Yoshimura Cams ??

[Mgriz]

When I purchased my bike it came with an extra engine. I started digging into it today b/c I wanted to swap the head onto my bike. Turns out its not in the greatest shape, but I did find that it had a set of what I think are Yoshimura Stage I ? cams (marked POPY). I quickly measured the cam heights, 37.3mm INT & 36.5 EXH. Are these indeed Stage I and can I get away with using stock springs with these cams? Thanks for any information you can give me.

[BadBillyB]

Without knowing the "base circle" the cams were ground at, you cant tell what the lift is....With valve lash correctly set on one lobe, measure the lift right off the top of the bucket or shim with a dial indicator.....The actual lift is the determining factor when deciding what springs to use......Billy

[RacingJake]

Take a second measure at 90 degrees of the first one, then substract the two and that will get you in the ball park.

[Mgriz]

90 degree measurements are 27.7mm INT & EXH so that makes the lift approximatley 9.6mm INT & 8.8mm EXH. Thanks for your replies.

[Mgriz]

So I ended up having these cams installed when I had the head rebuilt. I chose to use the valve springs that came out of the head they were used in so they should be fine. I am planning on setting the timming to the stock specifications and I'm wondering if I should be worried about piston to valve clearence? Thanks.

[robinjo]

So I ended up having these cams installed when I had the head rebuilt. I chose to use the valve springs that came out of the head they were used in so they should be fine. I am planning on setting the timming to the stock specifications and I'm wondering if I should be worried about piston to valve clearence? Thanks.

Check it with solder wire through the sparkplug hole first, if it doesn't work out I will have them off you. I would like to have pictures of the markings too.

[Mgriz]

Check it with solder wire through the sparkplug hole first, if it doesn't work out I will have them off you. I would like to have pictures of the markings too.

Haha, that seems to be the response I get when I ask about these cams. Are they somewhat rare? or... whats the deal.

I will check with some solder... are there any other methods for checking this. I have read about doing it with clay but it just seems like such a pain to take the head on and off.

And here is a nice and clear image of the markings on the cam. Each has one in this same location, other than the other standard markings (EXH/INT) I didnt notice any additional markings.

[robinjo]

It's just that they would feel right at home with the big-bore, worked head and racing carbs on my bike. :-D The Yoshi ones are kinda rare but there are several other readily available new right off the shelf.

I would have expect some other markings about which stage they are, stage one would be fine with just new springs, two or even three would require much more drastic measures to be taken, you could check your lift and duration against Megacycle and Web cams specifications and see what else those require like shim under bucket, valve to piston clearence and even clearence in the head itself. A tuning guy I know overhere built his own GS thou special and had to modify the cam cover itself because of the 10/11 mm lift.:shock: