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Grrr Carbs again.....

salty_monk

salty_monk

Forum Guru
Past Site Supporter
TGSR Superstar
:lol:

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 :D

Cheers,

Dan :)
 
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.
 
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 :)
 
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 :)
 
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
Click to expand...

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
 
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.
 
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 :lol:

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

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

Dan :)
Click to expand...

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

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:

239367721-M.jpg


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

Thanks,
Joe
 
Joe Nardy said:
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:

239367721-M.jpg


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

Thanks,
Joe
Click to expand...

Good looking couple of kids you got there Joe! \\:D/
 
Joe Nardy said:
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:

239367721-M.jpg


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

Thanks,
Joe
Click to expand...
Oh my goodness!! If cute looks could kill I'd be dead.
Enjoy those little buggers!
Again, so happy for Layla!!:-D
 
salty_monk said:
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...
Click to expand...
Sorry Salty about the subject detour. Hard to compete against those pups.
Kinda wondering if you really do have the correct carbs on there or if they're only "close". Not sure what else to do 'til you can make those high speed tests.
What bothers me is the backfiring, if I'm correctly understanding it as a true "bang" backfire. Usually, a backfire is from unburned fuel collecting inside the head and header and at a saturation point you get one big explosion. Unburned fuel can accumulate because of a weak/problem spark and/or rich mixture. If you say the jetting is close to stock if not identical, that leads me back to a spark quality/timing problem.
I've seen quite a few bikes with rich jetting and they didn't backfire.
I'd be sure to inspect the spark quality and timing first. If you have the tester and info to check the ignitor, I'd do that too. If it passes all tests and you know the connections are good and plugs are good, then I'd focus on the carbs.
 
hehe you're not wrong! They're too cute.

The carbs are as listed as a stock set for my bike. The K&N is the only real difference & running a GS1000 exhaust instead of a 1000G exhaust (only difference is a couple degrees in the bend as far as I know).

Took the bike out again today, I'm running sea foam in the gas at the moment (I didn't have it in there the other day. Trying to clean the valves up, they looked a bit sooty through the intake). Anyway, today it seems much better & there is no real other difference today, it's warmer out though than the other day but that's it.

I don't think it can be ignition, the ignitor set seems ok, the coils are new dyna greens & plugs & leads are pretty new too.

I wonder if my vacuum tube could be collapsing & shutting off fuel... It's due for replacement anyway so I'll be doing that soon & cleaning the K&N.

Regardless this is now the best the bike has run since I've had it so it's all a plus.

Dan :)
 
salty_monk said:
hehe you're not wrong! They're too cute.

The carbs are as listed as a stock set for my bike. The K&N is the only real difference & running a GS1000 exhaust instead of a 1000G exhaust (only difference is a couple degrees in the bend as far as I know).

Took the bike out again today, I'm running sea foam in the gas at the moment (I didn't have it in there the other day. Trying to clean the valves up, they looked a bit sooty through the intake). Anyway, today it seems much better & there is no real other difference today, it's warmer out though than the other day but that's it.

I don't think it can be ignition, the ignitor set seems ok, the coils are new dyna greens & plugs & leads are pretty new too.

I wonder if my vacuum tube could be collapsing & shutting off fuel... It's due for replacement anyway so I'll be doing that soon & cleaning the K&N.

Regardless this is now the best the bike has run since I've had it so it's all a plus.

Dan :)
Click to expand...

Sounds good Dan! Hopefully it will be okay from here on out..........

Thanks,
Joe
 
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