17 replies to this topic

[yeti21586]

its a 1979 1100 and it started miss firing on the thir cylinder i called the AA out and he discovered that its lost compression in that cyclinder down to 50psi hence the reason its miss firing. he reckons ive burnt out the exhaust valve.
what do you guys think?????

also if it is the valve how will i no and how do i change it??????



cheers in advance

YetI

Edited by yeti21586, 16 February 2009 - 10:17 PM.

[Saxo-Fiesta-Mini]

basically remove the head and see if the exhaust valve is seating properly may just need the set regrinding or a new valve plus engines are ace i love engines lol

[yeti21586]

ok cool

could it be anything else other than the valve>>???

[adcyork]

Could well be the valve yes. Check your tappets, have you adjusted them recentley? They could be holding one of the valves open. Another possibility is the head gasket. Either way you're going to have to have the head off if the tappets are found to be ok.

[yeti21586]

Could well be the valve yes. Check your tappets, have you adjusted them recentley? They could be holding one of the valves open. Another possibility is the head gasket. Either way you're going to have to have the head off if the tappets are found to be ok.

no i havent adjusted anything on the engine but am taking the head off tomoz hopefully so all will be revieled


YetI

[Pauly]

You will probably find the head gaskets gone and the valves are fine, would think a valve not seating properly could cause that much drop in compression.

Paul.

[nathansminis]

could be piston rings.

if you want to determine if it is or isnt a piston ring failure, put a teespoon of oil in the bore thats lost compression. then retest. if the compression comes up in that bore, its rings. if not, valve/headgasket problem.

[yeti21586]

ok me and my dad have taken the head off (it was a female dog because the exhaust didnt want to come off) and this is what we saw







and how do you clean the crud off of the top of pistons???


YetI

[minipac]

looking at your pics. it looks like your head gasket has gone between 1 and 2. head looks fine from what you can tell from a pic.
check to make sure you havent damage the block where the head gasket has gone.

[yeti21586]

looking at your pics. it looks like your head gasket has gone between 1 and 2. head looks fine from what you can tell from a pic.
check to make sure you havent damage the block where the head gasket has gone.

the gasket looks fine but am gunna be replacing it anyway (dad said we might as well as we have the head off)

[Retro_10s]

the gasket looks fine but am gunna be replacing it anyway

NEVER re-use a headgasket unless it's a competition thick copper one specifically made to be re-useable.

That gasket looks like it's gone big style, unless it's just dirty inbetween 1 and 2?

and how do you clean the crud off of the top of pistons???

whatever you do, make as little dust as possible, it has to be done in a very controlled way other wise you'll get allsort of muck on the bores,... potentially wrecking your piston rings when it's put back together and started up.

I find that wetting it with carb cleaner and gently scraping at it works well, I have used wet and dry with 3-1 as a lubricant before with great results.

[Cooper-202S]

Cleaning the top of the Pistons while there in the bores is a tricky one without getting a load of muck down into the rings.
WD40 or PlusGas left in the piston dish for a couple of hours will shift all but the hardest deposits. You can slide a feeler gauge between the bore and the piston if you have a set that comes apart and pick the tightest one. Then you can push the crud towards it and it will stop most of it going down the clearance.

Definity and engine flush and an oil change after anything like that though.

I'm intrigued by your engine though because they look like flat top pistons and that looks like a 12G295/206 head, if so it should be a real barnstormer with the oselli manifold too. Can You enlighten us?

[Saxo-Fiesta-Mini]

to clean the pistons in block theres only one option put the pistons so theyre all half way down and put some redex in each bore

b4 you rebuild the engine clean the majority of the excess and when you start it it will mean all the *melon* will come clear

also works in car remove plugs pore in the redex and then leave overnight then turn the engine over without the coil and cover with a cloth gets all the *melon* out refit the plugs and watch the exhaust spray all the *melon* out the back lovely

Edited by Saxo-Fiesta-Mini, 16 February 2009 - 11:55 PM.

[Sprocket]

Gasket has failed between 1 and 2

[Pauly]

With everyone else and saying the headgaskets gone, even though its not pysicaly perished you can see its been blowing between 1 & 2.

Paul.