I do appreciate the responses but it seems that many did not read carefully my stated problem ! The rocker box is NOT fitted, hence any issues with rockers or the valve lifter mechanism interfering with the valves are obviated.
It must be a failure of the seal between the barrel and the head. I take the point made by Richard that the fitting of a gasket spoils the possibility of the spigot sealing and thus a double joint seal is impossible with the gasket fitted. So should I just attempt to go for the single seal afforded by the gasket or should I lap the head and barrel, spigot and all, and go for a no gasket seal ?
If the aluminium gasket isn't doing the job, are there any alternative agskets out there that may do the job better ?
Thanks,
Mike
My three singles are all…
- Log in to post comments
Lapping head to barrel
Dan,
It sounds relatively easy. I may well have a goa at this.
Thanks,
Mike
- Log in to post comments
Lack of compression
Hi Mike
You have answered your own question! If you have not fitted a rocker box,and pushrods, you will be unable to get any air into the barrel to compress !
A compression test can only be done with the valves operating. On my M50 the compression is very poor, even after new rings and a cylinder hone with new valves and seats (via Mike P), also like Dan I did away with the head gasket, and lapped the barrel to the head, it was easy to do, as Dan intimated .
The lack of compression doesn't seem to hinder the performance in any way, as long as I keep the revs up, (65 - 70 max.)......nice 45 - 50 round the Yorkshire Dales. Nowhere as good compression as my clubman Velo, but still a nice bike to ride, It is what it is!
Regards John O
- Log in to post comments
If you get a low compression…
If you get a low compression test then the next step is a leakdown test. This is to find out where the leak is, air is pushed into the combustion chamber with both valves shut and the crank locked from moving. The hiss of air tells you where the leak is.
- Log in to post comments
These comments
Have already been made on another thread on the same subject!
- Log in to post comments
My three singles are all lapped with no gaskets and seal well. It does require removal of the barrel. George Cohen showed me how he did it and it worked for me - I used fine grinding paste on the top of the spigot and course on the barrel/head face. You then turn the head in the same way as you grind a valve .... back and forth and round and round! put on some music and get into the rhythm! George recommended the Stones ! After a while the paste stops grinding so wipe off the paste from both surfaces and repeat until you have a nice even grey colour on both faces. Fastidiously clean all the paste paying particular attention to the oil ways in the barrel where it can hide! George recommended a touch to Wellseal around the drain holes to keep everything oil tight, I have also used silicone or better still machine the barrel to take an o ring.
I should add that the idea of using different grade grinding pastes to to give sufficient clearance to clamp the spigot down firmly.
Dan