Larger Valves for 81 650 head

[Guest]

Dose anyone have any experience with installing larger valves? I dont plan to machine the head myself, I would just like to know what aspects to take into consideration when planning something like this?

[rapidray]

I do it to customers heads all the time. It is all in cutting the valve seats correctly. Ray.

[Nessism]

Waste of money. The 650 is already hot rodded compared to some other GS bikes. If you want more speed get a bigger bike.

[trippivot]

master piece theater

I have not done a 650 but it's only money and time

it only gets expensive if you cannot find compatable length valves in the diameter you want.

new valves have to have matching keepers.

keepers have to work in the retainers. retainers have to have adjusters.
buckets have to work with retainers, buckets have to fit in head.

installed heights for the springs you intend to use plus the lift cant smash the retainers into the valve seal.

I hope you don't plan on using stock 650 springs with increased mass of the bigger valves. Valve float happens when the spring can't handle the cam lobe profile/ weight.

grams turn into pounds at 8K< and higher

[ashdricky]

Thank you this dose help to send me in the right direction. I figured it would be expensive, I am striving for 80hp which seems like a pipe dream, but we still intend to do our best. how will larger valves affect plans to shave material off of the entire head to slightly increase compression?

[tkent02]

Waste of money. The 650 is already hot rodded compared to some other GS bikes. If you want more speed get a bigger bike.

Ed,
If I wanted to ride a bigger bike, I would wheel one out and ride it.
Some of us prefer smaller, quicker, lighter more nimble bikes at least some of the time. Some of us prefer our smaller bikes to be very fast. Big GSes are heavy slugs. I like the 1100G, it's like riding a cannonball, a big heavy pig of a cannonball. It's powerful enough already. But I also like the little stuff.

I hope this thread takes off. Any info about bigger valves in my GS 550/650/700 cafe clone or anything else that would help wake it up would be great.
I want a little rocket.

Ray, you have done this stuff to some GS 650s? Porting, hotter cams and things like that? What works the best? Not looking for a drag race motor, but one to blast around my little canyons and mountain roads.
How big can the displacement go on a 650 cylinder? Bigger than 700cc or is that about it?

This will be on a 1979 GS 550 bottom end if that matters.

[rapidray]

tkent, call me at 714--356-7845. Ray.

[Nessism]

Go for it Tom, I just don't think it's worth the money. The GS650 has a bathtub shaped combustion chamber and higher compression than the typical GS 8V engine, so how much more power do you think can be squeezed from it? $500 for head work will net you maybe five hp. Add some oversized pistons (another $500?) and you might get another four hp...maybe. Sounds like fun but before you know it your wallet will be empty.

[tkent02]

Sounds like fun but before you know it your wallet will be empty.

No, it won't. A stock Suzuki 650 top end with the largest oversize piston gives more power than a GS 750, almost as much power as a GS 850, according to someone who has done it. That's a huge increase from what the GS 550 had originally. Something like a 50% increase already.
I'm thinking I can do a lot better, while still spending far less than it would cost to buy another bigger bike that I don't want anyway.
I know the 550 bottom end is indestructible, so why not?

[Steve]

, I am striving for 80hp which seems like a pipe dream, ...

If I remember correctly, the 650 was rated at 72 hp. Of course, that was probably crankshaft hp. You want that 80 at the crank or the wheel?

A stock Suzuki 650 top end with the largest oversize piston gives more power than a GS 750, almost as much power as a GS 850, according to someone who has done it.

Not sure how much a 750 was rated for, but I think the 850 was rated for only 78 hp.

With the 650 having only 6 fewer ponies and about 100 pounds lighter, it is a rocket, compared to the 850.

Yeah, I have both of them here, I can compare them directly.

.

[Nessism]

No, it won't. A stock Suzuki 650 top end with the largest oversize piston gives more power than a GS 750, almost as much power as a GS 850, according to someone who has done it. That's a huge increase from what the GS 550 had originally. Something like a 50% increase already.
I'm thinking I can do a lot better, while still spending far less than it would cost to buy another bigger bike that I don't want anyway.
I know the 550 bottom end is indestructible, so why not?

I'd love to see another good 550/650/700? hot rod thread. Don's was a lot of fun to follow. Go for it. What the F. It's only money.

[1_v8_merc]

Turbo! Turbo!

[ashdricky]

Custom valves are proving not to be cheap, so I am looking for a slightly over-sized set of valves. Dose anyone know the dimensions of the 650 valves? dimensions of 750 and 850 valves?

[Suzuki_Don]

If I remember correctly, the 650 was rated at 72 hp.



Not sure how much a 750 was rated for, but I think the 850 was rated for only 78 hp.

With the 650 having only 6 fewer ponies and about 100 pounds lighter, it is a rocket, compared to the 850.
.

A web site I use regularly states the hp figures for the main GS models as:

550 -- 49hp
650 -- 73hp
750 -- 72hp
850 -- 77hp

As Steve states the 650 is a rocket. And it's great advantage is it's lighter weight and when mounted on the 550 crankcases the added advantage of an extra gear.

After I had my bike on the road for a couple of months I did a power-to-weight ratio comparison between my bike and other models in the late seventies. And to my surprise my bike has a greater power-to-weight ratio than the CBX1000-6 which was a real performance bike of that era.

[ashdricky]

A web site I use regularly states the hp figures for the main GS models as:

550 -- 49hp
650 -- 73hp
750 -- 72hp
850 -- 77hp

As Steve states the 650 is a rocket. And it's great advantage is it's lighter weight and when mounted on the 550 crankcases the added advantage of an extra gear.

After I had my bike on the road for a couple of months I did a power-to-weight ratio comparison between my bike and other models in the late seventies. And to my surprise my bike has a greater power-to-weight ratio than the CBX1000-6 which was a real performance bike of that era.

do you know where i can find the valve dimensions for the larger gs models?