rejetting my 1981gs1100 question??

[kflaggs1kevin]

hey everyone i was wondering i have an 81 gs1100ex with a kerker 4 into 1 header on and a k&n airfilter on it with no lid on the filter box im guessing that was for more airflow. when i picked the bike up it came with extra jets. the stock jets are 107.5 and the jets in the box are 120's. so i took it out and opened it right up and it wont clean out it just kinda spudders at high rpms and cruising. i was wondering what size jets you would start with to see if that fixed the problem. i was told you usually go up one size for a header and another size for an air filter so either 110's or 112'5 any ideas???

[tkent02]

What jets are in it now?

IS it too lean or too rich? It's hard to tell from here.

[kflaggs1kevin]

its got the 120's in it now the stock jets i have for it are 107.5 i also have 115, 117.5 and were thinkin its too rich cause we ran it up the street with no airfilter real quick and it got a little better

[rapidray]

With the airbox lid gone & a 4 into 1 on the bike, it is LEAN with a Dynojet 120 main jet!!! A MIKUNI 120 main jet should be pretty close. the Dynojets are smaller than the same # Mikuni jets. Ray.

[Katarat]

http://www.jockeyjournal.com/forum/s...ad.php?t=64769 heres a jet size comparison chart

[kflaggs1kevin]

the 120 jets in it right now are pro jets is what the carrying case says and the carbs are mikuni

[Rudeman]

the 120 jets in it right now are pro jets is what the carrying case says and the carbs are mikuni

Have you done a plug test?? If not, put in a fresh set of plugs and do a plug test.

I tend to agree with Ray though; 120 may be a little lean with the cover off.

Do a plug test if you haven't already.

[kflaggs1kevin]

i put fresh plugs in it 2 weeks ago and the thing that makes me believe its rich is it wont clean out when ya really get on it.

[trippivot]

clean out is such a bad term...

you put new plugs in it? what color are they now?

[kflaggs1kevin]

i pulled the plugs and they are grayish white so that would tell me its lean so i guess ill go up to 122.5 what would the bike do if its running lean?

[Rudeman]

i pulled the plugs and they are grayish white so that would tell me its lean so i guess ill go up to 122.5 what would the bike do if its running lean?

Run it in top gear at about 6K WOT for a few seconds and simultaneously chop the throttle, pull in the clutch and hit the kill switch, and then come to a complet stop. Do not engine brake. Then check your plugs.

[kflaggs1kevin]

well i put 122.5 main jets in it and it runs great from half throttle to wideopen but still kinda studders from a quarter to a half (cruising). so im thinkin if i go from 45oem pilots to 47.5 pilots that will help alot

[cleiper]

If you can get a hold of another lid for the air box I suspect the issue will be sorted. These things had enough air going through them with the standard air box setup imo. and the CV carbs love their standard air box!

May save ya lots of fiddling with jets.

Cheers!

[Katarat]

Id be shimming or if you have adjustable needles try lowering the clip {raising the needle} if thats hwre you problem is. Try marking you grips into 4ths from idle to full throttle to see what circuit youre on when youre having the problem. It sounds like the needle to me

[kflaggs1kevin]

i put 122.5 main jets in and it cleared up all my problems just to let ya guys kno