Cylinder swap 450-->500

[Burton]

Hi all,

I'm new to the forum but a longtime motorcycle rider and a builder. I recently picked up a -82 GS 450 that I'm currently modifying to better suit my liking. Among other things, I want to improve the bike's performance and at first was thinking about boring the cylinders closer to 500cc but then I thought that the cylinders from the much newer GS500E might fit too since the 500's engine is based on the 450. Will it fit? Has anyone done this swap before?

I also want to get rid of the stock carbs and replace them with flat slide carbs. Any recommendations as from which bike I might find suitable carbs?

Thanks,
Burton

 

[Guest]

Welcome to the forums Burton!

I'm not the man to talk to about performance upgrades, but I know it is possible to do some upgrades and there are guys who have done wild things with them and there's one in very slow progress on here now.

http://www.thegsresources.com/_forum/showthread.php?t=172422 is one, although it's for a 400 the same stuff should apply I would think.

Alternatively, BIGYAM has put a GS500 motor in his 450 frame and managed to get his exhaust to route around the frame also as the 500 head has the exhaust ports pointed directly at the 450 frame rails.

 

[bgmart450]

The rods and the piston pins are the same, you can get 500 pistons and have your head bored out. Its something I looked into a bit, but never got around to.

 

[Guest]

The rods and the piston pins are the same, you can get 500 pistons and have your head bored out. Its something I looked into a bit, but never got around to.

That's good to know Brent! Definitely will keep that in mind if I ever want a little more oomph from my 450...

 

[Burton]

[QUOTE

http://www.thegsresources.com/_forum/showthread.php?t=172422 is one, although it's for a 400 the same stuff should apply I would think.

[/QUOTE]

Thanks for the link Pete, that thread got me considering GR650 sleeves and +3 bore to up the cc's to the 560-580 range.

 

[Guest]

That'll be fun if you're up to the challenge! That work's a bit out of my league I'm afraid... but I reckon the end result would be a blast

 

[Guest]

Thanks for the link Pete, that thread got me considering GR650 sleeves and +3 bore to up the cc's to the 560-580 range.

There was another link that would be important to consider

http://www.thegsresources.com/_forum/showthread.php?t=170287


With the GR650 sleeves they are 77mm bore std.

on a stock 56.6mm stroke that makes a 527.1cc engine
78mm bore makes a 540.9 with 3.5mm left on the sleeve
79mm bore makes a 554.9 with 3 mm sleeve
80mm bore makes a 569.0 with 2.5mm sleeve
81mm bore makes a 593.3 with 2 mm sleeve

If you want to stay conservative go with a gs500 barrel and head.

keep in mind more displacement means higher compression ratio. your going to need to adjust the cylinder height to compensate and then you have to adjust the valve train to compensate for the height adjustment.

Bore them to 77mm, then use gr650 pistons or have JE make some pistons for you.

Like this guy.
http://www.youtube.com/watch?v=tQEVHd1cSyw&feature=player_detailpage

 

[Billy T.]

The rods and the piston pins are the same, you can get 500 pistons and have your head bored out. Its something I looked into a bit, but never got around to.

Now, this is just me applying general engine knowledge, here, and not specific to the 450/500. BUT, you should be able to leave the head alone and get a further performance bump from a little bit higher comp. ratio.

As long as you don't get any piston to valve contact, I would just run the 500 jugs with the 450 head as is.

The only other potential issue is that the 500 jugs will slip into the 450 block without machine work. I'm sure this has been done more than a few times, so the answer is out there for sure. Wish I knew it.