t500 carb ?

[Tamadrmr26]

i just got my t500 running yesterday. it hadnt been started in over 20 years but once i figured out some electrical problems and cleaned the carbs it fired up nicely. one problem im having is that my stock boot that goes from the airbox to the carb is in rough shape so i ran it without a filter when i first started it up. it ran ok but bogged out at any more than 1/2 throttle. i would like to put on some of the cone shaped filter pods. i like the look and there reasonably priced.

i assume i would have to rejet the carbs to make up for the increase in air flow, so i have a couple questions.

-t500 had the mikuni vm32 right?
-what size jets should i run?
-would i only have to change the main jets?

thank you

[titan performance]

Hi Tamad......the first T500's used a 34mm carb......but they soon reverted to the 32mm Mikuni.
I would suggest trying a 120 main jet if you fit pod style filters. In my experience the bikes run ok with this upgrade, and don't need alteration to the pilot jet. Some of our customers have gone to this set up, and have used their bikes on track days where they have been ridden hard without damage to the motor.........

[Tamadrmr26]

Ok. Do you think it would run better if I also did the pilot jets? Also, if I ran expansion pipes and filter pods what jets do you think I should run?

[tz375]

T500 used a carb that looks like a VM32 but it is configured somewhat differently internally. As noted above, early ones were 34mm with "round" float bowls and later 32mm had conventional "square" float bowls.

There were 3 different main jets and they were quite different. I'd pull your carbs and see what main jets are fitted. Go up 2 sizes for pods and see how it runs. You may have to come back down one size, but better to start rich and work down.

For chambers and filters start 4 sizes up and work down. Slow speed jetting can usually be tweaked with the air screw, but if it has to be less than say 3/4 turn or more than 2 turns out, change the pilot jets.

Get the idle and off-idle right first and then set the main jet for wide open operation and then fine tune the 1/4 to 3/4 throttle range on teh needle.

[Wingspan]

Question on pods...

The stock airbox provides a lot of support for the carbs, using pods obviously removes this structural element. When running pods is it necessary to fabricate a new mounting system or are the intake boots alone sufficient?

[Tamadrmr26]

Ok. Thanks. I think mine is the 34mm then. It has the rounded bowl (cylindrical shape, kind of like a barrel cut in half lying on its side). Anyone have a recomendation for where to order jets from? I'm in new york.
I'm not sure about the boots being enough support for the carbs. It couldn't hurt to add some support I guess.

[titan performance]

Your description sounds like a 32mm to me. Only the very early 500's ran the 34's. Here's a picture of a 32mm which might help. http://www.flickr.com/photos/suzuki_gt5 ... 4845440145" onclick="window.open(this.href);return false;

I have run my bike, carbs mounted only by the carb rubbers for 30 years without issue.......
Purchasers of our stainless pipes run 120 mains with pods, and the motors run well....

[tz375]

Ok. Thanks. I think mine is the 34mm then. It has the rounded bowl (cylindrical shape, kind of like a barrel cut in half lying on its side). Anyone have a recomendation for where to order jets from? I'm in new york.
I'm not sure about the boots being enough support for the carbs. It couldn't hurt to add some support I guess.

The barrel shaped bowls are 34mm and they came with a #410 Large Hex (most common Mikuni MJ) and they are available from your dealer. If they have #188 needle jets they need Large Round Main Jets and if they have #159 series needle jets they need Large Hex.

You will have to pull the carbs and strip them to know for sure and please post some pics so we can be sure what you are dealing with. Terry Grogan was kind enough to ship me a bunch of carbs including early32 and 43mm T500 carbs which I was able to strip clean and document before I returned them. I won't guarantee that my analysis was 200% accurate but it's not a bad start.

[Tamadrmr26]

ok. i cleaned my carbs last weekend and the jets were the round type with the flathead screwdriver slot. i will take some pictures tomorrow night when i get home and post them here.

[tz375]

Round main jets fit #188 series needle jets and Hex jets fit #159 series needle jets. Those two needle jets appear to be identical other than the threads, but the jets are VERY different. The threads are different to avoid using the wrong jet. Hex jets are rated in flow cc.min where ROund jets are a measure of diameter.

#200 Hex jet flows 2x the flow of a #100
#200 round jet flows 4x the flow of a #100 more or less. ( Pi R squared and all that stuff.)

[Tamadrmr26]

Nice. Pretty sure mine has the 32mm judging by that picture. I can check when I get home later. Thanks

[tz375]

Hey 500 guys. Can anyone confirm my assumptions about those carbs which came from Terry Grogan who knows way more about 500 twins that I ever will.

[geck0]

Your assumtion is correct. In 73 the carbs were detuned

[DAllen]

I just picked up my T500 Cafe' Racer from Johann Keyser in Raleigh NC. Engine is stock except for Jemco pipes and pod filters. A 1976 GT500 with 3,000 miles on the clock. Any advice as to jetting?

[Vintageman]

1973 and up the overall engine was detuned. Most of you know this ->
1) The carbs stayed 32mm but, changed to normal atmosphere venting not the vent at bell mouth as we know. Change for better IMO
2) The air box changed (same change on GT250A and that got bigger carb and more HP). I swapped GT250A with older air box and arrived back at same jetting, waste of time. This change was done IMO for ease of servicing filter only
3) Y boot (added inlet horns each carb). little more low rpm torque (maybe), but loose upper RPM power for adding to intake length and restriction
4) Little longer intake carb to cyle (but, less kink right at engine in my opinion)
5) The intake port timing was reduced via cylinder change.

Retune->
Those that have, take your 1973 T/GT500 and up and do two simple mods and little jetting to support

1) Change to early cyl or cut piston skirt 2.5mm - 3mm to get back longer intake duration same as early T500,
2) Take those extra horns out of Y boot to reduce some of the added intake path length and restriction,
Up you main jet 2 steps (if it pings up more) and maybe one step on pilot. If mid pings drop a clip on needle too richen, etc.

Now try your 1973 and up 500. And, it still look like a 73 and up, no one will know otherwise.


I would not run twin little pods streat, I would get OEM Y boot to use with filter box. Probably cost about the same . Even hard Y boots if not ripped can be softened.. enough to get on. Why? here's a few reasons. You wont have to mess with jetting so much. And, for support of those carbs as somone already said. Large factory air filter and thus less maintaince, and quiter (I like intake sound, but not to a point it hurts)