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cam markings on cam and cover

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After chasing down a starting problem as discussed in this thread:

http://www.thumpertalk.com/forum/showthread.php?t=477686

I decided to check the valve clearances. The intake valves are slightly out of spec and have ordered new shims. The exhaust cam has me a bit more worried

1. Right bucket, unable to slide up and off. It spins freely, but seems to be stuck once it reaches cam seat(not sure if proper term?) I am using a strong magnet to carefully pull each one up to check pad #s, but this one will not come off.

2. The cam itself has some noticable wear marks on it and the cam cover itself. See pictures below

dsc01861bq1.jpg

You can see wear marks in between the lobes on the shaft part. With my thumb, unable to feel any noticable groove or ridges.

dsc01866tc1.jpg

You can see the black marks on the cam cover on the right side. I include intake cam cover for comparison and there is a noticable difference.

When I seat the cam into the cam cover on the work bench firmly, the intake cam spins nice and freely, even when I apply pressure to the shaft. When I seat the exhaust cam into the exhaust cam cover, it spins, but with a feel that something is rubbing. Without a micrometer measuring tool, cannot check the specs, but obviously something is not right here.

Yes, I can get a new cam, but what about potential damage done to the exhaust cam cover and the actual seat in the valve head itself? There are no noticable wear marks on the head itself like you see on the cam and cover.

I was going to take off the entire valve head to check valve side and inspect piston wall and piston, but am unable to get the 2 bolts on left side of bike (inside cam assembly) to move at all. The 2 right (exhaust side) bolts came off as well as the 2 nuts on the outside left side down by the clutch cable. I stopped in fear of damaging something.

Any ideas or opinions here? Run Yamalube and change frequently, 3-4 long trail rides and after long races (3 hr plus.)

So, replace parts, ideas???

mx813

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After chasing down a starting problem as discussed in this thread:

http://www.thumpertalk.com/forum/showthread.php?t=477686

I decided to check the valve clearances. The intake valves are slightly out of spec and have ordered new shims. The exhaust cam has me a bit more worried

1. Right bucket, unable to slide up and off. It spins freely, but seems to be stuck once it reaches cam seat(not sure if proper term?) I am using a strong magnet to carefully pull each one up to check pad #s, but this one will not come off.

2. The cam itself has some noticable wear marks on it and the cam cover itself. See pictures below

dsc01861bq1.jpg

You can see wear marks in between the lobes on the shaft part. With my thumb, unable to feel any noticable groove or ridges.

dsc01866tc1.jpg

You can see the black marks on the cam cover on the right side. I include intake cam cover for comparison and there is a noticable difference.

When I seat the cam into the cam cover on the work bench firmly, the intake cam spins nice and freely, even when I apply pressure to the shaft. When I seat the exhaust cam into the exhaust cam cover, it spins, but with a feel that something is rubbing. Without a micrometer measuring tool, cannot check the specs, but obviously something is not right here.

Yes, I can get a new cam, but what about potential damage done to the exhaust cam cover and the actual seat in the valve head itself? There are no noticable wear marks on the head itself like you see on the cam and cover.

I was going to take off the entire valve head to check valve side and inspect piston wall and piston, but am unable to get the 2 bolts on left side of bike (inside cam assembly) to move at all. The 2 right (exhaust side) bolts came off as well as the 2 nuts on the outside left side down by the clutch cable. I stopped in fear of damaging something.

Any ideas or opinions here? Run Yamalube and change frequently, 3-4 long trail rides and after long races (3 hr plus.)

So, replace parts, ideas???

mx813

It kinda looks to me like maybe the exhaust cam cap was overtightened a little, and the hole where the cam goes thru isn't round anymore. It has a tendency to mess up the head too, and it kinda sounds like that 'cause you can't get the bucket off the one exhaust valve. I've rebuilt motors where the cam caps have been overtightened before. I use a big set of needlenose pliers to pull the buckets off. If you can't get it off with the needlenose, then more drastic measures need to be taken.

When the cam cap gets tightened too much it actually crushes the cam cap, and the head where the parting line is. This pushes the cam into the head a ittle further than it's supposed to be. This rounds over the edge of the metal where the buckets go into. So I use a very sharp exacto knife and I carefully cut the metal away until I can remove the bucket. Then take a very fine curved file, or a rattail is even better and radius the edges where the buckets go through.

Unfortunately, once the cam cap is overtorqued, the head needs to be sent out & align bored/honed. Or you could always replace the head, but that's expensive. Getting it repaired I believe costs like $150.00.

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Thanks Butch for the input. Guess I need to invest in a torque wrench to get things right next time I check specs and what not.

