MF, I have a few vintage trimmers and they are often great machines built properly. But it does give you a laugh how they built some systems. This one has the fuel pump sandwiched between the tank and engine, driven off the crankcase vacuum.
Feeds up to a carby with a bowl with about a 2ml volume which overflows back through another pipe back to the tank. Then there is a third hose running to no where which is a backup overflow I guess.
Is a nice smooth motor when running.
If its the crank seals causing the issue then its a problem.
I am hoping setting the points will sort it. The way it was running it misses/backfires at medium rpm and hits a brick wall at about 5000 rpm.
Working theory is the points being so closed is partly doing the timing but also not able to 'keep up'. ie they can handle 2200rpm idle but either bounce or break down over it.
This explains the strange behaviour of smoke out the exhaust.
It has smoke, then clean for 3 seconds as it dies then backfire and plume of smoke then clean and so on. Plug says very rich. My theory is it fires every few revolutions hence tonnes of fuel in there to burn with tonnes of smoke.
When there was fuel delivery issues it wasn't as bad but now sorted out it is flooding itself between sparks.
Last edited by Tyler; 29/11/21 03:07 AM.
