Author Topic: 1972 CB750K2 (start from scratch) project. Cases back together (Read 101590 times)

Davez134 · « **Reply #125 on:** January 12, 2015, 01:31:31 PM »

Quote from: timbo750 on January 12, 2015, 01:11:58 PM

I am no expert on cam timing but I do understand the maths behind it.

No matter where your cam sprocket is adjusted you will always get the same lobe centre measurement, this is because as you make the adjustment you are increasing one measurement and decreasing the other by the same amount so the formula will always have the same result because it is actually measuring something physical on the cam.

I think what you need to do is look at the centre point between intake opening and intake closing. it is a little confusing though as the true way to look at it is that the figure for opening BTDC is actually a negative number then if change this then the formula should be-
-32 + 18 / 2 = -7

This means that the centre of the cam lobe is 7 degrees BTDC with the current setting.

The Cam card reads that you should have the centre set at 17.5 ATDC using the formula I mentioned.

If I have got this terribly wrong someone please let me know but I am almost certain this is correct.

I got different lobe center numbers when adjusting sprocket. There is no way the numbers could be the same. It's frustrating cause I'm good with math, and as I'm reading instructions from webcam online, it makes sense, then everything is off. Must be user error, but I can't figure out what it is

timbo750 · « **Reply #126 on:** January 12, 2015, 01:37:01 PM »

Dave
ok, I misunderstood what the lobe centre measurement was. But from what I have read it seems that it is the best measurement to get right. it seems so odd that so many people have trouble with this, is cam manufacture a hit and miss procedure? I would not of thought so.

edwardmorris · « **Reply #127 on:** January 12, 2015, 01:42:45 PM »

Again, I'm sure you've gone through all of these, but in case you missed it, here's Ron's walkthrough on a K2 with the same cam

http://forums.sohc4.net/index.php?topic=36459.msg1007168#msg1007168

FWIW, apparently this cam should be a drop in, but best to dial it right. No one seems to have got this one to dial in exactly right $:-\$

Davez134 · « **Reply #128 on:** January 12, 2015, 01:53:09 PM »

Quote from: edwardmorris on January 12, 2015, 01:42:45 PM

Again, I'm sure you've gone through all of these, but in case you missed it, here's Ron's walkthrough on a K2 with the same cam

http://forums.sohc4.net/index.php?topic=36459.msg1007168#msg1007168

FWIW, apparently this cam should be a drop in, but best to dial it right. No one seems to have got this one to dial in exactly right $:-\$

Thanks, yeah I saw that one and bookmarked it. After reading it, I thought this would be easy. Taking rest of day off and coming back fresh tomorrow

timbo750 · « **Reply #129 on:** January 12, 2015, 05:24:25 PM »

I read the web cam guide, which I should of done before making my earlier comment. The only thing I can think of (because I don't think anybody else has asked this) is are you doing this with zero valve lash? Or is there a chance that somehow you got the wrong cam in the box.

Davez134 · « **Reply #130 on:** January 12, 2015, 07:15:46 PM »

Yeah, I am doing this with zero lash. It is marked "web41" scribed into it. None of the numbers I'm getting even match anywhere close to their other profiles. I got back into it tonight. Weird thing is when I check the lobe center on the intake side, I get close to timing card info, but exhaust is way off. I got 108 lobe center on intake, and 123 on exhaust. I figured I would try and get them closer, so I adjusted and got 114 lobe center intake, but exhaust jumped up to 140?? I don't get it. I'm just going to line up timing marks like a stocker.

Trad · « **Reply #131 on:** January 12, 2015, 07:40:38 PM »

Quote from: Davez134 on January 12, 2015, 07:15:46 PM

I'm just going to line up timing marks like a stocker.

Dang, I read through this and my head is starting to hurt now too. haha. Your above comment is all I'm doing with my webcam when I install it so don't feel so bad.

