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Top end tear down for an Idiot


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I have a 2009 KLX 450r that was in need of valves. I am waiting on some stainless valves and springs from Kibblewhite. In the meantime, I was tearing into the bike to prepare for the valves and a new piston.

I have installed cams on a few cars, but that is as far as I have ever dug into a motor. This is my first dirt bike adventure, so I may just have to total the bike and start walking through the woods.

I have run into a couple things that I would like some input with.

1. The exhaust cam looks a bit worn on one lobe. (picture to follow shortly)

2. I dropped a heavy wrench onto the head and caused this.....I hope it can be fixed. I feel incredibly stupid and defeated on this one. (pic to follow)

I assume a machine shop could do something with this. Is this the type of thing that I can very carefully smooth somehow? I feel the material intruding into the smooth area where the cam makes contact, so it needs some sort of attention.

I am sure I will have more questions up untill I run out of money. Then I will just push my bike around the yard without a motor when I need a fix.20141117_164621.jpg20141117_164621.jpg20141117_164545.jpg20141117_163024.jpg20141117_162957.jpg

Edited by AODRN
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Ive had some input saying I can prolly smooth the cam journal nick.

As far as the cam itself. There are no marks anywhere else on the cam or on the other cam. The wear on the side of the lobe is very strange in my mind. Almost like it was out of round from the start and it ground smooth over time.

I could use some input from somebody smarter than me....this means you.

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Based on the pics I believe your goof up can be fixed fairly easily.  I suggest you have a qualified machinist take a look at it and guide you through it.  You can goof it up worse in just a few strokes of a file if you are not careful.

 

Cams do get discolored, usually not an issue.  Based on the info given I would put a dial indicator on it to verify it's shape and wear.

 

Are you getting the seats cut?

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I am waiting for my new valves to arrive. I was using a youtube video for reference. They suggested marking the valves to check contact with the seat. If the contact wasnt right, I was going to get the seats redone.

 

I suggest you have an experienced machinist look at the old valves and current seats.  I also suggest you have the seats cut.

 

Think of it as replacing brake pads on your truck and not turning the rotors.  Yea it can be done but the brakes don't work quite as well.  The valve situation is different but that is the best visual I can come up with right now.

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  • 4 weeks later...

I have an update with a new question. I took my head to the machine shop and got the seats cut. I assembled the head and I am adjusting valve clearance right now. Since I am running brand new valves, I was shooting for the top end of the spectrum on clearance. Intake spec is 0.1-0.15 and exhaust is 0.20-0.25. I was able to swap around shims and get within range with two valves. One exhaust valve needs a shim size I will have to buy. One intake currently specs out at .18 instead of .15. I need to buy a shim anyway, but I heard new valves stretch a lot right up front. Should I change to the correct shim or go with the slightly too large clearance?

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To answer your question directly, you are fine with the intake spec. valve lash of .18mm.  Go with the slightly too large clearance.

 

There are a lot of reasons to run specific valve lash distances.  A couple of the main reasons; you need to allow for expansion of the metal due to temperature changes and to keep the desired profile of the cam.  

 

Adjusting valve lash can be used as a tuning tool, but I suggest leaving that to the elite level racers as it will only gain very minimal performance and character changes.

 

In the general terms, valves don't stretch.  Much like drive chains don't stretch either, they wear, and when they wear they get longer.  When a valve wears, (more specifically the seat and face) the stem gets closer to the cam.  When this happens you need to decrease the shim size to make the valve lash larger.

As long as the seats are cut properly and you use new valves with the correct angle and contact surface you should not see a significant change in the lash (or mating surface of the seat and face) in the first 10 to 15 hours of run time of a non race machine, and most likely on a non race machine you will not see a major change in the first 50 to 75 hours.

 

With all that being typed, I suggest you never go below the recommended lash but, you can go as much as 2 to 3 thousandths (.05 to .08 millimeters) greater on the lash and you and your engine, for all intended purposes will never know the difference.  Other than the fact it will take longer for the next valve adjustment to be needed.

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  • 3 weeks later...

AODRN;

 

I would also suggest you take a look at the oil sump pump screen (behind the flywheel near your left foot) .  That discoloratiion might be due to clogged screen and limited oil to your top-end?  Fairly quick/easy to check now ... very expensive if you find out was a problem later!

 

Cheers!

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