Topic: Project "Evolution" 78' CB750K... the morphing continues...

[Retro Rocket]

Send it back mate...

[madmtnmotors]

Send it back mate...

That's the plan. The Webcam warranty states:

"sprocket flanges can break and are not covered under warranty"

but my contention is that this part is defective. I've started the communication process (with pictures!) and will post results here.

[Retro Rocket]

Send it back mate...

That's the plan. The Webcam warranty states:

"sprocket flanges can break and are not covered under warranty"

but my contention is that this part is defective. I've started the communication process (with pictures!) and will post results here.

To me, it looks like it was drilled off center...

[Stev-o]

Damn...

[Davez134]

It does look off center in the broken picture. Damn, I have that same cam too

[madmtnmotors]

Send it back mate...

That's the plan. The Webcam warranty states:

"sprocket flanges can break and are not covered under warranty"

but my contention is that this part is defective. I've started the communication process (with pictures!) and will post results here.

To me, it looks like it was drilled off center...

Yep. The stock sprocket would not line up. I was going to use the stock sprocket to establish some "baseline" degree data and then switch to the slotted sprocket. The slotted sprocket lined up with the offset hole and the bolts went in by hand without any undue effort. My contention is that the hole was too close to the edge of the sprocket flange. I had not even put final torque on the sprocket bolts because I was still in the process of degreeing the cam when I noticed the missing piece.

[Stev-o]

Send it back mate...

That's the plan. The Webcam warranty states:

"sprocket flanges can break and are not covered under warranty"

but my contention is that this part is defective. I've started the communication process (with pictures!) and will post results here.

Where did you purchase the cam?

[madmtnmotors]

While awaiting a response, I have decided to move forward and dip into the "private stock". I have selected the one pictured in the center:




It had a strange hieroglyph stamped on the end:




Well I'll be "D"amned!




I was reluctant to use a "D" grind at first based strictly on the numbers:

 
Per the "Satanic Mechanic"                                                                         
                                                                         
         Valve   Durat-                                                     In o/c      btc/abc
Cam      lift    ion       Description                                   Ex o/c     bbc/atc
---------------------------------------------------------------------------
D        .345    277       A famous grind. Excellent for a major HP     32/65
          .325    294       increase, yet a wide range of use. Long       77/37
                                 exhaust duration for sustained high speed
                                 cruising without excess combustion chamber
                                 temperature. May be used with stock
                                 springs if desired.



Holy crap! 290 degrees duration on the exhaust? Does the exhaust valve ever close? Intake opens at 32 degrees btc? SOB will have to idle at 3k!

Of course, once I realized that I was comparing apples to oranges, the picture becomes clearer. Kenny Harmon cams are measured at .020" lift while almost every other cam on the planet is measured at .050"! When open/close numbers are measured at .050" the "D" grind seems more sensible:


Intake open/close/duration @.050":  20btc/53abc/253
Exhaust open/close/duration @.050": 62.5bbc/22.5atc/265

I was saving this one for a more aggressive build, but I've got a deadline approaching... 

[calj737]

Wilbur, just double-check the valve-piston clearance. I am not nearly familiar enough with those cams to know whether that lift is going to punch the valve deep enough to knock a hole in your slugs.  I suspect because the new pistons are flat-topped you'd be fine, but given your timeframe and recent retrograde progress, never hurts to know before you find out...

[madmtnmotors]

Wilbur, just double-check the valve-piston clearance.

Well, I did clay the pistons (more for practice than anything else) with the Webcam 41. Now that everything is bolted up (and re-torqued), how do I check it now? Fish a piece of solder through the spark plug hole? Order another head gasket and rip the head back off? If I had to order a head gasket and rip the head off then I'd just as soon order another Webcam 41 and work on something else while I wait...

[calj737]

Is the lift comparable between the 2 cams? If you had sufficient clearance with the 41, then the D should be good (if equal in lift)

[madmtnmotors]

The lift numbers are close:

Webcam 41: 235/235

KHD: 245/225

The durations are the biggest difference:

Webcam 41: 237/234 @.050 lift

KHD: 253/265 @.050 lift

I may try a piece of solder through the spark plug hole.

[calj737]

Did you happen to measure the distance from piston top to deck while assembling? Add that to your gasket thickness to know what your stock "closed" valve position is. That should give you some reasonable data to work with, but soldering wire through the plug hole works well too.

On my 500 build, the lift of the Mega 126-20 cam, plus the Wisecos, plus a milled deck height required valve relief pockets to be milled into the pistons. I doubt yours will, but now is the time to know for sure.

[MRieck]

Wilbur, just double-check the valve-piston clearance.

Well, I did clay the pistons (more for practice than anything else) with the Webcam 41. Now that everything is bolted up (and re-torqued), how do I check it now? Fish a piece of solder through the spark plug hole? Order another head gasket and rip the head back off? If I had to order a head gasket and rip the head off then I'd just as soon order another Webcam 41 and work on something else while I wait...

