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1981 GS1000E Chasing a Nightmare Tuning Gremlin...

  • Thread starter Thread starter Phaedrus
  • Start date Start date
P

Phaedrus

Guest
I've reached the point with this project that I'm ready to call it quits and try to recoup my losses...

Here's the story:

Bought this '81 GS1000E off a friend of a friend for pennies. No history. Had been sitting in a backyard for ages. Engine turned over fine, ran pretty ****ty in the top end. Figured it needed to be tuned.

Stripped bike down to frame/harness. Bunch of cosmetic work. Rebuilt the suspension. Rebuilt the carbs. Thoroughly soaked and cleaned TWICE. New gaskets throughout, including intakes. Adjusted the valve shims. Bought a dynojet kit and K&N pods. Came with a 4 to 1. Started tuning. Couldn't get the dynojet to work. Huge lean bog in the midrange that I couldn't tune around. Was able to move the bog up or down with the jet needle, but wouldn't disappear.

Decided to scrap the DJ kit and started to tune oem. Still couldn't get rid of the bog. Countless hours of jet needle and main combos, no dice. Settled at 127.5 mains for WOT.

Finally, figured that the timing might be effing me up. Found that the advance governor was retarded slightly @<2350 rpms. Adjusted to proper specs and managed to move the lean bog way up to ~6-7k rpms. Progress?

Messed around with the jet needles some more and found that with 2 washers, the lean bog shows up at ~6k rpms. With 1 washer, there's not so much of a lean bog, but LOUD crackles and pops in the exhaust ~6.5-7.5K rpms (3/4 throttle). And, at 0 washers, the engine goes flat >6.5k rpms, crackles and pops ~7-8k rpms, until she opens back up at WOT.

The tuning attempts go from too lean, to too rich, without any sweet spot in between...

As a hail mary I decided to make sure my cam chain tensioner was operating properly. Pulled it off the bike, all functions were proper, popped it back on, no change in performance.

I'm at a total loss at this point and not really willing to put in many more hours into this project... She runs great, pulls HARD at low rpms. It's just this mid-high range gremlin that just won't go away...

I'm throwing this out into the universe in hopes that maybe one of you are familiar with this strange symptom and know what might be the cause. Thanks for any insight you can provide. I've learned a lot playing around with this one, but **** am I frustrated that I can't get her to be happy...

Cheers
 
Last edited:
pop a known good set of carbs on and see if it's fixed.
1100/1150 carbs with DJ kit or even a set or 34RS miks..
the DJ kits work...always have.
 
Phaedrus said:
I've reached the point with this project that I'm ready to call it quits and try to recoup my losses...


Bought this '81 GS1000E off a friend of a friend for pennies.

Rebuilt the bike's chassis and suspension. Rebuilt the carbs. Thoroughly soaked and cleaned TWICE. New gaskets throughout, including intakes. Adjusted the valve shims.
Click to expand...

Firstly I have to ask this... Was there even a 1981 GS1000E??? I'm pretty sure 81 was the first year the E has an 1100 16V engine? If you truly have a 1000E (chain drive 8V then it's not an 81... Are the valve caps circular or square... Also if it is a 16V she doesn't have shims. Adjustable rockers... FTW
 
Jedz123 said:
Firstly I have to ask this... Was there even a 1981 GS1000E??? I'm pretty sure 81 was the first year the E has an 1100 16V engine? If you truly have a 1000E (chain drive 8V then it's not an 81... Are the valve caps circular or square... Also if it is a 16V she doesn't have shims. Adjustable rockers... FTW
Click to expand...

It's a chain drive, 8V. Circular caps. In the shop manual it's the ES/EL model or whatever. The one with BS34 carbs.
 
blowerbike said:
pop a known good set of carbs on and see if it's fixed.
1100/1150 carbs with DJ kit or even a set or 34RS miks..
the DJ kits work...always have.
Click to expand...

Have any pointers on how to locate a set of known good carbs? Don't really wanna fork out the cash for a solid set just to find that it's not the carbs, but something with the timing/valves/compression etc...
 
i always borrowed a set to try.
are you in the US?
a known good set of DJ 34's or 36's have saved me a lot of work in the past.
either i had a set on the shelf or i called a buddy with a big GS to barrow his.
 
Pacifica, CA.

Don't know anybody local with an old GS. I do also have a perfect 1983 GS1100E. I don't want to **** with the tuning though. I have to assume that swapping the carbs without adjusting won't yield helpful results?

Also, there's some promising sets of carbs on eBay for reasonably cheap. Imma watch a few and see what the prices do as the auctions close.
 
does your 1100 have DJ kits installed?
if so pop them on...people get to involved in the tuning.
a set of DJ 1100 carbs will work near perfect on your 80 GS1000.
 
blowerbike said:
does your 1100 have DJ kits installed?
if so pop them on...people get to involved in the tuning.
a set of DJ 1100 carbs will work near perfect on your 80 GS1000.
Click to expand...

