GS1000 running rough...help!!!

[Jay B]

Have you got air comming in one of the fuel lines or in the intake boots. Could be causing it to miss at certain RPMs as well. Use the carb cleaner trick to find out.

[Anonymous]

Have I discovered the problem?!?!?!? (long post)

Checked all of the wiring again, and then double checked it to make sure. I added a couple of extra earths to make triple sure! Checked for air leaks round the intakes, none found. I'd previously cleaned the carbs and fuel tap thoroughly being careful to set the float heights correctly and check jet sizes. Points were replaced a while back and ignition timing is still fine. Coils, leads and boots were swapped with a (good) set from another GS1000.
It starts first push of the button, ticks over as well as any GS, and runs cleanly to 6500-7000rpm and then doesn't want to go any further. I felt that I had checked everything, so started thinking what there could be that I hadn't checked...well, when I cleaned the carbs and tap, and flushed out the tank I took the often given advice and put a (motorcycle) fuel filter inline between tap and carbs. It occurred to me today that maybe it is restricting flow, so I tried a brief experiment and measured fuel flow rate with and without filter. I used a brand new filter of the same type I had used before, and found it took about 60 seconds to flow 1 pint. Without the filter it took 30 seconds! This was with the tap set to Prime, but I guess the result would be the same in the On and Reserve positions. The filter reduces flow by 50%!!! 8O This type of filter had been recommended to me by more than one parts supplier, so I'm not very happy. But, have I found the problem?...when the rain clears, I'll found out and let you all know.

Regards
Yoshi

[saaz]

Sounds a bit like fuel starvation. It is a bit more difficult these days to find a fuel filter that works under gravity, not fuel pump pressure.

[Anonymous]

Running without the fuel filter makes absolutely no difference...oh dear, more head scratching to follow...

Yoshi

[Anonymous]

I'm now wondering how good those 'good' replacement coils, leads and plug caps are?!? New plug caps next then...

[Don Lobacz]

Again, I ask, what size main jets are in there? Have you shimmed the needles? It sounds like a simple jetting problem.

[Anonymous]

Hey Don, I hadn't forgotten you! I'll double check the main jet sizes - anyone know what's recommended with a 4 into 1 pipe and K & N individual filters???

[Don Lobacz]

With the big port heads (80 and up), the corresponding CV carbs (34s?), K&Ns and a 4 into 1 pipe, you should probably running around 125 mains and have 1 shim washer under the needles. This is just a rough estimate that will have to be checked by the jetting procedure.