Camshaft shims

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Joncal4
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Joined: Sun Apr 18, 2021 5:43 pm

Camshaft shims

Post by Joncal4 »

Hiya new to the forum , I have a firestorm which I'm now rebuilding but have run into a snag ,the problem is I've put two new exhaust valves back into the head after re lapping them the original shims were 195/190 these were too big and i couldn't get the right clearance of 0.28/0.34 so downsized to 160 /165, still couldn't get the right clearance so removed them and bingo got the clearance to 0.28 my question is can this head run without the shims :D
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freeridenick
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Re: Camshaft shims

Post by freeridenick »

Sounds like your valve seats have been cut too many times. That or the valves are wrong. I can't see how you can end up with the right clearance without shims and the heads still good. Something is wrong there.
Joncal4
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Re: Camshaft shims

Post by Joncal4 »

The valve seats haven't been ground before, the bikes got 32000 on the clock, is there a difference between Firestorm and Fire blade exhaust valves, might of been sent the wrong parts? 😀
tony.mon
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Re: Camshaft shims

Post by tony.mon »

Something definitely wrong.
No, you can't run without shims.
Are you shimming the head on the bench or on the bike?

I can't imagine that fireblade valves from an il4 engine would be the same diameter as a Firestorm which has a much larger bore. But it's possible.

Are the spring retaining collets correctly seated? After fitting, take a wooden dowel, place it on the end of the valve and spring assembly, (without the shim or cup fitted) and tap it with a hammer in the direction the valve would normally move. That ensures the valve is seated properly and ready to shim.

Also, when you install the camshaft to measure the clearance, when tightening the camshaft cap bolts, ensure that the camshaft is free to rotate. If you have it slightly off position laterally it is stiff and won't rotate freely. This messes up valve clearance measurement. Slacken off ( if manual) or remove the cct ( if auto) to test for ease of rotation.
Last edited by tony.mon on Mon Apr 19, 2021 9:34 pm, edited 1 time in total.
It's not falling off, it's an upgrade opportunity.
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sirch345
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Re: Camshaft shims

Post by sirch345 »

I agree, most certainly something wrong there.

I'd start with checking the new valve(s) part numbers (unless they are replacement valves from another c/head of course). It looks like this is the exhaust valve part no: 14721-MBB-000,

Chris.
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Joncal4
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Joined: Sun Apr 18, 2021 5:43 pm

Re: Camshaft shims

Post by Joncal4 »

Hiya, does anyone know the torque settings for the camshaft plate, I've tried giving the top of the valve a tap, checked the collets we're sitting properly there's a slight gap, failing that I'll strip it down, only asking as the other side isn't that tight at all
tony.mon
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Re: Camshaft shims

Post by tony.mon »

Joncal4 wrote: Thu Apr 29, 2021 4:55 pm Hiya, does anyone know the torque settings for the camshaft plate, I've tried giving the top of the valve a tap, checked the collets we're sitting properly there's a slight gap, failing that I'll strip it down, only asking as the other side isn't that tight at all
Clarification needed. Where exactly is the slight gap?
If you mean that the camshaft cap casting isn't sitting flat and mating with the head, it could be distorted.
This can happen when the dismantler hasn't loosened the bolts evenly, and has removed three and left the cap with only one bolt in place when the cam lobe is pressing on the valve spring.

To check, remove the cam, take the dowels out of the cap, and lay it in position. It should contact the mating surface evenly.
It's not falling off, it's an upgrade opportunity.
Joncal4
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Joined: Sun Apr 18, 2021 5:43 pm

Re: Camshaft shims

Post by Joncal4 »

It's the gap where the two collets meet at the top of the valve, I take plate off and put a steel rule across it to check for warpage
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freeridenick
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Re: Camshaft shims

Post by freeridenick »

Joncal4 wrote:It's the gap where the two collets meet at the top of the valve, I take plate off and put a steel rule across it to check for warpage
There should be a gap between the two collets, the are not quite half circles. Also a gap between the top of the collet and top of the valve as the groove they sit in is about 3mm down the valve. I don't think you mean that one though. Can you post a picture?
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