Cams question

[Anonymous]

Let me try this again - it is supposed to be an 8 ) - with no space between them. That was intentional.

[Jethro]

I need a new head for my 81 1100E. When you figure out what those puppies are all about, PM me. Maybe we can figure it out together?

[Anonymous]

OK, I measured them.
The cheap calipers I have should get me close.
Base on both cams is 1.18
Intake lobe height is 1.37
Exhaust lobe height is 1.35.

Stock cams?
Stock exhaust with a slightly warmer intake?


Jim

[Anonymous]

From the spec sheet url I gave you - an '83 stock GS 1100 exhaust cam has a 'lift' at the valve of 0.282". My '80 GS 1100 exhaust has a base circle of 1.18 and a lobe height of 1.353. This gives a rocker ratio of ~1.6886. (I'm using valve lash of 0.006" as the sheet specifies - I subtract that from the lobe height). I say approximately because that is for an '83 cam not an '80 and 0.006" valve lash is a bit much for a stock cam. So I'm off a bit, but probably not by much.

I reread the spec sheet and noticed that the valve lift was measured at 0.000" valve lash (at least that's what it looks like - hard to read) instead of the 0.006" that I assumed they used. That changes the rocker ration from 1.6886 to 1.6786.

Now, to your cams. Are these the cams that have R1 stamped on them? If they are then the lobe heights are not what I expected.

My stock cams have the folloing measurements:

Base on both cams is 1.185
Intake lobe height is 1.363
Exhaust lobe height is 1.353

Which is in the same ballpark as your cams. The cams that I purchased and I thought were Yoshi have the following specs:

Base on both cams is 1.185
Intake and exhaust lobe height is 1.385

This gives a valve lift of 0.335", which is close the the data from Bertaut which lists a lift of .330" for the Yoshi Stage 1.

If you have the cams back in the motor, you could run some measurents on the duration to be absolutely sure what you have. I'm going to do that tomorrow if I have the time. I'm going to purchase a dial indicator with at least 0.5" of travel so I can measure the valve lift also. The dial indicator I have now only goes to 0.2" of travel which is good enough to measure the duration since you measure it at 0.050" of lift.

Measuring duration is not difficult, you just need a dial indicator, piston stop (to find tdc), and degree wheel. You need these if you are going to degree your cams anyway.