By Meteorstorm
The only Twin i have that i can't remove the oil cap while eng running is the mk1a without copping a faceful of oil.Re the over pressurization,i did a test many years ago by drilling a rocker stud and attaching a plastic tube up through a loop and added some oil,marked off both levels and tested original and reed valves etc you can do the same there's conclusive results to be found.
By Marko
Regarding engine breathing on twins:

Many years ago there was a very good article in The Gun, probably the best advice on twins i've ever seen, which goes into detail on how to sort the problem once & for all. I dont know how to upload a PDF of it here but if you are on FB & join British Motorcycle Mechanics group you can find it here: ... 4399348520
By Jakub
Thanks for info on breathers, however I don't have Facebook, did try my daughters but this group is for members only.
Any chances you can copy and mail it to me please?
By Rasp
The oil return pipe in the filler tube on my Constellation has a flatend end and a hole in the side that directs the oil against the side of the filler tube. If the pipe had an open end I'm sure it would splash out if run with the cap removed. Something could easily be attached to an open pipe to deflect the oil which would solve one of your problems.
By Marko
Jakub if you can give me your email addr i'll see if i can send it you as i have a pdf of the article on my computer. Best regards Marko
By Jakub
To sum up the thread. Cylinders have been rebored, valves and valve seats regrinded, heads resurfaced. Everything back together and it seems to work. Did about 50 miles today, no oil in the exhaust, bike starts very nicely and pulls pretty strong with very limited throttle opening I was using.
Interestingly when back to the garage I retighten head nuts with torque wrench. Every nut would give about quarter of rotation. Pretty much if you ask me.

I have taken exhaust pipe out, no oil to report, on the contrary with engine running there is really hot exhaust gases coming out. I am not fully sure what was wrong before but whatever it was it seems to be gone.

And the funny bit is that compression pressure is exactly the same as it was. 7.0 bar. Perhaps measuring compression is just waste of time.

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