Topic: Reground cam off center!

[bistromath]

Hi all,

I started the 500mi teardown/checkup on my 550 build today. It pulls fine, but it's idled badly since the rebuild, no matter what I did with the carb balancing and idle air screws. Setting valve lash was a struggle, too. It always seemed like I'd get different results every time I measured.

After getting frustrated setting the valves again this afternoon I finally rigged up a bracket for a dial indicator referenced off the head, and lo and behold, the CB650 cam I had sent out for resurfacing is four thousandths off center, on every single lobe! That is to say, the lobe base circles are not concentric to the camshaft bearings. No wonder I couldn't get the .002 valve lash set consistently. It also looks like the intake lift is ten thousandths low compared to the specs I could find on the forum.

I'm running standard bore, 10.5:1 compression Wisecos, so bigger cams with more overlap are preferred over the stock 550 cam. So my question is: should I just find another old 650 cam in decent condition and run it, find an old Yoshi cam, or pay to have this one built up, heat treated, and ground down again? And if so, who would you recommend to do it?

[calj737]

Just buy a new Webcam or MegaCycle unit and be done with the re-grinding. Easier and cheaper in the long run. You’ll need to have the tappets hard faced with the Megacycle.

[flatlander]

Just buy a new Webcam or MegaCycle unit and be done with the re-grinding. Easier and cheaper in the long run. You’ll need to have the tappets hard faced with the Megacycle.

webcam is also hardweld.

[bistromath]

Thanks guys. I guess I'll go with a Megacycle, since they're right nearby. Looks like their 126-00 grind is a takeoff from the old Yoshi cam with the same name. Anyone have any recommendations for a cam profile for a 10.5:1 CB550F with ported/polished heads, stock valves, and high-rate springs?

If anyone's interested, here's the intake profile on the reground (and off-center) cam. I won't name the cam company here. Wish I'd measured it before I had it sent out for resurfacing. It's referenced to 180 degrees on the cam. As you can see, there's a significant "dip" past the 180 degree point caused by being ground off center.

[flatlander]

yes, 126-00 will be good for street use. the 126-20 will give you higher max hp but comes in later. it will also need modified piston tops to make space for the valves.
the webcam 358a is very similar to the 126-00 but builds up torque a bit earlier. at least in my engine that's what it does. it's almost a toss between those two.
i must have a dyno chart somewhere...let me look.

[flatlander]

here ya go: http://forums.sohc4.net/index.php/topic,134461.msg2025855.html#msg2025855

[bryanj]

The Yoshi street cam in a standard engine needed a lot more advance on the timing and at least 2 extra teeth on the rear sprocket as there was less low down power/torque

[Don R]

 It took me a minute to understand the "off center" part. I was thinking lobe centers not base circle. Thinking of how I set valves on my V8 solid lifter motor I can see where the ramped base circle would be an issue.

[bistromath]

here ya go: http://forums.sohc4.net/index.php/topic,134461.msg2025855.html#msg2025855

Thanks a lot. Would love to see how the Yoshi cam varies with timing. Guess I'll have to find out myself. I'm running a stock 4-1 exhaust anyway -- I know it's the limiting factor keeping the bike from breathing, but it looks too good to give it up.

[Don R]

I had a 400f with a stock header but a supertrapp muffler, I went past the neighbor's house at 8K rpm. He followed me home and wouldn't leave until I sold it to him. It sounded awesome.

[flatlander]

I'm running a stock 4-1 exhaust anyway -- I know it's the limiting factor keeping the bike from breathing, but it looks too good to give it up.

that was quite a dilemma for me, too. the 4-1 is part of what defines the 550F's look. what made it easier for me is that i had some rust built up in the muffler which restricted it even more... so then it "needed" to go.

[bistromath]

I'm running a stock 4-1 exhaust anyway -- I know it's the limiting factor keeping the bike from breathing, but it looks too good to give it up.

that was quite a dilemma for me, too. the 4-1 is part of what defines the 550F's look. what made it easier for me is that i had some rust built up in the muffler which restricted it even more... so then it "needed" to go.

Yup. I've had this one for 20 years now. The 4-1 is what made me fall in love with it in the first place.

[bistromath]

I'm back with a real headscratcher. The cam came back from the builder again.

He said it had a bit of runout along the lobe. I took this to mean there was a bit of slope across the lobes, rather than the whole cam being runout. It's definitely not runout along the length of the cam, it's as straight as I can measure. I'd told him what I'd observed and he seemed to dismiss it -- said he fixed the runout and put it back in the mail. I put it back on the bike and stuck the dial indicator on it again, and lo and behold -- nothing's changed.

Here's a video of what I'm seeing, to maybe explain it a little better.

Am I losing my mind? Is this normal? If I set the valve lash to 0.002" at TDC I have effectively zero clearance for most of the stroke and will lose compression. If I set the valve lash to 0.002" at the lowest point on the lobe I have effectively 0.005" clearance when it comes back onto the lobe and it will sound like a bucket of bolts and wear prematurely.

