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Compression?

General Tech Talk

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Compression?

Post by mudmacaca »

Have a strait six (2f) dual fuel and have no compression between cylinders 1 and 2. I think it is the head gasket. What else could it be and how should I test for them?

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Post by DamTriton »

Given that it is between the cylinders the head gasket is the No 1 bet.

If it was limited to one cyl down on compression then you could be looking at valves or a piston/ring
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Post by mudmacaca »

Thats what I thought but do you know of any way to check/test for compression rings or valves?

And do I need a special head gasket for gas?

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Post by sudso »

No special gasket but quality valves help as gas burns hotter than petrol and valves get burnt.

Get your piston to top dead centre on compression stroke and squirt air from a compressor through the plug hole but make sure the fitting is the same thread as your sparkplug.
If air comes out the exhaust it's probably an exhaust valve, if it comes out the air intake/carby its probably an intake valve.
If compression is down on two neighbouring cylinders its probably the head gasket as was said.
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Post by mudmacaca »

Took the head off today and it was the gasket between the cylinders. :D

Should I get the head machined or not?
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Post by DamTriton »

mudmacaca wrote:Took the head off today and it was the gasket between the cylinders. :D

Should I get the head machined or not?
Just get a straight edge and make sure the mating surfaces are flat. If they are then you've come out of it pretty cleanly and cheaply.

While you have the heads off it may be worthwhile getting new valve guides and seats pressed in, a valve grind (given that it is dual fuel it will probably need it anyway), and a general clean up of carbon deposits on the piston tops, etc. Saves pulling it down for another couple of hundred thousand km.
George Carlin, an American Comedian said; "Think of how stupid the average person is, and realise that half of them are stupider than that".
Posts: 412
Joined: Mon Jul 10, 2006 10:53 pm
Location: 36 28'56 S 150 04'11 E

Post by mudmacaca »

DAMIKA the head is only 5 years old and I cleaned of the deposits last night with a cordless and a brass wire brush attachment the valves seem to be stainless. Oh and I am a tight arse dont want to spend the cash on a reco its about 380 but if they can do it today I will get it machined for 80 to 100

Of to the machine shop know then back to clean the block :armsup: and back on with its head :armsup: :armsup:
If you dont have panel damage you ain't trying hard enough
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