Benford TR1 Cylinder head shims/gasket

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adg
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Benford TR1 Cylinder head shims/gasket

Post #1 by adg » Mon Oct 26, 2015 5:56 pm

The dumper has been emitting a fair amount of exhaust smoke from around the cowling, so I've decided to investigate..

I've lifted the head and found three shims but it appears not to have a copper gasket on the top end of the engine, is this correct?

The new (genuine) head set has a set of shims of varying thickness and a copper washer that is slightly bigger than the shims , also bigger than the head recess.

Does the supplied copper gasket seal the other end of the barrel or am I missing the correct part? Should I simply clean the head/barrel, lightly grease the shims and replace to the recommended 0.035-0.038in piston to head gap?

Thanks in advance.

Cheers

Alistair

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FOWLER MAN
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Re: Benford TR1 Cylinder head shims/gasket

Post #2 by FOWLER MAN » Mon Oct 26, 2015 8:34 pm

Hi Alistair,
Yes, The Lister uses the steel shims under the head and the copper joint under the cylinder.
If you are using the original pot and piston you should be OK to just use the same size shims as you took out.

To set the bump clearance you would need to place a short length of soft solder or lead wire on the piston crown. stick it on with a dab of grease above the gugeon pin. Fit the head and turn the engine over then remove the head again, mike up the thickness of the wire and add shims to obtain the correct clearance.

It is sometimes necessary to grind the pot and head together with valve grinding paste if the sealing surfaces are pitted.
Good luck
Fred


Topic author
adg
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Re: Benford TR1 Cylinder head shims/gasket

Post #3 by adg » Mon Oct 26, 2015 9:12 pm

Thanks for this Fred,

Two of the three thin shims show signs of distress (distortion and partial splits) despite lifting cleanly when removing the head. Given this, I'll clean and reset the bump clearance with the new shims. The head and barrel surfaces don't look too bad, but I may lap them in for good measure, given how much gas was escaping. I won't get a chance to have a play for a few days but I'll report back progress as it happens.

Cheers

Alistair


Topic author
adg
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Re: Benford TR1 Cylinder head shims/gasket

Post #4 by adg » Thu Oct 29, 2015 10:13 pm

I had an hour to spare after work this evening so lapped the head to clean up and help ensure flat surfaces:

Starting with:

Image
Image

After 20 minutes and several lapping/cleaning sessions of different grit paste:

Image
Image

Looking a fair bit better, will repeat the process tomorrow night and check the valve seal over night before cleaning and reassembly.

Looking closely at the head, there are some pits in the combustion surface, is this normal or due to carbon or even poor filtration? I can't account for the little half moon shape in the shim area of the head, there's also an imprint on the shims. I expect it was from reassembly deposits during a previous owners service.

Al


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