lister st2 decoke

[daveanj]

I have just taken the heads off my lister st2 engine to de coke it i got a de coke gasket set but on the engine its self there were no head gaskets fitted all there was on the head its self was a small ring that fits inside the recess on the cylinder head and in the gasket set there are 8 brass rings 2 off what I thought are for the head gasket and 4 what I would call shims ? could any one advise on what to put on and where? im not taking the barrel and piston off and there seems to be no ware what so ever in the bores looking forward to all advice thank you

[steamraiser2]

They are shims. Listers have to have the bumping clearance (the gap between the top of the piston and the cylinder head set) To do this place a little piece of lead on top of the piston, Refit the head and tighten it down. Turn the engine over manually a complete revolution. Take the head off and measure the thickness of the ,now squashed, lead with a micrometer. Check the bumping clearance in the engine manual. Fit a measured number of the shims to make up the difference between the measured lead and the recommended clearance. Fit the required thickness of shims and refit the head. Repeat for both cylinders. Don't assume that any shims already there are correct. Measure it properly.

[daveanj]

thank you for your reply do I need to do that even though I have not disturbed the the cylinder barrel as the engine ran ok before all I have done is grind the valves in is it possible that it would not need any of these shims and that there isn't a head gasket at all and the head fits face to face with the cylinder barrel or would it be better to fit 1 of the shims as a head gasket ? once again thank you for your reply

[Chris Pink]

thank you for your reply do I need to do that even though I have not disturbed the the cylinder barrel as the engine ran ok before all I have done is grind the valves in is it possible that it would not need any of these shims and that there isn't a head gasket at all and the head fits face to face with the cylinder barrel or would it be better to fit 1 of the shims as a head gasket ? once again thank you for your reply

 

One of the rings (the fattest) is the head gasket. It should have one and if the one on there is in good nick you can reuse it. You could anneal it by heating it to cherry red to soften it.

 

eta: you must have a head gasket.

Edited September 23, 2011 by Chris Pink

[daveanj]

OK thank you as i said there was nothing fitted at all only a little ring that was stuck in the recess if its OK I will check my gasket set tomorrow and let you know exactly what is in there thanks Dave

[Chris Pink]

OK thank you as i said there was nothing fitted at all only a little ring that was stuck in the recess if its OK I will check my gasket set tomorrow and let you know exactly what is in there thanks Dave

 

that is the head gasket

[Timleech]

I have just taken the heads off my lister st2 engine to de coke it i got a de coke gasket set but on the engine its self there were no head gaskets fitted all there was on the head its self was a small ring that fits inside the recess on the cylinder head and in the gasket set there are 8 brass rings 2 off what I thought are for the head gasket and 4 what I would call shims ? could any one advise on what to put on and where? im not taking the barrel and piston off and there seems to be no ware what so ever in the bores looking forward to all advice thank you

 

Two thin copper rings, with cutouts for the studs, are joints for the bottoms of the cylinder barrels.

 

Tim

[daveanj]

sorry for not posting this last night ? in the gasket set there are 8 brass thin rings that from your replies I now presume are shims the internal circumference are the same size as the liner on the cylinder barrel there are 2 copper rings that have a larger internal circumference of which are for the base of the barrel that joins to the crank case and there are 2 thick metal rings that are 3 mm thick ish that have the same inner circumference as the 8 brass rings that fit over the top of the liner I presume these are the head gasket but as I said when I took the head off there is a ring that fit in the recess in the cylinder head if i fit the new head gasket will i need to put this back as it is the same thickness as the new head gasket ? sorry i will not be able to reply till 8 o clock tonight as im in Sheffield all day

[Chris Pink]

If the one in head is ok, reuse it, otherwise replace it.

 

Other than that you've got it sussed.

 

If it's purely a decoke and assuming it's running ok the bump test or re-shimming is unnecessary.

 

I notice from my ha2 service manual that decoke intervals are 150 hours, seems a bit extreme.

 

 

Re-reading your post use either the one still in the head or a new one , not both

Edited September 25, 2011 by Chris Pink

[daveanj]

thank you once again for your reply it is a bit confusing the one ii the head fits in to the recess of the head but the one iv have with the set fits over the barrel liner and will fit flush to the head its self so if I don't put the other one back there must be a void where it came from when refitted if you see what I mean

[Timleech]

thank you once again for your reply it is a bit confusing the one ii the head fits in to the recess of the head but the one iv have with the set fits over the barrel liner and will fit flush to the head its self so if I don't put the other one back there must be a void where it came from when refitted if you see what I mean

 

Something doesn't sound right there. The head joint and shims fit inside the head recess (as does the top of the barrel, surely?)

 

Tim

[Chris Pink]

You're confusing me now because I'm referring to an ha2 and my memory of an sr2 but I wouldn't expect the ST to be any different.

 

The stepped recess in the head is the same as the outside diameter of the gasket. The outer diameter of the liner is the inside diameter of the gasket. So the gasket fits there.

 

Try it and see. You should be able to mate the head and barrel with no clearance.

[daveanj]

would it help if i took some photos and measurements as you can emagine i do not want to cock it up cheers Dave

[DeanS]

Yes. Take pics of everything on the engine, and the kit. People will be able to offer you more advice then

[daveanj]

Yes. Take pics of everything on the engine, and the kit. People will be able to offer you more advice then

[daveanj]

just a quick up date after all your advise I eventually took the fuel pump cover of to clean it and also put an oil feed pipe back on and on the cover was a plate that said sr2 ??????????????????? on the air box is a plate with st2 on it I am really really sorry for any confusion I have caused I got in contact with stationary engine parts where I got my decoke gasket set from for an st2 and spoke to a man called who was really helpful and couldn't do enough to help the gasket sets for st and sr are completely different I eventually got the engine back together yesterday and it fired up like a dream i am glad I stripped it because the second head i took of the exhaust port was almost solid with coke there was a hole through that even the thickness of a pencil wouldn't of gone through thank you all for your help and advise I feel such a plonker leading you all down the wrong path to start with SORRY thank you again and all the best Dave

[Taslim]

just a quick up date after all your advise I eventually took the fuel pump cover of to clean it and also put an oil feed pipe back on and on the cover was a plate that said sr2 ??????????????????? on the air box is a plate with st2 on it I am really really sorry for any confusion I have caused I got in contact with stationary engine parts where I got my decoke gasket set from for an st2 and spoke to a man called who was really helpful and couldn't do enough to help the gasket sets for st and sr are completely different I eventually got the engine back together yesterday and it fired up like a dream i am glad I stripped it because the second head i took of the exhaust port was almost solid with coke there was a hole through that even the thickness of a pencil wouldn't of gone through thank you all for your help and advise I feel such a plonker leading you all down the wrong path to start with SORRY thank you again and all the best Dave

 

Hi daveanj

 

If the second head was so badly fouled don't you think you may have an oil leak into that cylinder? Like worn valve guides or (hope not) damaged piston rings/bore.

 

taslim.