Bobcat 743 Head Gasket Shim

warrenoliver · May 15, 2017

I am replacing the head gasket on my 743 with the Kubota v1702 engine. The parts manual shows both a shim and a head gasket. When I talked to the Bobcat dealer, they seemed unsure whether or not the shim is needed. The old head gasket may have a shim that is now smashed into the head gasket although I am not sure if it is a metal backed gasket or if in fact it is/was actually 2 different parts. Anyone know for sure if it needs both? Is the shim reusable? Bobcat wants $100+ for the gasket but I can get online for around $50. Any reason for me to pay Bobcat the extra $50+ dollars?

Tazza · May 15, 2017

I'd highly doubt there is a shim. They shim the gasket only when the block has been machined a few times. It is to ensure the piston to head height is correct.
To do it correctly, a machine shop will install the pistons, measure the piston to head height, then skim the top of the piston to get the correct clearance.
I see no reason why the cheaper gasket won't work.
Be aware, gaskets rarely fail, if there were issues, it could be the head. If it's off already, you may want to get it checked for cracks before putting it back on, or you will be pulling it again.
They generally crack between valves or around the pre-combustion chambers.

warrenoliver · May 15, 2017

Tazza said:
I'd highly doubt there is a shim. They shim the gasket only when the block has been machined a few times. It is to ensure the piston to head height is correct.
To do it correctly, a machine shop will install the pistons, measure the piston to head height, then skim the top of the piston to get the correct clearance.
I see no reason why the cheaper gasket won't work.
Be aware, gaskets rarely fail, if there were issues, it could be the head. If it's off already, you may want to get it checked for cracks before putting it back on, or you will be pulling it again.
They generally crack between valves or around the pre-combustion chambers.

Thanks for the quick reply Tazza. I agree, the shim doesn't seem to be needed unless the head is machined. I checked the old one very carefully and there is not a shim, just a little metal reinforcement around the cylinders. I just got a call from the machine shop. They tell me the head is junk. It apparently has a crack that can't be repaired so they are trying to source an aftermarket head. Thanks again.

Tazza · May 23, 2017

warrenoliver said:
Thanks for the quick reply Tazza. I agree, the shim doesn't seem to be needed unless the head is machined. I checked the old one very carefully and there is not a shim, just a little metal reinforcement around the cylinders. I just got a call from the machine shop. They tell me the head is junk. It apparently has a crack that can't be repaired so they are trying to source an aftermarket head. Thanks again.

Check ebay, they have aftermarket heads available at pretty decent prices.

dfjohn · Jan 25, 2024

On this same subject, I recently purchased a 743 with the engine out of it with a cracked head. I purchased it from a estate, the head had already been removed, and with the motor, in parts, there where 2 head gaskets, does a shim look the same as a head gasket, or is there a physical difference in the two? Not sure weather I have 2 head gaskets or a shim and a head gasket. thank you Don

laurencen · Jan 25, 2024

I have never seen a shim and worked on 3 743s, heads can be found on Ebay cheap either as plain heads and you switch your parts over such as valves ect or as complete, we have always used plain heads way cheaper

Tazza · Jan 27, 2024

There should be no shim, it should just be a composite head gasket. If top clearance needs to be adjusted, you remove material off the block surface or the pistons to get it right.

If you have two head gaskets, do you have one metal and one composite?

We rebuild multiple V1702 engines every week.

dfjohn · Jan 27, 2024

Tazza, No the gaskets are identical, I assume both are normal head gaskets. What are the specs for top clearance ? Thanks for your help.......

North Idaho Wolfman · Jan 28, 2024

Shims are included with alot of kits.
They are used if you need to take material off of the top of the block.
The shim does not look like a head gasket.
If you have 2 head gaskets someone messed up.
You will need to check clearances on the pistons.
It's in the service manual what the clearances should be.

dfjohn · Jan 28, 2024

North Idaho Wolfman said:
Shims are included with alot of kits.
They are used if you need to take material off of the top of the block.
The shim does not look like a head gasket.
If you have 2 head gaskets someone messed up.
You will need to check clearances on the pistons.
It's in the service manual what the clearances should be.

Thank you for the help,

North Idaho Wolfman · Jan 28, 2024

dfjohn said:
Thank you for the help,

Do you have the service manual?

dfjohn · Jan 28, 2024

yes , I do now, thanks again...

Bobcat 743 Head Gasket Shim

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