[Kevnz]

I admit I don't know a lot about this aspect of engines, but if you have a cam grind that changes the timing and\or lift, might you need to change the point at which the lash is set? What if you set the lash at 0.002 at the point the gap is maximum? Some builders time cams at a certain amount of valve lift, not tdc.

[bistromath]

This is (ostensibly) a stock CB650 cam, just resurfaced. So it should be settable as per a normal CB650.

[BomberMann650]

Dynomans link to the 358 cam card was broken.  So i grabbed their 335 for reference.
They lash at .004" - what op is trying to set at .002" is tighter than most factory specs.
(And - if the technician is keeping notes at service intervals.  Finding lash that tight could be interpreted as a sinking valve 😵‍💫 )

Fwiw - the 550's will never run as quiet as a modern valve train.
Rocker followers will add some percussion to the motor symphony. 
The words "sewing machine" is a fair onomatopoeia.  To describe the natural sound.

Good job on the consistent measurements though. 
Maybe another way to dial in your valves would be to read the rocker tappet as it moves through the lift.  Set the lash uniformly to start.  Do the math, subtract whats necessary to get those equalized.  WRITE IT DOWN. 
Then see how it runs.

[MRieck]

Thanks guys. I guess I'll go with a Megacycle, since they're right nearby. Looks like their 126-00 grind is a takeoff from the old Yoshi cam with the same name. Anyone have any recommendations for a cam profile for a 10.5:1 CB550F with ported/polished heads, stock valves, and high-rate springs?

If anyone's interested, here's the intake profile on the reground (and off-center) cam. I won't name the cam company here. Wish I'd measured it before I had it sent out for resurfacing. It's referenced to 180 degrees on the cam. As you can see, there's a significant "dip" past the 180 degree point caused by being ground off center.

You can run the 126-20 with the stock valves and Wiseco pistons. It is a very, very good cam. Retail on the Megacycle will be about 570.00 or so and you will need to send them another cam.....they can't use the one you have.

[flatlander]

mike, does the 126-20 not need some work to deepen valve cutouts on the pistons? or is that only needed with larger valves?

[bistromath]

Thanks Mike. I have another 550 cam I can use as a core. I might just do that.

[bistromath]

Dynomans link to the 358 cam card was broken.  So i grabbed their 335 for reference.
They lash at .004" - what op is trying to set at .002" is tighter than most factory specs.
(And - if the technician is keeping notes at service intervals.  Finding lash that tight could be interpreted as a sinking valve 😵‍💫 )

Fwiw - the 550's will never run as quiet as a modern valve train.
Rocker followers will add some percussion to the motor symphony. 
The words "sewing machine" is a fair onomatopoeia.  To describe the natural sound.

Factory is 0.002"/0.003" IN/EX for both 550 and 650 (although Hondaman says he likes to run 0.003/0.003). This is a resurfaced factory 650 cam. I sure can run higher clearance to ensure the exhaust rocker stays 4 thou off the tappet for the whole base circle, but it seems super fishy to have to do that and complicates the process considerably. The effective duration and lift of the cam will be changed by the extra clearance. And it's gonna sound like #$%* given the extra clearance to the "low spot" on the cam right before the lift -- I know what 0.007" clearance sounds like on these motors and it's... unpleasant. There's just no way the cam came like that from Honda. Has anyone here ever degreed a cam and seen something like this?

Good job on the consistent measurements though. 
Maybe another way to dial in your valves would be to read the rocker tappet as it moves through the lift.  Set the lash uniformly to start.  Do the math, subtract whats necessary to get those equalized.  WRITE IT DOWN. 
Then see how it runs.

Sure can. I'm gonna have to invest in real V-blocks to get decent measurements of all 8 lobes, because they're not all off the same amount. Only reason I found the problem was the offset makes setting the valves almost unrepeatable.

[flatlander]

Thanks Mike. I have another 550 cam I can use as a core. I might just do that.

or give this one a go: http://forums.sohc4.net/index.php/topic,188944.0.html
at 75 bucks you can't really go wrong 

[BomberMann650]

Just looked at my feel gauge set to see which ones i'd kinked for use in bloo. 
Give me a sec to pull the foot from my mouth.
Been working on the fj too much lately.  Yamaha spec is wider..

Kind of a pain there's that lump in your cam.  Though i don't see how v blocks will help you get a better measurement.  The head is an ideal holder for the cam after all 🤷‍♂️

[Don R]

A 550 cam goes in the rocker cover, No?  I saw one cut-away on FB yesterday so a guy could check cam timing.

[BomberMann650]

A 550 cam goes in the rocker cover, No?  I saw one cut-away on FB yesterday so a guy could check cam timing.

Together they make a camshaft sandwich. 

Talk about an iron supplement

Edit - though ya mention cam timing.

Did Op get an adjustable sprocket for that thing?  The dynoman cam i was considering wanted a 2° advance, and some exhaust calculator software thought a 5° advance was better.

[bistromath]

Yeah, no adjustable sprocket. If I'm going to go the Webcam route then I've got all that stuff in front of me yet. Just wasn't ready for another big project.