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NEw Crank?
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Posted by: YFZ#426

After i installed my athena 480 kit the quad ran great for about a week. Then i ended up bending 3 intake valve due to a bad timing chain. THe quad never ran the same the jetting is all different and it has a bog off idle. In the last race the motor siezed up. WHen i tore it apart i found that the crank bearings pretty much blew apart. What are your guys suggestions on this problem and on a new crank?

Posted by: jshtex

When you repaired the bent valves did you pull the crank and check it and the crank bearings? I would think that the piston hitting valves (thats what bent them right?) would put a lot of stress / load on the crank and bearings.

Posted by: YELLOW RR

More answers at www.yfzcentral.com

Posted by: nicker71

was it a stock crank?? I going to rebuild my soon and was thinking about the WR setup. And a 07 oiler update to the case.
But a big bore would be nice.

Posted by: dr.dyfz

redid my baby and put hot rods crank and jt oil upgrade. CANT WAIT TO GET IT DONE THIS WEEKEND

Posted by: YFZ#426

yes the piston hit the valves due to the timing chain jumping. That problem i fixed by putting on a new timing chain. I just inspected the crank bearings today and they are very worn so they will be replaced. My other prob is that after i fixed the vavles the jetting was never the same. It would have a bog off idle and not have 100% power. Can that be from worn crank bearings? I will be putting all new bearing and a complete new crank.