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timing specs. what's you rthoughts

jellywrestler

Well Known and Active Forum Website User
Non-VOC Member
I'm looking at finding suitable timing specs for my C series Rapide.
7.3 to 1 pistons terry prince mark 3 cams. what's the consensus out there?
 

Albervin

Well Known and Active Forum Website User
VOC Member
I hope this doesn't appear to be too dumb BUT are you talking ignition timing here? If so what sort of ignition are you using & what carbs? I reckon 36º would be a good starting point. Depends on fuel type as well; are they making bio fuel out of sheep, turnips or ? over there?
 

Tom Gaynor

Well Known and Active Forum Website User
VOC Member
Valve timing will be right with equal lift on both inlet and exhaust valves (on the same pot) at 4 - 6 deg BTDC. There are a variety of other ways of doing this, but until contrary evidence emerges, whatever method is used, there will be equal lift as above. Unless the cams have been blue-printed, there may be a variation on the BTDC figure between the pots, which you should split. Or alter the cams.
I'm running 34 degrees BTDC (the other TDC...) with a magneto, cooking unleaded (i.e. 95 octane RON) and 7.3:1 pistons. Must be about right since it'll readily do 100 mph.
 

jellywrestler

Well Known and Active Forum Website User
Non-VOC Member
I hope this doesn't appear to be too dumb BUT are you talking ignition timing here? If so what sort of ignition are you using & what carbs? I reckon 36º would be a good starting point. Depends on fuel type as well; are they making bio fuel out of sheep, turnips or ? over there?
I'm looking for ignition timing. we run 91 or 96 octane motion lotion the bikes running 30mm MK1 930 Amals. I've ridden the bike but the rear pipe is blueing up. in a very short distance. I did not set the timing so was going to check both carb settings and ignition settings to ensure all is ok just keen to see what other experiences people have had or may be able to offer with this set up
 

jellywrestler

Well Known and Active Forum Website User
Non-VOC Member
I'm looking for ignition timing. we run 91 or 96 octane motion lotion the bikes running 30mm MK1 930 Amals. I've ridden the bike but the rear pipe is blueing up. in a very short distance. I did not set the timing so was going to check both carb settings and ignition settings to ensure all is ok just keen to see what other experiences people have had or may be able to offer with this set up
just checked cams and they're MARK 2
 

Albervin

Well Known and Active Forum Website User
VOC Member
OK. Now to main jets, needle position & float height. How does it run? If you try to run only the front or the rear is there a big difference in the running? Change only one setting at a time to isolate the problem.
 

jellywrestler

Well Known and Active Forum Website User
Non-VOC Member
OK. Now to main jets, needle position & float height. How does it run? If you try to run only the front or the rear is there a big difference in the running? Change only one setting at a time to isolate the problem.
The motor was rebuilt by a third party and I have found some shortcomings shall we say so I was keen to check the basics first and also see what other experiences people had dealt with. I've taken it for a couple of short runs and it seems to work well one thing I will check is the exhaust temps with a ray gun in case the blueing is a result of different chrome plating on the two pipes that may be the cause.
 
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