2010 dragon 800 ran 10 min

[omernikski]

A buddy recently picked up a 10 dragon 800 that needed a bottom end. I had a used one on the shelf so I tore it apart, went through the crank, put in new seals and resealed the cases. New cylinder, pistons and all gaskets. Prefilled all of the oil lines bled the pump and filled line from the oil tank. Put everything in fired it up. Ran great but idle was at 1100. Pulled airbox turned the idle up and installed airbox. Restarted it and idled great. Water temp ran around 105. Took it out, burped it around and then the idle went down to 1000. Chopped the throttle and then it idled at 1550. Burped it a little more and then the motor came to an abrupt stop. Pulled it over and it fired right up. Ran at 1550 and then down to 1000 and then another abrupt stop. Pulled it in the garage, compression tested it. Mag side 90 pto side 30.

 

[tbergeron87]

The compression is too low to run. Did you set ring gap when installing them?

 

[omernikski]

Pulled the head this morning. Circlip came out. Need a piston and cylinder now

 

[Sheetmetalfab]

Pulled the head this morning. Circlip came out. Need a piston and cylinder now

Snap!

That always sucks.

I had a buddy buy a “freshly rebuilt) dirtbike
It was assembled with a standard piston in a big bore cylinder.

Piston slap broke the skirts off and lunched the thing.

 

[tater85]

That sucks, if no body has mentioned it make sure the opening on the circlips is down or up 6 or 12 o clock not to the side like 3 or 9 oclock, supposedly momentum can cause them to compress and come out.