ET: Engine (Twin) Richardson valve timing diagram

[youngjohn]

Can anyone tell me what position the crankshaft is in when the dot on the half-time pinion is at 12 o'clock as per the Richardson diagram? My pinion has a couple of marks that could be construed as dots so I'm trying to establish which (if any) is the correct one.
Thanks.

 

[chankly bore]

Four degrees B.T.D.C. One dot on keyway, one marking engaging tooth. And the "Richardson" Comet diagram is wrong. If you set valves rocking at 4 degrees B.T.D.C. you won't be far off. Easy on a single, more patience needed on a Twin due to the incubus known as the rear cylinder. Search the Forums, much has been written.

 

[youngjohn]

Thanks, is that 4 degrees BTDC on the front cylinder?

 

[stumpy lord]

Thanks, is that 4 degrees BTDC on the front cylinder?

no ,the rear cylinder is number one

 

[vibrac]

Look you wont get 4 degrees on both thats just a target,My best on the last twin was 6 and 3 of course on a Comet the impossible is very possible

 

[davidd]

YoungJohn,

I think of it as 4 degrees BTDC on the EX stroke. As I remember, the intake is closing and the exhaust is opening and they will definitely cross paths. But, if you think of it in terms of stroke, the ex is on its way open.

There is nothing wrong with setting it a TDC. Many have done so. When the Factory did the dyno testing they got the best performance by setting the crossover at 4 degrees BTDC. On the Racer I get the best performance at 7 degrees after TDC. Short of dyno testing you can set it between TDC and 8 degrees BTDC without too much worry. 4 degrees is a good target because it is what we all expect and try for on a street bike.

David

 

[timetraveller]

It is exhaust closing and inlet opening.

 

[davidd]

It is exhaust closing and inlet opening.

Thank you Norm. I could picture the graph, but not the colors. I should have looked!

David

 

[youngjohn]

Thanks for all the advice, much appreciated.