Blackfin5 · « **Reply #132 on:** January 12, 2015, 07:52:18 PM »

Without a slotted adjustable sproket, you can only adjust the lobe CL number by moving the cam sprocket by one tooth either way. Even then its frustrating because each time you measure with the dial indicator is slightly different and make sure you find exact TDC with a piston stop.

I was suppossed to be 104.5 for both intake and exhaust lobes. At 104.5 intake I was about 105.25 exhaust. I finally averaged out both libes to about 104.75. I say "about" because each measure is slightly different than the last.

Davez134 · « **Reply #133 on:** January 12, 2015, 11:25:29 PM »

Quote from: Blackfin5 on January 12, 2015, 07:52:18 PM

Without a slotted adjustable sproket, you can only adjust the lobe CL number by moving the cam sprocket by one tooth either way. Even then its frustrating because each time you measure with the dial indicator is slightly different and make sure you find exact TDC with a piston stop.

I was suppossed to be 104.5 for both intake and exhaust lobes. At 104.5 intake I was about 105.25 exhaust. I finally averaged out both libes to about 104.75. I say "about" because each measure is slightly different than the last.

I have an APE adjustable sprocket. I am able to make the adjustments, just can't figure why exhaust is so far off.

MRieck · « **Reply #134 on:** January 13, 2015, 04:29:58 AM »

Quote from: Davez134 on January 12, 2015, 11:25:29 PM

Quote from: Blackfin5 on January 12, 2015, 07:52:18 PM
Without a slotted adjustable sproket, you can only adjust the lobe CL number by moving the cam sprocket by one tooth either way. Even then its frustrating because each time you measure with the dial indicator is slightly different and make sure you find exact TDC with a piston stop.

I was suppossed to be 104.5 for both intake and exhaust lobes. At 104.5 intake I was about 105.25 exhaust. I finally averaged out both libes to about 104.75. I say "about" because each measure is slightly different than the last.
I have an APE adjustable sprocket. I am able to make the adjustments, just can't figure why exhaust is so far off.

Because it is a Web cam. You will never achieve the LC #'s on the card. First off put the lash you will be running in place. You want to time a cam with the actual lash in place to get a real idea of what will be happening under running conditions. Your opening/closing #'s will be less but who cares.....they are just #'s.
Split that cam timing trying to get opening closing #'s the same. Example...intake opening 6 degrees BTDC and exhaust closing 6 degrees ATDC. I used lower #'s because having the lash in place will lower the #'s.

Davez134 · « **Reply #135 on:** January 13, 2015, 08:03:38 AM »

Quote from: MRieck on January 13, 2015, 04:29:58 AM

Quote from: Davez134 on January 12, 2015, 11:25:29 PM
Quote from: Blackfin5 on January 12, 2015, 07:52:18 PM
Without a slotted adjustable sproket, you can only adjust the lobe CL number by moving the cam sprocket by one tooth either way. Even then its frustrating because each time you measure with the dial indicator is slightly different and make sure you find exact TDC with a piston stop.

I was suppossed to be 104.5 for both intake and exhaust lobes. At 104.5 intake I was about 105.25 exhaust. I finally averaged out both libes to about 104.75. I say "about" because each measure is slightly different than the last.
I have an APE adjustable sprocket. I am able to make the adjustments, just can't figure why exhaust is so far off.
Because it is a Web cam. You will never achieve the LC #'s on the card. First off put the lash you will be running in place. You want to time a cam with the actual lash in place to get a real idea of what will be happening under running conditions. Your opening/closing #'s will be less but who cares.....they are just #'s.
Split that cam timing trying to get opening closing #'s the same. Example...intake opening 6 degrees BTDC and exhaust closing 6 degrees ATDC. I used lower #'s because having the lash in place will lower the #'s.

So right now I have intake opening at 23degrees BTDC and exhaust closing at 3 degrees ATDC. So you're saying get those numbers closer ( like 13 degrees, the middle, if possible)? Right now still zero lash, will change that next go around.

