1986 Yamaha 80 Moto 4

[smyk33]

I recently bought a 1986 80cc yamaha moto 4 in good condition. It has a new battery and new spark plug but will not start. It will start by push starting and once it is really warmed up it will start with the electric start most of the time. Can anyone offer any suggestions as to what the problem may be? Any help is appreciated.

[smyk33]

Can anyone offer any help? Why would an atv be able to be push started but not started with the electric starter? I dont have any experience with this kind of thing and could really use some help. Thanks

[LT80]

It could be low on compression. Do a compression test.

[smyk33]

what should the compression be? If it is low what would be the fix and would it be expensive?

[Terrellster]

I'm not the board expert on anything, but I have a Badger 80 (96 model) and it should have a similar or the same motor.

I spent a bunch of time looking up just such an issue and came to the realization, that the valve clearances weren't set right. The clearances were 2-4 Thou on intake cold, and 3-5 thou exhaust cold.

Once adjusted properly, mine starts great.

There is a possibility of worn cam and such, but let's start with Valve clearances huh?

[smyk33]

I spoke to the gentleman I bought the unit from and he tells me he put new rings in a year ago and the compression was good after. I checked the spark while cranking today and it doesnt seem too strong and not consistent. It actualy disappears and comes back. Would a bad coil cause this?

[Terrellster]

Originally Posted by smyk33

I spoke to the gentleman I bought the unit from and he tells me he put new rings in a year ago and the compression was good after. I checked the spark while cranking today and it doesnt seem too strong and not consistent. It actualy disappears and comes back. Would a bad coil cause this?

A bad coil, coil ground, ignition pulse generator, other wiring. As old as the bike is, I suggest going over all grounds really good.

[smyk33]

Thanks, I will check all of that out.