Sorry for blowing up the forum with all my threads but everybody like pictures right??

So the engine has 5700 miles. Attached are 4 photos. Two are from the RH side of the Exhaust Cam and Journal showing heavy wear, two are from same spot on intake cam/journal.

No radial play and there is more resistance to rotation on EX vs IN

Might just polish the Aluminum and buy a new cam due to loss of bearing material.

Chain too tight? Oil starvation?

 

If the PO tried to take care of cam drive noise by doing the short ucuts it might be from cam chain too tight. One maneuver was putting a screwdriver or the like in the OEM tensioner and giving it a whack to force the plunger forward. The other was to loosen the tensioner body bolts until the ratchet clicked over then tighten them up again. Both an invitation to have no idea how tight the cam drive was and ignoring the fact that the cams run in the head and if the film of oil is broken they get what you see.

Could also be oil starvation, a rider here or at the ADVrider forum had his son run their KLX low and hosed up the head.

I'm on board with your idea, you can't hurt the head much more. If you get it smoothed down enough the whole idea is that there is a layer of oil working there. Maybe someone has tried it.

There is a rider at the ADVrider thread who has done some head repair, but left the job where he had access to the equipment to do it and hasn't gotten anything else to do the work.

 

I used to rebuild old Hondas from the 1970s

This engine was still running but the points lived on the cam and couldnt keep it timed right. All this play was from same issue, the aluminum was worn pretty bad! lol

 

looks like oil starvation to me. common on the KLR. I fixed a few, mostly by replacing the head but it is also possible to hand fit a cam... done a couple of those too. I have smoothed down the roughest spots with sand paper taped to the cam, then lapped fine with compound on the cam. to keep things in line you have to do both journals. then, to bring the clearance back I ran the caps on a surface plate to remove some of the parting surface. that makes the arc of the circle a little out of whack, so then some more lapping on the cam to the cap. repeat until you make the clearances. if you don't have a surface plate use a piece of glass & sandpaper. and BTW, this is easier to do with the valves out. check the shim thickness & see how much room there is to work with (like, is there a small enough shim to make valve clearance when you are done) you may need to tip the valve (grind) to give a decent service life

 

Exactly the route I was thinking. But I didnt think about flat sanding the surface plate. Your method sounds like the best way to save the head/mounting plate. What do you think about the wear pattern on the cam bearing area? Thats the bad side. The other side has about 30% of that wear. The "bad" side is exactly oppose the cam peak which tells me its from the force of driving down the valve(s). Funny its just the right side of the EX cam. My first thought it was from the force from the cam gear on the crank pulling down on the T-chain.

I mic-ed the cam with a NSK mic and the new shinny area on the left side is .9043 The rough area is less but not much. .9042 -- .9041 depending on how you want to interpret the veneer scale. My friend has a lathe and is a dam fine machinist and I had half a mind to polish that area but since its less then factory means there is nothing to remove.

When I snug down the plate now there more resistance to rotation on the EX vs the IN Cams. So no radial play there.

I might just use my super fine lapping compound and use the old cam to make that area round again, polish it smooth and lay in a new cam. Plenty of shims to make resulting clearance good.

Its a bad design on the head also. Look how little bearing area there is vs the bearing area on the same spot on the intake cam.

So if the Cam is shot I think I will spring for a new one and make it fit and rely on high quality clean oil and maybe get the manual tensioner so not to have the auto tensioner add to the problem.

$601 for the head from partzilla ouch!

I love working on my bikes .... but ......



Thanks for your help guys, any more ideas send them my way. PLEASE!!!

 

Set up the cam in a lathe then use some ultrafine grit wet/dry. A pack of 3000/5000/7000 on Amazon is $10. it should take off a tenth or two, no where near a thou. Maybe consider a bit of polishing compound to boot.

I am the tensioner guy and it wouldn't hurt to have one. It is worn right where it would be if the drive was too tight in my opinion,

 

think Mr 678 is right..... I had klr in my head & was not paying attention to where the chain is in the pic. maybe have your machinist friend turn a dummy shaft the size of the cam journal & use that to polish the journals back into submission (.904ish if compound only but smaller for sandpaper). you will want a handle on it too so you can turn it. make it long enough to do both journals at the same time so they will be even and not bind and do something like "When I snug down the plate now there more resistance to rotation on the EX vs the IN Cams". the whole works was line bored in one shot, so changes to the bottom half of the journal on one side affects the other side. the cam cap is probably more important than the bottom part because thats where the load is when the cam comes up on the lobe. I have fitted caps from a different head using the method above. it works, but time consuming. bear in mind you have a couple or 3 thou to work with for clearance. you can get the contour close, then plastigage it and lets say its a thou too loose, measure the bolt flange thickness. subtract 1 thou, and then run a couple figure 8s of the surface plate. check. or screw it, plop down some bucks for another head

 

So I have a new Ex cam coming from partzilla. $177. Bikebandit was $198 and most everyone else was full retail at $248. Spent some time tonight using the old cam with some super fine compound to true up the journal. It looks near perfect. Using minimal compound. Then after cleaning and wetting the contact area with oil I again assembled it, and snugged up the bolts to about half torque. It rotates with the same feeling as the intake cam. Smooth as butta. No radial play can be felt. Going to mic the ID of the journal next. More concerned about achieving the min number right now which I know I wasn't there due to rotating resistance I felt. On every step I could see the contact area getting larger and larger. Going to stop till I get the new cam and I have access to some good mics.

Had a great talk with klx678 today and got a manual tensioner coming.

If I can get my clearance within spec and the journal is flat and smooth, laying a cam in there with a shinny bearing area ..and knowing my T-chain isn't too tight ..... well what could go wrong??? (don't answer that)

 

sounds good & from what you say, it looks like you might get off easy. Plastigage works a treat... quick & easy, but if you have T-gages and a mic and know how to use them then thats good too.... go for it. don't think the new cam will be much different, so you should be able to get a good idea of the clearance with the old cam. give it a check, but obviously, set clearance with the new parts

 

Yea your right about the measurements old vs new. The dull area mic-ed at ..9041 and the shinny area at .9043 on the old cam. It was the dull area that was the part I didn't like. I am an aircraft mechanic and when we see a bearing surface like that we "red tag" it. But I probably should have red tagged the head too! I believe the max clearance can be .15mm (.0059"). But I need to get the min number, don't know that yet. My guess is around .001 ? Need to have something so its floating on oil.

Really jones-ing to ride this bad boy. My last real dirt bike was an 03' YZ 250 2-stroke, sold it 4 years ago. I have about four CT70s (69' thru 71') and one Trail 90 but some how its just not the same.