1978 GS550E running too rich - where's the mixture screws?

[adamb]

Update, guys.

I've been riding the bike to work the past couple of days. The plugs in cylinders 1-3 look good - some of the plugs have a little bit of tan stuff on 'em, on one of the plugs, it was very clean looking - the ceramic protector in the middle was even white.

Cylinder four (far right, as I sit on the bike) is still pretty dirty - I've been easing back the richness on that cylinder the past couple of days (1/8 turn per plug check). I have a feeling that it's been running especially rich on that cylinder for a while, and it's going to take a while before I finally back it off enough to get the plug 'clean'. Either that, or there's a jetting problem and that plug won't be clean until the carbs are broken down and given a thorough cleaning.

As for "how rich" I'm running it, for each time I check the plugs and find them clean, I give the mixture screw a minute turn to the right to try to richen it up a bit. I'd like a *bit* of residue on the plugs to make sure I don't run it too lean. My pipes aren't bluing, the bike isn't pinging (or doesn't sound like it) and there's not any other signs of being too lean. It runs out very nice. At the low end the power is a bit flat, but a)I don't spend much time there, and b) it's only really noticable when I'm going 35 MPH in 6th gear. So obviously, mileage varies.

My last "tank" of gas I got about 35 MPG - (I put in 2.1 gallons of gas, went ~75 miles) BUT I also dropped the bike while working on it (broke my right mirror, too!) , and gas spilled onto the floor - so obviously I can't count that tank of gas. I've been riding it pretty easily on the roads, not working it too hard.

Thanks for all the help so far, guys - let me know if I'm missing anything!

 

[Steve]

Don't forget that you have two screws for each carb to control the mixture.

Under the carb outlet is the pilot fuel screw that will control how much fuel is allowed into the pilot circuit.
On the side of the carb is the pilot air screw that will control how much air is mixed with the afore-mentioned fuel flow.

Yes, you are definitely controlling the mixture by tweaking the side screw, but there is a possibility that the fuel screw needs to be tweaked, too. I think the recommended guideline for stock bikes (stock airbox and exhaust) is between 3/4 and 1 turn out for the fuel screw and about 1 1/2 turns for the air screw.

.

 

[adamb]

Evenin'.

My one "dirty" cylinder is cleaning up a lot now - the plug in cylinder #4 is now a lot less black than it was. I haven't checked the other cylinders yet today, but I did check that one after a 14 mile ride. It's idling better while warm, that's for sure - and there's no hesitation along the entire span of revving.

Yay. Tomorrow, if it's a nice day, I'll go for a nice, long ride and see how the bike acts.

 

[basta]

Guys
Just to let you know I think Ive solved my problem on the CV carbs
my main jets were 142.5 and according to the carb article by Ryan should be 92.5 so a change of jets should sort me out thanks and sorry to Adam
for butting in on this thread
cheers Roy

 

[BassCliff]

Hey Howdy Hey!

Hey Howdy Hey!

Hi Mr. adamb,

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************
Every GS850 (and most other models) 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.
***********************************
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

***************************************
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
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
Salvage/Used
http://www.ricepaddymotorcycles.com
http://www.ozpowersports.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
http://www.bikepics.com
Basic motorcycle maintenance/repair:
http://www.dansmc.com/mc_repaircourse.htm
Online Clymer manuals:
http://search.ebscohost.com/ Click on "Small Engine Repair" then "Motorcycles". User=library, password=library. Note: This link may not work if you are on a school campus.

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)

 

[daWrench]

mixture screws

mixture screws

The mixture screws should be located on top of the carbs just in between the intake runner and the diaphragm cap. If the carbs have never been taken apart before, you won't see the screw itself. There are small aluminum caps that cover the screws. To get them out, use a small drill bit an drill a hole in the cap, then use a sheet metal screw to screw into and pull out the cap. When you clean the carbs you "must" remove those caps and clean those screws. If not, you will never get it running right. I had the same problem with my bike. Good luck...

 

[doctorgonzo]

Guys
Just to let you know I think Ive solved my problem on the CV carbs
my main jets were 142.5 and according to the carb article by Ryan should be 92.5 so a change of jets should sort me out thanks and sorry to Adam
for butting in on this thread
cheers Roy

Depending on the size bike, that's (142.5) mains for pods and exhaust not stock for sure.

 

[adamb]

Thanks. I haven't found the other screw yet, but I think I'm going to find out. The bike hasn't been running well the past couple of rides, and today for some reason one of the cylinders stopped firing altogether for a bit. It started back again, but the engine isn't running smoothly. I don't think it's been running too lean, as I don't have any pinging, blued pipes, backfires, etc - I think I just need to rip out the carbs and start there. Bummer.