1974 T500 Father and Son Build

Retro, Wild, Cafe, etc. The stuff only your imagination can come up with.

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sportston
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Re: 1974 T500 Father and Son Build

Post by sportston »

I suggest you completely strip the rest of the carb and put it in soak in diesel or something. Make sure that no idiot has put the wrong idle screw bolt in. Also on some carbs there is a bolt halfway up on the side of the carb body. This should be removed for now to allow oil to penetrate. You might have found some idiot has replaced it with a longer bolt or lost the washer. This can stop you from removing the slide.
Nice bike by the way. I'm sure it will be great when it is finished. Your son is doing a great job of polishing.
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Grey_Ghost
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Re: 1974 T500 Father and Son Build

Post by Grey_Ghost »

To everyone, thank you for all the great suggestions. It gave me a lot of variations and options to think about.

I had already soaked it pretty extensively with PB blaster and even used some other solvents, but short of letting it steep in a tea of WD-40 and MMO, I believed I had to rely on good ol' mechanical action! When I said it was stuck, it was stuck solid.

Since I had already damaged the slide there was no point in being gentle with it. I drilled and tapped the slide with a 5/16" tap and ran a 4" long bolt through a couple washers and a piece of steel plate. I then proceeded to "tighten" the bolt which drew the slide up the barrel. It was shocking how much effort this took to raise the slide. I finally got the slide up to the top of the barrel, but it was still not letting go. To get it the rest of the way out, I rigged up the bolt in a way that allowed me to beat it the rest of the way out with a hammer. Not the most professional method, but when you have limited tools and shop space, you make do.

When the slide came out it was relatively clean. Their was a little bit of residue on the slide and the barrel that was fairly gritty and appears to be the culprit. Had I the time and space, Alan H's suggestion of letting it soak would probably have been the best option and I wouldn't be needing a new slide.

Next step is to get the parts cleaned up and order the rebuild kits. I will hopefully get this done by next weekend so we can rebuild the carbs when I'm back in Utah.

On another note, I also finished up the polishing of the primary sprocket cover. For now, I'm done with the polishing experience. :clap:
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kb75ts250
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Re: 1974 T500 Father and Son Build

Post by kb75ts250 »

Very creative solution to getting the slide out. Aside from the mechanical damage the slide surface looked clean. That's to be expected since it's machined from bar and anodized. Unfortunately the carb body is made of some kind of diecast alloy (maybe alum or zinc or a mix?) and isn't nearly as corrosion resistant. How are you going to clean it?
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sportston
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Re: 1974 T500 Father and Son Build

Post by sportston »

I'd try to get a replacement carb if I was you. The end of that emulsifier/jet looks pretty buggered. It might be possible to get a replacement but by the time you add on the extra expense of getting a slide and factor in that the carb body has been damaged by prying (which would make it slightly difficult to balance with precision) you may as well just get a s/hand carb off ebay or a breakers.
These look ok. Shame they are in the UK. Are they the same model as yours?
http://www.ebay.co.uk/itm/Suzuki-T500-G ... SwOAZZfPeC" onclick="window.open(this.href);return false;
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Grey_Ghost
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Re: 1974 T500 Father and Son Build

Post by Grey_Ghost »

sportston wrote:I'd try to get a replacement carb if I was you. The end of that emulsifier/jet looks pretty buggered. It might be possible to get a replacement but by the time you add on the extra expense of getting a slide and factor in that the carb body has been damaged by prying (which would make it slightly difficult to balance with precision) you may as well just get a s/hand carb off ebay or a breakers.
These look ok. Shame they are in the UK. Are they the same model as yours?
http://www.ebay.co.uk/itm/Suzuki-T500-G ... SwOAZZfPeC" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;
Hi Sportston, they do look correct and are the same size (32mm) as ours. His replacement bowl is incorrect, however. The carbs look great (You gotta love vapor blasting) but notice he does not say they have been rebuilt...just cleaned!

