GS500 Camshafts and Carbs into a GS450

[Chuck78]

swapping gs500 carbs onto a gs400/425

swapping gs500 carbs onto a gs400/425

The schematics for 78-79 400's & 425's show an aluminum spacer & gasket bolted to the head, called an "insulator." So if making an adapter, you already have a gasket to make this work. The only thing to do is put the intake boots on the gs500 carbs & hold them up to the head and see if the bolt holes in the head will terribly interfere with the wider placement of the gs500 boots& carbs. It may even be possible to countersink the bolt heads on the spacer so that the intake boots could slip over them slightly as long as it wasn't too close to the intake boot o-ring.

If that adapter idea was total no-go due to bolt pattern interference, then you could search ebay or better a local parts place or Japanese bike junkyard for a set of factory Katana or GSXR intake boots that had the right carb size & close enough offset. With patience, research, & maybe buying a few wrong boots, you should be able to come up with something that is a bolt-on.

 

[Guest]

For some reason I thought the carbs were narrower... not sure why...

Best bet is for me to try for some photos. I'll have the carbs out of the boots when I do the 500 boot replacements so I'll get some photos then although they won't be the best. I have limited time to do this stuff at night so I'll be leaving them attached to the throttle cable while I replace the boots.

I'm hoping they'll arrive today so I can do them tonight but I'm not sure if that will happen yet.

With the adapter, I was thinking slanted slightly left/right for each side, not up or down... but no not the best solution.

 

[theironlung1976]

I THINK im the dude Chuck was talkin about w the 78 400 doin the carb swap... If not, i just so happen to have a 78 400 and im doin a carb swap on n sent Chuck a pic of the carb spacing bein different... Lol.

I got the spacing difference figured out. 2 custom "t"s r needed. One for the vent, one for the fuel inlet. U could probably get away w takin the oe lower fuel inlet "t" n use it as the upper vent " t" w some tubing n pinch squeeze clamps after the width is lengthened. No pressure, just a pathway for fumes. 2 tie brackets n choke link rod need to b lengthened .474". The lip on the left side carbs throttle shaft needs to b lengthened .474" n shaped to allow for sync adjustment. My "t"s r being turned as we speak. Ill send a pic when theyre done. The rest is simple weldin. The bottom tie bracket holdin the carbs together hits the cam tensioner by the way. Needs to b relieved to clear it. Petes later carbs have a different bracket system n choke setup... N kinda looks easier to overcome. Im gonna do a thread on it soon. Just waitin to have all the shhhtuff together for pics before i do it. Stay tuned Chuck!

Pic is of my old 400 carbs next to the 500 carbs.

Didnt mean to impose Pete... Just wanted to get the info out there if someone was lookin for it. Anxious to see where yer jetting settles in to a sweet spot.

 

[theironlung1976]

And since Pete n Rich hit on this earlier, just figured id show how light these r... Compared to my old carbs anyways.

 

[theironlung1976]

Crazy! This swap is worth it in more ways than 1.

 

[Guest]

Wow I didn't realise there was such a difference in the spacing! I always knew the 400's and 450's had some differences but not that much... and yes the 500 carbs are sooooo much lighter!

I did get some photos when putting the new intake boots on but they're not real flash. Let me know if you want me to post any up... they sort of (but not really) show the spacers and how the throttle cable mounts.

One catch with the new intake boots was that it lifted my carbs up. The weight of the stock carbs without the support of the airbox distorted the old boots quite severely. Something to keep in mind guys! I'll be fabricating some sort of mount to let the weight of the carbs hang off the frame rather than the boots in future.

And you can also see how much of a difference there is between the 450 and 500 boots, so definitely grab the 500 boots when going with the 500 carbs:



As a result of that, I had to shorten the velocity stacks 20mm to clear the right hand frame rail which it was now hitting.

The big downside with that is there is no way I can get sock filters to fit any more as there is just no clearance. Same with the fuel tap on the left side.

I've purchased a sheet of filter material with stainless steel mesh from the UK to make my own:

http://www.ebay.com.au/itm/Ramair-P...75?pt=LH_DefaultDomain_15&hash=item3f29609d17

Hard to see the lack of clearance in this shot but it's almost touching the tap:



It's service time this weekend so if my valve clearances are still good I'll be swapping the GS500 camshafts in as well. Hopefully I've got enough spare shims here to account for any differences.

I definitely need to sync the carbs again too once that's all done.

Once I'm done with the camshafts, carbs, and sync and get some filters in place, I'll try to get the jetting as close as possible then pay a visit to a dyno to get some AFR readings done and see how far I'm off.

I can't wait to get all this sorted!

 

[theironlung1976]

Huh, there is a noticablle difference to the new boots bein smaller.

I didnt even think about the carb weight w/out the airbox holdin em up. Those bull **** thirty fours (bs34s) musta been bouncin around like a puppet on a string. Mighta been why my idle was hangin so bad... Im sure the orings on the back of the boots that crumbled in my hand when i pryed em off didnt help either. Never even gave it a thought. Think i might find a way to support the 500 carbs. As light as they r, sooner or later that weight is gonna catch up to those rubber boots.

Cant wait till u get yer cams in dude! Been watchin this thread for a while waitin to see when this service was gonna happen. The big payoff is here!

Really curious to see where yer jettings gonna b w it all. Hope ya get it dialed in Pete. Good luck man. Keep us posted. Cant wait to see the dyno sheet either!

