MZ/MuZ Riders

Are we sure the float actually floats?

Are we sure the float actually floats?

Another very good point. Has the float been checked?

Thanks guys, some great ideas and potential clues there. The blocked frame holes and routing of air to the intake would never have crossed my mind.

Ref the choke plunger when I stripped the carb the choke seal had indeed become detached and was on its side so I was quite convinced this would be the cause, I replaced the plunger with one from another carb but it clearly did not help.

Flooding too is a potential as the crankcase may well be full of oil rich fuel due to the tap issue and pure oil incident described early on in the thread so it could be linked to the issue.

I’ll check out these latest suggestions in turn and report back.

Bob.

I would double check the choke plunger, and make sure that you have some free cable when the choke is in the off position.

If the crankcase has accumulated a lot of oil and petrol. you could try taking the plug out putting the piston at BDC so that the ports are uncovered and leave it a few days for the excess fuel to evaporate, but that would still leave the oil.

If you think the crankcase is full of petrol / oil one way of removing it is to take the top end off, get a syringe with a short length of tube attached and suck out the petrol / oil, hpefully it will not come to that.

Finally, have you checked the float to make sure that it is floating - all it takes is for it to have a small leak and it will not float, also have you checked the float valve, these cans sometimes leak.

Good luck.

Well it's running again!

Revisited the carb to look at the choke plunger, I had previously replaced this with another as the end had come off and was on it's side so I swapped it out for another from a spare carb I had. The spare dropped right in no problem but the bike would still not run; so having removed it again to check all was still ok, everything did appear normal.

Upon reassembling it, the plunger would not fit in the bore yet previously it dropped straight in? Further examination showed the rubber end had swollen and was now about 1mm all round too big for the bore, so guessing being old and unused for years when in contact with fuel it had swollen and would no longer fit right nor close as it should. So I basically trimmed the excess edge on a grinding wheel and it dropped right in, fitted yet another new plug and it just fired straight up and settled on a nice idle, revs cleanly and restarts ok. Not had a chance to ride it as the weather here is awful, still a lot of snow and ice about. Fingers crossed it's finally all sorted now and I can actually trust it to get me more than a mile or two, surely there is not much that can possibly go wrong with it that's not already been fixed or replaced.

Thanks again for all the suggestions.

Great news Bob - at least if it plays up again you know where to look - it might be worth buying a new rubber.

Hope you get to enjoy riding the bike now.