Crazy thought. Sleep Deprivation Induced

[Ironriot]

Was thinking about turboing my 550.... Crazy I know... BUT according to the Factory Service manual these bikes DO have 8.6:1 compression which just BEGS to be turboed.... The only thing that turns me off of the whole idea is whether or not the internals can hold up to the boost. Does anyone know what the stock internals are made off? Would they happen to be cast or forged?

[spchips]

One good thing, it is roller bearings, unlike the 650 motor you've been thinking about with journal bearings!!!

[8trackmind]

Was thinking about turboing my 550.... Crazy I know... BUT according to the Factory Service manual these bikes DO have 8.6:1 compression which just BEGS to be turboed.... The only thing that turns me off of the whole idea is whether or not the internals can hold up to the boost. Does anyone know what the stock internals are made off? Would they happen to be cast or forged?

Look for info on the old GPZ/KZ550's that "TC" (?) did back in the 80's. They held up, I'm sure a 550 would. (for a while anyway)

[Griffin]

The original two-valve GS550 engine is probably the most overbuilt air cooled inline four ever built. If you were to take one apart and compare the internal components size wise to a four valve GS750 engine, you'd see that many of the 550 components are actually beefier than the 750s. That, plus roller bearings made for a heavy for displacement, utterly reliable engine.

If any engine from that era could stand up to turbocharging, that would probably be the one. I like this writeup on it:

http://www.umgweb.com/ click on "Buyer's Guides", then "Cheap Speed: Low End Bikes", and page about 2/3rds the way down.

The GS550's the safest way of going fast. Not only is the tough engine unlikely to seize up and cause a fight with the tarmac, but the chassis geometry instils the bike with fantastic stability. It never comes close to a speed wobble, doesn't even weave unless the suspension and bearings are really shot. Backing off the throttle in corners tightens up the line without inducing any back end traumas...
...The bearings were long-lived and even the suspension didn't go off with age and mileage, although the back end benefited from an alloy swinging arm and set of newish Koni shocks. Forks, in reasonable shape, absorbed most of the bumps, helped along by a good a riding position...
...The 550cc four cylinder engine only develops 54 horses, so is mildly tuned by Japanese standards. The hefty build quality would suit a 750cc (and, indeed, there are big bore kits that take it out to as much as 740cc - try to avoid as reliability suffers), so it's not surprising that a lot of them would run around the clock even under a regime of neglect...
...If your idea of speed's rapid cruising then the GS is near ideal. A useful tip's to run it on a larger gearbox sprocket, the taller gearing making for a much more relaxed 100mph gait and improving the economy by as much as 10mpg. The gearbox remains slick even at high mileages, although the linkages on the Katana's rear-sets wear at the joints when their protective covers perish. Any GS with a box full of false neutrals has probably done over 100,000 miles...
...Because the engines are so tough some bikes were run right into the ground, totally neglected until the chassis rotted away. Amazing tales are told about the indestructible nature of the GS550, running them for 20,000 miles without even an oil change not uncommon. Other people were inspired to refurbish the chassis, lose some mass and upgrade the brakes. Others were left stock but kept in a very nice condition...

[tone]

There was a guy who turbo'd an otherwise standard 550 around here years ago & the biggest problem he had once he got it running sweet was blowing head gaskets but dont know if that was down to him or tha bike itself

Have seen pics somewhere of a turbo'd gs750 & remember it having an extra base gasket & a spacer plate to lower the compression further maybe thats the way to go with a 550 ?

[Ironriot]

One good thing, it is roller bearings, unlike the 650 motor you've been thinking about with journal bearings!!!

I love GS motors. Roller bearings ROCK. Although I thought it was only the 450 that didn't come with roller bearings. Lol and I wasn't thinking about getting the whole motor I only want the top end. According to posts a little north of this one a 550 bottom end is burly. Which is always good

[Ironriot]

Look for info on the old GPZ/KZ550's that "TC" (?) did back in the 80's. They held up, I'm sure a 550 would. (for a while anyway)

What do you think about a mildly ported head running low boost?... Should make for a nice increase in power

[Ironriot]

The original two-valve GS550 engine is probably the most overbuilt air cooled inline four ever built. If you were to take one apart and compare the internal components size wise to a four valve GS750 engine, you'd see that many of the 550 components are actually beefier than the 750s. That, plus roller bearings made for a heavy for displacement, utterly reliable engine.

If any engine from that era could stand up to turbocharging, that would probably be the one. I like this writeup on it:

http://www.umgweb.com/ click on "Buyer's Guides", then "Cheap Speed: Low End Bikes", and page about 2/3rds the way down.

Awesome info, thanks for the link

[Ironriot]

There was a guy who turbo'd an otherwise standard 550 around here years ago & the biggest problem he had once he got it running sweet was blowing head gaskets but dont know if that was down to him or tha bike itself

Have seen pics somewhere of a turbo'd gs750 & remember it having an extra base gasket & a spacer plate to lower the compression further maybe thats the way to go with a 550 ?

Hmm interesting that it would blow head gaskets seeing as it has studs already. Although what should I expect for a machine that'll leak oil on its own.

I don't think I'd want to lower compression further. 8.6:1 is already might low