Davez134 · « **Reply #136 on:** January 13, 2015, 09:47:14 PM »

So I've never been one to give up...

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edwardmorris · « **Reply #137 on:** January 13, 2015, 09:51:23 PM »

Its still going over my head, but I see two 103.5s in there so I take it you got it lined up?

PAARTAAYY!

Davez134 · « **Reply #138 on:** January 13, 2015, 10:04:57 PM »

Yeah! Having a few drinks to celebrate! Cam was way advanced (and I was a little retarded) I actually made a call to webcam, talked with a girl named Faith who straightened me out! Spent over 30 minutes on phone with me. Now I can move on to other things...

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Nuffsa Fugginnuff · « **Reply #139 on:** January 13, 2015, 11:29:47 PM »

Subscribed. And, enjoying the ride.

timbo750 · « **Reply #140 on:** January 13, 2015, 11:55:57 PM »

Dave, congrats on getting the cam sorted. The lobe centres didn't end up too far from spec. I am actually using a web cam in one of my engines now know exactly what I need to do to set it up right. Thanks for documenting this so well.

disco · « **Reply #141 on:** January 14, 2015, 02:09:10 AM »

Well done on sorting out the your cam issues.

btw that's a real neat job you done with the Gordon kit! Looks factory!

iron_worker · « **Reply #142 on:** January 14, 2015, 07:50:32 AM »

What did you end up doing to sort it out?

IW

Davez134 · « **Reply #143 on:** January 14, 2015, 08:31:54 AM »

Quote from: iron_worker on January 14, 2015, 07:50:32 AM

What did you end up doing to sort it out?

IW

After a day and a half messing with it, I was starting to get so far off, things were just getting worse. My head hurt. Realized that at one point while adjusting I jumped a tooth on chain as well (long story) So I went back, double checked I still had TDC right (using piston stop), then started from scratch again, lining up marks on cam like stock cam. I called webcam and started going over numbers with them. Turns out, with my engine, lined up dead straight cam was about 7 degrees advanced. So I kept retarding cam until I reached my numbers. Now I really understand it though. Learned a lot.

MRieck · « **Reply #144 on:** January 14, 2015, 05:30:30 PM »

All that matters is you got it right and will get it right in future....just a lot faster.

I think now you understand what I meant with the opening and closing #'s on the valves. You can see how close they are.
That is going to be a nice engine.....it will definitely will let you know it isn't a 45 or 50 HP stock thing.

Davez134 · « **Reply #145 on:** January 14, 2015, 07:23:12 PM »

Quote from: MRieck on January 14, 2015, 05:30:30 PM

All that matters is you got it right and will get it right in future....just a lot faster.

Yeah, as soon as I started getting closer, a light just came on and I "got it." Glad I didnt just settle, with all the time I put in to the rest of the motor to make it right. Should be easy from here on out, as everything else on the bike I have done before.

Davez134 · « **Reply #146 on:** January 15, 2015, 10:59:38 AM »

Installed all balls steering bearings, not too hard. Quick question about adjustment/tightness. I know it's hard to quantify, but (without forks installed) should the triple stay in place or easily move back and forth? Right now I can move easily with my hands but it stays in place if I move frame around. (Hope this makes sense)

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edwardmorris · « **Reply #147 on:** January 15, 2015, 11:30:50 AM »

Lester wheels?? I see lester wheels! Sorry I get excited

Davez134 · « **Reply #148 on:** January 15, 2015, 11:45:27 AM »

Quote from: edwardmorris on January 15, 2015, 11:30:50 AM

Lester wheels?? I see lester wheels! Sorry I get excited

I just have a front

iron_worker · « **Reply #149 on:** January 15, 2015, 11:47:35 AM »

A tooth out on the cam sprocket ... makes sense now. Your engine will thank you later for getting it right.

IW

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Author Topic: 1972 CB750K2 (start from scratch) project. Cases back together (Read 101590 times)