Compression ratio choice

bmetcalf

Well Known and Active Forum User
VOC Member
I don't have chokes on my Rapide, so I let it squirt. I am having trouble visualizing "the threads on the bottom of the carb body get wet". More details, please.

Also, from here in the frozen North (average December high 27F/-3C), what temperature is "extra cold" in the land of Surf and Sun?
 
Last edited:

TouringGodet

Well Known and Active Forum User
VOC Member
VOC Forum Administrator
VOC Forum Moderator
The threads for the piece that holds the jet block into the body, the piece that the banjo for the float bowl screws into.

It was probably down in the low '50s, upper '40s F.
 

bmetcalf

Well Known and Active Forum User
VOC Member
Ticklin'

Okay, that makes sense. I'll have to try it; can you see it from the saddle?

I've probably already said enough about cold temperatures.:eek:

The threads for the piece that holds the jet block into the body, the piece that the banjo for the float bowl screws into.

It was probably down in the low '50s, upper '40s F.
 

TouringGodet

Well Known and Active Forum User
VOC Member
VOC Forum Administrator
VOC Forum Moderator
Not much harder to see the bottom of the body than the float bowls. Just lean out a little farther for the front carb, rear is no problem.
 

Mickthevin

Well Known and Active Forum User
Non-VOC Member
i agree. Stick to the 9:1s. If you want to reduce to 8:1 you might find it more tractable in traffic but it is completely the wrong thing to do to use compression plates as you end up with an inefficient combustion chamber shape. Better to change the pistons before you use them if you really want to go lower.

Regarding kick starting; i am continuously appalled at some of the ways i see people starting their bikes. They fiddle around with the valve lifter and gently turn the engine over until they think that they are on the cylinder with the longest dwell before it fires. They then let go of the valve lifter and try to kick the engine over against the compression, hoping that they have enough momentum built up by half way down the stroke of their kick. No sir. Prime your carbs or use the chokes or whatever you have, turn the engine over gently with the kick starter a few times to get the oil started on its journey, then turn on the ignition, unless you still have a magneto in which case it is already on and the slow turning of the engine will have prevented it firing, then with the valve lifter lifted, kick down and half way down the stroke let go of the valve lifter. That way there is no fiddling about trying to find the correct position of the engine. You have lots of inertia built up because there is no resistance to the turning of the engine and hence the kick starter and you have given the whole kick starter mechanism a much easier time of it. Trying to boot the engine over against compression might be good for your right leg muscles but it is an abomination for the kick starter mechanism. If the bike does not start first or second kick with the above approach then there is probably something wrong.

Be gentle with it and it will serve you well.

the problem i have found, to my cost, with starting the bike this way is if the valve lifter cable snaps or comes adrift. Twice this has happened and you have to strip half the engine (slight exaggeration) to refit the cable(comet)
i turn the engine over several times using the valve lifter and also the clutch then try and find t.d.c.. With electronic ignition plus the rest of my routine the bikes inariably stat first kick
try not to wince bu it works for me

mick
 

roy the mechanic

Well Known and Active Forum User
VOC Member
mick the vin re valve lifter cable breakage

i hope for your sake, and your machine's that the same bloke that made valve lift cable has not supplied front brake cable also.
 
Top