I purchased a used Cater XTV 150 that was not runnig. The top end of the motor was off with a broken intake value. I replaced booth valves and lapped them in I also replaced the piston, rings, cylinder, gaskets wrest pin and a new carb. I got it started and took it for a ride and it quite after a few minutes. I took the valve cover off and found that the timing chian had jumped a tooth. I replace the chain tensioner as there was quite a bite of play. I started it up again and it will only idle at around 2800 rpm any thing less and it stalls. So I tried to drive it again and it quite and would not start again. At that piont it was either time to get a hammer and start beating on the buggy or go inside and watch football and nascar. So I decided to go inside. Tomorrow I am going to take the valve cover off and am asuming that the same thing happened again. With the valve being broken when I got the buggy I assume that something happened to cause the piston to hit the valve. I have been looking for some kind of break down of the bottom end of this motor with no luck. So can any one tell me what the problem could be? The other thing is when I go to set the timing. I put the fly wheel on the TDC mark but i can't get the cam to line up with the side of the head. It's either a little to 11 o'clock or a litte to 1 o'clock. It won't start if I put to the 11 o'clock side. Thanks for any help

Was there damage to the piston? I had a valve get hung on a piston and it did some real damage. The valve broke first though.

I use a screw driver in the plug hole to get tdc. I've heard of the marks being up to 180* off

Take the head off while at tdc. Put some sockets on the studs to take up the gap. Torque it to 16ftlbs. Take a straight edge and go across the center of the piston to check deck height. You need at least .025 which is exactly what I run.

The tensioner may be wore out.

The holes on the cam should be side to side. The big hole should be up. If you have a number on the cam it should face down

Yes there was damage to the piston. I replaced it. I also replaced the tensioner already.

I have the three holes on the cam gear. The large hole is at the top. The small holes side to side. I just can not get the side holes straight across with the piston at TDC. The top large hole is either close to 11 or 1 o'clock.

How can you tell if the mark is 180 degree out.

I have found the marks on the flywheel don't line up 99 % of the time, remove the spark plug and use a small screw driver to get to tdc on compression stroke. loosen the chain tensioner via a small screw driver thru the top of the tensioner.

remove the rocker assembly and chain, turn the cam back one tooth from having the holes line up and install the chain, reinstall the rockers and torque them to 200 inch pounds. release the chain tensioner so it puts pressure on the chain.

This may be a one off situation cause I've never heard of it... When I was working on my buggy I had to tensioners. One fit perfect and the other would'nt work. Like I said it could have been just me but it happened.

Erics right. Mine did'nt line up perfect. One tooth should'nt stop it from firing. Thee only go one way. If the piston is up and the cam is right your not 180 out. 180 out would be an upside down cam.

There are several different ways to set timing. Everything you have heard works, I do Piston TDC, lobes down on the cam. Cant go wrong with that.

Thanks to every one for there help. I am learning alot about this engine. Also getting really good at putting the motor in and taking it out of the buggy. When I installed the new piston I didn't know about the in marking on the piston. I had a 50/50 shot and I lost thats way I don't gamble. I was sitting here last night and found the GY6 service manual. By the way the link on this web site does not work. Thats where I found that bit of information. So last night when I got home from work at 10:30 I pulled the motor again. Sure enuff I had the piston in wrong and the timing had jumped by two teeth. I think the reason why it jumped was I had not put the pastic chain guide in right. So I turned the piston around reassembled everything with the new chain tensioner which is about a 3/16" larger then the old one and it seemed good. I put the motor back in the buggy and tried to start it. Once again won't start this is really getting old! So I check the spark which is still good. I pull out my shiney new Harbor Freight compression checker. Any time you have reason to go to Harbor Freight is ok with me. Well theres the problem no compression. So here we go again pulling the motor out. Put the motor on the bench and do a leak down test and find air coming out the intake. Pull the head and sure enuff bent the intake valve that I bought last week. So tomorrow back to the local scooter store to get a valve. It's a good thing a have a good sense of humor and parts don't cost very much for this thing. Hope fully tomorrow it will be up and running. I will check back in with the on going story.

At least it would'nt fire cause thats alot more money as you know. I dropped a valve and it put a 1/4in gash in the cylinder wall, broke the reliefe out of the piston, snagged the top ring, and then slamed the valve back into the valve seat and ruined the head. That every thing but cam and crank

Put a new head onit today and it fired right up. Thanks for all the help.