GS 400 E running poorly when hot

[Guest]

Hey, and good Morning, Happy Canada Day!

I need some help.

Please bear with this long explanation, I tried a lot on my own prior to finding your site.

My son purchased a GS 400 E back in the spring.

It needed a little cosmetic help, so we completed that.

He took it around the block for a test drive, and it did not go well. Bogging down when in gear and trying to accelerate.

We drained all of the fuel (found to be old and dirty) drained the bowls of the carbs, and tried again.

No real difference.

We decided to pull the carbs, and do a full clean.

We tore the carbs apart, soaked the jets in carb cleaner overnight, used the aerosol cleaner to blow out all of the jets, and proceeded to put it back together.

After remounting, and setting up a fuel source without the tank, the bike restarted right away.

NOTE: one plug seems to be always black (left cylinder), and the other seems to be very clean (right cylinder).

Playing with the air/fuel screws on the carbs to see what happened, the right carb screw would stall the engine, and make a big difference to idle etc, but the left carb screw made very little difference at all, like the bike is only running on one cylinder.

I set both air/fuel screws to (2) turns, and put everything back together.

It was backfiring on throttle up, but i realized when the carb vacuum hose was connected this stopped.

Put everything back together, and took around the block a couple of times to see how it was.

First couple laps went well, with good acceleration, and no stalling issues.

third lap was not so lucky.

It seemed that getting hot, the bogging started again, and it stalled.

Was able to restart, and ride home, but definitely not the same performance.

The bike starts first crack, every time.

Left spark plug still black, and right still totally clean.

BTW, also put in NEW plugs.

thanks so much.

My son is a university student, so we are trying to fix ourselves, but I am running out of my high school AutoShop knowledge.

Sincerely

Rob

[tom203]

When you say left cylinder, do you mean the one under the clutch hand lever?

....."It seemed that getting hot, the bogging started again, and it stalled.
Was able to restart, and ride home, but definitely not the same performance."

might be fuel delivery related, so let's rule out this first. Check petcock for correct operation - on "PR" fuel should flow nicely even with engine off. Since carbs were gunked up , petcock innards probably are too and might be restricting flow.

put your bike /model/year in your "signature" .Your approximate location might draw hands on help.

[Gorminrider]

Yes, what year? Happy Dominion Day to you too! God Bless John A. wherever He is!

It sounds like one cylinder is still not firing. per "Bogging "
When bogging, take the offending side's plug out, ground/clamp to fins and see if there's a difference in engine. If NONE, I am right. One cylinder not working.
Spark: test is easy. is the plug sparking?
Carb: my likely choice

...I know you "did "a decent carb job but so did I: when I tore into my carbs I had to do it twice....

Valves: did you adjust? Unlikely a BIG issue here but possible. They need checking anyways should be done

[Rob]

Hello to all and thanks for assistance

There is good spark on both cylinders, and what I think is good compression. (just my finger over the hole test)

Left cylinder/carb to me is on the left side when sitting on the bike, clutch side.

question... If it was not firing at all, would the spark plug be black?

I did not adjust valve, this is a little beyond my capabilities, I think anyways...





1982 GS 400 E - Uxbridge, Ontario

30,000 kms

Thanks

Rob

[tom203]

Got spark,good - but we need right amount of fuel, not too much, not too little. Up to carbs to do this, but a bad petcock can cause problem, so that's why we need to confirm petcock is working right before you have more carb fun.

valve clearance check is essential- who knows how long it's been waiting.