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RM85 only starts when bump start

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I have a RM85 it always started really nice (like you could kick it with your hand and it will start). Today I went out riding and the thing would not start. I just threw a new plug in it. I checked for spark and nothing. Tried another new plug nothing. Sanded off where the coil hooks to the frame now it shocks me pretty good but only little spark. Cleaned all the yellow color stuff off the rotor and it sparks pretty decent.

Still the little fetcher wouldn't fire. Put the coil from my cr125 (same size coil almost same serial number on coil). Still nothing. I cleaned out the carb and adjusted the float as it would leak on the ground randomly (I didn't measure it I just bent the tab a little).

Fired up first try. My girl friend took it on a 5 min ride and came back. We talked for 3 min or so then it wouldn't fire. Kicked it a few hundred times then I got pissed and ran down the dirt road like a mad man and threw it in gear. It turned the engine over then sputtered for a second then fired and took off. Since it was running we went riding.

Strangest thing happens now half the time it fires very easily with the kickstart lever the other half I can kick it a million times very hard and the only way to get it to fire it is to push start it.

Any ideas what's wrong?

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You may be right. The top end only has about 10 hours on it, but the guy I got it from did it and who knows if he did it right. I have a compression checker. How much compression should it have?

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You may be right. The top end only has about 10 hours on it, but the guy I got it from did it and who knows if he did it right. I have a compression checker. How much compression should it have?

Are u sure he even did it? Pull the pipe and look into the cylinder and you can see how most of the cylinder/piston look or if there is any blow-by past the rings

If you don't have a compression # from after it was rebuilt doing a compression test now will not give it anything to compare it too to see what kind of a loss you have

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shouldn't be able to kick it with your hand.

(though i have seen guys hand start yz490s and 500s)

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How fresh is the motor/topend? Sounds like it time for a rebuild

Me to that sounds like low compression to me. Or maybe so earning in the fuel system. When u would bump start it it would turn over

the engine with enough force to either bypass or suck up any chunks of contaminants. This actually happens a lot with things now that there is so much ethanol

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"NEW TOP END" could mean a new piston and rings put into an out of spec cylinder, in which case once the rings wear, the motor wont run unless bump started. If it always starts when bump starting, Top end is toast! Minimum compression for a good top end would be about 160psi.

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I'm sorry guys. I though I replied to this thread. It had 155lbs of compression. The problem ended up being that when I cleaned the carb once a metal ring that holds a breather hose fell of the carb and into the intake.

I found this out by taking the reeds off and looking at them. The metal thingy was wedged between the reed and the plastic triangle thing. Luckily it never made it into the bottom end or the combustion chamber. I've since sold the bike, but it was back to it's amazing easy to start self with loads of power (at least for a bike that small).

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