Stock 72 T500J using 1973 carbs

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Original T500J
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Country: USA
Suzuki 2-Strokes: TS100, GT185, T500J, GS850G

Stock 72 T500J using 1973 carbs

Post by Original T500J »

Hi all, I have a near mint 6000 mile green 72 that had a gummed up
Piston that was seized. Freed up
Piston, decarbonned everything new rings and great compression. New points added. Carbs were full of crud and I buggered right carb body thanks to pilot jet that wouldn't leave. I bought used carbs for a 72 (not!!)but they are 153-13 and are from 1973 and up. My original say 156-02.
I tried using my original jet needles, from carb kit 150 mains, pilot jets and needle valve float assembly. Bike will not start. Occasionally hiccups. I revived an orange 72 back from dead without a problem.
Any insight would be appreciated

Thanks Bruce
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ConnerVT
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Suzuki 2-Strokes: T500R (now), T500M (40 yrs ago)
Location: North of Albany, NY

Re: Stock 72 T500J using 1973 carbs

Post by ConnerVT »

A big change took place between 1972 and 1973 model years. My bike is the opposite of yours - a 1971, with a 1973 engine, running the 1971 carbs.

1969-1972 used homopressure carbs, which the float bowl vent is internal to the carb, and utilized the 150 Main Jet.
1973 and beyond have an externally vented bowl, and utilize a 97.5 Main Jet.

Most of the rest of the jetting (Pilot Jet, Needle Jet) remain the same. The Jet Needle is a little different, with the post-1973 jet being just a hair richer (skinnier).

Suzuki made a few other changes (a longer intake boot, a slight change to the cylinder intake, switched to a foam air cleaner), but this differences are insignificant in the grand scheme of things.

You should start by replacing the Main Jets with the 97.5 sized ones. Make sure you have the slides installed correctly (cutout faces the airbox).
Original T500J
Still in the Driveway
Posts: 8
Joined: Tue May 29, 2012 3:30 pm
Country: USA
Suzuki 2-Strokes: TS100, GT185, T500J, GS850G

Re: Stock 72 T500J using 1973 carbs

Post by Original T500J »

Thanks for the input. The 72's were also the last of the full power 500's. The extreme jetting differences I believe helps to explain why she just wouldn't start. The bike is too nice to not do it right. I am pissed but looks like another trip to buy old carbs is required to get this old girl right.
I will have a nice clean set of 73 carbs up for sale as a result.
I sincerely appreciate the feedback

Bruce
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ConnerVT
Novice racer
Posts: 963
Joined: Wed Jan 18, 2012 8:01 pm
Country: USA
Suzuki 2-Strokes: T500R (now), T500M (40 yrs ago)
Location: North of Albany, NY

Re: Stock 72 T500J using 1973 carbs

Post by ConnerVT »

I am unsure if the change made to the later carbs is fully responsible for the detuning/loss of HP in the 1973-later models.

The change made in the cylinders (intake port) may be partially responsible. Lengthening the intake boot definitely will cause a decrease in signal (read:responsiveness) with changes in throttle, and may also result in lower HP at steady throttle. I just don't have hard evidence either way.

The homopressure carbs have their own set of headaches. While they were to help smooth out differences in atmospheric pressure (sea level vs mountains), some excellent carb tuners have found them to be a royal PITA to consistently find a happy tune.

I would be moderately surprised if there is a noticable difference between the early and late model carbs, with them both jetted with the correct stock brass. If you do go this route, please keep us updated.
Original T500J
Still in the Driveway
Posts: 8
Joined: Tue May 29, 2012 3:30 pm
Country: USA
Suzuki 2-Strokes: TS100, GT185, T500J, GS850G

Re: Stock 72 T500J using 1973 carbs

Post by Original T500J »

At this point, I am leaning towards the original carb set up. All I need is a right hand body. By the way I did check the slides and thanks for the idea. They were installed correctly and were not switched from left to right.

Will let you know when I finally get this time capsule running.
Bruce
argo1974
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Re: Stock 72 T500J using 1973 carbs

Post by argo1974 »

Over a decade ago, when I still had my T500J, I had the same problem. Since stock carbs were toast, I swapped in K model carbs. As a result the bike ran crappy. After playing with the jetting few days, I decided to buy J model carbs.
1x T500 Cobra (1968)
4x T500K (1973)
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