valve clearance 750twin

steell wrote:

It involves removing the cams and valves from the head and taking the bare head and cam sprockets to a motorcycle machinist.

If I took the head and cam sprockets to the local motorcycle machinist, I'd expect to pay no more than $50 to have .030" removed from the head mating surface, and the sprocket bolt holes elongated by .1".

Fortunately I have a vertical mill in my shop so I can do the work myself, to bad it don't have enough travel on the table to do a four cylinder head though

Cool, thanks for the info, Steell . In this market, that's more like $100-150, but now I have an idea of what it would cost. I think I have a good machinist, he's working on my buddies R90 and only charged me $10 to bead blast my valve cover. He's also fabing me a couple of covers for the "air suction valve" hole's on the valve cover. Would the increase in HP be worth the time/$? I've already gone down one tooth on the front drive sprocket and was thinking of changing the rear also, to give me more top end crusing. I was thinking a bit more HP would help that.
Thanks again...
...I wish I had a shop w/a milling machine:(

I have the cylinder head that was the first one I ever tried (I don't even qualify as a novice machinist) if you want to try it out.

I think I only cut around .060 from the surface

I think that would probably boost your compression up near 10.5:1.

Compression by itself don't really add a bunch of hp, but then no single improvement will (excepting turbo/supercharging and NOS).

I think Bowling and Grippo's website contains a calculator that will tell you how much hp you will gain simply by increasing compression. I ran the numbers once for a 10.5:1 750 twin (vs stock 8.5:1), and IIRC it calculated a 3-4 hp gain.
Found it www.bgsoflex.com/auto.html


Question is, how are you going to start that 10.5:1 750 twin? I don't believe the electric starter is going to do much, just look at the problems we have with them now.

Kick start? It's got 25% more compression, do you really want to kick start it, do you think the kick starter mechanicals can handle it??

Ok, I'll admit it, I am still thinking about it. And those hot cams for $272 (I think at MegaCycle ) :evil: :evil: :evil: :evil: :evil:

It sounds strange, but I keep ignoring my 1105 150 hp J motor in a Turbo framed GPz750 project and working on the 750's

Post edited by: steell, at: 2007/03/19 17:34

steell wrote:

I have the cylinder head that was the first one I ever tried (I don't even qualify as a novice machinist) if you want to try it out.

I think I only cut around .060 from the surface

I think that would probably boost your compression up near 10.5:1.

Compression by itself don't really add a bunch of hp, but then no single improvement will (excepting turbo/supercharging and NOS).

I think Bowling and Grippo's website contains a calculator that will tell you how much hp you will gain simply by increasing compression. I ran the numbers once for a 10.5:1 750 twin (vs stock 8.5:1), and IIRC it calculated a 3-4 hp gain.
Found it www.bgsoflex.com/auto.html


Question is, how are you going to start that 10.5:1 750 twin? I don't believe the electric starter is going to do much, just look at the problems we have with them now.

Kick start? It's got 25% more compression, do you really want to kick start it, do you think the kick starter mechanicals can handle it??

Ok, I'll admit it, I am still thinking about it. And those hot cams for $272 (I think at MegaCycle ) :evil: :evil: :evil: :evil: :evil:

It sounds strange, but I keep ignoring my 1105 150 hp J motor in a Turbo framed GPz750 project and working on the 750's <br><br>Post edited by: steell, at: 2007/03/19 17:34

Are you telling me that you have already milled a head and you havn't put it on? Are the megacycle cams necessary when you increase the compression. It's deffinitly not something I'm gonna do this year, but if I pick up another head, I might give it a try. I don't know how strong the racheting mechanism is on the kickstart but I'd think putting a longer kickstart lever might help starting it. Right now when she's warm and running right she'll start on a half kick and 4 or 5 started her up on our coldest days, this winter, w/a low battery. I'm half convinced that half the problems we have w/the electric start is oil type. Also, wouldn't a higher amp battery give the starter a bit of an extra boost?
Thanks again for all the information.
Ron

OK, I got the cheap valve tool from Z1, had it here in 3 days, Jeff really has great service. Managed to compress the valve and used the tool to hold it down. The shim rotates freely and I can get one edge of the shim lifted above the bucket. The problem is that I can only get one edge of the shim lifted. The opposite edge won't lift, it kinda gets jammed against the edge of the bucket. It's like I need to get something under the shim, to lift up the back edge. Any ideas or thoughts on lifting the shim out of the bucket. The valve I'm working on is the exhaust that had a clearance of 0.03, the others had a clearance of 0.05. Is there some order I remove the shims, to get better clearance, to remove the shims:blink::S:unsure:?

ronjones wrote:

...Is there some order I remove the shims, to get better clearance, to remove the shims:blink::S:unsure:?

If my memory serves, you rotate the crank to cause any given valve to the lobe points away from the piston (giving you the biggest gap possible). Then you cram the lever in, put the batwing in place, remove the lever, and use a $2 magnet wand from AutoZone (right by the checkout counter) to pull out the shim.
Then you rotate the crank a bit and repeat on the next valve..
I hope I'm right, it's been quite a while since I did it....

The $2 magnet wand from autozone is the bit of info I needed thanks, Toast. I was stumpt at that point.

ronjones wrote:

The $2 magnet wand from autozone is the bit of info I needed thanks, Toast. I was stumpt at that point.

Glad to help! I thought I'd over-specify in case somebody else reads it..


Man, that $2 magnet wand has come in handy countless times for everyone in the house. Here's a tip - get 2, one for "inside" and one for "outside". And get the fluorescent orange one, so it's easier to spot on your workbench, amongst all the carb parts and metric wrenches...
:laugh:

Biquetoast wrote:

"... And get the fluorescent orange one, so it's easier to spot on your workbench, amongst all the carb parts and metric wrenches...
:laugh:

So, when where you in my garage and saw what my workbench looks like :laugh: I think I have a magnetic grabber, already, lost in the pile.:blush: