wr 426 piston worry

hi , today while out riding the camshaft cap came loose and as a result one of the intake valve collets popped off and dropped the valve onto the piston while it was running, its marked the piston up and in justxwondering if i would get away with re using the piston? im sending the head away to have new vales and new seats i think but in strapped for cash and justxwondered if this would be ok? any help much appreciated



Doesn't look too bad. I would check for roundness though.

Roundness at the top of the crown isn't an important issue, as the ring lands, the area from the crown edge to below the oil rings is cut back smaller than the skirt, and is not in contact with the cylinder under any normal condition.  Note that any indication of the ring lands having run against the cylinder is evidence that the piston is worn out.  What needs to be carefully checked is the piston to bore clearance.


The damage doesn't look bad enough to worry about, but you also need to check the clearance the top ring has in the groove near the damaged area compared with the rest of the ring groove to see if the ring has been pinched.

ok cheers for that! also i changed my oil and put a fresh filter in before taking it out, its done aproximately 1 hour since, and the is the oil filter, iv seen on a forum that wr's tend to give out metal in the oil but this seems abit extreme? the gears work fine and i cant see any obvious damage, theres no play in the crankshaft other than slight side to side?


That is defiantly too much metal... Especially for only 1 hour of running, you might want to look deeper before you have a catastrophic failure and ruin a case

The first thing here is to find a magnet and see whether the bulk of those chips are steel or aluminum.  If there are a bunch of more ore less uniform, squarish looking steel chips in the oil, it usually means there is a failing bearing in the assembly that is shedding metal chips (spalling) from a race or some of the balls.  


Aluminum from the clutch should be more in a "splinter" form.  Small filings of aluminum may indicate that something has come into contact with one of the cases internally. 


How long has the filter been in service?

only done an hours riding? i bought a magnetic sump and fitted that at the same time but when i dropped the oil out there wasnt a single bit of metal on the plug, all the gears change smoothly and clutch works fine, think il take the clutch off and check that too anyway though before i pull the bottom end out of the bike, cheers for the help i really appreciate it

should i be worried about the blue on the crank? shaft moves fine with ease but its obviously getting hot?


The blue is from manufacturing.

Check for verticle freeplay, there should be none at all.

good job lol, yh theres no upwards play at all, think il leave the bottom end but check the clutch out then once the head comes back re assemble everything so its running with fresh oil etc then take her for a spin and check the filter again, iv since found out that the wr's tend to have a few shavings on the oil filter and not too worry as long as there only ally so hopefully if i keep an eye on it it will turn out to be nothing! well see

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