Top End

Acblind · Jan 19, 2011

How often do you do a rebuild on the top end? Do you do the whole thing or just the rings?

I haven't touched the top end since I bought my bike a year ago. the previous owner put a wiesco piston and new rings in it so i'm not sure if I should tear it down or just leave it.

SS109 · Jan 19, 2011

Do a compression check and go from there.

pesky nz · Jan 19, 2011

To comment accurately we need to know bike model age and usual riding type

Acblind · Jan 19, 2011

its a 95 kdx 200. all the mods are listed in my signature. the new piston was put in in the winter of '09.

I take it out just about every weekend in the spring/fall and a few times a week in the summer. it's mostly trail riding in the woods, but occasionally i'll take it to some open riding areas.

I just installed a tach/hour meter so i'll be able to keep track of how many hours i put on the motor. Right now it runs beatifully, never had a problem. Just curious about the top end because i keep reading about how everyone is serviceing it and replacing rings and pistons and wanted to know if there's something i should be doing that i'm not. I've always worked on engines in the past as i've ridden ATV's but i'm new to dirt bikes let alone 2 strokes so any help would be apprechiated.

SS109 · Jan 19, 2011

Trail riding (ie; not wringing the hell out of it) a KDX it could literally be years before needing rings and/or a piston.

1990kdx · Jan 19, 2011

my 1990 kdx 200 has never had a rebuild. if you do the maintains on it they will last for a very long time.

reepicheep · Jan 24, 2011

I'd pull the head / jug as a unit every winter, or maybe every other winter. Throw calipers on the piston and rings, and look for damage to the bore, look for crank play, and look for cracks in the piston skirt.

Like others have said... if you aren't beating the heck out of the bike, I wouldn't be surprised if you went 5 to 10 years between rebuilds with a Wiseco.

Dirtdame · Jan 24, 2011

I even got 4 years out of a Pro X piston kit on my 86 KDX. :cool:

pesky nz · Jan 25, 2011

As mentioned above if your air filter maintanance is accurate aqnd often a KDX will not need top end inspection/replacement for 30 to 50 rides or around 150 hours of average use (sooner if you are a racer or thrashbag).
Once your cylinder is off checking for wear is relatively easy, when your piston was made it had machining marks around it. If those marks are still all around the piston and top to bottom then no significant wear has taken place. Then measure your ring end gaps. To measure your cylinder use your good or new piston and a feeler gauge equal to recommended clearance and with the feeler blade down the front of the piston from top down to middle of piston pin hole and oil on piston and cylinder wall insert piston to measure clearance ( it helps to secure the cilinder in a vise with soft jaws on the 2 gasket surfaces). I know it sounds a bit back yard but most micrometers and cylinder gauges are difficult to use and any miss-read can be costly.

sr5bidder · Jan 28, 2011

compression test is a good idea along with taking the pipe and reed block off for a sneak peak using a mag-lite for signs of wear

seeings how you have got a year on it the PO must have done a decent job with the wiseco

Acblind · Jan 28, 2011

Thanks for the advice. The previous owner did a great job of keeping records of everything he did with the bike. he sent the case out to be machined for the new piston and kept all the invoices for that along with all the race tech shock work he had done. he put it all in a binder with the service manual and all the stock parts and gave it to me when i bought it. it's helped alot since then.

Top End

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