I have a 1978 gs550e, where can I get performance parts/what should I do

[Chriscresw@aol.com]

I recently just purchased a 78 gs550e. I can't seem to find anywhere that sells performance parts for the motor. I wanna do a 4 into 1 header, bore it out,cams etc. The bike is in decent shape ,has 11000 miles I gave 300 bucks for it. I've got to pull the head because the previous owner cross threaded 2 of the plugs. Can I get some suggestions on what domain want it to be street able but peppy. Help please

[steveb922]

Search for '550/650 conversion', or maybe '674 conversion' on here. Might give you some ideas.

[Buffalo Bill]

Wow, I can't believe it! Web Camshafts sells cams for the GS550 8 valve.
MAC makes a 4>1 exhaust for the 550
I put a MAC 4>1 on my 550, but if I was to do one again, I'd just get slip on mufflers for the OEM 4>2, because I like duals mo-betta.
I found this source for overbore 550 pistons: Dynoman Performance

[Chuck78]

Dyna S ignition fits 550 as well, & Vance and Hines used to make a 4-1 exhaust for them. I see Kerker & Bassani exhausts NOS on ebay still.
We just had Wiseco make a run of 40 pistons at 65mm/740cc to fit the GS650 cylinder head and bored out 650 cylinders, which nearly every person involved was doing this on a 550 crankcase (requires slight grinding of 550 cases to fit 650 cylinder liners, & use of 550 cam sprockets NOT the larger 650 sprockets as those only match up to 650 crank gear)
The 650 heads and pistons design are a huge upgrade over the hemi design of the earlier 8v stuff, a much more modern design chamber and intake runners. On the GR650 Tempter, they advertised this as the TDCC - Twin Dome Combustion Chamber, similar to the 4 valver's TSCC Twin Swirl Combustion Chamber.

MAC makes exhausts as stated, Dynoman sells a 630cc GS650 big bore piston kit that is very high quality with many custom order fancier options available on the pistons, Web cams as stated, & MEGACYCLE CAMS as well.

A great build would be the Dynoman 630 pistons and the .380" lift mega cycle cams or .395" lift Web Cams, or the GS650 stock top end with the Megacycle .354" lift camshafts.

If you want the Wiseco k740 pistons and the more advanced 650 head for the ultimate build, just look up the thread on here for the 740 pistons and see if you can get a minimum of 2 other people to go in on the deal and Wiseco will make up a minimum batch run of 12 of them (3 sets).

Dyna-S/Dyna green cois
Ignition relay mod (read on forums for that)
4-1 exhaust
K&N filter (s)

Add some YSS/Hagon/Progressive $230-280 shocks, MikesXS fork valves aka cartridge emulators, and some good tires (Bridgestone BT45 Battlax or Pirelli Sport Demon), & maybe a brake upgrade to salty_monk's 310mm single disc variant using a 98-99 cbr900rr rotor and a ninja/etc Tokico caliper and a new-ish GS500 master cylinder... good to go, awesome performing big bore 740cc GS550 with better brakes and suspension & awesome gripping sticky canyon carving tires...

Don't forget to upgrade your regulator rectifier to a Polaris #4012941 "Shindengen SH-775 series-type" unit and do Jim posplayr's basic power distribution rewiring mods, as all GS's are very lacking in this department. And basic maintenance - wheel/swingarm/steering bearings, chain/sprockets, replace any gaskets/seals necessary...


Best of luck. There is a ton of potential in the 550's. If you are welding anything, add a brace from the center frame spine behind the ignition coils down each side to the outside seat rail tubes. Eliminates the wiggle/ squirm in the chassis when hitting bumps/dips in high speed corners. All other GS frames except the 400/425 had factory bracing there.

[thebrandonbeezy]

Chuck you just made me want a 550...

[Chuck78]

They are a great sized bike that's for sure. An aftermarket straight through performance baffle like the Vance and Hines or the optional MAC performance baffle (not their stock baffle) sounds KILLER with the stock GS550 cams, a very snarly and authoritative exhaust growl due to the high duration of the 550 cams... which also lends themselves very well to performance upgrades. A simple pods and 4-1 pipe mod with proper fine tuning / rejetting of the carbs on the stock 550cc displacement yields substantial more gains than most other similar makes of bikes of the era.

