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Carb Rebuild In Progress - 81 GS450S

  • Thread starter Thread starter jmaresca
  • Start date Start date
J

jmaresca

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I got my GS450 running after fighting with the electrical system. Right now I am in the middle of a carb rebuild (Mikuni BS34SS). Got the first carb soaking right now. I kind of broke the air box ripping it out. Doesn't matter, I wanted to get rid of it anyway. My plan is to use these K&N pods. The haynes manual says the main jet is 115, pilot jet is 17.5, and starter jet is 30. What would be a good set of jets to start at with this configuration? Assume the K&N pods and pipes with mufflers cut off.

Also, anyone have any nice examples of carb mounts?
 
For now, yes. I'm only doing a partial rebuild of the bike right now. Figured I should rejet while the carbs are open. I did see a set of pipes I liked, but I can't seem to find em right now. Later on I'm going to do a full tear down and rebuild and will replace my pipes at that point.
 
Can't help with jetting on open pipes.
icon_shrug.gif



What part of the country is going to be upset with yet another bike with open pipes?

I would like to know where to avoid, so I don't get targeted, too. :oops:

.
 
If you haven't yet cut the pipes, try to hold back the stupid. It's NOT a performance-enhancing modification. I don't have a personal position on the noise, but neutering your performance is silly. Removing then shortening stock baffles would be a better bet. Keep the crossover tube. Musclecar folks pay good money to ADD those because they work.

Hunt a 2-into-1 if you want a better exhaust.

Pine-Sol makes terrific carb cleaner by the way. I've used a variety of commercial dips and wish I'd learned about it years ago.

I'd just spring for a 60 thru 80 number size drill set (cheap) and gradually up the pilot jet size, starting from one size over whatever is a slip fit. Go slow, test carefully, take plug readings.
 
I knew I'd catch **** for running open pipes. That's OK though. I found someone with the exact same setup and I'm starting where they started. 142.5 main jet and 45 pilot. Second carb is being dipped right now. What a difference. I was going to order K&N filters, but I'm also reading good things about UNIs. What's everyone's recommendation for pods?
 
I run K&N filters, all styles, in all my bikes since the 1980s.

Uni sock filters and others not only age poorly and crumble (I keep motorcycles a long time) but if you get a backfire-induced carb fire they disintegrate.

Socks are for putting outside standard filters, but I will never run a Uni main filter.
 
First up, for an '81 your jet sizes sound way wrong... stock pilot is 17.5, so a 45 pilot is going to be waaaaaaaaaaaaaaay too rich! That reference info you found is likely for an '83 or later 450 as that's when they changed the carbs.

I have K&N pods and a pretty free flowing 2 into 1 custom pipe and still have the stock pilots and 145 mains with the needle richened up.

The correct K&N's for our 450's are the RC-1822 oval pods.

Have a read through this thread on tuning mine:

http://thegsresources.com/_forum/showthread.php?t=207055

I haven't got it perfect yet but much better than it was.
 
I ordered the K&N's earlier. But I ordered the RU-1822, same as the RCs, but black rubber instead of chrome. I'll see if I have the link I was referencing at home later. I think I'm going to go with the MAC 2-1 exhaust, but that'll probably have to wait a few weeks.

pete, I was perusing your thread earlier, good stuff.
 
I found this thread where he's trying to do exactly what I'm doing. That's where I got my starting point for my jets.
 
Ok, I'd be disregarding that thread! I went up to 22.5 pilots at one stage on mine and it was a pig... so rich it was stalling constantly, popping, not good at all. Stock pilots are good for me, I'd hate to see what would happen with 45 pilots on these!

I think the guys over there aren't aware of the big carb change from the '82 to '83 model... '83 is where the stock pilot goes to a 45 or something from memory.

RU-1822 hey? Cool, didn't know they had that as an option!
 
Is it possible to find a set of '83 carbs and just bolt them onto my 81 450S? Ive been reading all your carb threads, and im a bit nervous about rebuilding, modding, enhancing my carbs. Ive ordered the K&N pods, and because it got so much popping on decel i thought it was running real rich, but i just read that means lean? So i probably shouldnt pop the K&N on until i rework the jet to richen the carb?
 
GeorgiaBulldogs said:
Is it possible to find a set of '83 carbs and just bolt them onto my 81 450S? Ive been reading all your carb threads, and im a bit nervous about rebuilding, modding, enhancing my carbs. Ive ordered the K&N pods, and because it got so much popping on decel i thought it was running real rich, but i just read that means lean? So i probably shouldnt pop the K&N on until i rework the jet to richen the carb?
Click to expand...
I believe '83 and up carburetors were different. You might be able to bolt them up if the inlet/outlet diameters fit and you have the correct throttle cable, but they might require some tweaking before they run right.

I would really dial in the stock carbs before making any mods, like adding pods. Open them up, strip and dip them if you haven't already, make sure you have stock jets on there, set the float height etc. and adjust them so they're running perfectly. After that, you should be in a better position to a) do intake/exhaust mods and b) decide whether or not they're even necessary.
 
Yup, good advice.

If you're going to go newer carbs though, go for newer GS500 carbs.

Big Rich on here has them on his 450S and reckons they're great and are a straight bolt on.
 
pete said:
Yup, good advice.

If you're going to go newer carbs though, go for newer GS500 carbs.

Big Rich on here has them on his 450S and reckons they're great and are a straight bolt on.
Click to expand...

I assume that's only true if you're not running the stock airbox, right?
 
Definitely listen to what Pete has to say. I know on my 450 running the pods and aftermarket mufflers I had to up the pilot jet by one size, anymore would be way too much. The main jet however is up about 4 sizes if I recall correctly. I've also got the needle shimmed out to richen it up, runs really well, only under certain, rare, circumstances can you feel any issues. Keep in mind, I'm in Denver at 5000ft elevation.
 
Ya, you're right, strip, dip, clean, and sync the stock before doing ANYTHING else.
 
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