I have an SR125 which has been a poor runner for a few years but recently has become unbearable.
It either starts first time or not at all on the electric start, it usually just turns over and almost sounds like its trying to backfire. It can be started much more easily by bump starting which often works straight away. Once running it cant make up its mind how to run, it will go for a couple of miles running fine and I can cruise up to 60mph then it will loose all power for a few miles and I cant get above 25mph on level ground, if its being really awkward it will be even more intermittent and I will bunny hop down the street.
I’ve cleaned the carburettor and checked the float height, replaced the plug lead, plug cap and spark plug, checked the resistance of the coil all of which seams fine. Cleaned and WD40’d as best I could electrical connections easily accessible with the seat and tank off and noted they were corroded. When ever I remove the spark plug it’s in good condition and when I compare it to the images of spark plugs it indicates the engine is in good condition and running fine, if only someone would let the engine know.
If it was my old two stroke bike Id be checking the timing but the SR has a ubiquitous black box which whose operation is a mystery, is it possible the timing isn’t advancing or is there anything that can be adjusted or drift out of calibration?
Any help would be welcomed
Moo