Poldark

They were a good bike but only in North America for two years (81-82). Size and weight of a 550 with neary the power of a 750. Good flowing head, 673cc.

Yes, you need to replace that petcock. When in the "on" position, engine vacuum is required for fuel flow. "PRI" or "prime" does not require engine vacuum, constant fuel flow. California models did not have the prime position.

Take a look at this 78-81 Suzuki GS1000 1100cc Bigbore Piston Kits with Head Gasket | CRUZINIMAGE.NET They are in Japan but ship to the US; very fast shipping. I have not yet used their pistons, but a local friend has built a few hopped up CB750 street engines with their pistons and has not had any issues.

Here in the US, they went to fully electronic in 83. Earlier ones had mechanical advance. My 82 GS750E (16 valve) has mechanical advance.

I don't think 5 degrees extra advance would make too much difference, but be sure to check for signs of ignition knocking. Factory ignition advance settings assume: a new factory spec engine, factory carburetor settings, and the fuel available at the time. Fuel burns faster under higher compression, if your engine is a little worn out, a little more ignition advance can help compensate for a small loss of compression. A slightly too rich fuel mixture will burn a little slower; a little extra advance can help compensate. I don't know what the fuel formulation is where you live, but that can have an impact too, especially considering the formulation has likely changed in the past 40 years. The 550 is a smaller, higher revving engine than the 750, so it would need more advance. I'd say go ahead and try it, just be looking for signs of premature ignition.

Order of the three yellow wires should not matter. Yellow wires are carrying variable frequency AC, produced in the stator. Red and black wires DO matter, they carry DC current.

Welcome to OSS. Take some time to read the forum rules. They may appear overly strict, but the rules keep the forum functioning smoothly. [see rule about motor oil] How is your bike ridden? Normal street use or drag racing; makes a difference on clutch selection. Take some time to introduce your ( is this yours OSS bike, or have been messing around with them for years). Don't be a one-post wonder. Lots of very knowledgeable enthusiasts around here.

Normally 2-3 ohm for electronic ignition, 4-5 ohm for points. Older Dyna S ignition had an external module; newer ones don't because the electronics are small enough to all fit on the plate.

When that sleeve heats up, it should expand and make contact with the cylinder block. Cast iron does have a lower thermal expansion ratio than aluminum, so.... Take one for the team; OSS research. ????

I ride same model (82). 110/90-19 front and 130/90-18 rear. Those are one size wider than the recommended, but I've not had any adverse issues. I wouldn't go larger though.

My guess would be an early GS1000 hub re-laced to a replacement rim.

He did a great job; I bet it's crazy quick.

California model. That explains it. When it comes to motor vehicles and firearms, California is like its own country within the US with special emissions/safety requirements. If you dear friends across the Atlantic get a "USA" model bike that seems strange, check your paperwork. We've had that situation here on OSS. ...and please stop taking our bikes.

Glad to hear it's running well. Sounds like your fuel runs well with the stock jetting. Does your fuel contain corn-based ethanol?

If it's just the speedometer and not the entire gage cluster, most early 80's GS models should swap out. I'm looking at a GS650GL frame. The frame is drilled just forward of the front tank mounts for an alternate mount location. A larger tank off some other GS model lines up nicely on that location. If you have access to a welder, you could cut the old forward tank mounts and weld in new ones, then fit a larger tank. Brighter light: the stock light bulb has an equivalent automotive size that is very common. Auto parts stores will have brighter options.

Stock jetting is wrong. He said it is a US import bike. They came from the factory jetted too lean in order to meet US environmental regulations. The idle mixture screws were pre-set and capped off (easy to remove caps though). Our fuel content has changed a lot in the past 40 years. I don't know much about fuel in the UK, other than it's probably better but more expensive. If your bike is a US-California model, may God grant you patience to work on it.

Could you introduce yourself first?

Doh, I should have read more carefully. He's talking about wires on the ignition switch. Earlier the question was about the ignition module.

Two extra wires: On older bikes, the tachometer was normally cable driven off the engine. On newer bikes, the tach is often electrically driven off the ignitor box. The other wire could be a part of a safety interlock system. Engine won't start or run without a certain combination of conditions being met between transmission, clutch, and side stand.

I see part of the frame was left on that engine. Go get the welder; it's project time.

Johny, what is it you want to achieve in the end? If you want to build a custom bike, go have a look through the projects section of the forum, or do a search for "GS550", and you can find examples of upgrading suspension, wheels, brakes. If you just want to enjoy riding your motorcycle, fix what you have. A properly set up and maintained single disc will stop you just fine. If your single disc is capable of locking up your wheel, you're not going to be stopping any faster with dual discs. Main advantage to dual discs is the ability to do more repeated braking before over overheating. Brakes convert the kinetic energy of the machine and rider into thermal energy (heat). Dual discs double the amount of rotor material to heat up, allowing them to share that burden between them, and there's double the amount of surface area to dissipate that heat to atmosphere.

I took my son to the MotoAmerica race event; well worth it. Very nice venue. Next time I'll try to draw more attention to it, and maybe a few other OSS members can attend.

MotoAmerica 2022, May 20-22 Virginia International Raceway MotoAmerica Superbike at Virginia – Virginia International Raceway (virnow.com) Anyone interested? I might be taking the family.

Elimax, did you find a solution? We need closure. ...and don't be a one-post wonder.

Take a look on jtsprockets.com They show drawings with dimensions for their sprockets. Looks like plenty of 80's Suzuki's had same dimension rear sprocket with 530 chain. Many other models show same size splined output shaft for the front sprocket, but different location for the retainer plate screw. Example: comparing GS1150 to GS550, the sprocket dimensions are the same except the location of that small hole in the front sprocket (and of course the GS550 uses a 530 chain). Maybe try finding a cheap used set of GS550 sprockets and retainer plate, to do a mock-up before ordering any "performance" parts. On one engine I have, sitting nearby, I don't even see a retaining plate; just a flat washer between the sprocket and the big nut, with one edge of the washer folded up against a flat of the nut. A rusty GS550 front sprocket I found on the floor doesn't have the hole in it either; must have used the washer method too. Can you remove your front sprocket cover and take a photo for us? Meanwhile, go take a look at those drawings at JT Sprockets. I've just reached my threshold of how may times I can type "sprockets" in one day.