82 GS750EZ carb tuning issues

[redruM69]

Hi guys, I'm new here!

I recently aquired an 82 GS750EZ that I have running quite well... "almost". Having issues with the carbs.
The bike refuses to run on stock needles!

When I got the bike it had the wrong carbs, one of the carbs was different than the other 3, and one was damaged from somebody overtightening the idle mixture screw. BUT, they did have aftermarket needles of some sort. They are adjustable with 6 notches, much narrower, and with a steeper taper, rather than the almost straight stock needles. So I pulled those carbs, and bought a decent set off ebay from another 82 750ez.

I have completely dismantled them, and THOROUGHLY cleaned/rebuilt them, numerous times. They are SPOTLESS inside. Boots are in great shape. Carbs are eyeball syncd, All jets/needles #'s are stock, according to the carb spec thread on this forum. idle mixture screws are at 1.25 turns out for now. Float levels adjusted, using a clear tube on the bowls determines the level is about flush with the bowl screwheads (where the screw rests on the bowl). I live at ~3700 feet, it has the more decent quality XS oval pod filters, and (I think) mac 4-1 exhaust with a loud "Gemini" can on the back. I adjusted the valves over the weekend too.

Now it gets weird. It will NOT run on the stock needles, not even close. It idles fine, but just falls flat on its face after 3-4k, Completely starved for fuel. Will die entirely if I hold the throttle open. HOWEVER, It runs "almost" perfect on the aftermarket needles! (Richest position)

I would like to get it to run right on the stock needles because I think the taper is too steep on the aftermarket ones. Even though it idles great, revs great, and pulls clean and hard at WOT all the way to redline, the carbs will load up a little AFTER a quick hard run, and then let off the throttle some to cruise at mid RPM. It stutters rich for a moment, sometimes for a couple of seconds, then clears up and cruises smoothly. It also studders rich for an instant between shifts on WOT runs.

Plugs are dark around the edges, with a tan tip. I have tried 1 and 2 sizes larger mains (115, 117.5), and it still will not run on the stock needles.

Do I have the fuel level at the correct height mentioned above? Maybe this bike is bored out to much larger than 750? Any other ideas??

Thanks guys!

-JJ

[Nessism]

What about the pilot jets? You may have to go up one size before you play around with the needles.

[redruM69]

Oh ya, forgot to mention that. I have tried 1 size larger pilots, idle got a little rich, but overall ran about the same.
Also, according to the CV tuning guide below, I start with the mains and work down, not vice versa.

http://www.factorypro.com/tech_tuning_procedures/tuning_carbtune,CV,high_rpm_engines.html

[chef1366]

With the pods use the aftermarket needle and you need to drill the slides. The slides aren't raising fast enough to make up for the extra air from the pods. That's why you are falling on your face.
If your dead set on using the stock needles I'll take the others.
The Factorypro is a great site. I used that method when I was learning along with this site. Plug chops work better than "if it pulls better ect..."
Remember you will be lean compared to people at sea level so take that into consideration also.

[BassCliff]

Hee Haw Howdy!

Hi Mr. redruM69,

All work and no play makes Jack a dull boy. :-D

Heeeeeeeeeeeeeeeere's your mega-welcome! \\/

Dear fellow GS rider,

Let it be known that on this day you are cordially and formally welcomed to the GSR Forum as a Junior Member in good standing with all the rights and privileges thereof. Further let it be known that your good standing can be improved with pictures (not you, your bike)!

Perhaps you've already seen these, but I like to remind all the new members. In addition to the carb rebuild series, I recommend visiting the In The Garage section via the GSR Homepage and check out the Stator Papers. There's also a lot of great information in the Old Q&A section. I have some documentation on my little BikeCliff website to help get you familiar with doing routine maintenance tasks (note that it is 850G-specific but many tasks are common to all GS bikes). Other "user contributed" informational sites include those of Mr. bwringer, Mr. tfb and Mr. robertbarr. And if your bike uses shims for valve adjustments, send an email to Mr. Steve requesting a copy of his Excel spreadsheet that helps you keep track of clearances, shim sizes and other service work.

