13 Pro, top end bog after rebuild???

[Brappinthrottle]

looking for some insight here.

I have a 2013 Pro with about 1700 miles on it. This summer, I put in a mtntk fix kit, just as preventative maintenance, nothing wrong with the motor just felt it was time to refresh the top end.

This was my first rebuild on a Pro... I have pulled apart a bunch of 4 stroke and 2 stroke top ends in dirt bikes, did not find the install to be hard at all. Everything inside was to spec, cylinders looked great, same with pistons I pulled out.

What I am experiencing is top end bog. The sled fires up great (1 pull), pulls clean and hard to about 7k rpms, then just falls on its face. Ride #1 off the rebuild the wife rode it, no complaints from her but she doesn't ride super hard, put about 25 miles on.

Ride #2 I rode it yesterday, and its like clockwork, when you get above 7k it just falls off, almost like its running out of fuel. drop the throttle, blip it a few times, and it screams up to 7k rpms no prob, then falls off again. It just can't hold power in the powder above 7k. On the trail the thing rips, however i don't really hold it above 7k rpms for a long time on the trail.

Anyone have any insight on what it might be?

 

[nighthawk285]

Deleted: wrong thread

 

[tinkerjohnson]

Bog

I would look at the power valves, sounds like they are not opening, check all your connections and check your gaskets and make sure they are sealing good especially around the small hole in the cylinder to the power valve. Also make sure the bellows are good. I'm pretty sure thats where your problem is

 

[Brappinthrottle]

I ran through the power valves last night, everything seems likes its in working order. anything else to check?

Took it for a spin today, same story, runs crisp at low throttle but anything above 6800-7k rpms falls on its face.

 

[xc6rider]

Compression checked yet??

 

[rambino]

I'm actually experiencing the same thing as you. I just replaced my top end as well with a friend. When we put the injectors back in we must have pinched the o-ring on the injector. So when breaking in the top end it was fine but then must have snapped. It felt like power valves weren't opening but when I looked i could see a ripped dangling o ring. I'm fixing it tomorrow and will let you know how it works out...

 

[Jeffdutch123]

Did you use proper torque on the det sensor? Also are you sure the orings on the fuel injectors are there and intact? Possibly a lean bog from base gasket leak? Are you sure you installed a base gasket on both sides of the spacer? Power valves?

 

[rambino]

So I just got done fixing my sled. I thought it was the o ring on the injectors. Which I fixed, but that wasn't the problem. I actually had a hole in my power valve bellow. I really would check that because your experiencing exactly what I was. Let me know what it was I'm curious if it's the same as me. Fixed that and it's running like a raped ape again...