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81 Suzuki GS450T Carb specs

  • Thread starter Thread starter Tweeker
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Tweeker

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Looking for info on my 81 GS450T for Carb Specs and specifically the Fuel screw, how many turns out on both carbs. Also Tab on float, how much shall I bend tab. A little info on the Fuel Screws, I am calling them fuel screws because they are located on the engine side of carb and not air box side. As your sitting on the bike the left carb had 2 1/4 turns for the fuel screw and the right carb had 1 3/4 turns on the fuel screw. Here is a little info on my motorcycle, I got the bike about 4 years ago and sat for 4-5 years prior to me getting it, once I received it, it sat for 3 more years. I got it running this spring of 2008 and it does idle very nice, but once your at a stop sign, it jerks and sputters until the rpms are up and then gets going, in 6th gear on lower rpms it doesn't seem to have the power to get up past 55-60 mph. I have completely stripped down the carbs and soaked them and thoroughly cleaned them. I have replaced with brand new parts both floats, needle and seat including screen and washer, 2 air Jets, bowl gasket, and both needle jet gaskets. I have looked through all the forums b-4 posting this to make sure the info wasn't already out there. So hopefully this carburetor info and float info will help others out there with 1981 GS450T Motorcycles. Thanks for your time in reading this. :)
 
I just recently acquired and "tuned up" my GS450 with some great off line help from forum members here...

After drilling out and using a deck screw to remove the EPA aluminum plugs over the fuel screws I started with 2 turns out after lightly seating the screws. I tried the highest RPM method (searching in 1/4 turn increments for the highest idle) but ultimately found that adjusting in until I could + ID a reduction in idle then out 1/8 to 1/4 turn. Bike ran about 10% better off idle and does not bog down after 1 minute of warm up (used to be 2-3 minutes).

Float height is [FONT=&quot]22.4 +/- 1.0mm (0.88 +/- 0.04 in). Measured from bottom of float (or top if off bike) to the gasket seat with the gasket removed just as the spring pin in the float needle starts to move[/FONT][FONT=&quot]...something I need to do.[/FONT][FONT=&quot] (it was easier on my dirt bikes when fuel started flowing out the float valve)

You did not mention if you thoroughly sprayed the rubber inlet boots (especially the mount area to the head) with WD40 or carb cleaner? If you get an idle change that could be a clue. Many would reccomend changing the inlet o-rings anyways after 27 years...like the Mag Mopus tires that came on my bike.[/FONT]
 
Thanks Houdini, I did spray WD40 around both inlet and outlet sides of the carbs, no leaks what so ever.

I guess I don't really understand what those numbers mean, the 22.4+/-1.0mm(0.88+/-0.04in). If I'm using mm should I be reading 22.4mm? whats the -1.0mm mean and the + behind the 22.4 mean? I understand I measure the highest point of the float if the carbs are off and turned up side down so the float is up, correct?

The other question was , how do I know if I damaged the fuel screw, are there visible signs on the screw itself. The reason I ask is because I used a little force to seat it then back it off, not much force, but i tightened it. I read what you said about lightly seating it and I thought how I actually tightened it.

Any comments on this would be great. I hope I didn't damage anything, ack.Thanks again for responding to this Houdini. :)
 
The float height in parenthesis is in inches (0.88+/-0.04in) if that helps. The +/- means a tolerance of 0.84 to 0.92. You will see tolerances throughout your manuals.

You know if you damaged the fuel screw / seat if the RPM does not change at idle.
Again start at 2 turns out if no idle change by ~1/2 turn out troubleshoot.
 
...and don't trust the WD-40 method to determine if you have intake leaks, it's unreliable. Just change the intake pipe o-rings unless you know they have been changed recently. They are almost sure to leak, or will be leaking soon, so best to just refresh them while you have your sanity or you will be chasing inconsistent idle issues in the near future.
 
Thanks for the help guys, waiting on some new intake pipe o-rings and will install them.

Hopefully everything goes well. :)

Any other insight regarding when I turn the choke on while I'm in 6th gear and I have instant power for a short period, I understand it floods after being on so long, but when it is on I have instant power in all gears. Is this from lack of fuel and by turning the fuel screw out 1/2 of turn at a time this might remedy this?

Remember, it idles fine and runs good, except when ever I come to a stop sign and let go of the clutch from a complete stop, it spits and sputters, then kicks in after I gun it . Hopefully since I have done a complete overhaul of the carbs it should run better.

Cant wait to get it running to find out this week after the new intake o-rings get here.

Thanks again everyone for the input! Any new input is greatly appreciated.:)
 
Mixture screws are only for low throttle positions, not full throttle. Sounds like there is something more fundamental wrong. You didn't ditch the airbox did you? The carbs sound too lean so look at the basics.
 
Well now that you are off the idle circuit...
Here is the list of things I performed to get this "little beast" tuned up:

Symptom – Engine running lean / bogs at idle / mid throttle positions
?[FONT=&quot] [/FONT]Pulled float bowls and cleaned pilot jets – found caked dirt in jets - helped 5%
?[FONT=&quot] [/FONT]Installed air cleaner – pre-oiled from factory – helped 5%
?[FONT=&quot] [/FONT]Pulled slides and swapped needle washers – put white thick below clip & thin steel above – helped 20%

?[FONT=&quot] [/FONT]Pulled idle mixture epoxy plugs & adjusted screws – no highest idle, so turned in until lower RPM, then out ? turn – helped 10%; however, mid range feels slightly less – 5%?
?[FONT=&quot] [/FONT]Checked carb synch – Found to be equal vacuum readings



 
Wow, thanks for the info guys. I will be looking into all this first thing Monday afternoon.

Hopefully I can put to use what you guys posted, sounds confusing to someone like me..lol.

Not to mechanically inclined. :)
 
cant wait, the rest of my parts come in tomorrow on Wednesday by noon........WOOT !

I'll keep you updated on my results on performance.
 
Well, They sent me the wrong jets.

They sent the pilot jets, I needed both pilot air jets...lol

They are overnighting my order to correct the problem, they said they will be here on Friday.

Lets cross our fingers
 
So to inform everyone that was watching this thread, I have the carbs in and working 110% !!!! The bike runs like a well tuned machine !!! I cant believe how well it runs.

Everything that I replaced on the carburetors I replace on both Carbs. The Floats, gasket for bowls, the O-rings on the air screw and choke + needle jet o-ring, I replaced air idle jets, Needle and valves with the washer and screens, and new t-Nipple for the main fuel line that connects both carbs.

I took it around the block to see how well it was going to perform and it ran like a charm. I decided to take it for a longer trip and drove it to town to fuel it up with some new 91 octane gas and reset my odometer to see how my MPG was. That went so well I decided to take it for a longer trip out in the country and put about 60+ miles on it. AWESOME RIDE !

It has sooo much power now, I cant believe it! Its instant power when I throttle it. It doesn't spit and sputter at stop signs any more and in 6th gear I have so much power.

So Thanks everyone for your input on my problem and appreciate all the advice and tips !!!!!! :p:):p:D
 
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