GS500 Camshafts and Carbs into a GS450

[pete]

Cheers Rich, yep, simplest mod ever! Even simpler than the carb swap... just gotta make sure you have the right size shims for the 500 cams

[CrawlingForward]

There are two issues... the idle knob interferes with camchain tensioner and the right hand carb mixture screw is going to be incredibly awkward to get to also due to the camchain tensioner.

I'd highly recommend looking into GS500 intake boots for the head as well as the ports on the carbs are slightly smaller than the 450 ports so I had to use some alternate hose clamps to get a good seal on them. If the boots are slightly longer that would also resolve the camchain tensioner/idle knob issue.


I had to swap the idle knob with the one from the 450 carbs which also meant cutting down the spring on it which makes it a bit less effective but it seems to work. Hopefully there's enough adjustment left to be able to get a good idle setting.


If I cut some length off the stock 500 knob it will work much better, but I can't see a way of safely getting the plastic knob off to do that yet.


After all that the GS500 throttle cable is identical to the GS450 cable despite different part numbers....





Installed:





The painful idle adjustment... no longer interferes with the camchain tensioner but nearly touching the starter motor cover:

A couple questions for ya:

First: Here's the weight comparison of a GS450 carb vs a 2nd gen GS500 carb - 60% less weight! More volume and smoother operation with almost half the weight? Yes please!



Question about camchain tension/idle clearance:

You mention the GS500 intake books would help. Do you think that would be enough or would more clearance still be needed?

If so, instead of trimming the idle knob, would installing a GS500 cam chain tensioner fix the issue? (It has to, right? A GS500 carb has the same base, so it would be designed for it....right?)

GS450 Cam Chain Tensioner:


GS500 Cam Chain Tensioner:


Final Question:
You probably answer this later on and I'll edit this out when I find it, ha ha, but what did you do about a dual cable vs single cable despite being the same part?

[pete]

The 500 intake boots are a must, not for the clearance as such but for the fit of the carbs. The groove in the 450 boots is different enough to be an issue, so I would always recommend the 500 boots for the 500 carbs. The extra clearance for the carbs from the boots in my case was due to the stock boots being distorted from holding the weight of the stock carbs...

I'm pretty sure Big Rich has gone with the the GS500 cam chain tensioner with the 500 carbs on his 450, so yep that should work. I didn't go down that path myself as they don't come up too often here (and I didn't think of it at the time).

I didn't directly answer the cable question I don't think, but the answer is nothing... stuck with the stock 450 single cable. The return spring on the 500 carbs was a bit stiffer than the 450 spring, so I saw no need to even think about a dual cable setup.

[CrawlingForward]

Awesome, thanks!

[Big Rich]

Yikes! Sorry for the late response..... but the GS500 CCT won't work on the GS450 cylinders. Look in the pics above: see the solid aluminum shaft on the GS500 cct? That's the reason it won't work.... the 450 cylinders won't take that big of a shaft.

There's nothing really "wrong" with keeping the 450's cct, you'll just learn real quick to be wearing gloves while adjusting the idle.

[CrawlingForward]

Yikes! Sorry for the late response..... but the GS500 CCT won't work on the GS450 cylinders. Look in the pics above: see the solid aluminum shaft on the GS500 cct? That's the reason it won't work.... the 450 cylinders won't take that big of a shaft.

There's nothing really "wrong" with keeping the 450's cct, you'll just learn real quick to be wearing gloves while adjusting the idle.

Oh, good point!

I'm building two engines. One stock one that came with bike, bone stock, and one that I'll be doing a full rebuild and using the 500 jugs, pistons, 450 head, and Gr650 cam.

So I would use the CCT that goes with the corresponding cylinders?

[pete]

Thanks for the heads up Rich! Not sure why I thought you had the 500 CCT on yours? Must be getting old... well older anyway...

So yep, keep the CCT with the cylinders...

[Big Rich]

All good Pete! I think we just have engine swap info jumbled in our heads.... you more than me!

CF: sounds like a plan to me! Always good to have a spare motor around....

[tkent02]

Thanks for the heads up Rich! Not sure why I thought you had the 500 CCT on yours? Must be getting old... well older anyway...

So yep, keep the CCT with the cylinders...

Putting on the 500's tensioner is a great idea, especially because you have to use the 500's pistons and cylinders to do it! 10% more displacement for an easy afternoon's effort and the price of a gasket, a good deal in my book!

[Chuck78]

Has anyone done an actual compression ratio calculation using the 500 pistons with the 450 head? I'm curious as to what it may be, & how the valve pockets match up (for use with high lift cams up to .380" or .395")

[tkent02]

Don't know, but I bolted it together and it hauled ass, much quicker and more powerful off the line than my 550 was.

[GregT]

Has anyone done an actual compression ratio calculation using the 500 pistons with the 450 head? I'm curious as to what it may be, & how the valve pockets match up (for use with high lift cams up to .380" or .395")

If you're using the 450 head, 500 pistons and big cams you must copy the 450 valve cutaways onto the 500 pistons.
The accepted safe max lift using the stock shim over bucket is around .418in. Standard depth 450 valve cutaways will accept this safely.
The 500 pistons have enough material to do the pocket cutting safely - and could go deeper if needed.

[Chuck78]

I recall Mekanix had compared the lift specs of the gs400c vs gs450 vs gs500 vs gr650 cams. Has anyone figured the duration specs from the factory service manual valve timing sketches?

I'm Summing the gs400c will have the most duration but lesser lift (most high end hp), GR650 has the most lift by far but I'm guessing fairly short duration (cruiser torque but not a high rev'er), GS500 cams may be the best compromise between low torque & high end hp with decent lift and faster ramps.

This is all just speculation on my part from what I've learned from people's comments and steven's lift specs. Oh the Haynes manual calls the 78 gs400c cams a performance upgrade for the gs450, btw.

I got a set of gr650 hollow core cams with the intention of sending them off to have them hardwelded and have megacycle profiles ground into them. I might recommend a set for my buddy's gs450s however, but that amount of lift may require machining the valve pockets. GS500 cams may be the easier bet. The drop in CR from expanding the pockets may slightly negate the benefits of the bigger lift cams. Milling the head could help correct that and then some, however.

[Swindy 84]

Glad I stumbled across this thread! I also have a bit of a question... I bought a set of 2003 GS500 Carbs a while ago due to my GSX400 carbs being pretty much dead in the water. I also have the GS500 intake boots and I am slowly collecting other bits and pieces. My question is (which most probably has been answered before) If I run 2-1 exhaust, pods or velocity stacks and the GS500 carbs on a GSX400 motor that has been bored out 0.5mm will I have to change the jetting? If so, does anyone have any idea on what I should be looking at getting?
Apologies if this a repeat question but I could not find what I have been looking for in any threads. Thanks.

[pete]

The 500 carbs I found are jetted pretty lean, and in fact the needle is one notch up from the middle, so quite lean really.

On my 450 with the stacks and foam filters and the 2 into 1 I'm running 20 pilots (one size up), 127.5 mains, 65 mid mains from memory, and needles on the middle notch. I'm toying with the idea of shimming the needles half a notch because she still seems a bit lean. I haven't spent any time on doing plug chops or anything like that to confirm though.

So, yeah, I reckon you'll need to look at jetting changes with that setup... how much of course only testing will tell.

We should probably catch up at some point considering we live in the same city

Just don't expect a pristine 450 if we do... a pretty bike she is not any more...