Hard starting my 1979 50v

Nathan DeVore /

Ok so here's my situation. I have a 1979 Moby 50v that due to stripped exhaust and spark plug threads, I decided to refit with a 74cc airsal kit, a dellorto 15.15, and new stock exhaust. Well the other night I finally got it up and running, and with a few minor adjustments she was running better and faster than ever. So I took it out for a maiden voyage, and it ran great for a good while but upon subsequent start ups I first noticed idling problems, then trouble starting up at all. What I'm experiencing now is extreme difficulty in starting(it'll get going barely, and will only finally take off with a ton of pedaling). Once it's up and running it'll run just fine at high speed but at low speed almost no power and real trouble idling unless it's real warmed up. Throttle and decompression are adjusted fine, As is the idle pin. I'm just wondering if that one ride with the new added power would be enough to mess up the variator or ignition timing, which seemed fine before? Sorry for the long post just trying to be thorough.

Re: Hard starting my 1979 50v

Check if you have healthy bright blue snappy spark. Might have condenser issues and the arching is carboning up the points.

Check if the carter can contain vacuum by doing a leak down test. Extra stress on the engine could have started a rupture at the spi seals or one of the gaskets might be not a goodly seal.

Re: Hard starting my 1979 50v

Nathan DeVore /

I've got a good spark...I'm sorry but what exactly is the carter? This is my first rodeo...

Re: Hard starting my 1979 50v

Carter is the bottom end of the engine. Search out leakdown test.

Re: Hard starting my 1979 50v

Nathan DeVore /

Well I felt air shooting out one side of where the head and block meet. I checked the head gasket...it seemed fine... flipped it over, retightened the head and tried again and sure enough air was shooting out the other side. So is that a blown head gasket? I mean it looked completely fine. If so, here's my question, I put a cheap sito replacement stock exhaust on my new airsal 74cc kit. Could the cheap exhaust be a reason a head gasket would blow on a the slightly more powerful kit?

Re: Hard starting my 1979 50v

Uneven deck, uneven head, insufficient torque, faulty head gasket are the most likely reason for a blown head gasket.

To check the head or cylinder for true you can paint the mating surface with a marker pen and do 3 figure 8s on some 800 aluminium oxide cloth mounted onto a sheet of glass. Then look for where toe marker is not removed from the surface.

Also check that the cylinder seats fully into the carter, if it is not seated well then when everything heats up it will seat and leave a gap up top of the cylinder.

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