another carb and head q

[Anonymous]

firstly it would seem no-one out there actually knows if a 4 valve head will fit a 2 valve (gs 1100 g)barrells,my gs has a 4 into 1, 2 1/2 inch system with a very low restriction can,carbs balance well and jetting is good but where should the air needles be set at? it is set at the second last clip on the needles(2nd richest setting) on the main jets.one more thing .....the clymer manual is a piece of crap.if i wanted to take certain parts to the suzi dealer for repair i would not have bought the flamin manual! :x

 

[Dink]

No !!!! a 4 valve head will NOT fit a 2 Valver the cylinder stud patterns are different. The final setting on any jetting changes are always decided indiviually, as every bike is slightly different, any one elses settings are only going to be a ballpark figure.
What year model is your 1100g I will see if the genuine manual is still available.
Dink

 

[KEITH KRAUSE]

To get plug reads to tell you what the needle circuit is doing, ride the bike at 1/3 throttle position for a couple miles and chop off.
Before this, you should be sure the carbs are synched, filter(s) clean, ignition timing is correct.

 

[Anonymous]

ahh there we go ask folk who for one care and two who know and thankyou very much.the gs is an 1982 gs1100g shaftie with 2 1/2 inch 4 into 1 pipe with a very low restriction muffler(read extremely loud).i have the clymer manual for 850 - 1100 shafties but it is worth about 2 pounds of the finest greyhound excrement (steaming).running the standard jets but set up on the second last clip on the needles and 3 1/2 turns out on the air needles,runs fine but for a few niggles.when taking it up to 110 mph approx(the speedo is in kmh...170-180kph)then rolling off te throttle the bike actually accelerates momentarily.do you think this is because the carbs are running a little lean or the air needles are incorrectly set? :roll: also i run all carbs balanced equally not with 1 and 4 slightly higher in vacuum as suggested by clymer.this gives much better acceleration,why do they suggest to run them uneven like this?is it because as standard they have the 2 and 3 exhausts running through a pre muffler? :?:

 

[KEITH KRAUSE]

Your roll off test says the main jet circuit is lean.
This could be a small main, or not enough fuel flow.
Be sure the carbs are clean, float levels are correct, and you have no intake leaks. If that stuff is good, go to a larger main. Double check your main jet sizes against a factory manual. Some models run richer mains in the middle carbs.
I always set the vacuum levels as even as possible. Seems like most everyone here does the same without any problems. But I rarely tune for stock exhausts.
With 2 and 3 flowing a little more with the stock exhaust, the factory wants a little richer mixture (as compared to the others) to keep things equally cool.

 

[Anonymous]

thanks mate, gunna have a crack at changing the mains and will consult my suzi dealer (mat mladin motorcycles narrellan nsw) for their opinion on what size.It does confirm my thoughts especially considering my fuel economy is unbelievable,did 200 kms yesterday 2up for half a tank.I did have my 17 year old brother as pillion(65kg`s) and as such took it real easy with my precious cargo. :wink:

 

[KEITH KRAUSE]

OK, good luck with it.
Just remember, if your latest ride was mostly below 3/4 throttle position, and I'm guessing it was, then the great gas mileage isn't because of the main. At below 3/4 position, you're on the jet needle. I still suggest the 1/3 throttle test to determine needle setting.
Your 110 mph test suggests you need larger mains too.

 

[Anonymous]

will try the 1/3 throttle test Keith and yes most riding was done under 3/4 throttle.what about the pilots? i guess i should just try one thing at a time.since there is no lead in the fuel anymore it makes it a lot harder to read the plugs.Thanks Keith your are most helpful as is this truly wonderous site,thank you all

 

[KEITH KRAUSE]

If the air box is stock, not modified and still has its lid, I don't think you'll need to change to a larger pilot jet for the 4-1 pipe. Try adjusting the mixture screws out a little farther. Maybe an additional 1/2 turn to start? Keep a record of where the screws are or any adjustments, so you can put them back if you don't like the results.
If turning the screws out as far as around 4 turns doesn't richen it up enough, then you may have to try a larger pilot jet. Be sure the carbs are clean first and the float levels correct. Any fuel passage partially plugged up will cause mixture problems.