426 eating cams and camchains. need help.


4 replies to this topic
  • sergey

Posted September 11, 2007 - 02:45 AM

#1

recently got 2002 wr426, it had a wasted main bearings, crankshaft, and cams were loose in head. changed everething but now it seems to waste another head with cams and new cam chain. oil pump is within specs, and oil is coming to the head. cam caps are torqued properly. what to look for? It seems to me that at some point when i push it hard oil level seems to drop in oil tank and raise in crankcase causing clutch not to work properly.

  • Birdy426

Posted September 11, 2007 - 05:33 AM

#2

Sergey- Welcome to TT. There is a wealth of knowledge and some really smart folks here to help solve your problmes. We could use a little more info...

What do you mean "waste"? Are the journals worn? If so, how much? Galled? How did the cam chain fail? What does the crank side cam gear look like? Maybe post up some pics of the failed parts to help us evaluate. I don't think too much oil in the bottom end would cause the clutch to not work properly...not enough, maybe. Can you 'splain how the clutch behaves? Also, how many miles or hours are on the rebuild and how did you repair the head damage?

Right off the top of my head I's say one of the oil passages is partially blocked. You need to get the oil, under pressure, to the head to give the journal bearings in the cam a film of oil to roll around in. If there's not enough pressure, you will get metal on metal contact. You also won't get enough oil volume up top to splash lubricate all the other parts. Could also be that if you changed the head or barrel that the oil passages in the head, gasket, and barrel, or barrel, gasket and case aren't properly alighned. Rare to get a manufacturing quality defect like that these days, but it can happen...

That's one thing yu really didn't have to worry about with pingers is cleaning the oil passages after machine work or motor damage...of course, you did have to worry about radiusing the edges of ports...

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  • GCannon

Posted September 11, 2007 - 08:00 AM

#3

As stated Previously More information is required.
If the Cam Caps were incorrectly torqued previously then they may be distorted causing a too tight or too loose situation allowing the cams to deform the Head.

Exactlly what parts were replaced?

  • sergey

Posted September 11, 2007 - 08:47 AM

#4

Thx for reply. This summer i bought used wr426, and had to rebuld it completely. Bike seemed to have a very low mileage (around 1000miles), but for some reason engine parts were worn. Changed main bearings, crankshaft(as the cam chain sprocket was worn), piston, cylinder, camchain, and head assembly which i bought used from ebay.

The original cylinder head had camshaft to cap clearance pretty much out of spec, and journals were worn. In а few riding hours after rebuild it seems to do the same thing with new head, also stretching the cam chain. Cam caps are torqued according to the manual. Checked oil pump - within specs.

My idea was that for some reason on high rpms oil is coming from the frame faster than it gets back from the lower end, causing an excessive oil level in lower end and emtying the oil tank. At some moment all oil gets into the crankcase causing a lack of oil supplied into the head. I think this is also a reason for a draggind clutch that does not disengage completly, but it works ok if I dont push bike hard, or let it idle for some time.

  • maxtherat

Posted September 14, 2007 - 09:59 PM

#5

Sounds like your chain tensioner may be faulty or not engaged at all. Have you checked or replaced this?




 
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