Rear Cyl compression low.

I'm started to look into my spare engine I have which is supposed to be smokey.

Never had it running to confirm this but I have it on the bench ready to strip down.

I have hand cranked the engine to see whether this is something obvious like crunching souned etc and it looks to be turning over fine.

One thing I have noticed is the front cylinder has loads of compression and the rear doesnt seem to have any, this is by feel as I haven't put a compression tester on it to confirm but it seems obvious.

Is this a 'character' of the SV engine or should I get the rear head open.

[fastdruid]

I bought a s/h engine for spares (for £50 ) with 'low' compression and it had had water ingress into one of the cylinders which had stuck the ring to the piston with rust. Probably could have 'fixed' it with just a hone and a clean, maybe new rings but as it stands its still my 'spares' engine.

Druid

Do you not have a compression tool handy? might aswell just rip it apart, as you are going to have to whatever the cause.

[yorkie_chris]

Check the valve clearances

beabert - its fairly obvious if you cover the inlet and crank the engine the front cyl has loads of pressure the back has none but I will compression test it as a final precaution when I've found the issue with the back cyl.

thanks for the input guys, off to the garage this afters to check the clearances and if not that the head is coming off.

may as well bite the bullet mate, strip the whole thing down and rebuild. No point tinkering when there may well be other underlying issues as well as those known about. Be sad to get valves, bores and rings fixed up to find it has lower end problems?

I must admit the heads I dont have a problem with but I'm wary about pulling the bottom end apart but its sound advice.

Originally Posted by hardhat_harry

I must admit the heads I dont have a problem with but I'm wary about pulling the bottom end apart but its sound advice.

Same, done everything above, but not been in a crankcase yet, a spare engine is a great way opportunity to get stuck in.

Well rear head and block off

Piston looks great.

Bore looks ok

mmmm Im thinking valve issue.

Another question, if I split the cases to get at the crank will the gearbox be a right pain.

[jambo]

If you're doing this to learn about the innards of an engine then fine, if you're pulling apart a block to see what's wrong with it, but not certain what you're looking for then you won't know when you've found it. Cam timing being off (but not leading to valve-piston interface) could have described everything above and required no major intervention.

None the less, enjoy the experience.

Jambo