GSX750 1981 carb problem

[christos31]

Hello friends,
my name is christos and i come from greece. i am brand new here so i need all your help.

my uncle owns a gsx750 1981 which we decided to put it on the road again after 17 years.
i managed to start the engine, put new tyres and almost everything that it needs to run.
i have a slight problem with the carbs. the bike runs with mikuni bs32ss. i bought from ebay a set of the same carbs in order to have enough parts to rebuild a good set to put on.
i have some questions:
1) why are the pilot jets blocked with rubber? do i need to leave these rubbers on?
2) although the bike starts and revs nice and strong (petcock is on on) when i take it to a ride and gets hot it starts to feel like taking more air and it dies.if i turn the petcock to rpi to givew more fuel the bike starts to overflow fuel.
i am really confused with this. the carbs have all jets stock (main:112,5, air 150 and i think pilots are 45 - not quite sure, but the setting are as the manual says)

now i am thinking of taking the carbs out again and check all rubbers whether it sucks air from somewhere and also to see what happens with these rubbers which block pilot jets. at the moment i took them off. it was the only way to make the bike rev properly.

is there anything else that i should check????


thank you
christos

[Hoges]

Leave the rubber plugs in place, don't remove them. An easy check for air leaks is to spray some WD40/RP7 around the carb intake boots both at the head and also at the airbox. If the revs increase whilst doing it, you've got an air leak at the boot. Seal them off or better still buy new. If you've got fuel coming from the overflow , you've got a needle and seat problem. It sounds like you need to remove them first and blow out all the passages,set the float level correctly and go from there. Pilot screw setting should be around 2-2 and 1/2 turns out.

[chef1366]

How's the flow on the petcock on "run"?

[BassCliff]

Hey Howdy Hey!

Hi Mr. christos31,

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)

Click here to return to BikeCliff's website.

[christos31]

Thank you my friends for your replies.
today i bought new rubber intakes to replace the old ones. it might be that the problem, however, i will take out carbs once more and check everything from the beggining. i also have to put the rubber blocks of the pilot jets back in.
The petcock works fine as far as i can understand. it does not cause any overflow when it is "on".

[Hoges]

Stick with it Christos, not too much wrong with it I think. You have picked up an excellent motorcycle there, and is very simple to work on. Your fuel prob is not a big issue and the carbs themselves are a credit to Mr Suzuki. The valves are adjusted by locknut and screw so you can do this yourself. Great bike, great country, good luck at the Olympics!
Hoges.

[Mysuzyq]

Thank you my friends for your replies.
today i bought new rubber intakes to replace the old ones. it might be that the problem, however, i will take out carbs once more and check everything from the beggining. i also have to put the rubber blocks of the pilot jets back in.
The petcock works fine as far as i can understand. it does not cause any overflow when it is "on".

The 'PRI' position on the petcock is only supposed to be used to let fuel flow into the bowls via gravity, if your bike has been sitting unused for a long time, or the carbs have been drained of fuel. Leaving it on 'PRI' while the bike is running could cause overflow/flooding problems as you described. If the bike has been unused for a few weeks/months, turn it to PRI for a couple minutes to let some fuel into the carbs, before using the starter.....then switch it back to Run or ON before riding away......leaving it on PRI could cause it to run pretty rough too.

Tony.