gsx1100 1980 running problem

[ASH]

Hi i have a GSX1100et 1980 which the Engine seems to brake down under load only,it gets to about 5000rpm then the bike almost seems like it has a rev limiter cutting in,not sure if it has one?,it just seem to die,so times it will ride throgh it if you give it half throttle,but it is much worst if you give it full throttle,if you ride under 5000rpm bike rides perfect.i have replace the spark plugs,also i have replaced both coils,carbs have been balanced.It has a 4-1 exhaust system.
Thinking of replacing the cdi unit?not sure how much they control or if they are troublesome? can anyone Help me,also compression is fine and i'm just in the middle of checking the valve clearances.Thanks Ash.

[Kaiser Sosei]

Is this a new condition or are we dealing with "I just bought the bike and it won't run"?

If you just got the bike I would recommend pulling the carbs apart and giving them a good cleaning. Then get a set of O-Rings from Robert Barr, can't remember his website at the moment. Aslo make sure the valves are adjusted.

I doubt it is the ignition and would lean toward a carb issue.

Have the carbs been jetted for the 4 into 1?

[hampshirehog]

Ash, I guess because you've called your bike a GSX you're in the UK? KS is bang on the numbers I reckon - sounds like your carbs need to be pulled to pieces (that's completely apart, everything out), very carefully cleaned, rebuilt and tuned in.

Good tutorial on here (your bike has very similar carbs):

http://www.thegsresources.com/gs_carbrebuild.htm

Oh, and welcome to the nuthouse

[ASH]

Is this a new condition or are we dealing with "I just bought the bike and it won't run"?

If you just got the bike I would recommend pulling the carbs apart and giving them a good cleaning. Then get a set of O-Rings from Robert Barr, can't remember his website at the moment. Aslo make sure the valves are adjusted.

I doubt it is the ignition and would lean toward a carb issue.

Have the carbs been jetted for the 4 into 1?

Hi this was my dads bike,he had it for about ten years but he never had a problem with it,don't think he drove it hard,i,ve just put it back on the road after some years,so had the carbs spritted down,clean and balanced by a bike shop,they said the float valves were poor,so i replaced them,still the same.they have been jetted up at some point and the air box has been removed.

[nisom512]

Hi this was my dads bike,he had it for about ten years but he never had a problem with it,don't think he drove it hard,i,ve just put it back on the road after some years,so had the carbs spritted down,clean and balanced by a bike shop,they said the float valves were poor,so i replaced them,still the same.they have been jetted up at some point and the air box has been removed.

Float Valves hu?...... I think maybe they didnt do such a hot job. cause it kinda sounds like carbs to me if you are doing or have done everything else then whats left......? jk but hey let us know how it goe's once you've done your clearances if you need help with that there is a guy on here Steve(actual user name) that will give you a chart that helps to get the right sized shims. and the O-rings From Barr for the cleaning of carbs can be found here. www.cycleorings.com that is something that I may guess the shop might have not done.

Good luck
Jake

[ASH]

Many thanks for that i will let you know how i get on.

[hampshirehog]

I presume the airbox has been replaced with pod filters? You're problem almost certainly sounds, from your description of the symptoms, as if it's carb related and if they have been cleaned properly (and I do mean fastidiously) then my guess is that they haven't been jetted correctly.

Personally I loathe pods on CV carbs - I can never seem to get them to run 100% all the way through the throttle opening sequence, though some people have managed it.

Not wishing to slag off a bike shop, but did they really take their time and do things properly? We're talking at least a 5 or 6 hour job for a pukka clean and rebuild, whereas I know a couple of shops who'll 'clean your carbs' for £75ish - can't be done (unless they're losing money).

Those carbs aren't that difficult to work on - plenty of advice on here and if you follow things step by step you'll know things are right.

[ASH]

I do not have an air box but i have restricted the air just the same,the bike shop did have it all day and it cost me £200,but i guess i will have to remove them and check them my self.

[hampshirehog]

How have you restricted the air? The intake set up is critical on these bikes.

[ASH]

Just by blocking them all off the same bit by bit until it would'nt even run.My guess was that it should make some difference,but it did not change it,aways come back about 5000rpm?

[ASH]

at the moment all it has is cones with meich filter,so no restriction?not sure if this is good?

[nisom512]

well thats gunna make it harder for you to get things right.but like i said once you do that adjustment let us know doesnt really sound like the solution but it is worth it to try.

Jake

[ASH]

Hi Jake found valve clearances to be all about 0.05mm which is good,so i,m going to get new air filters & remove carbs again and strip right down,does anyone know what size jets i should be running with a 4into1 exhaust and k&n filters?

[tkent02]

does anyone know what size jets i should be running with a 4into1 exhaust and k&n filters?

That's the problem, with CV carbs tuning for a pipe is easy enough, but getting it right with Pod filters takes a heck of a lot of experimentation, each bike is different, and they rarely run perfectly afterwards, if ever. A commercial jet kit may get it running fair enough but they usually do it by going overly rich, wasting gas, losing power, wearing out engines, and ruining all those pretty glaciers up North.

The earlier VM carbs on the other hand can be dialed in to perfection with a little effort and simple tuning procedures....

[SqDancerLynn1]

Blocking the air flow is NOT the same as having a proper airbox filter. You either need to reinstall the airbox or rejet the carbs