Guys,
I need your help on this one. I just put in the new 102mm 12:1 Je piston, oversized exhaust valves, kibblewhite springs, and stage 2 hot cam. I ut everything back together, timed it correctly and turned it over at the crank for 6 revolutions just to make sure everything was lining up correctly. When I tried to start it using the starter I broke al of my rocker arms! This is the second time this has happened.
Has anyone else had this problem? I know Iam putting everything back together correctly and the timing, valve lash i spot on but after about 10 evoluions the timimg/camchain seems to jump and causes the rockerrms to brake clean off.

Help

 

do you need to grind down the tops of the valve guides like on the 400ex to run the stage 2 hot cam?the spring keepers could be hittin the guides and binding up then breakin the rocker arms.just a thought.

 

Thanks for the suggestion but tht's not it. The sprig is not fully compressed. After the arms break I went aead and tried to turn it over at the crank with the sparsk plug out and the piston was actually hitting the intake valves. For some reason the timing chain is actually jumping. The only thing I can think ofis is either the timing chain is stretched ( unlikely since it only has 40 hrs on it )orthe gear on the camshaft is worn, not sure why it would wear so uickly.

 

what about the cam chain tensioner?is it working properly?

 

It is a good Idea to not put the cam chain tentioner on the motor until you have the valve cover installed. Other wise it could put the cam in a bind and that might be your problem. Just a thought.

 

As mentioned elsewhere. What RRTX said about the chain not being on the bottom gear sounds like the most likely cause. It slipped over on one I was putting together and I can see how it could be over looked and may work OK when turning it over by hand but slip when you try and start it.

 

for the guys that have replied so far, Thank You!
Let's hear from a few more of you. Don't let this thread die just yet.

 

Remember when the tensioned is installed the timing will back up about a tooth....so if you were perfect, you will not be a tooth off and she will not run.

 

I agree. What I am seeing is that it is jumping several teeth, not just 1 or 2.

 

The chain tensioners "arm" should be fully decompressed and the tensioners bolt and spring should be removed before the tensioner is bolted too the engine. This way the tensioner only takes up the necessary chain slack for proper operation. If you have installed the tensioner fully extended, then you have stretched the chain and this could easily be the reason why the chain is slipping. When guys first start modding Raptors we had a lot of people with major problems until they realized how too correctly install the chain tensioner.