03' CRF450 too much compression to start?

[Captain Billy]

I have a 05' crf450 that I can start easily, and is well taken care of. A buddy of mine just got all new valves and associated parts for his 03' 450 and the bike is so difficult to start you can't even ride it. I weigh 190 lbs and know how to start a bike I've been riding for years and own my own 450, but this bike is beyond hard to start. All your weight on the kick start will barely budge it.

The bike runs great once you get it going, but if you stall and you're tired, good luck getting it going again.

The decompressor seems to have no effect.

The work was done by a shop, and they are willing to look at it again. They say everything is in spec but the bike is so hard to start I feel something isnt right. Any reccomendations as to what I should ask about when I take the bike in?

[Lead Head]

Decompression clearance is off, or the timing is off a tooth.

[GTXR]

Timing is off one tooth and the decompression setting is off making it hard to start etc. Happens lots if you do some searching. I just answerd this type of problem last week and it was the excact reason for it. Get the shop or yourself to reset the timing and then the decompressor. Everything will be fine after etc.

[Shawn_Mc]

Timing is off one tooth and the decompression setting is off making it hard to start etc. Happens lots if you do some searching. I just answerd this type of problem last week and it was the excact reason for it. Get the shop or yourself to reset the timing and then the decompressor. Everything will be fine after etc.

This is truth.

I run a 13.5:1 piston in mine and it starts as easy as a stocker.

[Captain Billy]

Thanks guys forget that shop, I'm just gonna fix it myself. just needed to know where to start!

[willbilly]

Agent Smith has an excellent way to set the decompressor clearance without math. I dont remember the details but it involves two feeler gauges and is much easier. Do a search on this site for CRFs Only.

[Shawn_Mc]

Check the sticky at the top of the forum to verify the timing.

Then set the decompressor with a feeler in the valve, and then set the decompressor using another feeler. Stacking the feelers up to achieve the "net clearance" doesn't work because of the timing of where the lobes are verses where the feelers are.

Its just more accurate to use a .014" in the decompressor and a .011 or what ever fits the best in the valve.

[Captain Billy]

A friend of mine expressed some concernes about the piston possibly hitting the valves, causing the extreme difficulty in starting.

I do believe you guys nailed the problem, but is this something I should be concerend about? Could it possibly have damaged the bike?

[GTXR]

If it is only out buy one tooth? Then that wont be a concern!! I ran mine for 2 rides before I realized the problem I made when re-assemly etc. If it was out enough for the piston to hit the valves, Its already to late!

[Captain Billy]

Well if it is hitting the piston, it's the shops fault for faulty reassembly. They did guarantee their work, so I guess we will see. This is why why I do all my own motor work!

[Captain Billy]

So, I took the spark plug out to see if the piston would move freely without any compression.

There is still a point where it appears to be a bit tight. I havent checked the timing yet, but I'm curious why its tough without the plug in. I hope its not hitting the valves.

[MELK-MAN]

it isn't gonna whirr over with no resistance like a 2stroke with the plug out. When the cam lobe goes to push the buckets down it will create some resistance due to spring pressure..

[durkot]

leave the spark plug out and put a screw driver in when the piston is near top dead center. My bet is that the cam chain has stretched and even though the timing marks were lined up when it was reassembled it is no longer timed correctly. When the piston is at its highest is where the timing mark on the crankshaft should be lined up with the arrow. You will probably find that the timing mark on the sprocket on the cam is not lined up at this point.

Happened to me and they symptoms were the same.

[Captain Billy]

So with the piston at TDC via the marks, this is what I'm seeing:

And this is not lined up:

So I need to release the cam chain tensioner, unbolt the gear and then adjust it into alignment and replace the chain.

Sounds correct?

[Captain Billy]

So I fixed that, but it's still no easier to kick. So I guess that leaves the decompressor?

[Rocksalt]

Once you reset the timing did you rotate the engine a full turn and re-check the timing? I usually rotate the engine until the marks are aligned on the cam gear and then look at the timing marks on the left hand side cover. If this is good then...

Remove the valve cover and look on the right side of the camshaft. There is an arm that moves with spring tension on it. Lift the arm and see if it is under tension and returns to the inside of a circle. Sometimes the spring will move off the arm and the arm will not return to center.

Then check the pin that the decompressor arm is connected to. It should rotate freely with the arm and have a halfmoon shape to it. It is flat when the decompressor is flung out and rounded when in.

Move the engine to TDC on the comperssion stroke (cam lobes facing rear) and check the gap in between the decompressor arm and the rocker. There should be about .025". The larger the gap the more cranking compression you will have.

You can get an idea if the decompressor is working by slowly cranking the engine slowny with your hand. You will hear a slight "click" noise when the roller falls off the halfmoon.

If you want to crank over the engine to feel for drag do not use the kickstarter. Open the right side case port hole and stick an allen wrench in the bolt hole and crank it with an allenwrench. It is much easier to turn and you can feel any binding at that point. I use a "T" handle allen for the job but you can use a 3/8" socket driver with the correct socket allen.

[mad99horizon]

Had the same exact problem on my 03 after I had my valves done. I went back in and found my valves still a little out of spec. and my decompression setting off a little. Made some adjustments and it made a huge difference.

Best of luck.

[Captain Billy]

Yes after I finished I second guessed myself and checked it again after a few rotations. It was still lined up.

I was also using an allen socket and a driver to rotate the engine, versus the kick starter.

I can kick start the bike now, but only if I slowly push the kick start down until the compression stroke tops out, and then kick it. I have a feeling it has to do with the decompressor for sure, which is tomorrows project.

[GTXR]

Because the cam was out a tooth and the decompressor was set that way! You will need to recheck the valve clearances and then reset the decomp clearances etc. If the valves were set with the cam like that?? Its possible the valve clearances are out as well.

[Captain Billy]

Does this cam chain tensioner look aftermarket to you guys?