is 115. Following the general suggestion of 2-4 sizes for a header and 3-5 sizes for pods, even the most extreme case would be 137.5s.

I wonder why they would suggest such LARGE jets?

Have you done plug chops to see what's happening when it starts to break up like that?

.

[TheCafeKid]

I just looked on the comparison chart, the DJ165 is equivalent to the Mikuni 155.

Stock is 115. Following the general suggestion of 2-4 sizes for a header and 3-5 sizes for pods, even the most extreme case would be 137.5s.

I wonder why they would suggest such LARGE jets?

Have you done plug chops to see what's happening when it starts to break up like that?

.

You silly guy... Always gotta get all methamatikal n stuff. I didn't bother doing the conversion as once he said DJ kit I assumed he got what he needed for his model. But 155 is a set a biggun's I'll say. You SURE you got the kit for your model?

By the accepted standard " Pods and Pipe" formula (yeah...standard heh) would seem to me you're up in the range of what a 1000/1100G would need with 34mm carbs. Dunno for sure. But double check. Eliminate the possibilities from the equation one at a time, or you'll never know what fixed it, if you fix it.

[OldVet66]

When I was adjusting my carbs for Pods and a Vance & Hines 4-1 pipes I got the same thing. In my case the suggested needle settings for the setup were two rich and it was fouling plugs trying to go through the mid range. It would also run perfectly up to that point. When I dropped the needles one notch, it started running perfectly.

[Darin Jordan]

When I was adjusting my carbs for Pods and a Vance & Hines 4-1 pipes I got the same thing. In my case the suggested needle settings for the setup were two rich and it was fouling plugs trying to go through the mid range. It would also run perfectly up to that point. When I dropped the needles one notch, it started running perfectly.

Interesting... Since I have the tank off right now, I'll give that a try and see what happens.

I think one of the reasons why they use those jets is because their needles are thicker in relation to the stock needles. This would would require larger jets to actually make it richer.

Thanks for the tips. I'll try adjusting the needles and see what happens, because it does run VERY well right up to that 6000 point. Pulls well, smooth, etc.

Did find tonight that the Off-Run switch had over 12 Ohms of R in it... cleaned it up and now it only measures 0.5 or so... Me thinkist that a complete electrical system cleanup and checkup is in order!

[cleiper]

Just a thought, are you just doing the first set up on the bike to run with pods?

Reason I ask is that following an initial strip down to replace the piston rings and hone the barrels on my GS1000 due to it burnin oil, I have spent the better part of 2 years building & rebuilding my engine, replacing the entire Suzuki electronic ignition system with Dyna S and coils. Buying leak down testers, different strobe/timing guns, plugs, H.T leads, carb balancer and I have lost count of the amount of cam cover gaskets I have gone through suspecting issues with valve timing, shims etc....and on and on.

All just to try to find out why it wont go above 5-6K RPM anymore.

At last I bought a second hand air filter box, cut out the section I had removed from my original box during my first rebuild then bolted/sealed it on. (And believe me I did not expect this would result in any improvement but I was out of options)
This effectively reinstated the 2 inlet holes to the air filter box I had removed to help it breath better with the new 4-1.
I did this in desperation and was surprised as hell at the difference. Pulls like a train again!
Opening air boxes on things like my KTM is a must when you change exhausts/carbs etc, but on a GS with C.V carbs it was a disaster.

All's well that ends well, so they say!
And I do have a hell of a collection of diagnostic tools now.
But it is amazing how much trouble 60 seconds with a Stanley knife can get you in.

So if you can put back on your original air box and see how it runs it may point you in the right direction a lot sooner than I managed.

Cheers