Which engine? GT380 or GT550

[mixalive]

I purchased an engine last week to install in a newer chassis. Possibly a GSXR600 or 750 chassis. I wanted to build an updated triple. I purchased what i thought was a GT550 engine. Turns out it was a GT380 engine. The guy has agreed to refund but i am debating whether to just keep it for the build. Are there any good reasons as to why i would rather have the 380 over the 550?

[Craig380]

In its favor, the 380 motor is a little (but not much) more compact and lighter than the 550, and has a 6-speed gearbox. Parts like pistons, piston rings etc are also easier to obtain because of commonality with the 250 twins, whereas on the 550, pistons etc are unique to the bike. In the UK, Suzuki sold LOADS more 380s than 550s so most engine parts are much more readily available ... but the picture may be different in the US.

A stock 380 motor put out a claimed 37bhp, a stock 550 a claimed 48/49bhp if memory serves. Both are VERY conservatively tuned as standard and a little porting work plus chambers will get a good boost in power out of both motors.

[mixalive]

Thanks. Just the info I am looking for.

[tz375]

A stock 380 is not exactly a powerhouse, but as Craig380 mentioned, it has 6 speeds, shares pistons (sort of) with the 250 twins, so it shouldn't be too hard to get 50 HP out of it with a little porting, 550 carbs and decent pipes.

That is still not a lot to drag a big chassis around, so maybe look for something smaller and lighter than a GSXR600/750.

Many years ago, Barton modified a 380 with watercooled barrels and had Spondon make a frame and sold it as the SPARTON. A replica would be fun, but use it for ideas and inspiration. It is probably possible to fit larger pistons from something else in a 380 to get closer to 500cc with stock bottom end. That could be a really nice project.

A 550 is obviously a larger more powerful motor and more able to drag any road chassis around. It's a personal preference. Either is a lot more work that tweaking a bike that's complete and already runs.

[Vintageman]

If I was to take the time to do what you say, no doubt it would be the GT550 over the GT380. I own one of each at the moment and love them both. T500 is another option to consider.

[mixalive]

I think the 380 goes back.