jetting and air filter questions for a race bike

[ConnerVT]

Started in VT. Lived in/around Burlington for over 25 years. Took a new job, and moved a bit south.

You said your bike is a 1970. But your carbs and intakes make me suspect that the engine isn't 1970, but is 1973 or later. Been through that (my T500 is a '71 with a '73 engine, '71 carbs/intake/airbox).

As I said before, you'll find that the carb type will have the greatest influence. So my guess, without seeing things in front of me, is that you will be starting with a stock late engine. Totally stock, you are 97.5 Large Round for the Main Jet, 30 for the idle jet, a P-4 Needle Jet, and 5FP-17 Jet Needle. Don't trust any of the aftermarket jets or needles, all are junk, and you'll hate life for saving $5 or $10 bucks. Stick with real Mikuni parts.

Mains are pretty cheap. Don't know how your pipes will affect your jetting, so I would probably buy the next three sizes up - 105, 102.5, and 100. Start big, and work your way down. After you have done it a few times, you can pull those carbs, rejet, and have it back together and running in no time.

edit: forgot to add the link: Suzuki Service bulletin Specifications 6-9

[petermbooth]

Thanks a bunch.
All of your info actually makes sense in terms of what year the motor is. I've had some other clues that the motor is not 1970. The stamp next to the oil fill is stamped 1400cc and I believe the 1970 motor called for 1200cc. In addition when I had the top end apart, someone had written 1974 on one of the cylinders.
Anyway, thanks for your insights. I'll get the jet sizes you've recommended and have at it.

Peter
ps I'm in Jericho and work on my T500 at a shop in Essex. When were you last in the Burlington area? I've been here since 1986.

[ConnerVT]

Was in VT 1984-2011. Lived a bunch of places around Chittenden County over the years.

[tz375]

Agree with Conner and Jimroid, Those are 32mm later type carbs and not 34 or homopressure. That's a relief.

[oldjapanesebikes]

The original carbs do have a model number stamped on them eh ? Late GT500 carbs are stamped on the left side near the engine inlet side. Earlier ones were stamped on the upper body casting. I give a few examples at this link, but if they are original Suzuki carbs, then with the stamped numbers you can tell exactly which ones you have.

[petermbooth]

Well I looked at my carbs and there is clearly a 15313 stamp on them. (photo below) According to the link oldjapanesebikes posted here, that would indicate that the carbs are off a GT500. I have a suspicion that the whole motor is off a GT500. Does anyone have a way to confirm this?

Also I'm going to start looking for jets for these carbs. Does anyone have a good source? (Earlier someone posted here saying "Do NOT go aftermarket/knock-off. Pay the extra $5 for the real deal." So that's what I'm looking for.)

Again, thank you to everyone.
Peter

[Vintageman]

Doesn't matter if GT500 or later T500 same carb.

GT500 has electronic ignition not points like T500.

Stay with real Mikuni. Google/eBay for best prices.

When I ride it's mostly in Vermont, even though I live in New Hampshire on the border. My Home in NH has nice views into VT. back in 2011 Irene storm messed up many road, but after the recovery it is much better than even before the storm. Even riding interstate 89 or 91 is not boring due to hills and views. NH is OK too but like VT a little better with respect to doing just 1 -3 hr cruises.

[petermbooth]

So if I have points, I must have a late model T500, yes?

[Jimroid]

Correct. And I used to have a boat load of the round main jets. I double checked for you and I did indeed sell them all off. So I can't help you with main jets. But if you happen to need needles I still have a bunch of those. johnu just ordered from jetsrus and he seemed happy with their service and $hipping.

[Vintageman]

T/GT500 picture history

https://www.youtube.com/watch?v=Ub51Pz-7yw0" onclick="window.open(this.href);return false;

[petermbooth]

Thanks for the video!
Is anyone able to hone in on an age/model for my motor based on these two photos (and the carb number of 15313)? (And I suppose the carbs and motor could be different models, though I imagine they were installed together and match.)

[jabcb]

You have a later model T500.
You can determine the year by looking at the motor VIN & comparing it to:

[petermbooth]

My VIN is 25230. Not sure how to date it based on that chart. Is that chart a collection of sample VINs?

[jabcb]

The list has the starting frame & motor VINs for each model year.
There are several lists that vary a bit because the starting VINs varies a bit from country to country.
Documentation wasn’t that good back then, so lists like these may also have a few errors.

Here is another list with just the frame VINs:
http://www.suzukicycles.org/photos/iden ... x-wide.jpg

Suzuki did not restart the VINs when they upgraded the bike and labeled it a GT500.
Those VINs are here:
http://www.ozebook.com/compendium/suzi/ ... /page2.gif

Your motor VIN suggests its a 1970 motor but that conflicts with 1400cc oil capacity.
Maybe a forum expert can provide more info.

[oldjapanesebikes]

Your motor VIN suggests its a 1970 motor but that conflicts with 1400cc oil capacity.

There is something odd about that case - the change in oil capacity wasn't made till around the end of the 1973, start of the 1974 model. Engine cases earlier than 1974 have 1200cc cast into the case. You can reference Suzuki service bulletin T-3 at this link for additional information about the change, and the metal foil 1400cc label that was glued over the old 1200cc cast marker. And as a third reference point for numbers, you can take a look at this link where I've compiled numbers from several sources into one convenient location.

So - based on the number, as jabcb offers, it is a 1970 engine number, but the 1400cc casting matches a 1974 or later engine case, the points indicate something prior to 1976 and the 15313 stamped carburettors point towards something later than 1973. Not sure how much that helps you - is the engine number close to the frame number ? If so you have a 1970 that has just had some maintenance over the years !

Another cross check I use is to check the wheels. If the wheels are original, there is a manufacturing date stamped on the rim which is usually within 2 months of the actual date of manufacture. You can read about how to decode that at this link.