My box-o-500 that showed up a week er 2 ago. Waitin for my next service too... N my forks to get mounted... N my swingarm to get mounted... N my caliper brackets made... N my bore job finished... THEN my cams... Lol! Im a long ways away from my cam swap i fear.

 

[theironlung1976]

Started this today. Should b postin more soon.

http://www.thegsresources.com/_foru...ting-early-gs400-to-gs500-carbs-not-a-bolt-on

 

[Big Rich]

Pete, I had the stock carbs on my GR rip off the boots with no airbox as well. Luckily it was in the garage and not away from home! Ever since then I've used long zip ties going from the backbone of the frame to the carbs (on my 650 and 450). They at least stop them from bouncing down, are cheap to replace, and detach quickly when fiddling with the carbs.

 

[Guest]

Oooops, haven't logged in for a while again! Sorry guys...

Anyway, service is done and dusted but GS500 cams still aren't in there

The 01 cams have the spacers/shims on them to prevent cam walk which is great, except that the shims on mine are one size up (1.10mm) and make the cams too wide to fit between the journals. Leaving them out isn't an option as there is way too much left/right movement. When I get motivated again I'll order the 1.00mm shims and try again.

I addressed the carb hanging issue with a cable tie too Rich, although I added an aluminium "hook" as well.

I was finding it too difficult to get a cable tie down and around and back up to the frame so I decided to make a "hook" out of some scrap 2.5mm thick aluminium sheet I had laying around. It seems to be fine so far:





I've also gotten hold of a sheet of Ramair filter material with a stainless steel mesh from the UK to make up a filter for the stacks as well: http://www.ebay.com.au/itm/Ramair-P...75?pt=LH_DefaultDomain_15&hash=item3f29609d17

Should be plenty big enough for what I need and I think I'll just make one to cover both stacks but I haven't given it a lot of thought yet as I haven't had much time since it arrived.

 

[gofika]

Hello Pete
Don't know if you remember me, had a thread on an old forum (this must be new since I didn't have a user here) with a bike that's running a bit funny (weak) on one cylinder. Still haven't solved that issue (!) but still ride the bike and it doesn't run either worse or better
Some day I'm thinking I'll take down the head and maybe find a burned seat or something else that's funny but right now the suzuki serves me well enough. When I get to the plonkering with the engine I'm thinking of maybe doing the same cam swap you're thinking about (but of course keep my single SU from a mini cooper that accelerates better than the original ones, but 3 mph lower top speed. Maybe try out a power jet set up!?). Would be nice! Good thread and I'm very eager to see your results

Cheers from rainy northern sweden

 

[Guest]

Hey mate, no don't remember you in particular... but if it was more than two or three months ago then I definitely won't

I still hope to get the cams in at some point, hopefully before too much longer.

Right now after the service and carb sync and replacing the boots she's now way too rich at low throttle openings so I need to do something about that yet.

 

[gofika]

Hey mate, no don't remember you in particular... but if it was more than two or three months ago then I definitely won't

I still hope to get the cams in at some point, hopefully before too much longer.

Right now after the service and carb sync and replacing the boots she's now way too rich at low throttle openings so I need to do something about that yet.

Get an SU

I remember you having some answers when I was clueless and frustrated. Now I'm just clueless

Anyway my gofikar?ser looks very fast so it would be nice to also make it fast

 

[Guest]

Hmmmm... those pipes do look a little familiar

 

[Guest]

Well I finally got the GS500 cams in yesterday. Had a weep on the valve cover gasket become a leak over the last few weeks and the cam chain tensioner gasket I re-used by mistake also had a weep, so I figured if I'm going in there I might as well chuck the cams in.

I've had the 1.0mm washers for the cams sitting there for a while now along with a spare valve cover gasket and a couple of tensioner gaskets so it was definitely time.

Hopefully I'll get a test ride in today to see how she runs. I also dropped the needles half a notch back to the middle notch as she seemed a bit soggy just off idle.

Incidentally, I checked the valve clearances before/after the swap and the exhaust valves were going to need one size down shims, but after the swap both inlet and exhaust clearances have all opened up again and she starts much better now. I didn't think there were any issues with starting but definitely an improvement.

 

[Guest]

Got a short test ride in yesterday.

She definitely starts/idles better with the valve clearances now in spec, and the leaner needles have definitely made that low throttle response a touch crisper.

As for the camshafts, I reckon it starts picking up earlier in the rev range but I'll have to wait for a proper ride next weekend to really see for sure.

 

[Guest]

Got my first good ride in with the new camshafts yesterday, and she pulls noticeably harder than before, especially up hill.

The whole midrange is definitely improved and I swear she's building rev's a bit quicker when she's on the boil too.

My butt dyno says there is more torque on tap.

 

[Guest]

Do you have any specs for the differences between the 450 and 500 cams? I found specs for the 500 readily, but nothing on the 450.

 

[Guest]

Have a look here:

http://www.thegsresources.com/_forum/showthread.php?205995-GS-Twins-Wiki

The duration of the 450 cams isn't listed but I did see it listed as 280 degrees on a Google search result once... unfortunately I cannot find that page again. Should've bookmarked it!

Essentially the 500 cams are a bit less duration and a bit higher lift.

 

[Big Rich]

Good to see some progress Pete! Sounds like the cam swap was pretty painless for you too..... and much cheaper than the other options.