ive got about 500 miles on my bb351 now.

Got home friday from a ride and could hear clattering in the valvetrain and saw the oil was dangerously low (and coolant reserve down just a bit). Oiled it up and started it after cool down and got a puff of smoke out the exhaust and constant ticking. Shut it down quick.

Im assuming either gasket issue or rings not seated right, but I need some help troubleshooting what's going on and how to assess any damage that may have happened. Help please? What to look for? Best approach to fix?

valves overheated and gone out of spec now?

 

First, who put the piston rings on? and did u get them installed in the right direction up?

I would suspect a blown head gasket, probably the oil channel leaking into the cylinder. Did you torque the head?

 

the rings were preinstalled on the piston i got from bill. i aligned the gaps per the service manual

head was torqued per the service manual and rechecked before final assembly

i'll have a better idea once i open it back up, but im still unsure as to what else i need to look for to remedy the clatter/knock sounds i'm hearing

 

I would fix the oil issue #1.
The clatter/knock sounds like the automatic cam tensioner has given it up. You may want to check the valve clearances before removing the head, just to verify that they have no issues. No way the valve clearances should change, unless you ran it without oil and your cam journals are shot now.

 

10-4

reckon the cam tensioner need replacing or just "reset"

 

If the ACT is not doing its job anymore it is because of minute amounts of wear on those tiny teeth. I would think there is no cure but replacement. I intend to get the Krieger MCT when that time comes for me.

 

alright thanks. once i tear it down i'll post back to see what all needs to be done.

 

sphen,
Here's another vote for Krieger's manual cam chain tension adjuster. The KLX250 OEM ACT sure has a knack for failing, and forcing an adjustment could be bad.

 

thanks for the tip - had no idea such a device existed.

is there a method to determining how much tension to put on it?

 

Yes, there is. If you read his materials, you'll see that 'finger tight' is just about perfect. You can fine-tune from there if you find it's needed.

paging klx678....(he's a member here; send him a PM if you're curious).
He and another member here worked on the design for the KLX CCT, but he's done many other makes before this one.

Krieger Cam Chain Tensioners

The KLX cam chain rattle is pretty classic, usually worse around 5,500 rpm and to my ear sounds kind of like a few rocks shaking in a metal coffee can.