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[Brazilla]

Don't worry thack, I have the tools with me to adjust the pushrod before I set off. When I lost compression it neither span nor moved up or down, this was after I parked up and turned engine off. This happened once before,I think it may be getting them settled in as part of the run in. Thanks Presto I'll get them sorted before riding!

[Paul M H]

If this has happened before and it happens again now so soon after you adjusted them last time I would make sure you are adjusting correctly this time and If the push rods tighten up again within a few hundred miles you may have valve seat regression.

[Brazilla]

Sounds scary Paul, let's hope not! There was one time I didn't do one up tight enough and I felt in the engine when it came loose but stopped straight away. I think I am adjusting correctly, there seems to be a biggish spot where it is done up enough to rotate but not move up and down, fingers crossed! Bike has only done 380 miles!

[Brazilla]

Bike this morning started several times and then died before long. A few times it sounded like it fired once or twice then didn't carry on. I am suspecting an issue with the valves now, when I push the kickstart to get compression it doesn't feel particularly strong, if I'm not quite gentle I can feel the air escaping without using the decompressor. I think a compression test may be a good idea? Is there a rough way of telling how good it is without getting a compression dial? I'm going to try hear where the air is escaping from this weekend!

[Thack]

Don't waste your time with a compression test - it won't tell you anything you don't already know, which is that you've a loss of compression somewhere.



If you are absolutely sure the pushrods are correctly adjusted, i.e. they will spin with a slight resistance when the engine is cold, then it's time to whip the head off.

[Thack]

Sorry, forgot to mention that your idea of listening is a good one. If the exhaust valve is leaking you will hear it if you put your ear to the end of the exhaust pipe while moving the engine through the compression stroke. Ditto (but not quite as easy) with the inlet.

[PeteF]

Decomp valves have been know to stick open.

[Norm]

Pull the rocker blocks off and see if compression returns, if it does pushrods are too tight, if not possibly exhaust valve seat has dropped out and not seated itself back have to start checking somewhere

[Brazilla]

There is still some compression but it seems weaker. How strong a resistance should I expect to feel? I had read about about people actually standing on their kick starts. I know the kickstarter only operates for a proportion of its full swing but mine has a click near the top end before it engages the actual mechanism and it's pretty easy to just push through the compression lately. I was going to remove and clean the decomp this evening as well as replace the seals in the carb. I hope I don't have to take the head off! Is fitting the improved valves/pushrods/rockers advisable while I'm in there?
Thanks for advice chaps

[Norm]

Please don't touch the carb, you won't fix low compression messing with the carby you only complicate things,