Motorcycle Discussions > British Bikes

J.A.P. vtwin engine timing

<< < (2/3) > >>

de oude gek:

Leon, thanks for the information.
I googled for that table, but got nowhere.
The engine I was working on was a LTOWZ (ohv watercooled) out of a Morgan.So thet would need even more  :o
Is that table part of a book?
Would like a copy.
Thanks
Frank

cardan:
Hi Frank,
Not everything in life can be Googled! The settings for the water-cooled SV and OHV 60 degree twin engines are identical to those for the AC 60 degree twin (listed above) - I assume they were all built on the same base. All are listed at 1100cc, but there is a larger 1323cc SV AC twin as well in the same family.
Until this query, I didn't know that JAP made a 60 degree OHV water-cooled twin, so it's fun to learn something new! Of course it would be unlikely to find such a beast in a motorcycle - I wonder if they were used exclusively by Morgan.
Cheers
Leon

de oude gek:
Hey Leon,
It sure is fun learning something new(every day :))
On this engine the timing cover needed repairs on the hand cranking snout after a crash.
On removing the cover the cams fell out.
The cams had minimal painted (maybe) timing marks and of course the
ignition cam had none at all.
Thoughts were that starting should be with the ignition fully retarded and not before TDC.
As total advance/retard is about 20 degrees total advance was set at 20.
We'll see how she runs as is,keeping in mind that advance could/should be more.

Frank
je leert hier elke dag wat

cardan:
Interesting, because the magneto standard is to have 30 degrees advance/retard variation. But 20 degrees should be OK, as 20 degrees on the magneto is 40 degrees on the motor. If you set the ignition to 38 degrees BTDC fully advanced, then fully retarded will be essentially at TDC, just the thing for hand cranking so maybe Morgan designed it like that.
I have a JAP twin in one of my bikes. The bike is single speed and belt drive, but only rarely do I retard the ignition from its fully-advanced position.
Re timing marks: I always ignore them! There are too many mixed-up motors out there, and while lining up some marks might feel nice, it won't always lead to an engine that runs properly. On any motor I build or work on I always check the valve timing with a degree disk.
Let's know how it runs!
Leon

de oude gek:
Leon, the morgan has a coil ignition, the advance/retard mechanism is spring loaded toward advance, pulling a lever sets the retard.
From full advance to full retard is 20 crankshaft degrees.
Not knowing what to expect re the timing marks on the camshafts I set the cams on the markings and timed the 2 cilinders with a degree disk. As both open and close symmetrically I think cam timing is ok.(Valve lash was set to 0 and valve assumed to open at 0,5 mm. lift to compensate for ramping problems,cams are not really new.)
The owner is putting the rest of the car together, I'll let you know how it goes.

Frank

Navigation

[0] Message Index

[#] Next page

[*] Previous page