Ok, so Ive been having problems with my raptor. I installed a stage 1 hotcam. We turned the air fuel screws out a little and it ran great about a month ago. I was even out running a 250r framed yz426 quad. The next week we put in a wiseco 11:1 piston and the problems began.

We took it to the track the next week. The bike had problems starting. Granted it was -5 before the windchill, but the starter wouldnt even turn the motor over. We pull started it and let it idle a while to warm up. Race time came and it started when i rocked it back and forth for a while. Went out on the track and a 440ex beat me out of the hole. I ran like junk, then on the 3rd lap the tappet cover came loose and spilled oil all over. I limped the machine back to the trailer, one of the bolts was missing. I assume the cover wasnt tightened back down. We had rejetted the carb to a 180/175 and put the needles on the 3rd clip from the top. We lost a small spring and replaced it with one from a pen, and moved the needle up one more notch and backed the air fuel screws out to about 3 and 3 1/4. Took it back out and i was able to beat most of the bikes off the line, but I seemed to lose more and more power as the race went on. Eventually the 440ex passed me again.

So we got home and did a compression check, 25 psi. Not good, I know... Timing was way off, I mean way off. We fixed that per factory specs, adjusted the valves and put it back together.

Next week we went to another race. I could tell the power we had before the piston was still not there. I was having problems with a banshee that I had literally smoked 2 weeks before when I had just the cam. I saw the temp light on as I was sitting in the staging area. I shut it down immediately. 2 minutes later we had to go line up. The temp light was still on. As soon as i started around the track to the start line it went off and stayed off. 2 zillas jumped the gun, two times. After the second false start the temp light went back on. The green light went on and I had to go, so I did. The bike kept the light on for the first lap or so, and went off. On the last lap it went on again. I exited the track at the end of the race and shut it down, throwing snow all over the engine to cool it and leaving the key on so the fan would run. A few minutes later I again limped it back to the trailer and shut it down. The coolant resivour was half full, but when I removed the radiator cap, I couldnt see any coolant at all. I grabbed a few bottles of water, it took an entire liter. I started it back up and ran it for a few. No temp light. I opened the radiator and could still see the coolant at the top. Went back for the feature, a 10 lapper. On lap 7 I noticed a very bad vibration. I was having problems hanging on to the bars. I limped it through the rest of the race and took fourth ahead of a kfx 400 and 440ex, but I still couldnt pull on that banshee.

Took it home to the shop. One of the jug bolts was broken and another was loose in the hole,it had stripped. Apparantly they were over torqued. Took the engine all apart. We replaced all of the jug bolts and hela-coiled the stripped bolt back into the jug. The right carb had a stuck needle, it wasnt holding back gas like it should. We set that back in and went back through the carbs. The left carb needle was binding on the slide a little, fixed that too. the slides work and the needles are put back in correctly.

The rings seem to have seated well, as we broke them in just after install. Gap seemed large when first installed, but like I said, they seem to have seated ok. One valve is obviously loose because the rattle is obvious. We screwed the air/fuel screws back in about a half turn. Aside from the loose valve, I cant see what the problem is. I am lost and dont know what to look at now. I have a friend who has run 2 and 4 stroke quads racing for about 15 years, and my dad ran a lot of 3 wheelers and quads back in the 80's as well. My uncle is a professional auto engine builder for drags, dirt and asphault, and other applications. He's also a certified airplane mechanic. We cant get this thing running like it should.

So please, offer any suggestions you have, because I will take anything at this point. Thanks in advance, I know this is complicated and long.

 

 

There is 2 different sizes to those bolts. If you put them in backwards, or mixed up they will likely pull the threads are break the case. The cylinder jumping can break the other bolts after a little bit.

I have seen it happen more than once

 

Will one valve still bog the entire machine down? The case is entact, and new bolts are in and tight. The bolts that were broken off/stripped were the bolts that hold the jug on, not the head bolts themselves.

This is a pic of the side of the jug. The two bolts on the bottom flange on the outside of the jug is what I am talking about.

 

The jug has two different size bolts.

 

if you have constant excessive valve noise and installed or reinstalled a cam recently check that the pin for the decompression mech isnt 180 out. If it is it will open one of the exhaust valves all the time. Here is a page with a picture of what I am talking about. Hover over one of the pics to see the dot on the decomp mechanism. Either its 180 out or its not working.

 

thanks for the help. Ill remove the head this weekend and check the alignment like on the picture and also the valve lash. I think the different sized bolts must have been our problem with the stripped threads and broken bolts. Its been helacoiled now so it should be just fine. Thanks again, I really appreciate it.