Topic: New valve springs vrs stock cam chain adjuster.

[seaweb11]

Took the Tracy down to the guy who built the motor to have him adjust the valves and sync the carbs. There was a ticking sound for sure. I didn't want to mess with it before he looked at it 1st

Spent a couple of hours with him going over everything and still had a clicking sound although some of the racket had quieted down.  We also found 2 of the adjuster screws had stretched?? He was pissed and said we'll just take off the head and have a look.

Thank god for the frame mod    20 Min's later we were looking inside.  Long story /cut to the chase............
He said the old cam chain adjuster can't put enough pressure onto the cam chain because of the stiffness of the new valve springs.

No racing on the track for me today.

He showed me a custom box he had made for one of his sand drag bikes because of the same problems, so he's making me one now too

Left it with him for a couple of days.

P.S. This guy adjusts the valves with his fingers ...NO.... a feeler gauge When I asked him about it he laughed and said if you had done this 10,000 times, so could you

Here is the drag bike I was referring to.


Another of his stable


Anyone else run into this issue?

[Jerry Rxman Griffin aka MuthaF'er]

Mine's always had a ticking in the top end since it became 812 with full race cam and S & W springs with stainless intakes. I attributed it to the high lift & longer duration cam coupled with the stiff springs closing the stainless valves. I've never felt the cam chain was adjusted good enough even with forcing the "plunger" inwards prior to tightening. However it has held together for 25,000 miles of abuse. I'm looking forward to this last build using a new cam chain and new primary chains for the first time especially since I know more about building engines now and I can afford to do it the right way.

Keep us informed. Pictures of your new pieces required before they go into the engine.

[seaweb11]

Just thought I would post TT's thoughts on this thread from another one.

"Changing the cam profile would also require an amendment to a static cam chain adjustment procedure.  If you are increasing the valve spring strength, it stands to reason the adjuster spring strength may need to be changed as well for a static adjustment.
Stiffer valve springs and a more radical profile cam, can easily place more stress on a cam chain.  If you are adjusting the tensioner with the engine running, you may have to modify standard procedure to accommodate other changes made to the engine.

Just an observation.  Things needed for a race engine are somewhat different than things needed for a street engine or one operated within manufacturer parameters.  Not all special needs apply to the street.  One of the early lessons in engineering is that changing one thing in a design often effects other things in the overall design.  It's the ripple effect.  Which sometime resembles the "whack-a-mole" game".

Cheers,

[Terry in Australia]

Well I'm sorry to hear about your engine troubles Derek, and from your main thread the actual damage was the wrist pins not getting any oil and siezing in the little end bush of your conrods? I haven't seen this before in a CB750, but it's common in two strokes, caused by oil starvation. Is there any damage to the cam, cam towers, pistons, cylinders etc? Make sure your man checks the oil pump is working, and that you don't have any blocked oilways. 

As far as the ability of the stock cam chain tensioner to cope with stiffer valve springs, well, once the cam chain tensioner rod is locked, that spring doesn't do squat. Like Jerry has suggested, most times the chain just isn't adjusted properly. The problem lies in the method employed to adjust the chain's tension, it's too "hit and miss".

In your case though, thanks to Gordon's magnificent removeable frame rails, you can adjust the cam chains tension with the cam cover off, so that you can physically check that the chain is tight. Using Jerry's method, you can "push" the tensioner rod in, lock it off, and rotate the crank while watching the chain on the cam sprocket. If there's a lot of "jump" in the chain, it's too loose. The important thing is to get the slack at the back of the engine, so you need to rotate the crank clockwise until all the slack is at the back, then reset the tension. While the cam cover is off you can re-adjust your valves too. Cheers, Terry.

[WHALEMAN]

With all due respect I don't believe this man understands the cam chain adjusting system. You can put all the pressure you want if you push on the shaft with the lock bolt loose. I would not suggest this. I am at a loss for the connection between valve spring tension and cam chain tension. How can a tappett screw stretch? They are in compression. If cam chain is loose the shaft is most likely siezed as my last post talks about. Dan