Motomarina Sebring not starting

Robert Susinski /

I have a 1985 Motomarina Sebring with the Morini engine. I had a mechanic put the Polini 60cc kit on it. The bike has been causing trouble since the kit was installed. Here is how it goes....

I got the bike back from the mechanic with the kit installed and a new #66 jet in the dellorto carb.

I ran it for 15 minutes when i got home and it broke the flywheel key.

I took it back to the mechanic and he put a new flywheel key in.

I took the bike home and tried to start it for 15 minutes, but no start.

I rolled the bike down a steep hill and the engine started at about 15mph.

The bike ran for less than 15 minutes and the engine died.

I tried to start it the next day and nothing.

The mechanic has the bike now and he spent a week looking at it with a Morini rebuild book and he has no clue.

I do know the following things....

i tried running it with the original carb and a new carb fix,

the flywheel key is not broken again,

the points were set to the specs in the manual,

compression is 160, spark is good, all lights work, and the bike is getting gas.

Any suggestions?

Re: Motomarina Sebring not starting

sounds like the engine develops a lot more torque now and so sheared off the flywheel key. Exactly what were you doing at the moment you lost the flywheel? Were there any other problems (other than the lost flywheel) after the new kit was installed?

And, since the flywheel got thrashed around a bit, i would suspect you developed some sort of ignition / timing problems. The mechanic might want to look for something unusual.. like magnets will sometimes lose their magnetism if you just bang them with a hammer..

Re: Motomarina Sebring not starting

Robert Susinski /

I was riding the bike when the flywheel key broke. It was the first time i started the engine since the speed kit was put on. The bike ran perfect for about 15 minutes. Since it is a new kit , I stayed under 15 and gave it no more than 1/2 throttle. It took lots of speed to get it going at first and even more to get it going after the flywheel key was replaced. I never had trouble starting the bike with the 50cc parts. I could walk slow and it would start up without trouble.

Re: Motomarina Sebring not starting

If you were not gunning the engine or something, i don't see why that flywheel key would snap. It may have been weak? Was there even a key in the keyway?

As far as having to get the bike up to 15 mph to start it, it could be a couple things (i'm not familiar with your bike).

On my bike, there is a lightweight start-clutch that engages when you pedal at low speed.. When it engages it grabs the crankshaft and turns the motor over, producing spark and compression. Another larger clutch takes over and drives the output-shaft/sprocket/pulley/whatever.

..and then timing/magneto area could offer other reasons.

So, coincidentally, you may now have problems on both ends of the crankshaft.. the flywheel side and the clutch side. Makes me wonder if your crankshaft was removed or modified during this rebuild..

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