Twin Valve Timing

Cyborg

Well Known and Active Forum User
VOC Member
Thanks again gentlemen. When my mag went through the final bench test it showed 1 degree difference.

I'm not sure at this point I want to know why you took them out Greg. I already have a box of cams.

What sort of end play should be on the breather? Almost 0 at the moment.
 

Bill Thomas

Well Known and Active Forum User
VOC Member
Thanks again gentlemen. When my mag went through the final bench test it showed 1 degree difference.

I'm not sure at this point I want to know why you took them out Greg. I already have a box of cams.

What sort of end play should be on the breather? Almost 0 at the moment.
A lot, Or they jam up and do bad things, I am thinking 15 thou ish, Cheers Bill
 

Martyn Goodwin

Well Known and Active Forum User
Non-VOC Member
Thanks again gentlemen. When my mag went through the final bench test it showed 1 degree difference.

I'm not sure at this point I want to know why you took them out Greg. I already have a box of cams.

What sort of end play should be on the breather? Almost 0 at the moment.

In the timing chest, for all but the timed breather the end float should be within 0.004 to 0.008”. The timed breather needs a minimum of 0.015” end float to allow for its aluminium tube to grow in length when in service.
 

Bill Thomas

Well Known and Active Forum User
VOC Member
In the timing chest, for all but the timed breather the end float should be within 0.004 to 0.008”. The timed breather needs a minimum of 0.015” end float to allow for its aluminium tube to grow in length when in service.
Thanks Martyn, OVR 37 was a nice Shock !!, I owe you a Pint, Cheers Bill.
 

Marcus Bowden

VOC Hon. Overseas Representative
VOC Member
Except if one has an all steel one on the workshop windowsill, also bronze but mostly aluminum, I've always shimmed till they are free, to rotate.Coefficient of expansion is not that great.
Sat in Melbourne air port for Dubia then Heathrow after completing the Tasmanian Tour having a try of Martyn Goodwins bike with the upgraded design, so bugger all those eccentrics, shims and stick-tion of bushes that are difficult to keep lubricated, also tried one of the new "A" Rapide Replicas of Rodney Brown, better handling than "C's" & "D's" and plenty of power, Brian ? outfit rider on the tour tried Neal Videan's "A" then the 1300 "C" and he concidered the "A" being better !!!
If I knew how to start a new thread I would have done one for each topic, please excuse me.
bananaman
 

Martyn Goodwin

Well Known and Active Forum User
Non-VOC Member
Except if one has an all steel one on the workshop windowsill, also bronze but mostly aluminum, I've always shimmed till they are free, to rotate.Coefficient of expansion is not that great.

Linear Temperature Expansion Coefficient of Aluminium is 21 to 24 depending on the alloy; for steel its 11 to 12.5. What this means is that Aluminium will expand (grow) at TWICE the rate of steel. As the motor warms the aluminium tube in the breather will get longer at twice the rate of the steel spindle its on. To avoid running out of clearance and having the breather sleeve seize (it happened to my motor) it is VITAL to have a minimiun of 0.015" end float on the timed breather. Actually 0.010" would JUST be OK - the extra .005" provides a safety margin .
 
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