550 650 head differences

[Suzuki_Don]

The issue with choosing cams for the motor is that the 650 cams have more lift and the 550 cams have more duration. If there was one cam that had both (more lift and more duration) that would be great, but that is not the case. I went with the 650 cams and slotted the sprockets myself. I knew that old chain saw file would come in handy for something.

My bike pulls away from 30mph in either 5th or 6th with no problems and has lots of torque low down. My friends CB750 cannot get even close to me on the road. I don't know why anyone would choose the more peaky 550 cams over the torquey 650 cams unless you want to be riding in excess of 5000rpm continually or intend on racing your bike.

On the issue of degreeing the cams, it is not really optional. When you go to do the cam timing after fitting the cams to the head you will find that things do not line up properly.

[Sci85]

So if I want to go this route, I need to buy 650 cams. Can I use my 550 sprockets or do I need to buy 650 sprockets?

To slot the sprockets, how much material needs to be removed? What did you use to do it?

Will the cams have to be cut? I don't really have a way to cut the ends off.

Can you use a dial gauge to determine TDC or is there another tool required?

What degree wheel do you use and are there any fitment issues that need to be addressed?

And you mentioned squish band. What is that exactly and how do you measure and then modify it? What should it be?

Lot's of questions I know but this is new territory for me.

Thanks,
Sci85

[Suzuki_Don]

I will anwer your questions in turn:

So if I want to go this route, I need to buy 650 cams. Can I use my 550 sprockets or do I need to buy 650 sprockets?

I did not use my 550 cam sprockets because they had rubber dampers bonded to them. I used 650E sprockets. DO NOT USE GS650G sprockets under any circumstances even though they may be cheaper to buy. They will wreck your engine big time. If your 550 cam sprockets do not have the rubber dampers then they should be ok to use.

To slot the sprockets, how much material needs to be removed? What did you use to do it?

About 1/4" of material each side of the existing holes, maybe not even that much. I used a small round file. From memory it was a file for shapening chain saw teeth. The existing holes in the sprockets is 7mm I think so a 1/4" round file will be ok.

Will the cams have to be cut? I don't really have a way to cut the ends off.

One end of each cam needs to be removed. I used a hacksaw. It did not take that long. I mounted the camshafts in the vice between two pieces of board (soft wood) so as not to damage them

Can you use a dial gauge to determine TDC or is there another tool required?

The best way to determine TDC is to use a degree wheel and a positive stop and then remark the TDC mark on the crankshaft behind where the points, ignition plate sits.

What degree wheel do you use and are there any fitment issues that need to be addressed?

You can use any degree whell you like, the bigger the better. There are plenty on the web, do a search or I can send you one to print out. I glued mine to a flat metal disc from an old set of scales. Anything to keep it flat so it does not wobble around and move away from the pointer. Simply mount the degree wheel onto the end of the generator rotor after removing the bolt.

And you mentioned squish band. What is that exactly and how do you measure and then modify it? What should it be?

The squish band is the distance between the top outer land of the piston and the lower surface of the mating cylinder head. As the piston rises the mixture is forced from the outside of the bore into the centre above the piston crown for the firing of the spark plug and better combustion. This distance ideally should be around 0.040" and definitely no more than 0.060". Some people run at 0.020" but I would n't on a street motor, that's more for race engines where the piston might actually be kissing the head under extreme conditions. You adjust this clearance by fitting thicker or thinner cylinder base gaskets. I made my own and it is still holding up well after 10k.

Lot's of questions I know but this is new territory for me.

There are pictures of all of these things mentioned above in my threads and I have plenty of pictures to share if you need them. You can email me if you like for advice and information or you can keep it all on here if you want to develop this thread. It's up to you.

[Suzuki_Don]

SCI85, here is some reading for you. Read the whole thread, about 22 pages to improve general knowledge. This link shows how the squish band clearance is measured.

http://www.thegsresources.com/_forum/showthread.php?t=164443&page=15

.

[Sci85]

Excellent. Thanks Don for the info and patience. Now, I need to find that money growing tree. The budget is imploding quickly!

And yes, I would appreciate the degree printout. That would save me a few bucks anyway.

[Suzuki_Don]

Excellent. Thanks Don for the info and patience. Now, I need to find that money growing tree. The budget is imploding quickly!

And yes, I would appreciate the degree printout. That would save me a few bucks anyway.

I will need your email address to send a copy of the degree wheel.

[Steve]

guess the info I was passed on by the previous owner was way wrong , sorry gang.

And this surprises you ... HOW??? :-K

SCI85, here is some reading for you. Read the whole thread, about 22 pages to improve general knowledge. This link shows how the squish band clearance is measured.

If you have your preferences set correctly, it's only 9 pages, but who's counting.

.

[dark7068]

that's a great write up don, I learnt a lot from that.. thanx.

I would be interested in that print out too if possible.

[Suzuki_Don]

that's a great write up don, I learnt a lot from that.. thanx.

I would be interested in that print out too if possible.

Remember guys -- the Search function