Finally getting around to the 550/699 project....

[tkent02]

Just got home today, let's see what happens this month...
Got to go riding a little bit first.

[Chuck78]

I, too, have crates of GS650GZ engine parts on the shelves, as well a CBR1100XX 310mm rotor and Ninja twinpot caliper, and a 77 GS550B engine as a spare donor! Also funny that the engine ran terribly, and after doing two very oil-heavy wet compression tests, the compression in either #3 or maybe #4 came up from 75 to 105! Stuck valve I figured, or nasty valve seat from sitting open and rusting. She rode it for a year and a half before the compression got to the lowest limit that was rideable. EMGO pods, cracked muffler, stock jets... that was how the bike came into her hands, exhaust discolored from the severe lean condition, hmmm... I wonder what happened to the top end of the engine to cause it to lose compression????!!

Also, riding hers on the highway with a 130/90-16 rear tire's diameter puts the rpm's pretty high, I'm thinking 5500? Google search for Gearing Commander and input your tire size and check the rpm's. I upped my rear about 1 tooth equivalent and I'm at 5350 @ 70mph, that's my max for freeway cruising. the 550 gearing is already pretty up there.

Lastly, both engines had tranny problems. I suspect that since they stuffed 6 gears into a case of similar width to a 5 speed, the smaller parts don't hold up quite as well. original engine would get stuck in neutral, 78 GS550 engine gets stuck in first! I have heard that on the 550's, shifting 1st to second and accidentally not fully kicking the shifter up to second will cause the engine to slam the shift fork into gear and bend it. I am expecting to find some serious wear on the shifter linkage mechanisms as well when I tear one down. Regardless, I'm willing to deal with it in order to build a killer 6 speed kickstart 9.4:1 673cc screamer!

That bike is very nimble and so easy to turn in at any speed, rides nice, and just with glasspacks and pods and some heavy rejetting, it is FFFFAAAAAASSSSSTTTTTTTTT!!!!!! The 550 cams are really hot, very long valve opening duration, they take very well to pods/pipes/jets. The cams and the EMGO Dunstall straight through glasspacks however combine to make long highway rides that lend themselves to blasted eardrums... the sound on accelleration is AWESOME though. As you probably know, the 650 cams have a shorter valve opening timing but higher lift. Probably make at least the same power but with more efficiency. The 550 cams sound AWESOME with op0ened up exhaust though... tough call but I think I will try the 650 cams with the 550 cam sprockets swapped (650 cam sprockets wont work with the 550 crank's cam chain sprocket).

A long term project I look to take on will be a similar build for myself in a lighter nimble racer styled bike minus the cafe racer seat treatment, but for mine it will probably be my neighbor's impulse "wow that's cheap!" buy of a 79 GS425 12K miles $350 titled barn find, no spark, needs battery and tires... Wiseco 844 pistons (makes 10.25:1 449cc) or maybe some custom made 70 or 71mm pistons, or if I could find some GS850 +1.0mm oversize pistons... I think the compression ratio of the wiseco's would give more performance than the extra 1mm of bore on the 850's however. stripped down, clipons, spoked wheels, disc rear brake, GS1100E swingarm to lighten/stiffen and lengthen the rear to keep from doing too many accidental wheelies! About $1100-1200 project, fun loaner/city bike, and real fun in the twisties with the light weight!

Good luck with your $100 score, I really dig the 550's and the GS650E's...

[Chuck78]

Also, look up Boontown_Mike's (I think that's the correct spelling etc) GS550 673cc racer project build, h e is using some 1991-ish GSXR600 flatslide slingshot carbs that are very light and very responsive. I picked up a similar set of BST33's. The intake boot configuration is a bit tricky, have to mix and match boots to get the correct offset but it worked for him.

[tkent02]

July update, Nothing. Went riding. All month.

[tkent02]

August update, same as July, except this...
I found an old thread about a guy doing the 650 top end on a 550 but boring it and using the 750 pistons.... I had thought they wouldn't work because of the different combustion chamber shape. Now I can't find the old thread.
Has anyone heard of this being done? Succesfully?

Edit, here it is:

http://www.thegsresources.com/_forum/showthread.php?t=107520

[850 Combat]

WILL A 650e MOTOR BOLT RIGHT IN?

sorry for the caps lock

[tkent02]

No, it's bigger, it's heavier, and it lacks the six speed transmission.

And I don't have one.

[dorkburger]

Also, look up Boontown_Mike's (I think that's the correct spelling etc) GS550 673cc racer project build, h e is using some 1991-ish GSXR600 flatslide slingshot carbs that are very light and very responsive. I picked up a similar set of BST33's. The intake boot configuration is a bit tricky, have to mix and match boots to get the correct offset but it worked for him.

Boontonmike.....his ride is coo-oool.

[Sci85]

So you ever get this going again tkent? I finished mine up and let me tell you, it's every bit worth the effort. So light and nimble, and now fast. I like it so much I may do another. Like a '79 or earlier. C'mon, "Get 'er done!"

[tkent02]

Got going on it the other day, trying to get all the lights working. then I saw this on Craigalist:



Thinking I'd take the pretty tank and such for my project, so I bought it today. Brought it home, rode it around a bit, now I need to rethink this thing. Everything works, just needs the routine stuff to be ready to rock and roll. I can ride it as a 550 for now, pop in the 675 or 740 or whatever engine when it is ready to go in, and ride it and take my time while the other project gets hammered out.

[Sci85]

That's cool. I really want a spoked wheel model and I just really dig the 550 weight and 6 speed. And the 650 head really makes it run. Amazing the difference.

Looks like you have the CL syndrome as well. But for me, I don't have any funds so that at least keeps me from buying things.

How many bikes now?

[tkent02]

That's cool. I really want a spoked wheel model and I just really dig the 550 weight and 6 speed. And the 650 head really makes it run. Amazing the difference.

Looks like you have the CL syndrome as well. But for me, I don't have any funds so that at least keeps me from buying things.

How many bikes now?

I just counted, back up to nine, five of which are up and running. This one was cheap, for a running bike. He took about half of his asking price. Key, title, new battery and everything.

I'm considering using the 650 cylinder, bored for 750 pistons and the 550 head, which fits the 750 pistons shape better. Might even go with with bigger valves out of the 750. Got to pull all of the pieces out and do some pondering.

Maybe I should just go the 675cc with the 650 head for the first one. Just get er done. Then go hog wild on the second one.

[Sci85]

Nine! Good grief. That's too many bikes for one person. I need to help you out by taking a couple off your hands

Maybe I should just go the 675cc with the 650 head for the first one. Just get er done. Then go hog wild on the second one.

Agreed. Do the 675 swap first. It's easy and cheap and makes really good power for the little investment. It may suprise you how much quicker it is that you may not feel the need for the 750 setup, which btw, sounds like quite a bit more expensive for 75 additional cc's.

[tkent02]

Which type bits work the best on aluminum???

Cutting the cases with a die grinder to fit the bigger 650 cylinders in, the stones clog up, the steel bits with the little cutting tips just wear out. What works the best?

[chef1366]

Rat tail file.
I took my cases to a machine shop to fit my 1150 cylinders.