These are some edited quotes from one of our dear beloved gurus, Mr. bwringer, with ideas on basic needs (depending on initial condition), parts, and accessories.
***********Quoted from Mr. bwringer************
Carburetor maintenance:

Replace the intake boot o-rings, and possibly the intake boots. Here's the procedure:

http://bwringer.com/gs/intakeorings.html

Here's an overview of what happens with this particular problem:

http://cycleorings.com/intake.html

You'll also want to examine the boots between the carbs and the airbox. There's a good chance these are OK, but check them over.
And finally, if things still aren't exactly right, you'll want to order a set of o-rings for BS carbs from the GS owner's best friend, Robert Barr:
http://cycleorings.com
Once you receive these rare rings of delight, then you'll want to thoroughly clean and rebuild your carburetors. Here are step-by-step instructions that make this simple:

http://thegsresources.com/gs_carbrebuild.htm

***********************************
Every GS850 has (or had) a set of well-known issues that MUST be addressed before you have a solid baseline for further troubleshooting. It's a vintage bike, and it's quite common (as in, every single GS850 I have had contact with) that there are multiple problems that have crept up and slowly gotten worse over the years. It's not like a newer vehicle, where there's generally one problem at a time.

These common issues are:

1. Intake O-rings (install NEW OEM or Viton only - common nitrile O-rings will quickly deteriorate from heat)
2. Intake Boots (install NEW -- these cannot be repaired)
3. Valve clearances (more important than most people think)
4. Carb/airbox boots
5. Airbox sealing
6. Air filter sealing
7. Petcock (install a NEW one)
8. On '79 models, install new points or Dyna electronic ignition (or at least verify that the old points are working correctly)
9. On all models, it's fairly common to have problems with the spark plug caps. These are $3 or $4 each, and often worth replacing if you're keeping the stock coils/wires.
10. Stock exhaust with NO leaks or holes -- good seals at the head and at the junctions underneath.
***************************************
OEM Parts/Online Fiches:

I would definitely double and triple the recommendations to use Cycle Recycle II and Z1 Enterprises as much as possible. These guys are priceless resources. Z1 tends to have slightly better prices, CRC2 has a wider range of goodies available. If you're near Indy and can bring in an old part to match, CRC2 has a vast inventory of used parts.
http://denniskirk.com - Put in your bike model and see what they have.
http://oldbikebarn.com - seems to be slowly regaining a decent reputation, but it's still caveat emptor. They don't have anything you can't get elsewhere at a better price anyway.
http://www.babbittsonline.com/ - Decent parts prices. Spendy shipping. Don't give you part numbers at all. Useful cross-reference if you obtain a part number elsewhere. Efficient service.
http://bikebandit.com - Fastest. Middlin' prices. Uses their own parts numbering system to obfuscate price comparisons -- can be very confusing for large orders. Cheapest shipping, so total cost usually isn't too bad.
http://flatoutmotorcycles.com - Slow. Cheapest parts prices, crazy shipping costs. Don't expect progress updates or much communication. Real Suzuki part numbers.
http://alpha-sports.com - Exorbitant parts prices. Different type of fiche interface that's quite useful at times, especially with superceded part numbers. Real parts numbers. Shipping cost and speed unknown due to insane, unholy pricing.

Stainless Bolts, Viton o-rings, metric taps, dies, assorted hard-to-find supplies and materials, etc:

http://mcmaster.com - Fast, cheap shipping, good prices. No order minimum, but many items like bolts come in packs of 25 or 50. Excellent resource.
http://motorcycleseatcovers.com - Great quality, perfect fit (on original seat foam), and available for pretty much every bike ever made. Avoid the textured vinyl -- it's perforated.
http://newenough.com - You DO have riding gear, don't you? Great clearances, always outstanding prices and impeccable service.
***************End Quote**********************
Additional parts/info links:

GSR Forum member Mr. duaneage has great used upgraded Honda regulator/rectifiers for our bikes. Send him a PM.
New electrical parts:
http://stores.ebay.com/RMSTATOR or http://www.rmstator.com/

http://www.ricksmotorsportelectrics.com/index.php

http://www.electrosport.com/

For valve cover and breather cover gaskets, I recommend Real Gaskets (reusable silicon):
http://www.realgaskets.com
The Rice Paddy (salvage/used)
http://www.ricepaddymotorcycles.com
Carolina Cycle
http://www.carolinacycle.com
Ron Ayers Motorsports
http://www.ronayers.com
MR Cycles
http://www.mrcycles.com
Moto Grid
http://www.motogrid.com
If all else fails, try this:
http://www.used-motorcycle-parts.org/
Used bike buying checklists:

http://www.amadirectlink.com/roadride/Riderresc/checklist.asp

http://www.clarity.net/~adam/buying-bike.html
Lots of good info/pictures here:
http://www.suzukicycles.org

http://www.cyclechaos.com/wiki/Motorcycle_Wiki

Thanks for joining us. Keep us informed of your progress. There's lots of good folk with good experience here.

