29 replies to this topic

[Richard e]

Hello

I've just got my 1985 998cc City back on the road. The engine is original 66k and unmodified aside from hardened valve seats just fitted. Oils seals replaced after sitting idle for 20 years...The engine is running and drives fine. But after a 10 mile run or so the next day the inlet valves are stuck open - 3 at the moment. Oil pressure is fine at 50 psi plus at speed and okay on tick over around 25 psi. Inlet valve stem seals now removed to see if this would fix the problem, but no. So, I am assuming that this is an oil feed problem. Is there likely to be a blockage somewhere? No unusual noises when it is running. I'd really appreciate your thoughts on what could be wrong.

[Maccmike8]

I dont quite understand.

If it runs normal then that would suggest the valves are operating correctly.

What makes you think the valves are stuck open?

[Richard e]

Leave it overnight and the valves are stuck - I assume as I crank the engine they stick as it was running fine the day before

[sonikk4]

How do you know they are stuck, no compression, not starting etc

[Richard e]

Does not start. Have taken rocker cover off and inlet valves springs compressed with 10mm plus play at rocker arm

[Maccmike8]

Oh I see, are the springs broken? Id look at replacing those first and foremost. 

[sonikk4]

I would be taking the valves out now and checking them to see they are straight. Something is not right.

[Richard e]

The springs are not broken and the valve stems are straight - the head has been off a couple of times with this problem. I am trying to identify the cause - If it is oil feed problem yet oil pressure is fine can I have a blockage somewhere and if so is there any thing I can flush through to clear it?

[nicklouse]

There is hardly any oil feed to the head so that will not be the issue.

 

so the problem is to do with the guides binding on the valve stems.

 

looking at what you have said.  It has had new exhaust seats fitted the guides were not changed and the valves are as they were and are in the same position? Having seals fitted or not would not make any difference.

[Tones61]

Prob fitted stainless valves into cast iron guides,they WILL seize,need to be run in bronze guides

[Turbo Phil]

Have you had new guides fitted?

Phil.

[Richard e]

Thanks for the replies. I'll need to check if the valve guides were changed. Getting closer to understanding the problem I suspect. Richard

[nicklouse]

Thanks for the replies. I'll need to check if the valve guides were changed. Getting closer to understanding the problem I suspect. Richard

Ask them to list the work that they did.

 

Not just a simple yes/no question as you will not get the right info.

[weef]

If the valves seize up, and it sounds like it has happened more than once, how do you free them off ?.

[Richard e]

Head off and work valves free. Yes I will ask for full list of work done. Ta