My GS450 -> GS500 Cylinder and Piston Swap

[sam000lee]

I've been meaning to do this for a while and have my GS450 fully disassembled right now. I have a set of GS500 cylinders, pistons and cams. Not sure if I'm going to do all three yet due to the clearance of the GS500 cams with the GS500 pistons and GS450 cylinder head. We'll see. I'll be using this first post to list information for anybody else who wants to do this later on.

Part's I'm using (will include part #'s once I order):

- GS500 cylinder block
- GS500 pistons
- Gs500 cam chain tensioner
- GS450 base gasket (p/n: 11241-44100-H17) and O-rings (p/n 09280-74002)
- GS500 cylinder head gasket (p/n: 11141-01D11) + Head gasket O-rings (p/n: 1114306b00)
- GS450 carbs for now but maybe eventually GS500 carbs + intake boots

Here's my main reference: https://www.thegsresources.com/_foru...ight=twin+wiki

And some others:

1. https://www.thegsresources.com/_foru...ht=GS450+GS500 (Discusses gaskets)
2. https://www.thegsresources.com/_foru...ht=GS450+500cc (Jetting stuff for later)
3. https://www.thegsresources.com/_foru...ht=GS450+GS500 (Cam discussion)
4. https://www.thegsresources.com/_foru...GS450+cylinder (Head Gasket O-ring discussion)

Here's what I'm starting with:

[John Park]

I have quite a few thoughts on this swap, the first being that you only gain about 7-8% displacement.

What I'd like to see is the difference in the air passage between the cam chain tunnel and the cylinder between 450 and 500. I know they sabotaged the 500 head by deleting the passage under the cam boxes and moving the exhaust ports inboard to clear the decorative perimeter frame. I know, it worked anyway, but....

Could you post a shot of the passageways?

[pete]

Gonna tag along Sam, still in the back of mind to do this as I took a few shortcuts on the 450 rebuild and now approaching 80,000kms later she's using a bit of oil and apparently starting to puff a little blue smoke out the back when I get the rev's up in the twisties.

As for the 500 cams and carbs, I can tell you from experience that both make what I feel is a great improvement just to the stock 450 motor.

I have 2001 cams and carbs on mine, the carbs were a no-brainer due to dead diaphragms on the stock carbs, but they are way lighter and the inlet diameter is huge in comparison (60mm from memory). I'm running velocity stacks with foam filters over the top and throttle response is much improved.

The cams definitely changed the power delivery and while she feels like she's lost just a tiny bit up top, the midrange definitely feels a little better.

Anyway, my 2 cents... keep us up to date!

[sam000lee]

Glad you're here, Pete. I've learned lots from following along with your threads.

I just ordered the head and base gaskets (added part numbers to OP) but am actually riding to Pittsburgh on my GS750 for a week and half trip at the end of the week. I'm eager to dig into this as soon as I get back.

I have quite a few thoughts on this swap, the first being that you only gain about 7-8% displacement.

What I'd like to see is the difference in the air passage between the cam chain tunnel and the cylinder between 450 and 500. I know they sabotaged the 500 head by deleting the passage under the cam boxes and moving the exhaust ports inboard to clear the decorative perimeter frame. I know, it worked anyway, but....

Could you post a shot of the passageways?

My goal isn't really to milk the bike for every drop of power. I just think it's a cool swap to do on a GS450. I'll be posting lots of pictures for anybody else who wants to do this and will put some up of the passageways when I get back.

[rekidiw]

tagging along to see how this turns out. seems like something i’d be interested in down the road.

[sam000lee]

So it took me a while to find some time to make the swap even though it only ended up taking a few hours which is usually the case for stuff like this. Part of the reason I'm writing this up like this is to show show how simple the swap is as a reference for others. Here's some pictures along the way:


These are the gaskets (part numbers in original post) I bought. I didn't end up using the GS450 base gasket O-rings as the GS500 cylinder doesn't have the grooves for them.



Where the O-rings would go on the GS450 cylinder:







Followed the Clymber manual to take everything apart. I advise that you stuff some rags into the crankcase before removing the pistons so that you don't drop anything in there:



Used some needle nose pliers to remove the spring clip securing the wrist pins:



The GS500 cylinder is the one in the back:




I rented a hone from Autozone for $25. There was some marking one one of the cylinders but this seemed to get it out. This was my first time honing a cylinder and I was quite satisfied with the results:





GS500 pistons installed with the GS450 base gasket:



I had also rented a piston ring compression tool from Autozone but ended up not using it. The bottom of the GS500 sleeves are chamfered which makes the pistons really easy to slip in. I almost forgot to make sure the ring gaps were spread out around the cylinders and had to re-do the first one:

[sam000lee]

Cylinder on:



I had previously seen a discussion of whether or not to use the O-rings with the gasket but never a definitive answer. Yes, use the GS500 cylinder head gasket AND and GS500 O-rings. You can see the space for them in the picture above.





I've never seen a gasket like the GS500 cylinder head gasket before - it's made of metal or something:



Scraping off the old one from the cylinder head:



What you have to remove to do this:



Putting it all back together:




Upon installing one of the cam bearings I broke one of the bolts. Ugh! It's funny this has actually the second time this has happened to me and I had replaced all of those bearing bolts a couple of years ago. Maybe I'm torquing them too much...

So I stopped here and am ordering another set of the bearing bolts but here's what it looks like put back together:



My other GS450 engine is jealous...