You can pry down on the rocker arm ( with a dial guage on the retainer) Wilber. You check @ 10degress BTDC and ATDC. I'd advise using a crappy cam cover as it can screw up the tappet cover threads. I use a long, square shaft screwdriver...it does roll off the rocker arm when prying down.

[madmtnmotors]

Wilbur, just double-check the valve-piston clearance.

Well, I did clay the pistons (more for practice than anything else) with the Webcam 41. Now that everything is bolted up (and re-torqued), how do I check it now? Fish a piece of solder through the spark plug hole? Order another head gasket and rip the head back off? If I had to order a head gasket and rip the head off then I'd just as soon order another Webcam 41 and work on something else while I wait...

You can pry down on the rocker arm ( with a dial guage on the retainer) Wilber. You check @ 10degress BTDC and ATDC. I'd advise using a crappy cam cover as it can screw up the tappet cover threads. I use a long, square shaft screwdriver...it does roll off the rocker arm when prying down.

Now that I can do! As long as I don't have to take the top end back apart again...

[madmtnmotors]

Well, thanks for the reality check guys. I actually found another thread from garage-guy-chris where he had already fitted and checked a KHD cam against CI's pistons and was too tight. 

As for my measurements, both the intake and exhaust valves come within about .012" within 10 degrees btc and atc (checked every 2 degrees). 

Looks like the duration is the deal breaker here. i.e. opens too soon (intake) and closes too late (exhaust)

Soooo.... looks like three options:

>Get another Webcam 41 (either warranty replaced or source another)
>Use a stock K8
>Use a stock F2



tick, tock....


I will probably just get on the other bike and ride for the rest of the afternoon. 

[Davez134]

Have you tried contacting webcam for an answer yet? In my experience, their customer service has been good. Especially since you have these pictures. Did you buy direct from them, or a distributor? (I looked through the thread and didn't see)

[madmtnmotors]

Have you tried contacting webcam for an answer yet? In my experience, their customer service has been good. Especially since you have these pictures. Did you buy direct from them, or a distributor? (I looked through the thread and didn't see)

Waiting on a response from the distributor before I weigh in on their customer service...

I have also reached out to Jim French, our resident microwelder, about a potential repair if the warranty efforts fall through.

[Retro Rocket]

Have you tried contacting webcam for an answer yet? In my experience, their customer service has been good. Especially since you have these pictures. Did you buy direct from them, or a distributor? (I looked through the thread and didn't see)

Waiting on a response from the distributor before I weigh in on their customer service...

I have also reached out to Jim French, our resident microwelder, about a potential repair if the warranty efforts fall through.

Don't let the "warranty" fall through mate, thats clearly drilled off center, I've looked at a lot of cams since you posted that pic and NONE were like that Webcam you have...

[calj737]

Bummer, Wilbur. But at least you found out before the cam poked a hole in those slugs.

[madmtnmotors]

Bummer, Wilbur. But at least you found out before the cam poked a hole in those slugs.

Oh yeah, I'm all for getting it right. As much as I'd like to use the hotter cam, I'm not going to tear it down to cut the pistons at this point. Leaning towards the F2 cam.

[calj737]

Ok, Wilbur, time for a footstep in some direction??? Is it forward or backward at this point?

[madmtnmotors]

Definitely moving forward now! Except for the part where I knocked the headlight off the bench and broke it...

Opted for the F2 cam since the Webcam 41 is on its way back to where it came from and the "D" grind will need flycut pistons (next build). Should have it running by this weekend, ready to start the 500 mile break in. 

>Cylinders and head painted to match the cases. Engine is in the frame!
>Increased the main jets from 110 to 125 since we're now rockin' 836cc with a mildly ported head.
>Dyna coils along with Dyna S installed and static timed
>Added a couple of relays to take the load off of the ignition switch, not sure how many more wires I can fit into the headlight bucket...
>Added a "trigger" wire from the coil for a shift light


Left to do:
>Install new custom rear fender
>Finish tightening bolts

After the 500 mile break in:
>Install 1/4 turn throttle
>Lower the forks and shorten the shocks
>Fit drag pipes
>Drag handle bars? (Time permitting)
>Add "go fast" decals
>Head for the local track for test and tune 



Work on the bike got trumped this weekend. Got to see the Outlaws perform Friday night, which would have been pretty cool all by themselves, but they were the warm up band for George Thorogood! Then turned around Saturday morning and drove to Gainesville for the Gator Nationals! Got to meet "Mr. Drag Racing" himself:




Courtney kept hitting on me, but I had to explain to her that I was happily married. She was disappointed, but didn't take it too hard, since right after this photo was taken she went out and ripped off a number 2 qualifying run at 325mph in 3.69 seconds!




    

[Stev-o]

That's awesome, Wilbur, I really like John Force.  Courtney, Ashley and Britney too, three hot daughters!

[madmtnmotors]

Yeah, he definitely got it right. Brittany won the event in top fuel (her first event win).