GS450 Crank in GS500

[kidsixteen]

Anybody know if GS450 and GS500 cranks are interchangeable? I know the bottom ends are, but I'd love to be able to use the way cheaper 450 crank in my build and use the $$ I'm saving for other parts.

I searched heavily and got nowhere. So I asked on TheGSResource and here. Let's see if we can come up w/ the answer quicker than they can.

[birdhandler]

Good thing i never got rid of the 450 manual cost a whole $7.00 second hand
450 bore and stroke 71 by 56.6
GS500                    74 by 56.6
So it may be worth giving it a try given the same stroke
The orther dimesions in the manuals are the same so I would give it a try
cheers

[burning1]

If I recall correctly, the GS450 crank is the exact same part number as was used in the early model GS500s.

Be aware though that the GS500 crank went through 2 revisions, and the counter-balancer was updated with the crank. You may potentially run into issues running a mis-matched balance shaft, and you won't have the latest crank.

[kidsixteen]

If that's the case it should be able to go in my '89 no problem. I'll try cross-referencing the part numbers.

[kidsixteen]

Looks like the part numbers are identical for both the crank and the rods.  for saving $200 on a rotating assembly!

[ghostrider_23]

What are you building??? Give us some specs, I have been looking for a cheap GS I could play around with as a second backup or bobber bike

[kidsixteen]

Looks like it's gonna be a mild/reliable build. Gonna use the cases, tranny and head from my '89 and stick the stocker from my '96 in it to keep daily riding it while the '96 gets track prepped.

Got a set of NOS GR650 pistons for it, planning on using those unless APE has a 78mm, higher compression piston solution up their sleeve when I send it off for machining. It costs more in machining to use my own pistons, and from the looks of the Tempter pistons a little more compression might be nice; but I like cast pistons in most N/A motors I build - especially air-cooled ones - so unless I come up with a cheap and relatively easy alternative I'll probably end up w/ a 527 instead of the high comp 555 I'd like to have. Who knows, maybe it'll stay together longer that way anyway.

The headwork will be mild. Just matching the combustion chamber to the pistons, installing bronze guides with +1mm valves and blending the ports to clean up casting flaws and match the valve job. I imagine I'll end up using the smaller megacycle cams if I go with the GR pistons, the next ones up if I get some 78's.

Not gonna do anything crazy with it. May have the crank lightened/balanced since I'm saving so much $ on it.

I have a couple sets of Amal 36mm MK2 concentrics that I'll probably end up using. I can't justify buying the FCR's I'd rather have since I have these and I know they'll work kick-ass on this motor. I do keep my eyes on cheap stock units from crf250's and yz250f's so maybe I'll end up with a set of Kehein 37's before the build's done. If not I'll probably switch eventually.

I have a V&H full system on my daily right now, but I think I'll probably just do a custom on the track bike. I'd like to do a pair of RGV500 style pipes, that'd be cool.

Not really in a huge hurry with it. Just 'cause I'm in SoCal doesn't mean I can't have a winter project like everybody else AND still ride every day

The only unreasonable thing I'd like to do is get rid of the electric start.. just seems like a huge mess that doesn't need to be there and a billet plate w/ a bearing and a starter lug would look/be rad and probably be easy to do.

I like stuff that looks rad. Half of the reason I build motors is the fun of building them, riding w/ it is only the other half.

All in all it'll net me a brand spankin' new motor that still doesn't make much power; but makes a good chunk more than stock, looks rad and will stay together as long as I treat it with respect (and maybe get a rev limiter).

Plus, stripped down this bike will weigh absolutely nothing, and the motor is going in a '96 with a K6 GSXR750 FE, Kat rear wheel, R6R rear shock and pretty much nothing else. Might be a little overkill, but like I said, I'm equally as into building bikes as I am riding them.. already have my eyes on a GS450 to start on after this one's done!

[burning1]

If you decide to build a plate and starter nut let me know; I was thinking of doing the same on my race bike. I'll go in with you on the costs; we can probably get them cheaper if we have a few units produced.

[kidsixteen]

it's last on the list.. but if you pull the trigger on one before I do, let me know.. I'm sure U wont take much convincing. How hot are the GS1000/1150 ones APE makes!? mmmmmm. 

[sledge]

Looks like the part numbers are identical for both the crank and the rods.  for saving $200 on a rotating assembly!

I might be telling you something here, I might not be 

Identical part numbers are no gaurantee of identical journal sizes. With this crank each journal can fall into any one of four tolerance bands so the chances of getting one with all 4 journals the same size as the originals in the same locations are...... slim!!... to say the least!!

You will need to go through the procedure and identify and use the correct size shells for each of the mains and big ends.

[kidsixteen]

I wouldn't just throw a crank in a case without at least plastigauging it first.

Honda motors (which I've built about a hundred of) use color coded bearings too. The procedure shouldn't be too much different. The manual says you can cross reference numbers on the block w/ numbers on the crank to extrapolate the stock bearing sizes too.. but a micrometer or plastigauge will always do the trick.

For that matter, our bearings are interchangeable with some of the older 4-Cyl GSs. I'm not super concerned with it.

[burning1]

The journal size thing is a good point, but that's a part of swapping any crank - not an issue specific to the GS450. FWIW the journal sizes are stamped on the crank, but it's still best to break out the micrometer and plastigauge.

[dgyver]

I have used GS450 cranks on several builds. They always seem to be in better condition than the GS500. They do only have a 3-magnet rotor but on a track bike won't be a problem.