Yeah, I noticed the emulsion tube is a bit banged up. I already have the rebuild kits coming and a bucket of Chem Dip, so we plan on giving it a shot and see if we can salvage it. Regardless, I'm going to have $100+ into the carbs.

Dime City has some nice VM32's that would fit the bill nicely or I can also get new ones straight from Mikuni. I do hope we can keep the originals, though. Fortunately, we are not on a time crunch on this!

Thanks for the tips!
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Re: 1974 T500 Father and Son Build

Post by Zunspec4 »

Hello Grey_Ghost,

The pair of carbs on eBay UK were mine and came from a GT500 that I bought for spares a while ago. They were stripped for vapour blasting and the choke levers were re-zinc plated at the same time. You are correct in saying that before use they will require the usual thorough cleaning internally. I passed them onto Gary May who is building a T500 race bike but we decided that a new set of 36mm Mikunis were the way to go. They will need a replacement float bowl, and I posted on the forum seeking one. When they were being vapour blasted the operator noticed a small hole had been patched with epoxy and thought he would do a "proper job" by dabbing the TIG welder to it. The result was an even bigger hole lol :lol: . Gary did source a new float bowl, and it may well fit, but it is not specific to the T500/GT500. Apart from that the carbs are in very good condition.

Cheers Geoff
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Re: 1974 T500 Father and Son Build

Post by old racer »

Hi Geoff were yo able to set-up the 36mm ok.

John.
sportston
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Re: 1974 T500 Father and Son Build

Post by sportston »

Grey_Ghost wrote: Hi Sportston, they do look correct and are the same size (32mm) as ours. His replacement bowl is incorrect, however. The carbs look great (You gotta love vapor blasting) but notice he does not say they have been rebuilt...just cleaned!
You could always use one of the fuel bowls from your old carbs, then all you need are some recon kits and voila! As good as new!
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Re: 1974 T500 Father and Son Build

Post by Zunspec4 »

old racer wrote:Hi Geoff were yo able to set-up the 36mm ok.

John.
Hi John,

Gary is selling the std. carbs to help finance a new pair of 36mm so not actually at the point of setting them up as yet. I will be dyno'ing my T500 race engine with a set of 38mm fitted in a weeks time, I'll let you know what settings I end up with.

Cheers Geoff
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Re: 1974 T500 Father and Son Build

Post by old racer »

Thanks Geoff.
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Grey_Ghost
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Re: 1974 T500 Father and Son Build

Post by Grey_Ghost »

Hello all,

Quick update on the bike...Pulled the carbs apart last week and soaked and scrubbed and scraped them clean. I didn't want to, but I ended up buying a can of Chem Dip and soaked the bodies for a couple hours apiece. That stuff is nasty, but it sure works great! Ordered a couple rebuild kits and shipped them to Utah for the weekend where my son learned how to reassemble/rebuild each carb with new jets, gaskets, and valves. Not surprising, the rebuild kits were not quite complete and I didn't check the description well enough before I ordered them. I am currently tracking down some O-rings for both the choke assembly as well as the idle speed and mixture screws.

I posted a pic of the inside of the carb which had the stuck slide. The corrosion you see on it is after the Chem Dip! I took some 400 grit wet-dry and carefully sanded off the rough stuff. I test fit the remaining slide in this carb and it operates smoothly within the bore. I also am sourcing a new emulsion tube, as well.

On a side note, my brother-in-law has an old Trail 90 he can't keep running due to bad gas and carb issues. My son is now officially tasked with training his uncle on how to remove, clean, and rebuild his own carb!

On another note, I have a couple questions I could sure use your help on...

1. Transmission - The two meshing gears on the left side of the engine (fifth gear?) are total chowder. Not broken, but heavily gnawed. See pic. Can I buy replacement gears separately or should I plan on buying the entire gearset? Also, can anyone recommend where I could find some of these (preferably in the U.S!)

2. Carb Balancing - When balancing the carbs, there is only one carb with a vacuum port on the engine side. I've balanced dual carbs on cars, but I always have a port for each carb. What is the best practice for balancing these carbs?

