Been looking for a light twin….

[tkent02]

Ben looking for a while, never even ridden them much. Just to use to blast around town or the local canyon and mountain twisties.

400, 425, 450, which is the best and why?

Power, weight, parts availability, economy?

Or are they pretty much all about the same?

[Nessism]

My vote is 425 (if you can find one). Roller bearing crank GS goodness.

[pete]

I'd go for any Tom, so many parts are either common, interchangeable, or adaptable.

The only catch with the 450's is the ignition can be a bit flaky if the charging system is dodgy, but the DS3-3C kit for the earlier 400/425 will fit easily.

The advantages with the later 450's are the two piece clutch pushrod and the oil seal for it hasn't got a flange so is easier to change without splitting the cases.

Also, if you want to hot it up you can easily put the GS500 barrels on the 450 and re-use the 450 head so you don't have to faff about with a custom header arrangement.

The GS500 cam's swap straight in for some higher lift also and is something I'm considering doing.

The 425's are the odd one out of the three, I think they have a roller bearing bottom end but may be wrong there...

I have far too much fun on my 450, I can tell you that!

Oh, and as for my ignition comments above, I'm still working on a generic replacement using the GM HEI modules so if I can get that going, it will be an easy and inexpensive solution...

And the other thing difficult on all three... SH775 location... it's huge!

PS: 20mm less slide spring length and ~3mm vacuum port hole will get those stock carb's responding very nicely

Edit: Looks like Ed beat me to the 425 comment

[tkent02]

I like the roller bearing engines on the bigger GSes, but are the plain bearing ones on the twins prone to failures? I am not the type to neglect the oil. The bigger barrels at some point might be a consideration. Will this be a no go on the 400 and 425?

How about weight and handling considerations?

Are they all physically the same size?

[pete]

I've only ever seen/heard of one bottom end issue on here and it was obviously neglect that had done it.

When I dismantled mine with 96K km's on the clock to rebuild it, everything measured in spec.

There is someone on here that is in the process of or has done a big bore on a GS400 but buggered if I can remember who at the moment...

Mekanix has done a big bore on his GSX 400 (the 4 valve) but that's not quite the same as the two valve.

I've seen a 400 from a distance once but never a 425... they look the same size as the 450 to me.

Here's some light reading:

http://www.thegsresources.com/_forum...gs400+big+bore

http://www.thegsresources.com/_forum...gs400+big+bore

"Clutchthirty" is the guy who's done the GS750 big bore into a GS400 but I can't find anything other than references to the fact he's done it. He just sort of mentions it in passing, might be worth a PM?

http://www.thegsresources.com/_forum...gs400+big+bore

[BigD_83]

There's a 400 here in the Vancouver area:

The ad is a bit messy, but there are three bikes in total:

http://vancouver.en.craigslist.ca/rds/mcy/4447134958.html

[Big Rich]

Speaking of the modern-ish GS500: a member on the Twins site has put 180,000 miles on two different GS500's (80k on one, 100k on another). I believe the first one died a salted / rusty death from being ridden in Ohio, and the second one has a yet unknown knock coming from the bottom end.

Any premature issues I've heard of from the 500's tend to come from being over revved of running dry of oil. So there's a testament to that motor as well......

Tom, what about a GR650? If you can find a well running example, I'd recommend it over any other twin.

[recycled64]

77-79 400's, and 425's, were all roller-bearing bottom ends-

[tkent02]

Tom, what about a GR650? If you can find a well running example, I'd recommend it over any other twin.

It's no where near as small and light as a 400 or 450, is it?

I want small and light this time. Big, heavy and powerful I already have.

[Big Rich]

By the numbers: a GR is about 20 pounds heavier, but has about 20 more horsepower (very approximate numbers pulled off the internet.....)

But I can tell you firsthand, a GR handles like it's much lighter than a GS450. Not only riding it, but pushing it around the garage as well. If you find one that has been taken care of, I don't think you'll be disappointed at all. The only downfall I can think of is the rarity of engine parts.

Wanted to add: a GR650 motor will for into a GS500 frame with some custom motor mount plates, but not into a GS450 frame. Just food for thought.

[BigD_83]

...and there is a GR here as well. The guy has been trying to sell it as a GS650L for over a year with no takers.

Rich, I've heard some horror stories of timing chain issues with the GR. As far as you know, is there any truth to it being a common problem? Or does it all come down to maintenance?

[Big Rich]

Common? Not that I'm aware of. I think what gets most people is when the chain has to come off the camshafts and needs lined back up. The service manual isn't very clear on how to do it. IIRC, the text doesn't match up with the picture provided on link spacing......I think the text says 18 pins apart, but the picture shows it as 19? Something like that......

[pete]

I wonder if it's as simple as in the 450 manual? Although it's pretty clearly written... 18 pins for all except West Germany which is 19 pins...

[GSX1000E]

How about this little gem? http://www.thegsresources.com/_forum...d.php?t=221849

[GS/GR PAUL]

Another vote for the GR, light and powerfull. No problems with reliability.