Right on. I'll give it a shot, see what happens.
 
pay attention to how it runs with the 1100 carbs verses how it ran with the old carbs on it.
the only adjustment may be the idle.
make sure your plugs are new or clean/no soot...gas fouled plugs never recover 100%.
if the engine is in a good state of tune your bike should pull from idle to redline pretty smooth and cruise at a steady speed nice and smooth.
all this will do is tell you is if you have a carb issue or other issues and keep you from going in circles aka chasing your tail.
 
Whelp. Got my hands on a known good set of carbs. Tried them out, and I'm getting the same lean bog at mid-high rpms (~6-7k)....

I'm finally understanding what the PO did with the needles. When I got the bike and dismantled it, it had obviously been used for drag racing (170/90/17 rear tire with 100/90/19 on front :ambivalence:, drilled out vacuum slides but no jet kit, messed up headlight fairing, geared up 530 chain/sprockets, etc.) When I dug into the crabs, I found that he had put in very high-tapered jet needles and I couldn't for the life of me figure out why. Turns out he was likely trying to tune around this lean bog that is apparently engine-related, not a fuel mixture issue.

So the question then becomes, what could cause an excess of air at mid-high rpms, and only mid-high rpms. She pulls up to 6k fine, and pulls past 7.5k through redline fine. It's just this little range that isn't breathing right.

Worn intake cam lobes?
Crusty valves?
Worn timing chain?
???

This thing is in need of a top end rebuild, but I was hoping to just get away with turning it into a rat bike and running it into the ground...

I might try out the PO's high taper jet needle work around one last time before shelving the project...
 
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so you tried a set of carbs with st.3 jet kits?

"So the question then becomes, what could cause an excess of air at mid-high rpms, and only mid-high rpms. She pulls up to 6k fine, and pulls past 7.5k through redline fine. It's just this little range that isn't breathing right. "

the above statement just about exactly describes a set of carbs with big mains and factory shaped needles.
without a jet kit the middle suffers but runs wide open fine.
 
blowerbike said:
so you tried a set of carbs with st.3 jet kits?

"So the question then becomes, what could cause an excess of air at mid-high rpms, and only mid-high rpms. She pulls up to 6k fine, and pulls past 7.5k through redline fine. It's just this little range that isn't breathing right. "

the above statement just about exactly describes a set of carbs with big mains and factory shaped needles.
without a jet kit the middle suffers but runs wide open fine.
Click to expand...

Nope. Didn't think to try the kit. I'll shop around for one and let that be the final shot. Thanks for the reminder...
 
After far more hours than I'd like to admit, the ratbeast is finally cruising along with smooth throttle response throughout the power band. :cool:

It turns out the gremlin was hidden somewhere in my failed attempts at tuning the carbs. Today, it was time to rebuild the cam chain tensioner on my GS1100E due to a leak, so while the carbs were off I popped them on the GS1000 (as per blowerbike's advice). She opened right up. Even idles better... Carbs are in desperate need of a proper sync and could probably do with dropping the jet needle a notch, but otherwise she rides smooth as butter. Total blast.

Next step will be to gut one of the GS1100 carbs and see what jets and needles it's running so I can clone it.

Very happy to have this beast back on the road... Thanks for all of the tips and advice. Aways appreciated.
 
be aware....
8 valve BS 34's and 16 valve BS 34's are not the same animal.
look at the throat's from the front.
8 valve has 2 holes and 16 valve has 4 holes.
glad you found it to be carb problems 100% so you can quit pulling your hair out.
 
blowerbike said:
be aware....
8 valve BS 34's and 16 valve BS 34's are not the same animal.
look at the throat's from the front.
8 valve has 2 holes and 16 valve has 4 holes.
glad you found it to be carb problems 100% so you can quit pulling your hair out.
Click to expand...

Good to know. Thanks for the heads up.

Amen. Was ready to chuck the thing... Though, the hair's been gone longer than this bike has been in my life... :p
 
blowerbike said:
be aware....
8 valve BS 34's and 16 valve BS 34's are not the same animal.
look at the throat's from the front.
8 valve has 2 holes and 16 valve has 4 holes.
glad you found it to be carb problems 100% so you can quit pulling your hair out.
Click to expand...

Can you explain exactly what makes the BS34SS carbs off of an 8 valve engine so different then the ones that came on a 16 valve engine? So much deferent that you would call them a deferent animal? It seems that the 2 extra holes on the 4 hole carbs are blocked and look like they would have been used as mounting points in a different application but were never drilled and tapped on the GS. I understand that the jetting would have been different, but other then jetting, what else is different?

Not trying to be difficult, or thread jack but definitely would like clarification on this since I have several sets in storage of both kinds.
 
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