motorcycle carb question...

Eric 951 · 09-22-2005, 07:21 AM

I have a Morini 500 I have been restoring(I have posted updates here in the past with pics)--well I finally got the bike running

First time it has ran in 23 years--to get the intial start we had to bump-start it--pretty funny towing a vintage motorcycle behind a pick-up on the streets of Pittsburgh, but I digress. The bike ran, and would restart that day(both with the electric start and the kickstart)--anyways, after sitting overnight, it would not start again--as if the carbs have lost their prime--we got it bump started again--but I am lost as to why it wouldn't fire again after sitting overnight. The carbs are Delorto PHBH venturi-types which I rebuilt. Just wondering if anyone has had a similar experience with their bikes and what exactly I should be looking at. Final pics of the re-assembled bike will be posted next week.

1967 R50/2 · 09-22-2005, 09:56 AM

Check the plugs. Some plugs will not fire...EVER...if they get hit by gas.

Do they throw spark?

Eric 951 · 09-22-2005, 10:10 AM

Quote:

Originally posted by 1967 R50/2
Check the plugs. Some plugs will not fire...EVER...if they get hit by gas.

Do they throw spark?

The first set were giving spark, but I changed them just to be safe. Pulled the new plugs on the second day after it wouldn't fire--they were clean--I even double-checked the gap, held them against the case and cranked--definately throwing spark--just the carbs losing their prime-and I can't figure out why...

BTW--Plugs are NGK BPRES.

Teutonics · Teutonics's Garage

I'm not familiar with those carbs, but do you think the fuel in the bowl is leaking out (into the cylinders or siphoning back into the hose/fuel pump) or evaporating? If evaporating, could the floats be set too low?

Fuel pump is working properly? I had a similar issue with a riding mower that the fuel pump was just working barely enough to keep up with fuel demand, but never enough to keep the bowl full (didn't know this was the problem at the time). I could never get it to restart after getting hot. Finally the pump (crankcase pressure/vacuum actuated) got bad enough that the motor started surging (from starvation), rebuilt the pump and now it starts and runs like a champ.

Good luck!