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GS550 to 650 cylinders questions, compression, heads, vm vs bs

Toasty said:
Hmm well it's something to consider, torque is always good but 650E stuff is kind of hard to come by. If I can use the G cams with E sprockets I may go with that. What other mods have you done to your engine?

Btw, my 550 has CV carbs (same body as the 650) do you think it's worth getting the dynojet kit (plus whatever it doesn't come with) or just get the 650 spec jetting individually? I appreciate the detailed responses btw, this is gonna be my first big engine build :o
Click to expand...

Glad to help, if you do a search on my user name there are many threads on my engine build: degreeing cams, adapting 550 4/1 exhaust to 650 head, fitting new fuel tap as old fuel tap fouled the new CV carbs (you will not have that issue), clutch plate issues, etc. A lot of stuff. I have fitted the 32mm BS carbs from a GS650G and rejetted to 650E specs, pushed mains up from 97.5 to 100 is the only difference. It's only if you use pods that you will need a kit from dynojet. I have a 4/1 exhaust and no jetting changes required. My bike looks standard with original air filter, etc, but goes like a bat out of hell.

Use the 650G cams and look out for a set of GS650E cam sprockets on Ebay.

There are a number of threads on my engine build, I split the crankcases and did everything from the bottom up.

Here is one thread worth reading - a lot of camshaft info, mainly installation:

http://www.thegsresources.com/_forum/showthread.php?t=155072&page=7



MyGS550a.jpg



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Great looking bike, Don, & I really appreciate all your advice & experience! Found a wrecked gs650, hope to swap dual discs to my 77 gs750 & engine to my wife's 77 gs550 if the cylinders check out okay or if I can track down some factory oversized pistons (may be real tough to find, discontinued I suspect).

Thanks!
 
Chuck78 said:
Great looking bike, Don, & I really appreciate all your advice & experience! Found a wrecked gs650, hope to swap dual discs to my 77 gs750 & engine to my wife's 77 gs550 if the cylinders check out okay or if I can track down some factory oversized pistons (may be real tough to find, discontinued I suspect).

Thanks!
Click to expand...

No problem, glad to help. A lot of people helped me with advice when I was doing my rebuild. If I don't chime in as this thread progresses then sent me a PM as I am involved in a Guzzi project at the moment and don't look at the GS site every day.

BTW Don't worry too much about O/S pistons, the extra capacity they provide doesn't affect performance much. You can hardly feel the difference.
 
I was referring to the odds that the cylinder sleeve walls will be intact and useable. My buddy at the junkyard said if we can tear the engine apart and see if the cylinders and pistons are in good useable condition with rings and a hone before I commit to buy. Score.

I am really excited at the thought of building this spare GS550 engine up this winter as a 674cc. Seems that the piston/comb.chamber design is definitely the best of any of the old GS's, and that the compression ratio and extra cc's with K&N filters, glasspacks, and rebuilt/jetted carbs will surely scream & give a mostly stock GS750 a serious run for it's money! So I HAVE TO up my 750 to a 920cc now! (550 is my wife's)
 
Chuck78 said:
I was referring to the odds that the cylinder sleeve walls will be intact and useable. My buddy at the junkyard said if we can tear the engine apart and see if the cylinders and pistons are in good useable condition with rings and a hone before I commit to buy. Score.

I am really excited at the thought of building this spare GS550 engine up this winter as a 674cc. Seems that the piston/comb.chamber design is definitely the best of any of the old GS's, and that the compression ratio and extra cc's with K&N filters, glasspacks, and rebuilt/jetted carbs will surely scream & give a mostly stock GS750 a serious run for it's money! So I HAVE TO up my 750 to a 920cc now! (550 is my wife's)
Click to expand...

Chuck the 650 puts out 1hp more than the 750 and weighs 10kg less. So it is comparable, but certainly quicker than the Honda CB750/4 with only 67hp as against 73hp of the GS650 and is a heavier bike anyway.

So you will have to watch out your wife doesn't flash by you while you're not paying attention.
 