A friend suggested the same thing along with perhaps a floating valve due to overtighting the cam cap and restrict oil flow. I'd like to pull the whole assembly off but am at a loss on how to get the 2 bolts out on L side of head that are buried under the cams themselves. Everthing is disassembled so I have access to the 2 bolts, but I am unable to budge them.

If push comes to shove, I guess I could button things back up and have a mechanic examine it.

On a side note, going to OEM store in thumpertalk, it showed the entire head being $360? Is this for everything or just the head and I need to purchase all the seats, valves, etc... and install?

mx813

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360 has got to be for a bare head.
That's what I thought...but doesn't hurt to hope!

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So at this point in time, would it be worth to install after-market cams while I take my valve head to get fixed? I would have them in hand to give to the mechanic to install so that would ensure everything is all good.

So HotCams? Anything else?

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So, do you think my existing cam is salvagble? Or go upgrade?

So right now, new springs and chain? Along with some resurfacing. Since the head will be off, thinking new piston, etc.

mx813

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So, do you think my existing cam is salvagble? Or go upgrade?

So right now, new springs and chain? Along with some resurfacing. Since the head will be off, thinking new piston, etc.

mx813

I don't think I'd put that cam back in there. Hotcams makes some good stuff.

Definitely new springs (way cheap) & valve stem seals. You can never have a new enough cam chain in there (unless you JUST changed it). When you pull the valves out, if they are worn, replace them too. It's expensive, but worth it if they're showing wear. I just re-read your first post, and if you had to shim once, it's time for them to be replaced before they do any damage, especially while the head is already off, and the valves will be out.

While it's apart, a high compression piston, stage 2 hotcams, new valves, seals & springs. You'll almost have a new bike. And it'll run way better than before to boot!!! ( I love spending someone elses money!!! JK!!) :applause:

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Thanks Butch,

The only problem with hi compression piston is you have to run a higher octane gas right? That is something I'd like to avoid if all possible.

Grayracer said the following

The exhaust cam has seized in the head, which can occur for a couple of reasons (low clearance, foreign material in the oil, lack of oil, overheat, etc. Improper torque on reassembly in a frequent cause, IMO.

The cure for it is to remove the head and send it to someone who can restore the camshaft bores. EDCo is good at this.

The one exhaust tappet is hard to remove because the lifter bore intersects the cam bore, and the smearing type damage to the cam bore has burred the top of the lifter bore. He will need to chamfer the top edge of the lifter bore where it meets the cam bore with a knife blade or a triangle file to break that burring back some. Then grab the top of the lifter with a pair of large needle nose or other suitable pliers.

There are a couple mechanics in the NW that do this so I will give them a shout Monday to see what they say.

I have also been thinking about doing an over-bore, to a 276 Icecube so I will call them as well to see what additional work they do. Spendy, yes, but when said and done, pretty new engine, more power, etc. But the alternative is way cheaper than a new bike, especially outfitting for off-road racing.

Right now, I buttoned everything back up to keep things from getting lost. Did notice when turning crank over with socket that there is a tight spot, when exhaust cam lobes start compressing those valves. This was noticable when I first started checking clearances.

Boy, things are adding up in a hurry!

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Thanks Butch,

The only problem with hi compression piston is you have to run a higher octane gas right? That is something I'd like to avoid if all possible.

Grayracer said the following

There are a couple mechanics in the NW that do this so I will give them a shout Monday to see what they say.

I have also been thinking about doing an over-bore, to a 276 Icecube so I will call them as well to see what additional work they do. Spendy, yes, but when said and done, pretty new engine, more power, etc. But the alternative is way cheaper than a new bike, especially outfitting for off-road racing.

Right now, I buttoned everything back up to keep things from getting lost. Did notice when turning crank over with socket that there is a tight spot, when exhaust cam lobes start compressing those valves. This was noticable when I first started checking clearances.

Boy, things are adding up in a hurry!

If you go with the Wiseco +.75 piston, you go from 12.5 to 13.25 CR. You will definitely need to run premuim in your bike then, but shouldn't need race gas.

Any more than the +.75 and running race gas would be necessary.

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Looking at that head, the bare minimum you should do to it is get the cam journals re-cut, get some new cams Hotcam, webcamshafts , or whatever you choose. Get new cam caps, new valvesprings (stock if getting hotcams)(Procircuit if you get something more crazy like a webcam), new valve seals, and new valves. I just had my head apart and I had to replace my valves, they only had 1 shimming done on them, but you could see the coating on the titanium worn off meaning they were going to start going downhill really fast with the new cam setup. Get a machine shop to measure the valve seats, if they are deformed get them re-cut before installing valves. Your looking at a expensive project, but it all needs to be done at the same time. You can get a higher compression piston if you really want to, , you will need a higher compression piston if you go with cams designed to aid in top end power such as the Stage 2 hotcam, or high rpm cut webcam.

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