GS450 carb setup - big problems

Diptenkrom

New Member
at the risk of getting yelled at here for pod filters, I have a couple questions. I have gotten mixed info in many places. This is a project bike that i have big plans for, and lots of cool parts to start building it, but i was wanting to get it running first.

bike is 81 GS450, PO removed airbox, and put shorty exhaust on it. it will not really run. still has stock BS34 carbs.

I would like a starting point for trying to get it to run. I plan on building an airbox, but I am only halfway there at the moment. Pods are on 6"long aluminum tubes attached directly to the carbs.

looks like stock idle jet is 17.5? that is what was in it, and the jet in it has no bleed holes. I have a second set of parts carbs that had larger idle jets, but they have 6 bleed holes. My son had some jets leftover from another bike, and we tried 25 and 27.5 on them, but they have 8 bleed holes. - which type of idle jet is the right style?

as far as running - the bike is hard to start, hot or cold, (little better warmed up) it will not idle, if you get it to run, it will rev and stuff, but doesn't always drop back to idle, sometimes it will rev up or hang after revving. it seems to rev out decently, but starting and idling are not really happening.
 

teazer

Over 1,000 Posts
DTT BOTM WINNER
I ran similar BS40 carbs on a two stroke with foam filters and bellmouths and never had any major issues, but those short pipes are likely to be an issue.

You can look for a pair of jets from your local dealer or from Jets R Us or try a 6Sigma jetting kit. I have no experience with them so you are on your own but they are here . https://www.6sigmajetkit.com/suzuki-gs-450-jet-kit.html

Dynojet also list a kit https://www.dynojet.com/jet-kit-for-suzuki-gs450/

There are also some on ebay, but I'd try 6Sigma or Dynojet and the carbs need to be spotlessly clean before you do anything and check the fuel level while you are in there.

Stock appears to be 17.5 if I looked up the correct model year and they appear to have no bleed holes which is unusual.

Poor cold starting and revs hanging up tend to indicate lean idle mixture. You could try to find the same series of pilot jets in much larger sizes, but it might be simpler to buy a kit.
 
Last edited:

coolio2017

New Member
Hi,
Years back I played around with the carb settings, jet sizes on a few of my bikes. I had lots of time and just loved working on my bikes. I spent hours trying every possible size of main jet and carb setting only to conclude that I couldn't get my bikes to run right.

I purchased a Dyno Jet Kit. Once you install it I found all that was required was a bit of tweaking the pilot screws to get the bike to run perfect. I did notice that with PODs I lost a little bit of power on the bottom end but was always happy with the mid and top end performance.

I like the clean look of the PODs and love the sound of a header. I have a few bikes that I run PODs and 4 into 1 exhausts on including gs750, kz750, kz1000.
Teazer's link https://www.dynojet.com/jet-kit-for-suzuki-gs450/
It's well worth the $$ and time installing...


Also, with the stock airbox remover (PODs) I found if you wet a towel and place it over all four carb intakes you can usually start and run the bike.

Hope that helps!
POD Lover
 

coolio2017

New Member
Meant to include...
With the stock carb setup (no dyno kit)
Also, with the stock airbox remover (PODs) I found if you wet a towel and place it over all four carb intakes you can usually start and run the bike...
 

Diptenkrom

New Member
thanks you guys. i have been sick and haven't looked here until today. after making this post,. i also broke the throttle cable and that is frustrating. I have used 6sigma jet kits in the past with my LTZ400 quad and my GL1200 wing project, so i might try that route.
 

Diptenkrom

New Member
okay. i have a weird thing happening now. I have replaced the crappy run/stop and start controls with one from a 99 GSXR600, have not replaced the left side yet, but the right was a problem with corrosion and the start button not working a lot of the time. i got a 6sigma jet kit, and installed it.

the bike will start and run pretty good with no filters on the carbs. with the filters, on or off the 6" pipes i made up for them, it will not start. Also tried another set of different filters, and no start there either. if i start it without the filters and then slip them on, it will run, but once you cut it off, it wont start again. any ideas why?

I have also discovered that i have an ignition system problem, and probably going to replace the whole thing with the Dyna S ignition for a GS400X like brick house builds did on the scrambler he built. But i do not think that this is the problem with the starting, though.
 

teazer

Over 1,000 Posts
DTT BOTM WINNER
What filters do you have? Some pods have an inner flange that obstructs some of the air jets and completely screws up fueling. You need a set with minimal change in inner diameter as they slip over the carb inlet. Ans not all filters flow enough air. Your may hve too much or too little restriction and could be messing with air:fuel ratio.
 

Diptenkrom

New Member
i have some cheap ones i bought that have not been used really at all, and i have a pair of K&N ones that came iwth the bike. i used the 6" aluminum pipes to extend the filters away from the carb to attempt to clean up the airflow, and reduce any turbulence there, but it doensnt seem to matter if the filter is on the carb or the pipe extensions. It wont start with the filters installed. i read a few other places and most of the info said that this is usually caused by too much fuel, very rich state. - do you think this is possibly the case?
 

Brodie

Gold Coast, Queensland
DTT SUPPORTER
Does the bike behave any differently with or without the intake pipes?
 

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