Hey guys, posted here a couple times with great help. My bike has low compression so I took the top end apart to look at see what im dealing with. Piston and cylinder actually look really good and theres some normal carbon buildup on the head but the valves seemed to be sealing well. Im getting around 55psi after I put it back together (yes I know I need new gaskets, theyre on the way) I just wanted to throw it back in and see if I can get it to fart. I have fuel and great spark (rewired the whole thing and new coil and everything else within spec). The only thing that is weird is when I kick it over Im getting a little air being pushed out the carb. When the top end was apart I pulled the intake valve because I read about how they just love to bend. I also checked and double checked the timing and that was good when I put it back together. I am beginning to wonder if I should have checked to see if some oil would leak down with the head upside down. I have also down a complete carb rebuild but Im wondering if one of the air passages is clogged or if it is just the intake valve not seating properly? Im going to pull the engine tonight and see if I get any seepage from the valves. But if not could it just be the low compression due to a now bad head gasket? Thanks for any input.

 

Quick update, I pulled the engine and took the head off, flipped her upside down, and let some oil sit on the valves. No leaking, I mean not a drop. Anyone with a bunch of trial and error on these machines? Specifically why I am getting air cominng out of the carb?

 

is your exhaust plugged up by chance? maybe not letting it flow so only place to go is carb. i dont know ive never heard of that

 

No plugged exhaust I just had straight header for now and its clear.

 

Well you either don't have the cam timing right or you have the valve lash too tight.

Where did you hear about bending valves? I never heard of that. But I did see one valve guide that had a rough place in it for some reason. It eventually broke the guide, but took years to happen.

 

Could have sworn I read about the bending valve on this forum somewhere just in passing. Thanks though.I'll check the valve lash and I thought timing was spot on but.I'm human so who knows. Gonna do a leak down on the rings today just to be sure those aren't blown. If lash and rings are good.I'm going to throw new gaskets on tonight and see what happens. What's the breaking in on gaskets? Basically the same as if a new top end was put in.

 

Breaking in gaskets?

How did you set the cam timing?

 

match flywheel and case marks and then markings on the cam parallel with the head with the pin at 11 o'clock. Is that correct?

 

And JustRandy while youre responding, is the ltf250 same cam as a lt250s cam? Theres a couple cheap ones on ebay right now and I would snag one while my heads apart.

 

The cam marks parallel yes, but not sure about the case marks and flywheel. I just use a screwdriver to find TDC. If there are case marks, great... I just don't remember there being any.

No, its not the same cam. I mean, it will fit, but its a different grind. There are letters stamped on the ends. I pulled an "A" from a 300 king quad. A "D" from a LT4WD which I believe is the same as the LTF250. The 230s had an "E". And if I remember right, the 250s has a "G". It seems the farther along in the alphabet, the longer the duration on the cam.