Mystery of the failed re-starts

Lay'emLow

Lay'emLow

New Member
Hey all. I tried doing some searching, but couldnt find anyone who has had this problem.

My '80cc' BoyGoFast motor has been displaying a very annoying tendency lately. Ill start it initially without issue and Ill ride it at least long enough for the motor to get hot. If I stop and shut the motor down for longer than a moment, it absolutely will not restart when Im ready to ride again. The stops are usually quick (between 5 and 15 minutes), and I find that giving it some time to sit after the failed starting attempts helps.

Ill wait and try and start and eventually get sputters, then wait and try and start and get more promising pops, then wait and finally it will start reluctantly.

This makes me think flooding, but I havent pulled the plug after one of these issues yet. Also, I cant figure why it would flood... weak spark? But why does it start without trouble initially...?

Anyone experience this or have an ideas cause I am flabbergasted.
 
It could be a air leak somewhere. When the engine heats up it may expose leaks and there for fail to start due to the lack of compression. I had the situation where my engine would not start.

After future investigation my head gasket had a leak. I tightened the the 4 head bolts because that had some thread still left and the bike started up right away.

I also didn't have that popping noise anymore too. The popping noise sounds like a leak.
 
I know theres no leaks on the intake side of things... Ive very carefully buttoned all that up. Ill check out around the head and plug tho next time i run it. I can run a compression test too to check the piston rings, but whats good pressure? 120 psi?

Also, the popping I mentioned is the motor firing, but not continuously. Just an succssful combustion here and there.
 
Do you turn off the petcock at the tank when you stop?,,,Does using the choke defeat the starting?,,,,Could the screws holding the mag coil down be loose?,,,
 
I can almost guarantee you that it is the magneto that is causing the problem.

Magnetic field strength decreases with temperature.

I've been doing some tests and recording data off of the magneto in a Grubee GT5.

Below 600-700 R.P.M. ,(cold), the plug fires intermittently...sometimes only for 2-3 seconds...and then nothing, no matter how long the engine is spun over.

Next time it happens...try pedaling really fast before releasing the clutch...I'm betting it will start.

Jim
 
relating to Jim's post above, make sure your wiring connections are clean and tight, soldered is best, and that your plug wire is tight, not only on the plug, but screwed into the CDI, too.
 
I had planned on upgrading the spark wire and cleaning the plug before the next time I ride already. While Im at it Ill give the rest of the electrical system a once over as well, and report back.

Jim, Ive got a shift kit, so I cant pop the clutch under way. Ive got to rely on my pedaling skills to turn the motor over. Is there something I can do to improve the the effects of the magnetic field? Move the coil closer to the flywheel? Close the spark plug gap?
 
Vapor lock in the float bowl? Next time put a ice gel pack on the float bowl for about a minute and then restart your engine. I wouldn't be surprised if it starts quicker this way. If so, consider a phenolic spacer on your intake o cool the carb down.
 
How much oil are you mixing in the gas?? Too much oil can stick to the plug & foul it.
General wisdom is to use 24:1 for break in & 32:1 after that.

Also, if you slowly raise the choke lever while pedalling to start it, it should start right up when the choke hits that 'sweet spot'. ;) try it!
 
You must log in or register to reply here.
Back
Top