Big Bore or Piston Options for 1980 Suzuki GSX400E

[xxenzor]

Hey guys,

I’ve got a 1980 Suzuki GSX400E (DOHC, 4 valves per cylinder), and I’m planning on replacing the piston rings since my compression is at 125. I figured while I’m in there, I might as well upgrade the pistons too. Problem is, there aren’t any piston kits available for this bike, so I’m thinking about boring it out for some extra power. The engine is 67mm bore x 56.6mm stroke, but I can’t find anything bigger with the same stroke.

Has anyone found pistons from another bike that would work, or what’s the typical way to go about doing a big bore on this model?

[chuck hahn]

My first question is has it sat for a long time. If so 125 isnt all that bad. If its sat a long time pull the plugs and put a few spoons of Marvels ystery Oil in each jug and let it soak a day or two. put rags over the plug holes and blow the left over oil out of the holes and run it a hundred miles or so then recheck compression.Rings might just be a little gunked up and you dont need to do pistons and rings.

[Rob S.]

...125 isnt all that bad.

That's what I was going to say.

[xxenzor]

My first question is has it sat for a long time. If so 125 isnt all that bad. If its sat a long time pull the plugs and put a few spoons of Marvels ystery Oil in each jug and let it soak a day or two. put rags over the plug holes and blow the left over oil out of the holes and run it a hundred miles or so then recheck compression.Rings might just be a little gunked up and you dont need to do pistons and rings.

It sat for 15 years and it’s got 23,000km/14,300 Miles. Seems like the compression should be higher with that low of miles. I’ll give the marvels a go.

[Nessism]

Get it running well and put some good hard miles on the bike. Check compression again in 500 miles. And remember, engine hot and throttle open for checking compression.

[chuck hahn]

And as Ed said. wide open throttle when doing compression check

[Syd]

Hey guys,

I’ve got a 1980 Suzuki GSX400E (DOHC, 4 valves per cylinder), and I’m planning on replacing the piston rings since my compression is at 125. I figured while I’m in there, I might as well upgrade the pistons too. Problem is, there aren’t any piston kits available for this bike, so I’m thinking about boring it out for some extra power. The engine is 67mm bore x 56.6mm stroke, but I can’t find anything bigger with the same stroke.

Has anyone found pistons from another bike that would work, or what’s the typical way to go about doing a big bore on this model?

Hi xxenzor

I was able to source a piston ring kit from https://imdpistons.com/ . They have piston and ring kits listed for the GS400. Not sure if they are compatible with the GSX400, but an email to them might prove fruitful