New cam touched
- Thread starter pierodn
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L.A.B. said:
Hi Les,
The Intake lobes of the new stock cam touched both against the bottom side of the tunnel of the 1970 crankases halves.
I had to ground (shave/bore/scrape) a very little bit of aluminum and so the lobes does not touch more.
Why it touched?
I dont have the old cam, the engine was a part.
Thank you.
Piero
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pierodn said:
A high lift cam is aftermarket (usually) or a bigger cam opening the valves more. giving more "lift" the lobes on the cam will be bigger; so a larger cam will require grinding the tunnel for clearance. u <---- stock cam U <---- high lift cam
Not the best example but you get the idea. bigger lobe giving more valve lift.
lcrken
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The early cases will have a clearance problem with any cam that has more lift (taller lobes) than the stock Commando cam, which is usually marked with the letter S. With the higher performance factory cams (2S, 3S, and 4S) cams, as well as most aftermarket performance and race cams, the lifter tunnel must be enlarged for clearance. A stock 1971 Commando engine should have had an S cam. What markings does your cam have on it? If it has anything other than S, it is probably not a stock camshaft.
Ken
Ken
Hi All,
the engine is closed now and i dont remember if the cam had an S stamped on.
But, if it came from a running 1971 engine, and was like new, i hope it works well.
I assumed it was stock!
Do you think i have to dismount the engine to see what this cam is?
Thank you.
Piero
the engine is closed now and i dont remember if the cam had an S stamped on.
But, if it came from a running 1971 engine, and was like new, i hope it works well.
I assumed it was stock!
Do you think i have to dismount the engine to see what this cam is?
Thank you.
Piero
DogT
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I would think if you can measure the valve lift, you may be able to determine if it's a high lift or not cam. Compare it to one of your known stock 750 bikes. You should be able to do this inside the intake and exhaust covers.
I'm probably in over my head here.
I'm probably in over my head here.
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pierodn said:
Piero
You should know what cam you have in your engine. Don't Assume! :shock:
Based on what cam you have will determine the valve tappet clearances.
Use a dial gauge and a timing disk to determine the amount of valve lift.
Regards,
Thomas
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pierodn said:
Hi P
https://images.search.yahoo.com/images/ ... rt=mozilla
dial indicator.
https://images.search.yahoo.com/images/ ... rt=mozilla
timing disk.
give us the lift value of the inlet push rod at top dead center. Not maximum lift but the value at Top Dead Center.
Cheers
Thomas
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Fast Eddie
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pierodn said:
The point is Piero, your bike has tappet settings "as per the manual" but the point made earlier is that some high lift cams require different tappet gaps. And re not covered by the manual.
If you don't want to dial gauge it as per the earlier suggestion, or strip it to check, there don't appear to be many other options for you but to run it and try it!
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