Thank you for your indulgence,

BassCliff
(The unofficial GSR greeter)

[redruM69]

With the pods use the aftermarket needle and you need to drill the slides. The slides aren't raising fast enough to make up for the extra air from the pods. That's why you are falling on your face.
If your dead set on using the stock needles I'll take the others.
The Factorypro is a great site. I used that method when I was learning along with this site. Plug chops work better than "if it pulls better ect..."
Remember you will be lean compared to people at sea level so take that into consideration also.

Slides have already been drilled. Didnt help. Also, the higher the altitude, the RICHER it gets, as there is LESS air compared to fuel.. not vice versa

[chef1366]

Sorry, I meant to say that you need to jet lean compared to sea level.
I've got to stop giving advice after a twelve hour work day and in the middle of the night.

[redruM69]

Sorry, I meant to say that you need to jet lean compared to sea level.
I've got to stop giving advice after a twelve hour work day and in the middle of the night.

LOL, no prob.


Im starting to lean towards float levels again. I will retest this weekend. Im using the clear tube on the bowl drail method, rather than measuring the float itself, as I feel this is much more accurate. I figured that the fuel level right at the base of the screwheads is about right, am I right here? Or does it need to be even further up?

[Muser3]

fuel level

I also use the clear tube method of setting the floats and you are probably OK where you are. On my 1100EZ I set the level at the top of the washer which is just a tad higher than you are. It seems to me that this method is pretty precise and probably better that measuring the float height but lots of folks get great results that way. If you have a richness issue it's probably not the level. I've never measured the float height after setting the fuel level have you? Hope you find the right combination.
Lee

[Mark M]

Also, according to the CV tuning guide below, I start with the mains and work down, not vice versa.
http://www.factorypro.com/tech_tunin...m_engines.html

I hate to say it, but that is back assward. You need to start on the pilots, then the needles, then the mains. You can get it to run fine on the pilots and onto the needles with NO main jets installed, if desired. The reason to start on the bottom and work up is that the lower circuits affect the higher ones, but not the other way around. Get your pilots and mixture screws set, then work on the needle.

Try setting your mixture screws out a bit, maybe a 1/4 turn at a time to see if that helps it get up onto the needle better. Can you shim the needles? I wouldn't expect it to run well on the stock needles at stock height with pods and 4-1 exhaust. No amount of pilot jet/mixture screw or main jet fiddling will compensate for the needles being too lean.

Mark

[chef1366]

In my experience you need the right main to get the needle straight. This isn't just from reading a website. I always dial in the pilot circuit last. For each their own. I guess both would work though. Trial and error with plug chops.

[redruM69]

Well, I made a couple of changes, and things got a little better in some areas, and worse in others, it just behaves bizarre.
I leaned the mixture screws down to 1 turn out, and raised the needle even more (I'm beyond the last notch, I had to shave the plastic spacers down to about half the original thickness).


Idle, is perfect
Quick small rev (throttle cracked) after idling for a minute, and it gets a little soggy for a moment then clears up. after that quick revs are fine, till I let it idle for a while again.
Bigger revs are fine.
Normal take off from stop, its soggy for a moment, THEN goes LEAN till it hits about 3k RPM, then goes well. (This improved when I raised the needle, but not cured)
Cruises fine, until I get to about 80mph, then cruising gets soggy (near bottom of needle,about 2/3's throttle), I get off the throttle a little, it clears up, I get on the throttle, it clears up. (This got a little worse raising the needle)
WOT is fine, and pulls HARD.
Hard runs still load up the carbs between shifts, or when I let off... It normally clears up after a few seconds at part throttle.

I bet these aftermarket needles are some designed for another bike/purpose. I dont know the history of them, or what they are. The bike just behaves as if the taper profile is all wrong.=

Anybody have some decent aftermarket needles that will match with good pods and 4-1 exhaust?

Other suggestions would be appreciated also!

[chef1366]

Sounds like your lean on the pilot jet and rich on the needle.

[redruM69]

Well, I have tried richer on the pilot and leaner on the needle, and some things get better, while others worse.

I still feel that the taper profile is wrong on these needles. I need some others to test.

[chef1366]

Get a jet kit made for the bike. I have a set of stock needles from an 80 1100 sixteen valve.