RM 125 elec problems

[PCMAX]

I am at my wits end with an ongoing problem with my 1981 RM125X. About 10 months ago it started missing & coughing etc when it was on the pipe.
I checked the stator coils resistance and one of them was not quite the book figure so I bought a second hand (almost new) stator on ebay it was originally bought from RM Stator is the US.
The bike ran good for a couple of races and then the problem came back.
In desperation I bought a NOS ignition coil and the bike ran OK for a couple of races then the problem came back.
I replaced all of the jets and needle/airscrew etc in the carby and reset the float height and the bike ran great for a little while then the problem came back.
Over the off season I had it rebored and fitted a wiseco piston, it ran well for a while then same thing again.
At one point earlier this year the bike would only run at flat out revs, it would cough and splutter down low so whilst ringing it's neck in a race I seized the big end.
I replaced the big/little end brg's, conrod, all the gearbox & crank seals & bearings and it ran OK for a little while then the problem came back again.
I then replaced the main 250 jet with a 270 jet as the latest problem was again at high revs and seemed to improve a bit when I raised the needle. After that the bike ran great for a little while and then the problem came back, this time it would cough & splutter and backfire at low revs to the point where it would not idle and then stall.
When I checked the spark it was weak and inconsistent so in a further desperate measure I bought a second hand CDI, bolted it on got a good strong consistent spark and the bike ran well for about an hour and a half and then started to break down high revs then would splutter and stall at low revs. Now it has a weak and inconsistent spark again.

I would love to put a match to it but I have spent too much money and time to let it beat me and when it runs well it goes like stink!!

Any of you Suzuki tech heads have any ideas? Pllleeeaasssee.

[TM BILL]

Make sure you have a good earth at the engine mounts and the secondry coil , clean off all the paint around .

[Lozza]

New plug cap? maybe checking you have adequate fuel flow through the tap and set the float height as high as possible.Only electrical part not changed has been the kill switch so try that.A carb rubber might be going soft when hot exposing and air leak.Check the cylinder base and case have a good flat surface.
I don't think the problem is electrical I think it's mechanical.

[DR500]

I had the same problem with my 125d,i fitted a new carby and goes like stink now.Also have a look at the main bearing,mind were worn and the fly wheel was grinding on the stator.I know how frustrating it can be when you think you have got it sorted and then it fZZZ up again.Keep smilling.

[suzuki27]

Similar nightmare with a 125D that went on far too long. Mine turned out to be a choke that wasn't sealing off properly-Thanks Paul!.  What Lozza said about poor seal between barrel and cases and also reed block casting on barrel due to casting distortions etc: check it is not leaking there- aerostart spray?  And it is worth checking the "air space" between the stator and the rotor- is it pretty even?

[PCMAX]

I eventually sent two full sets of ignition components to small coil rewinds in Gellong.
They tested everything and identified one bad ignition coil, one of the stators had a bad high speed coil and the other stator had a bad earth wire (the one that runs to the CDI) which they repaired for about $25.
They marked all the parts and I fitted the one good set and the bike is now running great.
Well worth the $117 total cost, should have tried this option first !!!!

[lukeb1961]

http://www.smallcoilrewinds.com.au/

I have seen this same issue occur on RM's and PE's now, 3 or 4 times. It seems they are at just the right age to need to visit the doctor for a check-up.

thanks for the pointer!
Luke