Suzuki_Don said:
Chuck the 650 puts out 1hp more than the 750 and weighs 10kg less. So it is comparable, but certainly quicker than the Honda CB750/4 with only 67hp as against 73hp of the GS650 and is a heavier bike anyway.

So you will have to watch out your wife doesn't flash by you while you're not paying attention.
Click to expand...

Especially with that close ratio six speed and her lighter weight. You may not be able to hang with her anymore..... Do you really want that?
 
I can barely hang with her as it is even though my bike is faster! Her leading a ride means 80-100mph & insane speed through turns, & she has a frowned-upon 130 rear tire even! Crap with some avon roadriders in the proper size, lookout!
... and to think she worries about me when I go out "riding with the boys" in Hocking Hills State Forest... sheesh!
 
She complained after I got my gs750 that her bike just wasnt running strong enough, "fix it" she sez... so I had my eyes peeled for a 650. I test drove it for her, thinking somethong was wrong, & it definitely ran better before I raised the jet needle one more notch, but holy smokes I practically melted the back tire off of it launching several times real hard on my "test ride!" The 550's are GRRREEEAT bikes for sure, especially with better air filters, exhaust, & rejetting!
 
I've been looking around for 650E cam sprockets but so far it's all G/GL/GX ones. I know it needs a 30 tooth sprocket, so is there a reason why the stock 550 (30 tooth) ones won't work? I'm undecided on which cam I should go with, but if I were to use the 550 cams why wouldn't the stock sprockets work with them?
 
I'd think so. In the other 550-650 threads they were using the 650 sprockets and drilling them to fit the 550 cams. I don't see why it wouldn't work...
 
Toasty said:
I'd think so. In the other 550-650 threads they were using the 650 sprockets and drilling them to fit the 550 cams. I don't see why it wouldn't work...
Click to expand...


You have this backwards. I used the 550 cams with 550 sprockets and it's a direct bolt in like this. If you use the 650 cams you need to drill out and use the 550 cam sprockets. It's been recommended to slot the sprockets when using the 650 cams to reposition them. My engine with 550 cams and sprockets feels great to me. It really wakes up past 5/6000 rpms.
 
boontonmike said:
You have this backwards. I used the 550 cams with 550 sprockets and it's a direct bolt in like this. If you use the 650 cams you need to drill out and use the 550 cam sprockets. It's been recommended to slot the sprockets when using the 650 cams to reposition them. My engine with 550 cams and sprockets feels great to me. It really wakes up past 5/6000 rpms.
Click to expand...

You have it wrong, you don't have to drill anything out and the reason for slotting the sprockets is to degree the cams to obtain correct cam timing to get maximum performance. Standard cams are not spot on with their cam timing even from the factory when the bike was new. If you want to go the easy, cheap, throw-in route, just throw the 550 cams in, but you will be missing out on the great, low down (750 style) torque of this motor. Mine will pull from 2k in 6th on the flat, not up hill. Just open it easily and it pulls away.
 
Suzuki_Don said:
You have it wrong, you don't have to drill anything out and the reason for slotting the sprockets is to degree the cams to obtain correct cam timing to get maximum performance. Standard cams are not spot on with their cam timing even from the factory when the bike was new. If you want to go the easy, cheap, throw-in route, just throw the 550 cams in, but you will be missing out on the great, low down (750 style) torque of this motor. Mine will pull from 2k in 6th on the flat, not up hill. Just open it easily and it pulls away.
Click to expand...


Hmmm... I remember not being able to put my 550 cam sprockets on the 650 cams for some reason. It's been a while so I may have forgotten exactly why. I have another 550 engine so I could always pull the cams out of there and play with both sets again. As far as torque goes, even with the 550 cams the engine still has a nice amount of torque down low. Then again I changed my gearing up to 14-49 with the smaller 17" wheel.

While we are on this topic. Is there any source for aftermarket cams for these motors? There has to be some even lumpier street cams available somewhere.
 
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Sorry that link is the mobile phone version but if you look it up, web camshaft makes high performance 550 cams. Might want to compare to the specs of the 650
 
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