I am not a very smart motor head so please try to bear with me on this. I bought a 2007 yfz450 bill balance, and have ridden it about 5-7 hours with not a problem at all, with just pristine sound. Me being a cautious person, i decide to get a full tune up with every quad i purchase, only after i have gotten a little riding time. so i get it back a week later, to find out the cam has problems.

After we talk for a while, he explains to me that the intake cam has siezed up when it is tightened down to specs. I didn't crack into the motor when i bought it but it was running like a champ and experienced no symptoms. the intake cams bolts were tightened corectly in the front, and as you go back on the bolts, the next set is about 1/16" gap, and the last set is about 1/8" gap.

After thinking about it, i thought to myself, wouldnt i hear symptoms, or feel something off about the quad. i am not new to quad's but am not a mechanic either. i was quoted about $2300 for the head, cam shafts, valves, and labor included. i'm trying to figure out if this could have been done as accident during the checkup and service, or i could have bought a crap quad. they say it was done prior to the check up and tried convincing me that the previous owner had most likely ran it without oil, it siezed, then he untightened it until it would work then filled her up with oil and sold her off to my lucky self.

I talked around to some of my friends that know a vast amount more than i do about engines and assured me that if the bolts were backed off that much and were "finger tight" as the shop said, i would experience symptoms like knocking, pinging, chatter, or any metal on metal noise, and that the bolts after not a long time would come off by them selves all together. So i turn to you, to get an unbiased informative opinion about what really could be happening. i hope to hear back soon and will be checking back regularly.
Thankyou,
Ryan

 

I don't know. I find it hard to believe if it was seized up you could get 5 hours on it with no issues, loose caps or not. You need to go buy a service manual and look at that cam yourself!! It is really pretty easy, and the gasket for the top half of the head is reusable. If the cam seized it should have scoring on it and the head as well.

BTW, Yamaha still sells a cnc ported complete head ready to install for $2245.95 on the website. It is listed as for the 450R/X models, but I am 90% positive it fits the 05-09 450 as well. Dig around on a few YFZ sites to find out for sure.

Yamaha YFZ450R Accessories, Yamaha YFZ450R GYTRŽ Ported Cylinder Head Assembly

 

Thank you for your reply, there was a little bit of damage on the housing of the cam, but besides that, it is fine. i am going to look around town to get opinions of other certified bike mechanics besides the shop's. The place that did this was not my regular place. The cost isn't a big issue to my dilemma, but mostly whether i need to take action against a shady mechanic group, or to own up and say i bought a bad quad. Thank you, and i hope to hear from you, and others soon

EDIT: I just wanted to mention that, when torqued to spec, it's seized up, but apparently, under the condition i took it in as, was the only way it could have ran, which i find hard to believe that i wouldnt have symptoms