Suzuki 2 Strokes

I have never been able to get my GT380 to run right and I think it is about time to give up on it after 3 years. I would like to see if anyone would want to buy some of the nicer parts I have invested stupid money into...Jemco 3:3 chambers, power dynamo ignition, brand new Sudco Mikuni VM26 carbs, uni pod filters, nos oil pump, Bill Bune rebuilt crank with new rods bearing seals and std size pistons. Anyone have internet in this stuff or is it a paper weight?

Hi and welcome, what are the running problems you've been having? Perhaps we can help with those ... strokers are a black art but most problems are usually pretty simple in the end.

And to answr]er your question, someone will bite your hand off for those good parts.

The manuals for these vintage bikes are pretty lame. It really helps to use a forum like this one.
You are probably closer to having a nice running bike than you realize. We might be able to help you get there.

I know I feel like I should be ripping it up and down the street. I brought it to a local shop who specializes in old bikes and he said it ran great! I don’t know what bike he was riding because mine pops and farts and will not take over 1/4 throttle while constantly fouling one plug while the other is bone dry.

Lots of questions here but they will help us narrow down the possible problems:

- does the bike start easily from cold, or is it a pig to start?
- does the bike actually run on all 3 cylinders below 1/4 throttle (do all the exhaust headers get hot)?
- is the bike still running the stock fuel tank, fuel tap etc?
- if it IS running the stock tank and fuel tap, is the vacuum line from the carbs connected to the tap?
- are all the carbs getting fuel?
- what kind of choke (cold start) mechanism is on those carbs?
- do all 3 spark plugs actually give a spark?
- does the Powerdynamo ignition still require a battery or is it completely self-generating?

- does the bike start easily from cold, or is it a pig to start?
Yesterday I rode it twice fired on the second and third kicks from fully cold.
- does the bike actually run on all 3 cylinders below 1/4 throttle (do all the exhaust headers get hot)?
I see smoke on all 3 at idle. I haven’t checked the temps yet.
- is the bike still running the stock fuel tank, fuel tap etc?
Stock tank and cap, Kreemed tank liner not flaking at all, nos cap seal.
- if it IS running the stock tank and fuel tap, is the vacuum line from the carbs connected to the tap?
I run it on prime the new VM26 don’t have a Vac port
- are all the carbs getting fuel?
Yes I turn the tank off and run the carbs dry at shut down. When turning fuel on I can see all 3 fuel hoses flowing gas.
- what kind of choke (cold start) mechanism is on those carbs?
The guy at the shop called it an enricher and said it only works at idle.
- do all 3 spark plugs actually give a spark?
Last I checked yes but that was a while ago.
- does the Powerdynamo ignition still require a battery or is it completely self-generating?
Mostly self generating but I have a very small 12v battery to hold the kill switch relay energized to allow starting.

Right, so its the older type of fuel tap with a separate feed for each carb, i.e. 3 feeds in total? And the tap is definitely flowing plenty of fuel on the prime setting? That is, it flows in a steady stream?

The fact it starts easy from cold is a good sign. I wonder if the enricher is sticking on and flooding the engine. How do the enrichers work, are they hooked to a cable, or is it like a tab or button that you lift?

Do you know what the ignition timing is set to (unfortunately, you really need a dial gauge for this unless you know for certain it is accurate).

The bike is running B8ES spark plugs and the plug caps have continuity, right?

Right, so its the older type of fuel tap with a separate feed for each carb, i.e. 3 feeds in total? And the tap is definitely flowing plenty of fuel on the prime setting? That is, it flows in a steady stream?
yes it flows steady it is one 1/4” barb with a splitter to feed the carbs together.
The fact it starts easy from cold is a good sign. I wonder if the enricher is sticking on and flooding the engine. How do the enrichers work, are they hooked to a cable, or is it like a tab or button that you lift?
each carb has its own lever. The carbs are a year old with 15 miles on them.
Do you know what the ignition timing is set to (unfortunately, you really need a dial gauge for this unless you know for certain it is accurate).
I have played with the timing and adjust it from the early to late specs somewhere around 3mm BTDC if I remember anything from last year or the year before.
The bike is running B8ES spark plugs and the plug caps have continuity, right?
I had b8es but the repair guy just switched them to B7ES, I have never checked the caps but they were new and the bike always sparked. Power dynamo has a note to always use caps with less than 5k ohms.

Were the carbs on the bike when you bought it? If so it may be worth checking they are genuine here
http://www.sudco.com/genuine_vs_fake_carburetors.html" onclick="window.open(this.href);return false;

OK, nothing definitive there BUT I would not run the B7ES plugs in that bike for any length of time. They are a hotter plug than the standard B8, and you're running chambers and filters. There's a risk of holing a piston.

Also, I would recommend retarding the timing to the later spec (around 2.25mm BTDC). The earlier spec of 3.00mm BTDC was intended to boost mid-range but is too advanced for serious usage, again there's a risk of holing pistons if you do any longer runs.

Carbs are from Sudco so unless they had problems...I believe I am using the later spec for the exact reason you stated. As for the plugs...it can’t run long enough or well enough to hole a piston from that sort of heat. The bike has 40 miles since being rebuilt 3 years ago.

Are the choke mechanisms definitely OFF when you are trying to get the bike running? You can check this as follows: start the bike from stone cold and let it idle on the chokes for 30 seconds. Then knock all three chokes OFF. The rpm should drop and you'll have to keep the engine alive using the throttle. If you don't have to use the throttle to keep her alive, one or more of the chokes is sticking on.

When warm, does the bike run smoothly and on all 3 cylinders if you keep it below 1/4 throttle? If it does do that OK, then it means the pilot jets and carb slide cutaways are pretty much OK (and probably the ignition too).

If the problems only start when you go for more than 1/4 throttle, it's likely the needles and needle jets are wrong for your set up (the float height could also be a problem).

One of the issues with bigger carbs, chambers and aftermarket filters is that at certain rpm and throttle openings, there will not be a strong enough flow of air through the carb throat to allow the fuel to atomize properly from the carb jets. So the engine will fart, stutter and surge.

Here's an idea to try. Cover half of the exterior surface of your pod filters with masking tape (the stuff you use when painting in the house), leaving half of the pod filters' surface exposed. Then try running the bike. Does it run better, or worse? If worse, your carb set up is way too rich. If better, the carb setup is way too lean.

What’s your location in the US? Possibly a member close by could give you a hand.

Put a fresh set of plugs in the bike and took the air filters off and the bike runs so much better. I can’t believe a dual layer foam uni pod can restrict the intake so much as to create a running condition vs no air filters at all.

Hi Craighjr,

Getting a T500 to run nicely when fitted with a set of pod style filters is a challenge that many before have struggled with. For a road machine it is almost always easier to use a stock air box/filter arrangement. I hope you continue making progress, the GT380 is nice a bike.

Cheers Geoff