Thanks in advance for your help!
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ConnerVT
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Re: 1974 T500 Father and Son Build

Post by ConnerVT »

Vacuum port on the carb is for the stock fuel petcock. Going to want that connected, else your carbs will be dry in no time, and very difficult to set up.

Good news is nobody uses a vacuum carb synchronizer on a two stroke motor anyway. The vacuum is too pulsed to make any sense of what you see. But setting up the carbs is pretty painless.

-- Remove air box
-- Set idle mixture screws (small ones) to 1 1/2 turn from gently seated
-- Back the idle speed screws (big ones) out enough that the slides bottom out in the carb body.
-- Check that your throttle cable has just a little free play at each carb, and that your adjusters (both carbs and at throttle) are somewhere near a mid way in their adjustment range.
-- Stick one finger in each carb (same hand) while turning the throttle slowly. What you want it to feel both slides moving at exactly the same time. Sounds so elementary, but surprising how sensitive your hand is at feeling this. Some people suggest placing two identically sized drill bits (I've done it with long bamboo shish kabob skewers) and watching when they move at the same time. The goal is to have the slides move at the same time. Make adjustments at the carb until this happens. Keep mind to keep some throttle free play, adjusting at the throttle if/when needed.

Small throttle sync is much more important than WOT, and there is little you can do full open anyway.

Once that is done, you can reinstall the air box. Start the bike, which may want to stall, as the idle speed (big screws) are not adjusted. You may need to grab a little throttle once started and off choke (as you never give throttle to a 2-stroke when starting, unless you like being tired). Temporarily adjust the idle speed screws until she idles around 1500-1700, and let her warm.

Now you can fine tune the idle speed. Remove one of the spark plug wires. Idle speed will drop, so be ready to grab a little throttle to keep her running. Adjust the idle speed for the running cylinder, around 1200-1500 (lower is better at this point).

Put the spark plug wire on. Idle speed will jump back up. Let it run for a moment (a throttle blip or two, to clear the cylinder that wasn't running, can't hurt)

Now take off the other spark plug wire. Adjust the same as you did with the first.

When you put back on the spark plug wire (and clear things out a little), the idle may be a bit high. Turn both screws out the same amount (1/8 turn or so at a time) until you are around 1500 RPM.

The last adjustment is the idle mixture screw. Again, this is done one cylinder running at a time (and you may need to temporarily bump back up the idle speed screw. Remember where you have it set before you start!). The beginning setting is 1 1/2 turns, it should not need to be less than 1/2 turn, or more than 2 1/2 turns, from gently seated. I recommend more rich than lean, as it reduces chugging/surging at low riding speeds. Basically adjust it for where it runs at max RPM (we are only talking 50-100 RPM difference here). That's your spot. If you can't find an exact spot, again I recommend the richer (turned in) setting.

Set the idle mixture for both cylinders, then revisit your idle speed setting, if needed.

Ride, and enjoy!
sportston
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Re: 1974 T500 Father and Son Build

Post by sportston »

That's a very good guide for setting and balancing carbs by ear Connor. Couldn't have put it better myself and I used to balance carbs as a daily job many moons ago. I always set them up exactly as you say, then do a small amount of fine tuning on gas analyser afterwards.
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Grey_Ghost
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Re: 1974 T500 Father and Son Build

Post by Grey_Ghost »

Thanks for the procedure, Connor! It's just like tuning VW's, only without the vacuum balancing.

If you don't already, you could easily moonlight writing technical specifications!!! :)
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ConnerVT
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Re: 1974 T500 Father and Son Build

Post by ConnerVT »

For the past few years, a small part of my day job entails writing procedures, work instructions, and Job Breakdown Sheets (JBS). I mostly fly a desk now, supporting factory automation, but spent many years turning wrenches on semiconductor production tools.

The carb tuning procedure I just shot from the hip, relying on my questionable memory. But I've gotten real good at pulling the carbs off my T500, adjusting/rejetting, and putting everything back together. I usually pull the seat, battery box, air box, then the carbs. Do it enough times, you can get back on the road in under an hour.
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