550 650 head differences

[Sci85]

So I'm in the process of the 550 to 650 mod and got the 650 head in today. My bike is a 1982 and the 650 head is also a 1982 model. I noticed that the valves are identical between the heads and other than the combustion chamber, not much else is different. Other than the chamber, are there any other appreciable differences? Why not just run the 550 head and save all that cost?

Thanks,
Sci85

[Sci85]

Bump? No one ever measure these two? Anyone?

[Nessism]

The combustion chamber shape is more efficient on the 650. Most likely the chamber volume is different too (larger).

[dark7068]

the pistons are different combustion (maybe compression as well) if you put them side by side (at least my 550 and 650 pistons are)

[koolaid_kid]

Seems to me that you would want the piston domes to match up with the squish area in the head.

[Sci85]

Yes, certainly pistons are larger but I guess I expected the ports and valves to be larger also but that is not the case. Even my 550 intake boots fit right up...

[dark7068]

the 550 cylinder bore is 56.00 and the 650 is 62. combustion pressure is 128-185psi for the 550 and 142-199psi for the 650.. so a lot different.. the valves,etc are the same height, shape,lift, stems,etc. cams are the same lift, intake and exhaust..

more compression in the 650 head and pistons/cylinders,, explains why the extra 40hp increase Ive read about.

so matching the cams with the head/clamps using for proper matching and wear is worth it. everything else being the same it should wake up the little 550 pretty good.. Ive tried selling my swap but no one is buying so I will rebuild the 550/650 top end this winter with help from a friend that builds the little cars with yam motors in them ... if the intake and exhaust are the same,, then I can use the 4-1 header I have, and have a nice 85hp motor rockin next yr. with a dyna 2000 ignition...

[Nessism]

40 hp increase? Don't think so.

[TeamDar]

According to the specs it is 24 HP increase. Still quite impressive.

[Suzuki_Don]

.. cams are the same lift, intake and exhaust..

...

WRONG -- the 550 and 650 cams have different lift and duration

[Suzuki_Don]

Seems to me that you would want the piston domes to match up with the squish area in the head.

KK has hit on part of the formula to wake these engines up. If you want the full power available then make sure you adjust the squish band and slot the cam sprockets and degree the cams accordingly.

This is all documented if you use the search function.

[dark7068]

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

[koolaid_kid]

Ah, degreeing the cams. That brings back bad memories.

[Sci85]

I've read Suzuki Don's thread but I got lost in the different sprockets, cams, instake boots, etc of the build. I guess I need to go back and read it again. I plan on using my original cams and sprockets. I've never degreed a cam before much less setup a squish band so I doubt I have the necessary tools. However, if there is a thread that is specific to doing these, please pass along. Build threads are awesome but they are usually specific to the OP's knowledge and views rather than a tutorial so I miss things that other folks already know.

Thanks,
Sic85

[koolaid_kid]

I read his thread also when I was in the process of degreeing my cams and I also had to read it multiple times. I ended up going to the web and reading up on it there also. Most were about car engines, but the concept is the same. You'll need to find a place to slot your cams, a degree wheel, a method to find exact TDC, and a way to set up a pointer.
I can't speak for Don, but all I did was mill my head for higher compression, which necessitated degreeing the cams.
I would suggest using which ever cams are the hottest (usually the highest lift and greatest duration). Even factory cams can benefit from being degreed, which dials in the exact position.