think Ive tried everything.

[(RIP) pastyman]

As some of you may know I have been trying for some time to get Bertha, my 100gs running smoothly. she has always had a rather "rough" feeling engine despite having had a complete engine rebuild. Ive tried everything as suggested, valves, timing all new carb internals and carbs cleaned with solvents and even ultrasonic bath. she pulls like a train, uses no oil, compression test shows even on both cylinders and good compressionSounds good does'nt it but on accelleration she just feels rough especially around the 3000 to 3500 rpm mark.
I am going to try new plug leads just in case, anybody any views on this? My timing strobe only works when the lead is connected to the right hand plug lead, wont light when connected to the left one.
Failing that , has anyone got a pair of spare carbs I can buy/borrow. especially the left one as I think it is this side that is causing the problem.

Airheads!!!! You gotta love them

 

[MickDB1]

I know it seems drastic but you are there I recon

When the bike is running try and just touch the metal HT cap if the insulation is braking down you should/may get a tingle on the side thats dodgy

I did - do it whilst your parked and at a few more revs than tickover

Made Jaber laugh - and It sorted it for me - or - just get some new leads and caps
HTHY

 

[Rob Farmer]

The strobe working on one cylinder sounds very strange. Have you measured the resistances on your coil? My Mono's coil had strange readings so I swapped it for a Dyna coil - big improvement.

 

[brassmonkey001]

The strobe working on one cylinder sounds very strange. Have you measured the resistances on your coil? My Mono's coil had strange readings so I swapped it for a Dyna coil - big improvement.

It sounds very suspect that your timing light won't work on the side that you believe you have a problem with. Sounds like a clue to me, scooby doo.
I would definately be looking at the electrical side of things

 

[brassmonkey001]

When the bike is running try and just touch the metal HT cap if the insulation is braking down you should/may get a tingle on the side thats dodgy

Don't try this. Especially if you've got a dodgy ticker.

 

[(RIP) pastyman]

The strobe working on one cylinder sounds very strange. Have you measured the resistances on your coil? My Mono's coil had strange readings so I swapped it for a Dyna coil - big improvement.

Now please excuse my thickness.. The 100 has a single coil doesnt it so surely it would be the same for both sides, if not, giz us a clue how to measure it. Ive got a multimeter (but not much idea about how to do anything more than simple)

 

[sycomoto]

I've a suggestion

Now please excuse my thickness.. The 100 has a single coil doesnt it so surely it would be the same for both sides, if not, giz us a clue how to measure it. Ive got a multimeter (but not much idea about how to do anything more than simple)

Sell the old girl or chuck it over a cliff and say it had been nicked then go buy a proper one like this.

 

[Rob Farmer]

The secondary side of the coil is common to both spark plugs (one at either end of the coil) so if it sparks on one it should spark on t'other.

My coil had a much lower resistance reading on the secondary than it should have.

If the coil checks out ok then it's got to be worth swapping the leads. If you fit non standard spark plug caps just make sure you don't have resistive plugs and caps with a resistor in them.

Have a read of this - taken from the Paralever manual.

 

[(RIP) pastyman]

Sell the old girl or chuck it over a cliff and say it had been nicked then go buy a proper one like this.

Bog Orf.. I see you parked the harley on the other side of flips car, didnt know you painted it orange though

 

[Rob Farmer]

Bog Orf.. I see you parked the harley on the other side of flips car, didnt know you painted it orange though

That made me chuckle

 

[(RIP) pastyman]

Rob. Thanks for the instructions, I recon I can do that. I'm going to try swapping the leads from the g/s first and see if that makes a differance. Let you all know soon

 

[(RIP) pastyman]

Right. done that and been out for a ride. Still rough up to 3000 rpm but pulls really well. Ive also had another go at balancing the carbs which has improved it a bit but I think it is still a bit too vibey. Will try the coil next but I still think one of the carbs must not be right. Will have to get some others to try.

 

[nud1e]

Right. done that and been out for a ride. Still rough up to 3000 rpm but pulls really well. Ive also had another go at balancing the carbs which has improved it a bit but I think it is still a bit too vibey. Will try the coil next but I still think one of the carbs must not be right. Will have to get some others to try.

coil/dodgy HT lead or cap - been there with the same symptoms which went when I changed the coils.

 

[(RIP) pastyman]

Took the coil off today, does'nt look at all like the one in Robs picture though I pulled the leads out and there was a lot of green mold looking stuff inside the hole where the left hand plug lead fits. this would no doubt affect the electrical connection so Ive now cleaned it all up and will give it another go soon. Let yo'all know how it goes.

 

[Beemerboff]

Last time I could only get the timing light to work on one side changing the plugs cured it.

Any dyno chart I have seen for a stock GS has a flat spot right where yours is.

There is an article somewhere where San Jose BMW got rid of it by richening up the carb , and derestricting the intake and exhaust.Try a Google on Eke Me out