Author Topic: 1st attempt at degreeing a 750 HiPo cam - consults please (Read 7025 times)

Jerry Rxman Griffin aka MuthaF'er · « **on:** March 16, 2012, 04:48:12 PM »

In my earlier wrench turning days when I built my 812 Yoshi engine I used the Yoshi Daytona cam and just slapped that sucker in there by aligning the marks. It worked but it probably coulda worked better. No valves bending on pistons. Well, now that I am older (!!) and wiser (??) I am putting a MUCH higher dollar engine together so I have much more than a few horsepower to lose. I have looked at a few videos and read a few webpages but I do NOT find a write up specific to our 750's! Why does this have to be magic?! Anyone have a link?? Anyway. through my anal retentiveness, I have managed to correctly find TDC using my degree wheel and Big Jay's TDC tool. I am confident in that step. On to degreeing the cam! So far I have played with the intake side.

Megacycle 125-75
open 26 degrees
close 56 degrees
valve timing @ 0.0400" lift
duration 262 degrees
lobe ctr 106 degrees

Here's what I've done so far:

1st stab at it - reset the degree wheel to 0 ; installed the dial guage on the magnetic base ; set the dial gauge pointer on the retainer ; zeroed the dial gauge ; rotated the crank in the normal running direction until the dial gauge read 0.040" ; took degree wheel reading of 26 degrees ; continued rotating back to .040" on dial gauge ; took degree wheel reading of 54.5 degrees. OK, time for math. 26 + 54.5 + 180.5 = 260.5 degrees of duration divided by 2 = 129.75 subtract the initial 25 = 104.75 lobe center - See target numbers above

2nd stab after very slight adjustment of cam chain sprocket - 1st reading 25 degrees ; 2nd reading 55 degrees ; 25 + 55 + 180 = 260 degrees duration divided by 2 = 130 (subtract the initial reading) - 25 = 105 lobe center - see target numbers above

My thought is that this is as close as it'll get. What do you think of where I'm at now? Once there is a general consensus I'll move over to the exhaust side. Any tips for that?

MRieck · « **Reply #1 on:** March 16, 2012, 05:04:01 PM »

That's good Jerry. I just subtract the opening # from the closing #, add 180 and divide by 2. It doesn't really doesn't matter but it is a bit easier to do in your head. Considering your age I think this kind of info would be very useful.

Jerry Rxman Griffin aka MuthaF'er · « **Reply #2 on:** March 16, 2012, 05:08:58 PM »

On to the exhaust then? same basic procedure for the exhaust? Any potential issues there?

Why is it that I can find you this way but not on yer phone, email, pm's etc?!

takin about old age!!

Michael, you really should do a nice simple cam degreeing write-up for our tech section!

bwaller · « **Reply #3 on:** March 16, 2012, 07:20:13 PM »

You're going to want to probably square that cam between intake & exhaust to even the LC's. It means a bit of back & forth, but you're in a pretty good place with the intake side to start.

It seems a rare deal to exactly match the cam card. Considering you're likely setting 0 lash and can be off a bit...it all adds up. Even the Lobe Centers Jerry, you're on the right track.

And I'm just back from the Pub, so I should probably hit the fart sac instead of responding here.

Jerry Rxman Griffin aka MuthaF'er · « **Reply #4 on:** March 16, 2012, 07:44:41 PM »

Brent,

Here's the exhaust info. Not sure what you mean by squaring the cam?? I'm taking the readings off the retainer so does zero lash apply? Hope I'm doing this right. Fisrt timer

Exhaust #'s per card

open 53
close 24
duration 257
LC 104.5

Bill/BentON Racing · « **Reply #5 on:** March 16, 2012, 07:58:02 PM »

Run it!!!!!

You good enough!

Bill

Jerry Rxman Griffin aka MuthaF'er · « **Reply #6 on:** March 16, 2012, 08:04:38 PM »

Haven't done the exhaust yet. Any tricks for it or just verify the numbers? Would the exhaust normally/usually be on the money if the intake is on the money since they are the same stick?

Bill/BentON Racing · « **Reply #7 on:** March 16, 2012, 08:41:10 PM »

Jerry,check the exhaust, tho intake more important,I thought when you posted that was your ex #'s! 105 in./104.75ex. would be just fine. If you change one you change the other. You getting it.

Bill

Jerry Rxman Griffin aka MuthaF'er · « **Reply #8 on:** March 17, 2012, 11:10:24 AM »

OK, first final results.

Intake and exhaust valve clearance/lash set to zero. Adjustable cam sprocket turned all the way to the end of the slot. .040" lift as measured on retainer.

Intake open @ 26.5^o vs 26^o per card (CLOSE but slightly over spec)
close @ 56.75^o vs 56^o per card
therefore LC = 105.125

Exhaust open 21^o vs 24^o per card (Off by 3^o))
close 56^o vs 53^o per card
therefore LC = 107.5

So, the intake is basically on the money but the exhaust is off by 3^o. This means to me that the cam is slightly off from it's specs. Now what's next? Brent has suggested "squaring" the numbers. Not truely knowing what that means and considering he'd been at the pub

should I intrepret that to mean splitting the 3^odifference on the exhaust and adjusting the intake by 1.5^o to near 25^o and near 55^o which should also adjust the exhaust by the same 1.5^o and have them the same number of ^o's off? ie make the lobe center as close to identical as possible?

MCRider · « **Reply #9 on:** March 17, 2012, 11:17:00 AM »

Quote from: Jerry Rxman Griffin on March 17, 2012, 11:10:24 AM

OK, first final results.

