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okay, so I should rejet . . . bike is all stock.

Redman

Redman

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About this GK I got in November:
- I replaced the intake orings, now runs smoother and doesnt rev so high at idle when warm.
- Intake boots and air box boots seemed plyable and soft, musth have been replaced in recent history.
- Compression was 125-130-130-140
- Have had carbs all apart a couple times, cleaned out the jets, was perrty clean anyway. Float valves all in real good shape, no visable wear. Float valve screens clean.

I posted a few weeks ago about it running hot and not having the power I think it should. Plug porcelan were white-white with white ash on electrode. Got a few suggestiong from you fine folks. And have checked into those things:
- Have checked the valve clearance and made adjustment, one intake and one exhaust were just below spec. Runs maybe a bit smoother now. (Havent checked compression since)
- Have checked the timing of the cams and that is right on, with the timing mark lined up: the 1 arrow on the exhaust sprocket is level with the cam cover surface, 20 links between the 2 arrow and the 3 arrow. Is no mechanincal advance to check.
- Have checked the air filter seal. It was gone. Made a repair with some adhesive backed rubber strip. Seems to rev up a bit faster.
- Pulled out the plugs over the air mixture(or whatever the proper name is). Tried to adjust to "high rev" but had trouble keeping it running on rigged up gas supply, and other problems. They seemed to be set at 1 turn, I just turned out to about 2 1/4th. Seems to have more low end power and doesnt run quite as hot, so that makes me think that this is the right area. Now plug porcelean shows a little bit of grey, with a faint line that is a bit greyer around about 1/4th the center electrode.
- Most suggestions were saying that the plug read is screamming that is way too lean. And said I should rejet it to larger jets. But I was thinking that, hey, its all stock, why should I have to change that. Now I am down to this rejetting the remaining item that was suggested to me.

Is still running real hot (as compared to the 650G and the 850G), not quite as hot as it was before adjusting the air micxture screws, but still almost burning my leg when going down highway. Still doesnt have the power I think it should, seems to have less power than the 850G (recently sold by the way). Does rev to redline, but doesnt have much as far as arm-stretching acceleration. 1100 should stretch my arms some, eh?

Main jets are 115 as listed in manual. Was suggested to go to 125 size jets. I see that they are in increments of 2.5, so going from 115 to 125 is 4 size difference.

So . . . Questions:
- Is changing by four jet sizes quite a large change or not?
- Any word of wisdom about having to rejet it if its all stock?
- Since changing the 2 shims I havent had the carbs balanced. Will balancing improve the power much or is the balanceing mostly for smoothnes?
 
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You shouldn't have to rejet if it is all stock. I won't be the only one to tell you this. Either you still have something still plugged up in the carbs, the float level is low (meaning higher number of mm's, when measured), or air leaks somewhere, still.
 
Redman, you can forget about changing the main jets to fix this issue. The main jet is not even in the picture until 3/4 throttle. You could leave them out of the carbs and unless you go past 3/4 throttle, the bike will run the same. Check your ignition timing next and make sure the advance assembly is not sticking.....I am not well versed in CV carbs but at highway speed you are not even close to being "on" the main jet......Seems others have had an issue with the vent hoses coming off the carbs not being properly placed. I think Jethro was one of them...Hope this helps....BadBillyB
 
Yeah, if everything is stock you should not need to increase the jet size.
You've seen first-hand how each of these "small" (but really big) issues has improved your bike incrementally.
You've covered many basics, so in addition to the other suggestions given, I'd do the following tests just for a sanity check:
1. Verify that there are no exhaust leaks (especially where the head and the pipes join) - I was really surprised at how sealing my tiny exhaust leaks really made a significant difference. That back pressure is really essential.
2. It sounds like you've verified the boots from carb to engine pretty well, but are you absolutely sure that the boots from carb to airbox are sealing prefectly? An air leak here can have a surprisingly large effect - Once again, I'm speaking from personal experience.
3. Raise the needles a drop (using washers - see other posts) - This seems to be a common practice for many GS bikes that were tuned super lean by the factory for emissions concerns. It helped my bike considerably - it's amazing how 1/64 - 1/32 of an inch made a real difference.
 
All good suggestions so far... but waaaaaait a minute.

115 is the stock jet size for a GS850. It seems that the 1100 should definitely come with bigger mains. Can anyone clarify this?

I wonder if those are the original carbs or if they came from an 850. If the main jets are wrong, then you would need to also verify all the other jet sizes as well as the float height setting.

Another 1100 owner would probably be a more reliable source of actual stock jetting information than the manual. This could explain a lot...
 
You shouldn't need to re-jet a stock bike. Maybe minor changes for certain elevations but nothing significant.
Yes, a good vacuum synch is important to jetting. With uneven vacuum, you can't really get accurate plug reads or gauge performance. Which cylinder/plug do you decide is the one to base all others on? I'm guessing your lean plug reads were after general riding around? Probably on the pilot circuit with some jet needle overlap?
I too have to wonder about the carbs being the correct size or if the jets were changed by a PO. Is the 115 main jet info from a factory manual?
I assume the plugs are the correct heat range?
Any sign that the air box holes have been enlarged?
You're positive the adhesive backed rubber stripping is sealing the airbox well? Does the bike still maintain its set idle if you cover up the factory airbox holes?
When you say "the bike doesn't rev so high at idle as it used to when warm", what rpm does it idle at when cold/warming up, and when completely warm/hot? Should be about 1,000/1,100 rpm's.
 
Hmmmm...

The 1100GK fiche sez the main jet is a 115, the pilot jet is a 40, and I think it sez the needle is 5058, whatever that means.

The 850G fiche gives 115 for the main, 40 for the pilot, and "5D50" for the needle. That may be a transcription error for "5050".

So I guess the main and pilot jets are the same (who'd a thunk it?), so that's probably not the problem. Of course, the fiche could be wrong, too.

My next guess is one or more leaky diaphragms -- how do these expensive little devils look, Dave? Are they fully seated and sealed at their edges?
 
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