2007 YZ450F will not start. Tried everything

[F-150]

Hey guys! I have a 2007 YZ450F and it will not start no matter what I do. I have kicked it so many times a blew a hole in my shoe. I have also tried to bump start it. I am really done with this bike, so any help would be really appreciated. Here is a list of what I have done:

Checked for spark

Put new spark in and adjusted the gap 

Set timing 

Cleaned carb twice 

Installed carb rebuild and set float height 

Changed oil - not sure if that is effective though 

Adjusted valve height 

 

You guys have any tips for what I should do next?

I would really appreciate any help! Thanks!

[William1]

How was it running just before it stopped running? What led up to this?

[BPPerformance]

You checked timing how? asking because if the key was to get sheared on the flywheel it can create timing off by just a bit or a whole lot. Pull flywheel and take a look its easier than kicking ....

[F-150]

I bought it used and not running @William1. 

I did check to see if my fly wheel key was sheared and it wasn't. It would make a lot of sense if it was though @BPPerformance.

[BPPerformance]

do you get any pop? have you looked into the exhaust pipe for mouse nests?

[William1]

Spark plug come out fuel wetted?

[F-150]

Yes. I have the exhaust pipe off, so the pipe comes out about as far as the kick starter. It backfires, and I get blue fire shooting out of it. 

Yes spark plug comes out kind of wet, but not too wet. 

I am getting fuel into the cylinder because you can see it shooting out of the accelerator pump in the carb. 

[William1]

You do know the starting procedure?

Petcock on

Choke on

NO throttle

press kicker until compression is felt, let kicker come back up and a firm press down - NO thottle

 

On carb 'rebuild', slide release plate, is in., square side down? about 3/32 slide raised preliminary idle speed setting? Fuel screw at 1.75 turns from closed?

[F-150]

Yes to all of your question. @William1

[F-150]

Also when I set the timing, I made sure there were 12 cam chain pins between the top dot on the intake and exhaust cams. Is that correct?

[William1]

17 minutes ago, F-150 said:

Also when I set the timing, I made sure there were 12 cam chain pins between the top dot on the intake and exhaust cams. Is that correct?

I do not have a service manual for your bike. IIRC, you set the flywheel so the cam timing mark is in the hole then align the dots on the cam gears with the flat surface of the top of the head. As the cam chain gets older, the dots will be higher off of the surface. The check must be done with tension on the cam chain (A finger pressing in the tensioner hole works fine)

[F-150]

Ok thank you @William1. I have done that and set everything right. It still will not start. Do you have any other thoughts? I am really at a loss of what to do. 

[William1]

3 minutes ago, F-150 said:

Ok thank you @William1. I have done that and set everything right. It still will not start. Do you have any other thoughts? I am really at a loss of what to do. 

You have spark, you have compression, you have fuel. The only thing that can prevent an engine from running is when these events occur. You are positive you have the cam timing correct and that the cams did not move in the sprockets (looks right compared to images in the manual). Did you check the crank position sensor?

[F-150]

Yes I have all of those. I have no idea what the crank position sensor is. What is it, and where do I find it?

[F-150]

I am going to have some time to work on it today. Does anyone know what I should check while I’m working? 

[cowboyona426]

You mentioned you cleaned the carb, did you by chance remove the carb slide?

[F-150]

By carb slide, do you mean the throttle slide? @cowboyona426

[cowboyona426]

Yes.

[shredmasterz]

I believe he was going to say that it is possible to install the slide backwards and that can cause your problem.

[F-150]

Ok yeah the carb slide is def in right. 

I took the bike into the shop and had them run a leak down test, and I was told the exhaust valves have a 90% leak. Thats def my problem, but what do I do to fix it. Did I blow a valve? What do I check first? Anyone done this before?