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Discussion Starter · #1 · (Edited)
Hi Guys,

I was hoping somebody out there might be able to provide some insight or provide me some advice. I bought a new, but left over 2008 Raptor near the end of last summer. Shortly after purchase, the quad started to seem like it was down on power on the top end... and you could tell the engine sound and exhaust note had changed a bit.

I took it to the dealer and they found it only had 80 pounds of compression. They said they tracked it to a faulty injector that leaked fuel into the cylinder (not just on compression stroke), which in turn washed the rings and carboned up the head/valves real bad.

They put in a new injector, new piston and rings, and did a valve job... all under warranty! It took them about 2 months of back and forth with Yamaha regarding warranty coverage and then to get the parts to do the work, so I didn't get the quad back until February. The weather has been crappy here, so I just got to take the quad out on the first ride yesterday. Only problem is, it is still NOT running right. In fact, it isn't really running that much better than it did before I brought it in.

It seems ok in the lower RPMs, but as it revs it just seems like the motor is struggling. The RPMs build slow in fourth and fifth gear and the motor seems like it is laboring... and this is on straight, flat ground.

I don't know if maybe the coil isn't putting out enough juice? I have already replaced the spark plug. The gas is reasonably fresh. It would be alot easier to get this sorted out if the darn thing just didn't run. I'm going to do a compression test this weekend and try to figure out just where I am at.

Any ideas? I would be greatfull!!! Hell, I'd even like to hear speculation over the cause at this point. I really hate to take it back to the dealership, as they have already bent over backwards for me since I didn't buy it from them. Plus, the 6 months warranty is now LONG gone, so I doubt there is going to be any more help from Yamaha. Could the ECU be causing the injector to be continously spraying/leaking fuel?

Any help or advice would be GREATLY appreciated!

Thanks in advance!
 

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Hi Guys,

I was hoping somebody out there might be able to provide some insight or provide me some advice. I bought a new, but left over 2008 Raptor near the end of last summer. Shortly after purchase, the quad started to seem like it was down on power on the top end... and you could tell the engine sound and exhaust note had changed a bit.

I took it to the dealer and they found it only had 80 pounds of compression. They said they tracked it to a faulty injector that leaked fuel into the cylinder (not just on compression stroke), which in turn washed the rings and carboned up the head/valves real bad.

They put in a new injector, new piston and rings, and did a valve job... all under warranty! It took them about 2 months of back and forth with Yamaha regarding warranty coverage and then to get the parts to do the work, so I didn't get the quad back until February. The weather has been crappy here, so I just got to take the quad out on the first ride yesterday. Only problem is, it is still NOT running right. In fact, it isn't really running that much better than it did before I brought it in.

It seems ok in the lower RPMs, but as it revs it just seems like the motor is struggling. The RPMs build slow in fourth and fifth gear and the motor seems like it is laboring... and this is on straight, flat ground.

I don't know if maybe the coil isn't putting out enough juice? I have already replaced the spark plug. The gas is reasonably fresh. It would be alot easier to get this sorted out if the darn thing just didn't run. I'm going to do a compression test this weekend and try to figure out just where I am at.

Any ideas? I would be greatfull!!! Hell, I'd even like to hear speculation over the cause at this point. I really hate to take it back to the dealership, as they have already bent over backwards for me since I didn't buy it from them. Plus, the 6 months warranty is now LONG gone, so I doubt there is going to be any more help from Yamaha. Could the ECU be causing the injector to be continously spraying/leaking fuel?

Any help or advice would be GREATLY appreciated!

Thanks in advance!
I'm a 660 rider but what does the plug look like? Run the bike hard and shut it off at high RPM then check the plug. Have you checked other things like put the bike on stands and see if the chain or rear axle is turning freely and not binding up -bearings and brake calipers can stick and hang up so check the front also. What about the compression release working properly? It's not missing just not pulling -right? There's also a chance that the cylinder wasn't re-honed or matched to the new piston when they put it back together with new rings. that's my 2 cents
 

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Discussion Starter · #3 ·
The plug was a decent tan color. Now, the compression release has got me thinking... I am going to do a compression check and if it is low, I am going to start there! I believe they honed the cylinder but I will have to check the work order.

Correct, it is NOT missing, but it isn't pulling as hard as it should... and the motor sounds like it is working really hard in the upper RPMs even without a load on it.

Thanks BlueRanger660!

Anyone else have an opinion? I'd like to hear it!
 

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take a look to the plastic container and screen of the fuel pump assy, the color will tell you if it was sitted with bad gas. or borrow a gas tank from a friend,also check grounds.
 
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