I had a little mishap with my raptor engine this weekend at the Ice races. Here's the story, any help would be great.

Two weeks ago my uncle, father and I installed a stage 1 hotcam in my raptor and adjusted the valves. I took the air screws out a little and had it running quite well with a 170/175 3rd clip, 2.5 turns out setup. Last week we put in an 11:1 wiseco piston, std bore. The install seemed to go ok. We honed, cleaned, and oiled the cylinder and put everything back together, rechecking the valve lash. We hit the starter and it fired right up. I rode it for about 2 hours on saturday and followed a mild break in procedure. It ran well, did not pop on decelleration, never overheated, and started up without a problem every time. We checked the valve lash again and it looked good.

Sunday morning it was about 15 degrees colder. I got to the racetrack and tried to start the raptor. It seemed to have troubles rolling over. After trying it for a while, I pulled it behind our rancher and started it up that way. I ran it for a while and it stalled. I repeated that procedure 2 more times and finally got it to stay running. After it warmed up I put it in the trailer with the heaters and shut it down. Race time came and it again had problems rolling over, but eventually started. We noticed a rattle in the engine, but it sounded like a valve and didnt sound immediately important. At the starting line everything was going good. I got a decent holeshot, but not as good as I had the week before without the piston. On the 3rd lap the bike seemed to lose power and I spun out. It took about 3 mins to get it going again. I got back to the trailer and found that the tappet cover had popped off and was hanging by one of the allen bolts. Oil everywhere. It must not have been tightened down after we checked it the night before. We tore down the bike and checked the valve lash, put the tappet back on and refilled the oil resivior. We also noticed the spark plug looked lean so we went another 3/4 turn out on the jets and up 1 more clip. We put the bike back together and noticed that it still had a rattle, and still had starting problems. I went out to feature and the bike ran alright but it seemed to have lost its power. I was getting passed by bikes I had run circles around the week before.

The bike has a rattle, difficulties starting, and a severe lack of power. I am almost positive that the piston and rings were installed correctly and that the bike was put back together ok. Any ideas on a possible problem? I have the bike in the shop and plan to tear it down tomorrow, but any insight beforehand of what to look for would be great. Thanks.

 

Just a guess but maybe your cylinder is out of round, your stock piston would wear with it and not show problems like the new one. It could cause accelerated wear on your cylinder and piston causing loss of compression and piston slap. It would probably burn a bit of oil too. Power would be noticeably worse as time wears on and get louder until the skirt breaks and drops onto your crankshaft causing the rod to spit out the side of your engine case, piston to wedge into the head and of course your transmission will shatter. Of course that just worst case scenario...... I'd pull her apart and double check everything, also be sure you didnt over tighten the cam sprocket. Use the proper torque spec provided with the cam, NOT the OEM spec.

 

My guess is, that when you put the quad back together your timing marks were not right on the cam sprocket. When putting around you don't notice the lack of power. Once you get on it, you may have bent a valve or it's just out of time. the noise leads me to belive you bent a valve. Where did you buy the stage 1 cam? Did it come with a new decompression pin? If so, did you use it?

 

I bought my stage 1 hotcam from Magicracing.com. I dont remember seeing a pin, nor it being mentioned in the hotcams installation checklist, so no, one was not installed. Where would this pin go, and how could I get one if I indeed do not have it?

 

Back a year or so ago. I was the first to get a bad batch of stage 1 cams. The end result was a new decompression pin that must be used with that batch of cams. The pin goes inside the cam, the lever that goes in the end of the cam is what activates the pin to stick out of the cam when the motor stops. When the motor starts it retracts, deactivates. On the defective cams, the pin is alowed to stick out to far and under load the rocker hits the pin causeing it to bend and stick out all the time and in my case, bent the left exhaust valve. This was some time ago though and I'd think they would have used up that batch by now. Once you have it apart and take the cam gear off the end of the cam, if there is a HHT written on the end of the cam, it should have had a new decompression pin with that cam. I'm pretty sure it has HHT written on it. I'll go through my emails with hotcams and see if I can confirm the HHT.

How loud is the noise? Is it a ticking sound?

 

the hotcam stage one doesnt come with a new decompression pin, you have to use the stock one from your stock cam, maybe this could be your problem, It should be really hard to start but then again maybe easy to start, I remeber reading in an old dirtwheels article about the 770 rap and they never ran a decompression pin and they claimed it started fine. hmmm...

 

heres a picture of the cam the #1 is the decompresion pin cam

 

oops just saw the reply, let us kno wshrdskin

 

Correct. Unless he was unfortunate enough to get one of the possible remaining, bad batch of stage 1 cams and Magic racing was not contacted to include the new, very required pin.

 

It's all good. [img]i/expressions/face-icon-small-smile.gif[/img] Hopefuly Maddog does not have this problem and it will be an easy fix for him.