The 650 heads and pistons design are a huge upgrade over the hemi design of the earlier 8v stuff, hence the stock '81 650 made 73hp vs the stock '77 750 made 72hp. The 650 was substantially lighter than the 750, but the 750 did make a fair bit more torque as can be expected due to the displacement advantage. So fitting a rebuilt junkyard 650G (shaft drive) top end to 550 crankcases REALLY boosts performance, & adding to that Wiseco K740 10.25:1 740cc pistons puts you into the stratosphere in terms of unleashing serious performance out of a 550cc four cylinder based bike...

On top of all of this, I have been wanting to measure the cc's of the 80-82 larger port (cv carb) GS550 hemi head combustion chambers to compare to a 77-79 750 chamber, as I believe just from the looks of the pistons and chambers that a 650 cylinder bored out to 65mm/740cc could potentially run stock GS750/GS400 pistons on a 550 head to yield a 740cc beast using all oem parts... the 80-82 550 cv head would be needed, as doing major porting to the earlier vm22 small port head would really be a chore.
EDIT - This is not really possible without a lot of custom machine work to sink the valves a lot deeper into te head, and machine much deeper valve pockets into the stock 750 pistons



All in all, the GS550 is a great platform that responds very well to performance upgrades and has a near bulletproof roller bearing bottom end... excellent lighter middleweight Japanese Four.
The KZ550 is also another one to not overlook. Slightly lighter and slightly faster stock, but not as tough of a crank and rods as the GS. The GPz550 head and cams were a real performance upgrade over the stock kz as well. With the GPz550 head and cams and a Wiseco 615cc (?) GPz550 big bore kit, you had one seriously fast lighter middleweight bike! The GS550/GS650E has more potential with the Wiseco K740 10.25 piston kit and 650 head/cylinders, but BOTH the GS's and BOTH the KZ&GPz's are awesome bikes with exhilarating performance potential in a package that is featherweight compared to a 750/1000 four cylinder.
A member on here with several GS's of all sizes describes in his signature "-GS650 - all the bike you need."
The agility and flickability of a middleweight 550/650 is very awesome, & there is excellent engine performance on tap waiting to be unleashed with these mods. No doubt that a K740 equipped 550/650 set up as described would beat out a tricked out GS1100E on the tail of the Dragon or other epic twisty roads...
Cheers...

[Chuck78]

The GS650E is another one to seriously consider, but being only a 2-year model, it is a bit scarce. It is basically a beefed up slightly larger 550 frame with a similar chain drive roller bearing crankshaft but no kickstarter and it's a 5 speed, whereas the 8v 550 all years (77-82) is a 6 speed and 77-79 are kick start AND electric start.
the 650G is shaft drive 5 speed and plain bearing bottom end, with a different frame. Still quite a performer however, hence the GS650M Katana being one of the first of its kind... it got factory oil cooler plumbing out of a special oil pan setup, dual discs, & special performance camshafts, as well as being the one to set the stage for the look of all sport bikes to come with its futuristic aerodynamic bodywork and fairing.
Also, another special one to not overlook was the Suzuki XN85 turbo bike. Guess what it was based on? The GS650! Talk about rare! This is the rarest of GS's next to the dealer promo '76 GS750A...

[Chuck78]

Yes my wife's GS550 and my friend David's are both getting this treatment in the distant future, & I ordered a 3rd set of Wiseco K740 pistons as well, as I may build a spare bike up with this for myself still... which could potentially bump my 920cc GS750 out of favor due to the lightweight crisp handling of the GS550/650-740cc... and I am building a Rickman road racer chassis with what now looks to be a GS1000/1100G 1085cc monster engine. My beloved monster GS750-920cc may get bumped out of the top position in my tool shed this year... I love that bike, never saw this one coming but that's a good thing!

[roeme]

Can't wait to get my 550s ready for upgrades.

[Chuck78]

There's another member on here wanting to do a group buy on GS550-650 / GS650 740cc pistons now, buy from a company in the UK. Another thread in this forum.