Intake and exhaust valve clearance/lash set to zero. Adjustable cam sprocket turned all the way to the end of the slot.

Intake open @ 26.5^o vs 26^o per card (CLOSE!)
close @ 56.75^o vs 56^o per card

Exhaust open 21^o vs 24^o per card (Off by 3^o))
close 56^o vs 53^o per card

So, the intake is basically on the money but the exhaust is off by 3^o. Now what's next? Brent has suggested "squaring" the numbers. Not truely knowing what that means and considering he'd been at the pub should I intrepret that to mean splitting the 3^odifference on the exhaust and adjusting the intake by 1.5^o to near 25^o and near 55^o which should also adjust the exhaust by the same 1.5^o and have them the same number of ^o's off?

That's my understanding, split the difference. BUT, what you have set now may run the best, or split it, or time the exhaust perfect and have the IN off. That's where the Dyno comes in. There are some rules of thumb but i don't know them.

Jerry Rxman Griffin aka MuthaF'er · « **Reply #10 on:** March 17, 2012, 11:18:32 AM »

Motorheads unite!

OK, so if I change the intake opening from 26.5^o to 25^o to split the difference, is this advancing or retarding? (Must be retarding as that word seems to fit me here

) So If I advance it gives more high rpm HP and less low end? Or is that the other way around?

Bill/BentON Racing · « **Reply #11 on:** March 17, 2012, 01:14:01 PM »

Other way around1

Advancing cam will move power curve lower.

Bill

Jerry Rxman Griffin aka MuthaF'er · « **Reply #12 on:** March 17, 2012, 01:18:14 PM »

Using Webcams page: ( warning do/do not go to webcams.com

It's Webcamshafts.com )

Cam Calculations - Lobe Center / Duration

--------------------------------------------------------------------------------

Overlap: 47.50 degrees
Intake Duration: 263.25 degrees (vs the card info of 262^o)
Exhaust Duration: 257.00 degrees (vs the card info of 257^o)
Intake Installed Centerline of 105.13 degrees ATDC. (vs the card info of 106^o)
Exhaust Installed Centerline of 107.50 degrees BTDC. (vs the card info of 104.5^o)

I'm going with it. I'd still like to hear your thoughts.

Jerry Rxman Griffin aka MuthaF'er · « **Reply #13 on:** March 17, 2012, 01:22:29 PM »

Quote from: bellcow54 on March 17, 2012, 01:14:01 PM

Other way around1 Advancing cam will move power curve lower. Bill

OK but.... Is going from 26.5 to 25 on the intake advancing or retarding?? See, told you I'm an anal retardive

You know, this #$%* will seem easy once I get it!

Bill/BentON Racing · « **Reply #14 on:** March 17, 2012, 02:52:29 PM »

Jerry,it would be opening 1.5 degrees later,therefore it'd be retarded.

...kinda like me!

Bill

Doctor_D · « **Reply #15 on:** March 17, 2012, 09:16:36 PM »

If it's supposed to open at 26deg and open instead at 25 deg, it's advanced.

Big Jay · « **Reply #16 on:** March 17, 2012, 10:21:02 PM »

The general consensus on the single cam motors is the intake timing is important. Put that in and let the exhaust fall where it does.

KRONUS0100 · « **Reply #17 on:** March 18, 2012, 08:58:35 AM »

where did you find the top dead center tool?

Greggo · « **Reply #18 on:** March 18, 2012, 09:01:17 AM »

Just subscribin' for some good info!

MCRider · « **Reply #19 on:** March 18, 2012, 09:07:23 AM »

Quote from: KRONUS0100 on March 18, 2012, 08:58:35 AM

where did you find the top dead center tool?

If I may (I know you didn't ask me directly) You can DIY, I bot mine from APE/Big Jay.

PS: I see in the OP, Jerry bot his from APE/Big Jay alos.

Leino · « **Reply #20 on:** March 18, 2012, 11:05:48 AM »

Just did this yesterday on my own CB, Megacycle 125-75, LC 105 / 108,5

MRieck · « **Reply #21 on:** March 18, 2012, 03:32:22 PM »

Quote from: Leino on March 18, 2012, 11:05:48 AM

Just did this yesterday on my own CB, Megacycle 125-75, LC 105 / 108,5

OMG....you WORKED ON THAT BIKE.

Jerry Rxman Griffin aka MuthaF'er · « **Reply #22 on:** March 18, 2012, 04:07:15 PM »

Quote from: KRONUS0100 on March 18, 2012, 08:58:35 AM

where did you find the top dead center tool?

From the man that posted right before you, Big Jay @ APE.

Big Jay · « **Reply #23 on:** March 18, 2012, 05:17:11 PM »

Quote from: Greggo on March 18, 2012, 09:01:17 AM

Just subscribin' for some good info!

Quote from: KRONUS0100 on March 18, 2012, 08:58:35 AM

where did you find the top dead center tool?

Right here sir; http://racetoolz.com/

bwaller · « **Reply #24 on:** March 18, 2012, 05:51:24 PM »

Glad you got it sorted Jerry. If it appeared I was avoiding you, truth be known I didn't even remember replying in the first place. Sheesh I don't get out much and was half in the bag. Sorry I wasn't aware what cam you were using but so often in. open & ex. closing numbers are identical as are the lobe centers, the reason I mentioned squaring the cam.

You must be getting close.

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Author Topic: 1st attempt at degreeing a 750 HiPo cam - consults please (Read 7025 times)