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Please help! 1981 GS450L cam caps binding

  • Thread starter Thread starter osterizer03
  • Start date Start date
If you have the head bolted down, I assume all the valves are installed. So how do you know the cams are locking up? Did you loosen all of the adjuster screws?
 
I tried to torque everything down both with and without the buckets over the valves. When I take the buckets out, there is no change.
 
I give up , does taking the buckets out mean the cam lobes can't hit the top of the valve stem?
 
Yup. The cams are only touching the journals when the buckets are out. As crazy or dumb as it sounds, I think making shims is the only option left....
 
Can you make your YouTube "public". It is currently listed as "private" so we can't see it.

I read somewhere of an OCD engine builder that would set the cams in the saddles before attaching the cam chain and before any valves were installed. He would check to see that they spun nicely before assembling the rest of the motor. In my manual for the GS1150 there is a procedure for using Plastiguage or what we in UK know as Engineers Blue. This will show you where the high and low spots are:

Cam1.jpg


Cam2.jpg


Then, as it says, measure the outside of the cam journal and the inside of the saddles. Is there any difference?

Could also be cam run out (they are slightly bent).

I have never done it but there are threads here about lightly sanding down (you know with the highest grade wet and dry with water) the high spots on any saddles that are binding. You might try the Engineers Blue first and see if there are high and low spots.

Make sure you are using the correct torque settings. Use this converter if you are not sure:

http://www.unitconversion.org/unit_converter/torque.html

Greetings
 
Sorry about that. I've changed the video to public now. I will try the plastigage later tonight to see where I'm at. I've heard of people sanding the caps' base down to decrease the clearance but I need more material.
 
osterizer03 said:
Yup. The cams are only touching the journals when the buckets are out. As crazy or dumb as it sounds, I think making shims is the only option left....
Click to expand...
Sorry to say this but looks like you should do as Earl said a while back .pull the head and send it to a shop. If the cam is binding is it because your head is now warped? If so you will probably just blow a head gasket.

I watched the video, did not realize that was such a small head. Same advice, pull the head and check the flatness of the compression surface. As strange as it may seem, by the way it binds on the last torque settings it looks like that head is warped. Since there are only two caps maybe a line bore will not be that much.
 
Last edited:
OK seen the video now.

I would oil up those bearings before tightening them down. The lubrication is what allows them to spin and they should never be allowed to get dry.

You say you need to "build them up". I don't understand why you need to build them up when they are too tight. Surely you need to sand them down to make the saddles and caps slightly larger?

Edit: I see what you mean now about sanding them down. I'm not talking about the bases, I'm talking about the round parts. Basically, boring them out a little using grit.

Greetings
 
Last edited:
On the twins, there is a point where both valves on the same cam are shut. With buckets removed, offer the cam up at this point and see if you can spin - or at least move the cam. If you can't then, yes, it's pull the head and get it checked out.
 
GregT, yes that's what I tried. Everything gets oiled up and cranked down to the proper 84 in lbs as the book calls for. I just tried this with the plastigage and found that I have absolutely no clearance. The book called out for 0.15mm clearance for the cams and the only readable one was 0.05mm BARELY. The rest just squished out and was not measurable. So now knowing this, Idk if it's the head that's warped because that should effect something that bolted down over a long, continuous plane. I'm bolting it down in only 2 spots and if this plastigage is showing fairly consistent "no clearance" readings, then something else might be causing this. The only thing I can think it might be is that when I used that 3M abrasive rubber bristle to clean up the gasket surface, I must have removed too much material. I tried to be SUPER carefull with it but any touching must be too much touching and now the caps clamp down too far. So it looks like either shims, or a new head and completely rebuild that one :/
 
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Pull the head and strip it - mount up the cam bearing caps and take it to a good engineering shop. They should be able to hone the bearing bores to the correct clearance. They should also be able to tell you if it's still flat on the head gasket face.
 
Are you absolutely positive you have the caps in the right spots? Maybe try tightening the caps with the cams out to see if you can see / feel any mis-matching of the bores. Or swap them around and see if they have clearance in the other positions.

By the way - was the motor running OK before you pulled it down? No chance you could have use caps off another (spare) head?
 
Yeah this was a running motor and all of the caps are in their correct ABCD order. I'm pretty sure my problem is that 3M bristle tool I used. My new (old) head comes in today so I'll go and rebuild that one without that bristle tool. What's the best way to remove old baked on gaskets from motors? I don't want to use a razor because you always seem to scratch or gouge something.
 
My guess is that you are overtightening the caps. Check your torque wrench. The caps don't have to be very tight at all.
 
osterizer03 said:
Yeah this was a running motor and all of the caps are in their correct ABCD order. I'm pretty sure my problem is that 3M bristle tool I used. My new (old) head comes in today so I'll go and rebuild that one without that bristle tool. What's the best way to remove old baked on gaskets from motors? I don't want to use a razor because you always seem to scratch or gouge something.
Click to expand...

I have even filed the valve cover and head surfaces on to get them flat, but I did not do it with the cam caps removed. I guess we don't really know how much material you removed. I would still take it to a shop of find a new head.
 
I dont know much on bike engines. But as a machinist and have built several V8 350's. I would get a set of bore mic's and with the cams removed torque the caps down and get a reading for all 4. Then mic. the cam. see if ya might have the cams backwards or the intake and exhaust cams in the wrong sides.
 
Gun-Nut said:
I dont know much on bike engines. But as a machinist and have built several V8 350's. I would get a set of bore mic's and with the cams removed torque the caps down and get a reading for all 4. Then mic. the cam. see if ya might have the cams backwards or the intake and exhaust cams in the wrong sides.
Click to expand...

I think that is why we keep telling him to take it to somebody that can figure out the issue.
 
I took pictures of each part of the motor while I disassembled it and i know everything is in their correct orientation. This thing is pretty simple not to mix up parts. The problem is I don't want to pay through the nose to have a shop tell me what I already probably know. I don't have enough clearance in between the caps. I just received my new head in the mail and checked the clearances on that one and torqued the caps down. The original head would have a line of no plastic in the middle of the plastic strip which means that there is no clearance between the cams and the caps. Now on this new head, there are all measurable plastigage strips and after I cleaned the plastigage off, and re oiled everything, I put them back together, and the cams spin nice and freely. So I'm now in the process of tearing down this new head and do some mods to a couple fins to fit my exhaust (2 into 1 pipes I made), clean old gaskets off, baking soda blast, lap valves, and re - enamel paint. Hopefully within the next couple weeks I'll have the new head in. I'll keep you guys posted
 
with the head off and the valves removed install one cap at a time till you find the one or more binding then take a ball hone and go to work with the cap torqued until the cam will turn with ease.
this is also done on larger HP engine to free up a little HP.
you didn't remove enough material with the 3M(i use a used red) to cause your problem and a razor won't do any damage either.
i have used both of these my entire life without a problem.
 
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