Has anyone had problems with the Cylinder Bolts pulling the threads out of the case after a top end re-do?

I had one pull out and warp the cylinder at the first full throttle run. Trashed the cylinder...got oil on my legs. I am wondering if it was a fluke or if I should put helicoils in all my cylinder bolt holes in the case.

I saw a cylinder on ebay where it actually broke the corner off the cylinder. So, this has happened at least once before.

cylinder

 

Not saying its the cause of your particular problem but the 4 bolts for the cylinder are different lengths, not by much either.

I have seen them frequently when put in a certain wrong way the longer ones can bottom out, you think they are tight but they arent, then the other side is short and pulls the threads out right away or after a short run.

 

You need to replace those bolts everytime or two you take the cylinder apart. The block will strip if you arent careful, I had it happen to me. Just throw a coil in the bad ones and replace the bolts and you should be fine.

 

I ran a die over the old bolts. I wonder if this was a good idea or not.

This problem cost me a lot of money and down time. I wonder if I should helicoil all of the bolt holes and get new bolts....just so I don't have to worry when I am hammering the quad up the hill.

But, I am always worried about messing up the hole when I put a helicoil in too...

 

What you experienced is common, especially on beefed up Raptor motors. The E-Bay pix is sympotamatic of a cylinder that comes loose, but the hex bolts at the forward base of the cam chain housing attempts to hold on. I experienced this myself. In fact, I bet if you look at the cross section of your old bolts, you'll note that the threads are slightly tapered down due to typical stresses experienced during engine use. Madog is absolutely correct in that you always replace the bolts with new ones. As you sit on the ATV, the right side are of one length and the same with the left, but I don't recall which are longer. I had case wear issues due to high engine stress and installed VW case savers. I wouldn't recommend re-helicoiling them if you are pushing high ponies.

By the way, mine happened because a machinist forgot to set the ring end gaps when I had my cylinder bored. So when the engine heated up, the rings grabbed the cylinder and pushed it, literally, off the case. Good luck.

 

Wow!
Thanks for the info. My problem was that I had a short bolt in a long hole. The long bolts go on the timing chain side of the engine. I didn't notice the length difference when putting the engine back together....but half the threads on the bolt were engaged. Not enough though I guess.

I will be sure and double check the ring gaps this time. I didn't do it last time either.

Thanks!