Large Spine Frame XS650 / Egli / Rau / Cafe Racer

[Jim]

Do you think once properly assembled the "clunking" might disappear?

Because of the cam lobes, you're alternating between the front of the chain... and then the rear being tensioned and untensioned (what the tensioner is supposed to prevent). I suspect (strongly) that's what we're hearing... the chain clicking as it loads and unloads. That make sense?

So yeah, a proper tensioner should take care of it.

 

[rehar]

Parts are ordered. With the holiday and shipping, it will be a few days to a week before I can get back at it. Thanks for the help. I will post results. I'm very optimistic at this point.

 

[rehar]

I just installed the rubber damping washer, wow - what a difference that made! Tensioner adjusted as expected - no strange/excessive movement. That specific clicking, clunking noise is gone. Rode a couple of laps around the neighborhood, the valves themselves are audible now that the other noise is gone.

I'll let it cool down and check clearances tomorrow. They were pretty close to spot on before dis-assembly/re-assembled of the tensioner/plunger. of course, the tension is different now. This is the Megacycle 250-20, it's recommended valve clearances are loose (.010 & .012").

Would the clearances change with Cam Chain tension being different? Kind of think it would impact it.

Would the Chain tensioner also make noise if too tight or too loose?

 

[Jim]

Would the clearances change with Cam Chain tension being different?

Chain tension has no affect on valve clearances and vise versa. You could remove the tensioner and it would still have no affect on valve clearances.

 

[rehar]

Chain tension has no affect on valve clearances and vise versa. You could remove the tensioner and it would still have no affect on valve clearances.

That’s my initial thought, but, if can tension were loose And now tight, the chain slop (in my minds eye) could allow the cab to shift ever so slightly… and impact the clearance measurement… ? Maybe, maybe not…?

 

[Jim]

For the clearance to change, the chain would have to apply enough force to deflect (bend) the cam. That might get ya a half a thou or so. Beyond that I'd expect the cam would fail prematurely.

 

[rehar]

No not bending the cam, but the thought is cam position VS Crank position VS loose tension VS tight tension - could maybe shift the cam enough to change the clearance? Guess it would depend on where it was in it's cycle when measured (of course it should be well in "valve closed" section of the cam lobe profile, but how close to riding up a lobe..? And this new cam has more duration...? I don't know... Just a thought, trying to understand why it's so noisy. Still more noise than I think there should be. I'll check clearances again. What else can cause valve train noise (up on the top end)? Or are the Megacycle 250-20 cam and it's recommended valve clearances (.010 & .012") just noisy?

 

[Jim]

Or are the Megacycle 250-20 cam and it's recommended valve clearances (.010 & .012") just noisy?

That would be my guess

 

[Max Midnight]

Valve clearance is governed by how far in of out the set screw is in the rocker. That can't change.
The slack in the cam chain won't alter the clearance but will allow the cam timing to change relative to the crank.

 

[rehar]

Well, Tightening the valve clearances again, helped reduce some noise. Next weekend - Try to dial in the carbs a bit more.

 

[GLJ]

Or are the Megacycle 250-20 cam and it's recommended valve clearances (.010 & .012") just noisy?

I think that is where you are getting some noise from. Yamaha originally spec was .006 and .012. Then they tightened it up to .003 and .006 because of complaints of valve noise. What are you using for adjusters? If you want to run them that loose elephant foot adjusters would quiet it down some.

 

[rehar]

Elephant foot adjusters? Hmmm, interesting idea. What fits the XS650? Does anyone else run these on the XS650?

These rockers are from Mike's XS, brand new for the new 277 crank/Megacycles Cam.

Going off on a tangent, there is so much slop in the threads on those adjusters... It is surprising. Of course - only when the lock nut is loose for adjusting. Maybe there is a reason for that. Once everything is tightened down the slop of course is gone. I don't know if its the threaded adjuster or the rockers - or both (more likely) that have - let's say - lots of tolerance. Not to get too technical here but - it's like these are ASME B18.31.2 1A or 1B. I would expect a 2A/B or even 3A/3B. But maybe they work best with the looser thread. ? A better thread would make it easier to adjust, perhaps more precision. Of course - that doesn't necessarily help the reduce noise from valve clearances, recommended by Megacycle.

Anyway... The Elephant foot adjusters might be worth it... Like to learn more about those.

 

[GLJ]

Anyway... The Elephant foot adjusters might be worth it... Like to learn more about those.

I bought 4 sets years ago. I do not remember who I got them from. They were recommended by @MaxPete maybe he can post the link. You do have to modify the rockers a little bit. There is a thread on them somewhere. I've been happy with them. I used my last set on the 743 I just built so I need to get a few more sets.

 

[Max Midnight]

Elephant foot adjusters? Hmmm, interesting idea. What fits the XS650? Does anyone else run these on the XS650?

As found in VW Beetle and some Porsche's. More here. Put 'Elephant feet' into the search here to find posts on the subject.

 

[MaxPete]

As found in VW Beetle and some Porsche's. More here. Put 'Elephant feet' into the search here to find posts on the subject.

Yup - those are the ones I got. Very nice and quiet and they seem to stay in adjustment very well.

Pete