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Thread: My GS450 -> GS500 Cylinder and Piston Swap

  1. #1
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    Default My GS450 -> GS500 Cylinder and Piston Swap

    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:





    Last edited by sam000lee; 08-13-2018 at 09:03 AM.
    1980/1981 GS450 - GS500 Cylinder + Piston Swap - "De-L'ed", custom seat, CB350 bits, 18" rear, etc.
    1977 GS550
    1977 GS750 - Cross country trip thread

  2. #2
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    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?
    '82 GS450T

  3. #3
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    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!
    1982 GS450E - The Wee Beastie
    1984 GSX750S Katana 7/11 - Kit Kat - BOTM May 2020



    450 Refresh thread: https://www.thegsresources.com/_foru...-GS450-Refresh

    Katana 7/11 thread: http://www.thegsresources.com/_forum...84-Katana-7-11

  4. #4
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    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.

    Quote Originally Posted by John Park View Post
    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.
    Last edited by sam000lee; 08-14-2018 at 09:04 AM.
    1980/1981 GS450 - GS500 Cylinder + Piston Swap - "De-L'ed", custom seat, CB350 bits, 18" rear, etc.
    1977 GS550
    1977 GS750 - Cross country trip thread

  5. #5
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    tagging along to see how this turns out. seems like something id be interested in down the road.

  6. #6
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    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:



    Last edited by sam000lee; 09-23-2018 at 06:38 PM.
    1980/1981 GS450 - GS500 Cylinder + Piston Swap - "De-L'ed", custom seat, CB350 bits, 18" rear, etc.
    1977 GS550
    1977 GS750 - Cross country trip thread

  7. #7
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    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...

    1980/1981 GS450 - GS500 Cylinder + Piston Swap - "De-L'ed", custom seat, CB350 bits, 18" rear, etc.
    1977 GS550
    1977 GS750 - Cross country trip thread

  8. #8
    Gorminrider is offline Forum Sage Past Site Supporter
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    good pix! It'll be very handy for people as a reference

  9. #9
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    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.
    '82 GS450T

  10. #10
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    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...
    1982 GS450E - The Wee Beastie
    1984 GSX750S Katana 7/11 - Kit Kat - BOTM May 2020



    450 Refresh thread: https://www.thegsresources.com/_foru...-GS450-Refresh

    Katana 7/11 thread: http://www.thegsresources.com/_forum...84-Katana-7-11

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