KTM RFS 450 sx Valve dilemma

[FastCletus552]

I have a 03 KTM RFS 450. I just did a whole new top end. Piston, rings, honed cylinder, valves, and valve guides. I put it back together and did the 1/6 turn out on valve adjustment. I tried to start it and it wouldn't fire. I could smell fuel burning while I was kicking so i know its firing, but i couldn't get it to start. I decided that maybe I was off a tooth of timing so took it back apart and triple checked timing marks and all was correct. So had to be valves clearance. I tightened the head cover and did the valves. Had to take head cover off as I needed to install gasket sealer. did that and put head cover back on and decided to to double check valves. got to TDC and valves were tight. feeler gauge wouldn't fit. Also so tight that I couldn't unscrew them out all the way. I thought maybe I was not at TDC so I put a dowel in spark plug hole and checked. got TDC and checked both rockers are moving so to my knowledge thats confirmed TDC. Valves still tight. When piston is at bottom valves are loose and I can unscrew them out all the way, but back at TDC they are tight. What have I done wrong?

 

[scootergmc]

Doesn't it have a crankshaft locking bolt thingy for when it's at TDC?

 

[FastCletus552]

Yes. Although it’s quite challenging finding it , which is why I was using the process of finding TDC by watching rocker arms move.

 

[usedtobefast]

There are two TDC where the locking bolt will go into the crank.

Normally guys will get it to TDC and see if the rockers both can wiggle (meaning valves closed). But, if you just put everything together maybe there is no wiggle? Like maybe you set the clearance initially on the wrong TDC?

This is considered one of the better RFS valve adjustment videos: https://www.youtube.com/watch?v=hWS9RuEQzc8&t=460s

I would:
- loosen the adjusters a lot
- watch the valves for intake and exhaust and make sure you are on the TDC for power stroke
- use the lock bolt to ensure TDC (I also use the straw thru the spark plug hole but use the bolt lock too)

Once done, unlock, rotate around to the next TDC, valves should be tight, then rotate around to next TDC and valves should be at proper specs, then you should be good to go. (this is just a sanity check)

 

[usedtobefast]

I'm sure you understand everything, but I get confused at times, I actually review something like this each time before starting.

So when intake is closing it is coming up on the correct TDC. If exhaust is closing it is coming up on the wrong TDC

 

[FastCletus552]

I’ve been thinking. I wonder if by chance in removing head cover or reinstalling it that I moved the cam so that it wasn’t set at TDC when I reinstalled head cover. I’ll check tomorrow. To me that would make sense why things seems amiss

 

[DannoXYZ]

Another thing you can do is not use TDC since you have 50/50 chance of finding correct TDC. Spin engine by hand to 2 different rotations and look at cam-lobe and rocker.

Find spot where cam-lobe is aimed 180-degrees opposite and away from rocker for one valve. You know for sure it's at max clearance. Adjust clearance.

Then spin engine again and get other cam-lobe aimed 180-degrees away from other rocker and adjust that one's clearance.

 

[Maddevill]

I agree with above. Sounds to me like you maybe set the valves on the Exhaust stroke.
I have an 04 450EXC and have a horrible time starting it when it's cold. Have checked everything. I'm taking the carb off and sending it up to Dave Hopkins. He's a wizard on these motors.

Mad

 

[kxmike]

I agree with above. Sounds to me like you maybe set the valves on the Exhaust stroke.


Mad

I agree with this assesment. :thumbup

 

[haybaler]

"I thought maybe I was not at TDC so I put a dowel in spark plug hole and checked. got TDC and checked both rockers are moving so to my knowledge thats confirmed TDC"

By now you realized there are two TDC's; you want the one on compression
stroke. Easier to do if one of the side covers off, then turn crankshaft; but even with pulling the rear wheel in 6th gear you should be able to see intake valve open then close, then the next rise to TDC is TDC Compression Stroke. :thumbup

 

[OaklandF4i]

There are two TDC where the locking bolt will go into the crank.

Normally guys will get it to TDC and see if the rockers both can wiggle (meaning valves closed). But, if you just put everything together maybe there is no wiggle? Like maybe you set the clearance initially on the wrong TDC?

This is considered one of the better RFS valve adjustment videos: https://www.youtube.com/watch?v=hWS9RuEQzc8&t=460s

I would:
- loosen the adjusters a lot
- watch the valves for intake and exhaust and make sure you are on the TDC for power stroke
- use the lock bolt to ensure TDC (I also use the straw thru the spark plug hole but use the bolt lock too)

Once done, unlock, rotate around to the next TDC, valves should be tight, then rotate around to next TDC and valves should be at proper specs, then you should be good to go. (this is just a sanity check)

This.... very easy to be adjusting on the wrong stroke.