Grrr Carbs again.....

[salty_monk]

Well so far, carbs are back to stock with Canadian adjustable needles (these are stock) in the stock CV carbs. Idle is great at 1100 starts like a dream.

All carb settings are stock EXCEPT the mechanic of the TPO drilled out the slide vacuum holes to 4mm. Stock is 2.4mm (measured on a spare set, would have used them but 2 have shot diaphragms...)
Carbs are clean, all new O rings everything inside is in good condition.
It doesn't have vent tube hoses on it.

Exhaust is stock GS1000 (but not the G model an E I think, just says GS 1000 on them & needs small spacers at the back end to fit).

Airbox with new air box boots, in box K&N.

The bike was running much better but idled like a dog etc until we synched it. The synch has improved idle & everything low throttle but made the needles & main really surgey... The bike also backfires if I go heavy into the throttle then back off (so coming to a stop sign or something)

It seems that they are still rich as if it's cold (ish) & I start it without the choke & blip throttle to keep it running the problem seems to be much reduced.

I think this could be a few things:

1: The K&N is over oiled (bought it ready oiled but unused from a guy on here, doesn't look like it but could be...)

2. The drilled slides are pulling the needle up too fast when I gun it so going rich & then slamming down to quickly when I cut the throttle (this is my favourite idea...)

3. There is some restriction in the exhaust.

Thoughts appreciated... anyone have any experience with going too big on their slide vac holes?

My next plan of attack is to clean & re-oil the K&N then pull the carbs again & JB weld those holes & re-drill them plus check the diaphragms for a third time just in case... (I have 6 that I think are good & two of those have stock holes in them).

See where that gets me... Have to get it done in time for Yosemite

Cheers,

Dan

[KEITH KRAUSE]

If you know the bike is tuned well in all areas, I'd see what the plugs say at solid 1/3 and full throttle, then a minimal throttle position check. Note any change in color.
You have mixed symptoms. You say it is surging and "backfiring" which I think you mean is deceleration popping?? Lean. You also say it starts without choke when I assume you mean it normally would need some choke? Rich. But these two opposites are at different throttle positions and are common problems.
I'd check at those throttle positions to see how each circuit is mixing.
It does figure that with a stock intake, the enlarged vacuum passages to the piston/diaphragm chamber will result in a very sensitive throttle and a bogging effect under "normal" throttling.

[salty_monk]

Hi Keith,

I don't think it's decel popping, I think it maybe unburnt gas in the exhaust burning off which would be a rich symptom.

It's more of a backfire than the pop pop pop you get with decel popping & usually just one BANG.

You're right it surges on high throttle but as I release the throttle it seems to start to pull harder, again this would lead me to believe it's rich....

I'm struggling with Plug chops round here due to location, to get anywhere to do them safely I'd need to go a ways, even the freeways are too busy to hold a throttle position for very long, no way i can follow your instructions unless I do it at 2am or 3am.... I suppose that's a possibility!

Anyway, seems we are agreeing for sure on one thing, those large slide holes need to go.

Dan

[salty_monk]

Keith,

Hope that didn't sound negative, I really appreciate all your input.

I will likely do the slides & try it. Following that if still no joy I will pay Bill (Chef) a visit, I believe he has a nice runway somewhere out there in Baco & we'll get the plug chops done!

Dan

[Nicholaschase29]

I'm struggling with Plug chops round here due to location, to get anywhere to do them safely I'd need to go a ways, even the freeways are too busy to hold a throttle position for very long

Don't hold the brakes to try to keep the bike at a slower speed while doing throttle chops, dangerous things happen.....ask me how I know.. I just about killed myself when the front tire locked up and I let off the brake quick and the bike snapped straight again... I suppose you could drag the rear though.. :-D.

Aren't the diaphragms changeable between the slides?

Nick

[KEITH KRAUSE]

OK, a true backfire it is.
If you can fill the vacuum holes with JB or an epoxy and re-drill to stock, do so. If you still have the problem, and considering the bike and jetting is stock, I'd inspect the ignition timing/spark quality next.

[chef1366]

The diaphragms are pressed on the slides.

[salty_monk]

Will get the slides modified sometime soon & test again.

Dan

[salty_monk]

Slides modified, used two stock ones from my part set & 2 with JB weld & re-drilled.

Goes much better now, need to ride it longer & really open her up but the initial test was positive....

Might still have problems towards WOT +5000 RPM, Friday night wasn't really ideal for testing round here

Still got the K&N to clean & recharge.....

By the way, anyone know what jets etc the GS1000E had as stock in an 80 model? Just a thought as the exhaust is not a G one.

Dan

[salty_monk]

Interesting... this one uses a 110 main.

1982 1000 SZ

Specs in mm.
Carb Type- Mikuni BS34SS
Bore Size-34 mm
ID# - 49300
Idle r/min - 1050 +/- 100 r/min
Fuel Level - 5.0 +/- 0.5
Float Height - 22.4 +/- 1.0
Main Jet - #110
Main Air Jet - 1.2
Jet Needle - 5D58
Needle Jet - X-1
Pilot Jet - #45
Bypass - 0.8, 0.8, 0.8
Pilot Outlet - 0.9
Valve Seat - 2.0
Starter Jet - #32.5
Pilot Screw -Pre-Set, Varies
Throttle Cable Play - 0.5-1.0
Choke Cable Play - 0.5-1.0

[Joe Nardy]

Might still have problems towards WOT +5000 RPM, Friday night wasn't really ideal for testing round here

Still got the K&N to clean & recharge.....

Dan

Dan,

You can try running with no air filter. If it runs better without the air filter you're fighting a rich condition. You can also go the other direction and restrict the airflow by taping off some of the air filter. If it runs better with the tape you're fighting a lean condition.

Thanks,
Joe

[KEITH KRAUSE]

"Layla is now living a great life on a Wisconsin dairy farm".:-D
Very cool Joe! Somehow I didn't notice this 'til now.
Salty, '80 GS1000E/ST w/34SS carbs uses a 107.5 main, jet needle is 5D50, needle jet is X-7.
Hopefully you can find a place to test at 1/3 and full throttle. Without a Dyno, it's the only way to really test how the jet needle and main are mixing.

[salty_monk]

So a much smaller main with pretty much the same everything else... maybe that's the issue. I hope to be changing to the Jardines soon anyway so I guess I might worry about it again then...

[Joe Nardy]

"Layla is now living a great life on a Wisconsin dairy farm".:-D
Very cool Joe! Somehow I didn't notice this 'til now.

Keith,

Thanks for the kind words. In case you missed the thread, here are the new canine members of the Nardy household, Koa and Norton:



Now back to Dan's carb issues................

Thanks,
Joe

[chef1366]

Keith,

Thanks for the kind words. In case you missed the thread, here are the new canine members of the Nardy household, Koa and Norton:



Now back to Dan's carb issues................

Thanks,
Joe

Good looking couple of kids you got there Joe! \\/