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GS450 Carb upgrade, whcih carbs?

  • Thread starter Thread starter djg42
  • Start date Start date
D

djg42

Guest
Hello,
I want to get a nice upgraded set of carbs for my 1980 GS450. Any suggestions? Is round or flat slide better? Heres a good selection of mikuni slide carbs, but are these worth upgrading too?
http://www.nichecycle.com/Items.aspx?code=CARBSING&key=cat
Thanks!

IMG000182.jpg
 
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What's wrong with the carbs you have on it now? :-k

They will already flow more air than the stock engine can handle. :o

.
 
Steve said:
What's wrong with the carbs you have on it now? :-k

They will already flow more air than the stock engine can handle. :o

.
Click to expand...

NO...NO...Steve ! More air/fuel...more POWER ! :D

Unless you have a cam, head work, and plan to spin the thing into the double digits...different carbs won't do you much good. Add to it, that the displacement of a 450 will also limit what you can expect for power.
 
I want better carbs that are easier to tune, and for better performance.
Im boring it out and using GS500 pistons.
 
You can probably find a couple of TMs on Ebay if you take your time.
 
Alternatively the GS500 carbs I believe are a bolt-on, but I don't know that will be an upgrade as such...
 
I put FCRs on the 93 GS500 we used to road race but don't know if those will work on the 450. Ignore the guys that AREN'T engine builders or tuners! Carbs, even on a stock engine, are a good source of more power! I speak from EXPERIENCE!!! Ray.
 
rapidray said:
I put FCRs on the 93 GS500 we used to road race but don't know if those will work on the 450. Ignore the guys that AREN'T engine builders or tuners! Carbs, even on a stock engine, are a good source of more power! I speak from EXPERIENCE!!! Ray.
Click to expand...
A good set of mechanical flatslides will wake any bike up.
 
Hmmm... Ray... was there a specific type/size of FCR? I believe the 450 and 500 share the same intake boot diameter so I'm guessing that they'd work for the 450 as well...

I'm just thinking for Dennis as well as for myself if I happened across a pair at the right price...
 
pete said:
Hmmm... Ray... was there a specific type/size of FCR? I believe the 450 and 500 share the same intake boot diameter so I'm guessing that they'd work for the 450 as well...

I'm just thinking for Dennis as well as for myself if I happened across a pair at the right price...
Click to expand...
2mm over stock is plenty and will usually fit the stock manifolds. Slide type carbs flow more air so you don't have to go ginormous with them.
 
Billy Ricks said:
2mm over stock is plenty and will usually fit the stock manifolds. Slide type carbs flow more air so you don't have to go ginormous with them.
Click to expand...

Cheers Billy! Dunno about Dennis but I'm a noob when it comes to that stuff... but it's real fun learning :)
 
yeah, thanks! Greatly appreciated. I guess ill go with a mikuni flat slide?I can get 34mm, or 33mm with accelerator pump($100 extra per carb)
Also, is there a way to figure a range of jets to start with, based on my stock carb set up?
I have 150 main jets (117.5 stock)
and 25 pilot jet (either 15 or 17.5 stock)
 
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djg42 said:
yeah, thanks! Greatly appreciated. I guess ill go with a mikuni flat slide?I can get 34mm, or 33mm with accelerator pump($100 extra per carb)
Also, is there a way to figure a range of jets to start with, based on my stock carb set up?
I have 150 main jets (117.5 stock)
and 25 pilot jet (either 15 or 17.5 stock)
Click to expand...
They'll probably be jetted close enough that all you might have to do is play with the needles and maybe change mains. I'm not sure what the stock carb size is, most likely 32mm. Either of those sizes would do if that's the case. The pumps are nice but not essential.
 
I checked the oem carb spec on this site and according to it you have 34mm carbs. The TMs will still flow much better than the stock CVs.
 
oops, I was thinking it was 32. So if its 34, what size do you think i should go with?
Its a shame its hex main jets, I have a nice assortment of round mikuni mains
 
djg42 said:
oops, I was thinking it was 32. So if its 34, what size do you think i should go with?
Its a shame its hex main jets, I have a nice assortment of round mikuni mains
Click to expand...
You won't need to go bigger. The 700s and 750s came with 32mm carbs and back in the day the hot set up was a set of 29mm VMs. The TM33s or 34s will be plenty of carb. If you go with the pumpers you have to learn to roll the throttle to make proper use of the pumps. Since there is no throttle plate in the carbs and the throttle operates the slides directly you can bog the engine at lower rpm by just whacking the throttle open. You lose intake velocity and the engine will bog. Once you get the rpm up you can just keep the throttle pegged through the gears. When I installed my RS flatslides there was so much more power that the clutch started slipping under hard acceleration.
 
I'm tempted... seriously tempted... but I need to get my 450 done by the end of the year.

If I was to add flastslides... well it ain't gonna happen yet ;)

Dennis, keep us up to date if you do it will you? I'm very interested to see how this works out... they'd be a very nice addition to my K&N pods and my Tranzac pipe...
 
Absolutely, will do! In going to order this week. Just have to decide if Im going with or without the pumps.
Also, Im curious what kind of carbs the GS500 has, and if it might be a good swap.
Thanks again for the help Billy Ricks, Pete and Rapid Ray!!!
 
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