[Gorminrider]

good pix! It'll be very handy for people as a reference

[John Park]

I was hoping for comparison pics on the inner air passageways - 450 vs 500 - before you put this together. Maybe you could put a light on one side and get some. ??

I like the black cylinder/silver head look, but then I'm a sucker for the old iron barrel vintage look. The difference in fin styling is more justified too.

The old gaskets may have had some asbestos in the mix. There's been a major move away from asbestos gaskets to various styles of shim type post millennium, with varying degrees of success. The GSX400 twin head gasket - a composition affair like the 450 - has no sealing strategy at all at the wet stud holes, and I haven't seen them leak, but then there's no rubber to poop out over time.

One of the reasons I'm here is that I'm a fan of air cooled engines, and motorcycles inherently have their engines out in the breeze - or used to. No hoses, radiator, water pump, thermostat, fan. And you get to hear the magnificent symphony of whirring internals amplified out through the finning so you can still enjoy hearing from the parts even after you've 'put them away'.

I'm also curious as to whether the old style knob cam chain tensioner would fit the GS500 block. I'm no fan of ratchet type tensioners; don't get me started. You'll also have to figure out how to back up and lock that one before you put the cams in. I've never played with one; just assuming it's a typical one way device.

[pete]

Thanks for the details Sam, very handy! One thing with the GS500 tensioner... might make it possible to remove the starter motor without having to remove the tensioner...

[sam000lee]

I was hoping for comparison pics on the inner air passageways - 450 vs 500 - before you put this together. Maybe you could put a light on one side and get some. ??

I like the black cylinder/silver head look, but then I'm a sucker for the old iron barrel vintage look. The difference in fin styling is more justified too.

...

I'm also curious as to whether the old style knob cam chain tensioner would fit the GS500 block. I'm no fan of ratchet type tensioners; don't get me started. You'll also have to figure out how to back up and lock that one before you put the cams in. I've never played with one; just assuming it's a typical one way device.

I'm not entirely sure which passages you're looking for but do have a bunch of pictures that I took during the swap. Could you be a little more specific?

I forget if you can use the GS450 knob style tensioner. I know from reading Pete's thread that it interferes a little with the idle set screw if you end up using the GS500 carbs (eventually I do want to do this). As for it's usability, you basically back the tensioner out with a screw and then tap it around, for lack of a better phrase, until you see the coils unwind and feel it click into place. I did this with the cylinder head cover still off so I could verify that it had tensioned the chain. I don't think that it's functionally any different than the original GS450 tensioner which is also a one way device.


Side note - I wired in the ignition system over the weekend and fired it up. Sounds great! I still have to finish the wiring for the rest of the bike and then I'll get to tuning.

[John Park]

I'm not entirely sure which passages you're looking for but do have a bunch of pictures that I took during the swap. Could you be a little more specific?

I forget if you can use the GS450 knob style tensioner. I know from reading Pete's thread that it interferes a little with the idle set screw if you end up using the GS500 carbs (eventually I do want to do this). As for it's usability, you basically back the tensioner out with a screw and then tap it around, for lack of a better phrase, until you see the coils unwind and feel it click into place. I did this with the cylinder head cover still off so I could verify that it had tensioned the chain. I don't think that it's functionally any different than the original GS450 tensioner which is also a one way device.


Side note - I wired in the ignition system over the weekend and fired it up. Sounds great! I still have to finish the wiring for the rest of the bike and then I'll get to tuning.

The tensioners are often just a one way ratchet, which is a brutally simple device that I'm sure Suzuki was well aware of. Instead, they used a spiral ramp which is reversible in cases of extreme tension. This is why racers who shift brutally can slow the engine faster than the cams can slow and put serious loads on the back of the chain prefer to use a fixed tensioner. The ratchet type is a self adjusting fixed tensioner which self adjusts when the engine contracts when it cools and then overtensions the chain on expansion. This can be compensated for by putting enough spring in the guides, but it still is pretty crude.

The best way is to use a fixed tensioner and set it with the engine hot as in Hot. Asbestos gloves time. Of course, it will rattle a bit when cold. Honda used to specify setting hot, but the non manual following crowd disregarded it and lots of chains, guides and cam bearings died prematurely as a result. I'm ashamed to admit how I learned that. GS chains and guides, sprockets and bearings, have a remarkably long life and the tensioner sophistication is the only real difference.

I just wouldn't bother with a ratchet tensioner when a spiral ramp would fit [??] or a fixed manual set type is available. If you don't think that significant forces happen when the motor expands and the cams get further from the crank, you're dreaming. I was changing the [spring tensioned] timing belt on a Subaru motor a while back and the timing marks were a half tooth out on both sides; I checked again when the motor was warmed and they were spot on. And that's a water cooled motor. The new chain timed Subie motors use a hydraulic tensioner. Honda CRVs use a ratchet and the chains and guides are inevitably pooched long before the motor is otherwise worn. The big Suzuki 1300[?] twin uses a ratchet and the force can strip the ratchet teeth; plus the tensioners are internal.

In short, something's gotta give. Make your own peace with it.

The passageways I'm referring to are between the central chain tunnel of the cylinder block and the cylinder castings. If you shine a light on the front of the motor you can see light coming through beneath the carbs. Probably too late to get a pic of that now, but maybe from the front with a light behind??? I'm just curious and don't have a 500 jug about.