Suzuki 2 Strokes

Hi all-

I'll preface this message by saying I'm an absolute newbie, so please bear with me.

I recently picked up a '74 GT380 from a guy that took meticulous care of the bike. The carbs are new and he just set the timing. He also dumped an entire can of seafoam in the tank.

The bike starts on the first kick and run flawlessly- until it gets warm, and then it kills when I come to a stop. I picked up a manual and it looks like there could be a few culprits:

1) Seafoam: running way to rich
2) Throttle cable needs to be tightened
3) Idle mixture screws needs to be adjusted (i understand it goes all the way in and then out 1 1/4 turn)

Here's my question- where to start?

Thanks-

Does it just not idle? Can you gently blip the throttle and keep it running while at the stops? If you gently open the throttle, does it keep running?

If the idle is too low, then that is easy enough to adjust but if it won't run unless you have to keep the rpms up pretty high (say higher than 2000), then that could be a problem with the idle circuit not delivering enough fuel.

If the engine is warmed up, will it idle at a stop if you put the choke on temporarily?

Hey buddy, glad to welcome you to the forum, from another GT380 guy.

Yes, like bobtech suggested, can you keep it running at 2000 rpm?

I like your option A to start, run 120 miles and then fill it with Premium gas, then run 10 more miles and see if the Sea Foam is inhibiting the idle.

My 380 had its carbs set by a nincompoop--me! Lots and lots of trial and error. If there was a guy here in Houston I trusted, I would gladly take it there. When I finally got the floats set about right and the starter plunger seat cleaned where it would not rev 6000 rpm every time I pulled in the clutch, then it would not idle. I had to blip the throttle every 10 seconds or so, or the engine would slowly decrease RPMs until it stalled. This went on for about 1200 miles. Then I added some Redline gas treatment from Cycle Gear, about 1/2 this bottle to a full tank of gas. Honest to god, I don't make claims it reduced carbon build up or seated the rings better, etc, who the hell knows

But I swear the bike changed in one tank to a near-perfect idle. I ran a couple hundred more miles and used it again, about 1/2 the bottle for a full tank at a time. The bike idles normally, I have lost the urge to blip for survival. I really think that stuff helped.


Once you run the Sea Foam out, try a tank of plain Premium, and see if it idles. If not, give Redline a go... let me know what you see.

One more thing, if the compression is low, there is a possibility that the engine will still start up fine but won't idle. I have an old chainsaw like that. Is got weak compression but still starts up and runs fine however it won't stay running unless I feather the throttle and that is with a completely cleaned out carb and new gas. Check your compression.

Gt380newbie wrote:
The carbs are new and he just set the timing. He also dumped an entire can of seafoam in the tank.

I assume you mean the previous owner cleaned or "rebuilt" the carbs, when you say the carbs are new ?? If the carbs were properly cleaned and set, I'm curious why he felt the need to add a full can of Seafoam. Thats usually only done by desperate people trying to make a crappy running bike, run better. I would probably start by emptying the gas tank, add fresh gas, and have the carbs properly cleaned, and set to factory specs.

+1 to all the above.

Safe way to work is to assume that everyone lies. Get a manual and read t from cover to cover. Twice.

Then drain the tank and the carbs.

Remove and strip the carbs and inspect and clean everything

Check and set float levels and check for leaky floats.

Clean and set the points and timing.

Drain and replace the gearbox oil

Replace the spark plugs and plug caps and shorten the HT leads 1/4"

In other words give it a complete service and inspection.

You will know what has been done and what hasn't and you will be much more comfortable and familiar with the bike.