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'79 GS1000 carbs factory set too lean at startup

  • Thread starter Thread starter vinny27
  • Start date Start date
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vinny27

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My '79 GS1000N has been very cold-blooded at startup since I bought it new. It's in the shop for a carb cleanup after sitting for some time. I've read that the 26mm Mikuni VM26SS carbs were modified in 1979 to satisfy EPA requirements. Also, that the '78 bikes had no such lean-at-startup problems. I'd like to know: a.what changes were made for '79; and b. how can I get my carbs like the '78s. Drilling, or any other fix is welcome. Please help; I'm excited about riding again, having spent some time away from the ER:)
 
You should have VM carbs, heres a rebuild link
http://members.dslextreme.com/users/bikecliff/images/vm_carb_rebuild.pdf

oring kit..1 kit per full rack.
http://cycleorings.com/

Bowl and top gaskets are on page 5 or 6..
http://www.siriusconinc.com/search_...art=1&partno=&x=20&y=13&search=search&start=0

Carb section here is the same as your carbs..In fact this entire manual will cover your bike. Note in the emissions regulations part ( think its like section 9 ) youll see that the preemission reg needles and jets have a different style print on them while the emission styled ones have more of a block letter style print. Look at yours and youll know what ones you have.

http://www.mtsac.edu/~cliff/storage/gs/GS1000_C-E-S-L_Manual.pdf
 
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Far as I know the only changes were in the jets and needle tappers. That and how lean they tuned them via the pilot circuit ( bottom screw ). We generally set them about 3/4 to 7/8 out from very gently seated and this will richen them a tad.

Set the side mixture ( air screws to some ) at 2 out as a start point then adjust from there.
 
vinny27 said:
My '79 GS1000N has been very cold-blooded at startup since I bought it new. It's in the shop for a carb cleanup after sitting for some time. I've read that the 26mm Mikuni VM26SS carbs were modified in 1979 to satisfy EPA requirements. Also, that the '78 bikes had no such lean-at-startup problems. I'd like to know: a.what changes were made for '79; and b. how can I get my carbs like the '78s. Drilling, or any other fix is welcome. Please help; I'm excited about riding again, having spent some time away from the ER:)
Click to expand...

Thanks for the speedy reply. I mean 5 posts in so short a time. ( I wish my isp was that vigilant about service issues.) I see that the font on the jets is different. Thanks. According to the VM26 stock Factory Specs chart, the pilot air screw and the pilot fuel screw are preset at the factory. Is there a more complete chart, one that covers the '78GS1000? That info would really help with the mods I think might really fix the problem.(Since my bike is in the shop now, I'm not even sure if there are even air screws and pilot screws on the '79 California model. BTW, I bought the bike new, so no mods, except a 4 into 1 exhaust, have been made.)
If there are no screws, can the carb be drilled, and screws installed? If so, I'm guessing I would then use the #15 Pilot Jet (non-italics version.) If the screws are there, I'm guessing they'd be adjusted according to the "VM Carb Rebuild" instructions from Paul Musser, on page 10.
Am I way out on this?
 
There are screws on your carbs. Youve got standard VM26s so the bottom one is the pilot jet..3/4 to 7/8 out from very gently seated. By this we mean you turn them in till they stop..do this slowly and DO NOT force them once they want to stop. When they stop go back out the presribed amount.

Then on the side of the carb throat just behind the front ( air box side ) lip youll see the mixture screws. 2 out on them to start.
 
chuck hahn said:
There are screws on your carbs. Youve got standard VM26s so the bottom one is the pilot jet..3/4 to 7/8 out from very gently seated. By this we mean you turn them in till they stop..do this slowly and DO NOT force them once they want to stop. When they stop go back out the presribed amount.

Then on the side of the carb throat just behind the front ( air box side ) lip youll see the mixture screws. 2 out on them to start.
Click to expand...

I guess these settings will help approximate the quicker "warm-up" of the '78 model. That's my goal, and to eliminate any stumble off idle. In my last post, I asked about whether to use the "EPA" #15 pilot jets or the non italic version. Does it matter? Would it help to install the older "needle tapers?"
 
vinny27 said:
I guess these settings will help approximate the quicker "warm-up" of the '78 model. That's my goal, and to eliminate any stumble off idle. In my last post, I asked about whether to use the "EPA" #15 pilot jets or the non italic version. Does it matter? Would it help to install the older "needle tapers?"
Click to expand...

The 78 has 15 pilot jets also

The jets are inside the float bowl. The adjustment screws are on the outside

The needle taper won't affect idle, but would help off idle

You sure the shop knows what they're doing?
 
Also you may need to go up a jet size or two with the 4 into1 pipe you have installed, Installing that and not rejetting will also cause a lean condition
 
The only other thing to add that hasn't been mentioned yet is float height. Make sure your float height is correct, if you're not getting enough fuel in the bowl, the other adjustments will help, but not like they should.
 
Big T said:
The 78 has 15 pilot jets also

The jets are inside the float bowl. The adjustment screws are on the outside

The needle taper won't affect idle, but would help off idle

You sure the shop knows what they're doing?
Click to expand...

'm asking so many questions of you because I want to make sure the shop does gets it right. And thanks for your concern about that. As for the the pilot jet question: p. 9-3 of the '79 service manual shows the pilot jet as #15 (italicized) and I'm wondering if the pilot jets used in the '78 model (assuming they are different) would help the too-lean problem. And you mentioned "needle tapers;" would installing the '78 needle tapers help. You see, I had a new '78 GS750 and it started up and took off JUST LIKE THAT! I sure would like that for the 1000.
 
Jets are jets, a #15 is the same regardless of the year

What method is the shop using to clean your carbs?

Is it anything like the link chuck sent you?

If not, take them back and do them yourself

A good deep cleaning and a valve adjustment should cure your problem. You can change parts later
 
vinny27 said:
Please help; I'm excited about riding again, having spent some time away from the ER:)
Click to expand...

Working there or as a patient? BTW, ALL of these GS models that were imported into the U.S.A. can benefit from one size increase in their main jets no matter how 100% stock they are.
Unless, of course, you only ride at 4,000' and higher elevations. Then, they are spot on. ;)
 
I've owned a '79 GS1000EN since new. There's no "cold-blooded" issues like you describe. Not with a properly tuned/maintained motor.
Not knowing the overall condition of your bike, it sounds like the carbs a not clean. The small passages in the pilot circuit become gummed up if the bike isn't ridden enough, etc.
 
Just been reading this thread and there seems to be a lot of over thinking going on here regarding the carbs. I've got a bone stock '79 GS1000N, except for Dyna ignition which didn't affect starting, with all original Suzuki parts in the carbs and it starts perfectly well even temps below freezing. 30 to 60 seconds warmup in summer and maybe a couple of minutes when it starts getting cold. If everything is cleaned, vacuum synced and the screws set as Chuck mentioned it should start and run., might need minor tweaking but it should run decently. One possibly could also be the little orifice at the bottom of choke reservoir in the float bowl might be plugged with debris, you mentioned it did it since new but it might be worth checking. If everything carb wise is in clean, in spec and you don't have any tight valves it should work. At least that part of it. Maybe you/us are looking in the wrong place. How healthy are the points and condensers? Coils?
 
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