Dies at4500 rpm

[TSCHEMPF]

Bike starts, idles, and runs flawlessly until 4500 rpms under load. Carbs have been cleaned (several times), all new o-rings and manifold seals. Tried richer mains & raised needles to compensate for K&N aircleaner & rusted through baffles in exhaust. New points & condensors-advance works fine. Soldered any questionable electrical connections (ignition & auxillary electrical system) Even replaced resistors in plug caps with solid metal cores (0 resistance). No fuel restrictions in petcock - all floats adjusted. Valves adjusted. Did coil relay mod. for 12 volts at coils. Plug wires look clean & not corroded-new plugs. No stray sparks detected in dark. All to no avail! Motor still just shuts down at 4500=/- rpms, save a few fires- all cylinders. (1978 GS 750C-only 15000 miles on bike) I don't know what else to try?

 

[Dave8338]

Float heights set correctly? Does it do it in any gear? Inline fuel filter?
Sounds fuel related to me... :-k

Welcome to the GSR, Basscliff will get to you with the MEGA Welcome, be prepaired to read, though it sounds like you've already done a bunch of homework.

 

[TSCHEMPF]

Does it in any gear & does seem related to throttle opening. Floats are set at 24mm per specs. & match original settings. Removed fuel filter-no change. Float bowls are always full after running. Fuel pilot screws are set at approx. 1 turn open +/- based on notches marked on carb housing.

 

[82Shafty]

Remove K&N all together and run with no air filter... see if it still dies at 4500 RPMS, or if it revs higher, you are too rich. If it cuts out below 4500, then you are still too lean.

I chased a problem one time where the bike would break up over 6500 only to remove the K&N and have it easily revving to 9500 through the first three.

 

[TSCHEMPF]

Runs about the same with no air filter & side airbox covers off-idles faster.

 

[Dave8338]

Another stab...

Another stab...

Remove K&N all together and run with no air filter... see if it still dies at 4500 RPMS, or if it revs higher, you are too rich. If it cuts out below 4500, then you are still too lean.

I chased a problem one time where the bike would break up over 6500 only to remove the K&N and have it easily revving to 9500 through the first three.

OK then, can I change my guess to ignition? If you have fuel (and you say that you do) and you have air (and without a filter at all, you would) than it has to be spark/ignition.

 

[SAN]

RPM power loss

RPM power loss

I have a similar problem with my 81 550T stage 3 K&N cones mac 4into1 pilots 3 1/2 out. ran fine this spring and last year. 6th gear tach 3grand i can open throttle Wide open untill 5,000rpm exactly then she breaks up,untill i roll back throttle. all gears 9,500miles i found slight gray ash deposit on #1 plug only also. On freeway wiht carefull throttle input she will tach past 5grand with out break up.i think its coil related? ohms4.2 both is this high. Ign, is all original. Read some where be cause i have light off switch power goes rec, to light switch, back to rec then coils. allways ride high beam on.that fuse was ready to fail. could turn one end. Also i use to turn head light off on start up. fuel is ok. tip of pugs look lean. all. I hope you find problem, let me know.good luck. SANView attachment 4502

 

[BassCliff]

Hey Howdy Hey!

Hey Howdy Hey!

Hi Mr. TSCHEMPH,

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)![FONT=Arial, sans-serif] [/FONT]

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)

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