[JayT]

Geez, I definitely want to do this to my 550. My budget can't go the Wiseco route. But I'm already shopping to find a 650 top end. It sounds too good of an upgrade to pass up!

[LeanMeanGsMachine]

I'd be willing to place an order as a group. I've been looking for ways to get a bit more power out of my 79 gs550e and those custom pistons sound perfect. Let me know if you'd be interested

[Chuck78]

Cruizin_Image_Co on eBay from Japan sells 63mm oversized pistons for GS650's now for just under 700cc's, FYI... And they're VERY competitively priced, too!

[JeremiG2001]

Dyna S ignition fits 550 as well, & Vance and Hines used to make a 4-1 exhaust for them. I see Kerker & Bassani exhausts NOS on ebay still.
We just had Wiseco make a run of 40 pistons at 65mm/740cc to fit the GS650 cylinder head and bored out 650 cylinders, which nearly every person involved was doing this on a 550 crankcase (requires slight grinding of 550 cases to fit 650 cylinder liners, & use of 550 cam sprockets NOT the larger 650 sprockets as those only match up to 650 crank gear)
The 650 heads and pistons design are a huge upgrade over the hemi design of the earlier 8v stuff, a much more modern design chamber and intake runners. On the GR650 Tempter, they advertised this as the TDCC - Twin Dome Combustion Chamber, similar to the 4 valver's TSCC Twin Swirl Combustion Chamber.

MAC makes exhausts as stated, Dynoman sells a 630cc GS650 big bore piston kit that is very high quality with many custom order fancier options available on the pistons, Web cams as stated, & MEGACYCLE CAMS as well.

A great build would be the Dynoman 630 pistons and the .380" lift mega cycle cams or .395" lift Web Cams, or the GS650 stock top end with the Megacycle .354" lift camshafts.

If you want the Wiseco k740 pistons and the more advanced 650 head for the ultimate build, just look up the thread on here for the 740 pistons and see if you can get a minimum of 2 other people to go in on the deal and Wiseco will make up a minimum batch run of 12 of them (3 sets).

Dyna-S/Dyna green cois
Ignition relay mod (read on forums for that)
4-1 exhaust
K&N filter (s)

Add some YSS/Hagon/Progressive $230-280 shocks, MikesXS fork valves aka cartridge emulators, and some good tires (Bridgestone BT45 Battlax or Pirelli Sport Demon), & maybe a brake upgrade to salty_monk's 310mm single disc variant using a 98-99 cbr900rr rotor and a ninja/etc Tokico caliper and a new-ish GS500 master cylinder... good to go, awesome performing big bore 740cc GS550 with better brakes and suspension & awesome gripping sticky canyon carving tires...

Don't forget to upgrade your regulator rectifier to a Polaris #4012941 "Shindengen SH-775 series-type" unit and do Jim posplayr's basic power distribution rewiring mods, as all GS's are very lacking in this department. And basic maintenance - wheel/swingarm/steering bearings, chain/sprockets, replace any gaskets/seals necessary...


Best of luck. There is a ton of potential in the 550's. If you are welding anything, add a brace from the center frame spine behind the ignition coils down each side to the outside seat rail tubes. Eliminates the wiggle/ squirm in the chassis when hitting bumps/dips in high speed corners. All other GS frames except the 400/425 had factory bracing there.

Hello, new member here. Currently working on a 79 GS550 project. I was wondering if you could point me in the direction of more info regarding the frame bracing you mentioned.

[Chuck78]

Look up pictures of a GS750 or GS450 frame. Look directly behind where the ignition coils bolt on. There will be 2 diagonal braces there that go from the bigger center spine tube down & rearward to the left and the right upper frame cradle tubes. You will see on the 550 that this is absent vs the 450 & 750 etc. If you need better clarification, I have a parts bike under a tarp next to my garage door that I can take a photo of. Or a few frames in the attic if you need better clarification, I can climb up there and take photos.

It was really just the earliest smaller cc bikes, the 400/425, & the 550, that were lacking this. All other 450cc+ Suzuki GS models had these braces.
I can't recall if the 1980+ GS550 had these added vs the older 550 frames or not. I had 2 of them (junkyard parts bikes bought for $50), but since I had no titles for them, I sadly had to cut them up for scrap