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Cyl Compression

  • Thread starter Thread starter Riding Again
  • Start date Start date
R

Riding Again

Guest
I'm glad I found this forum for the GS bikes. I've recently bought a 1980 GS850 GLT with 15110 miles. I'm the third owner. It looks much like the other POs kept it in the garage. :)

I've owned two other GS's in the past. An '81 450L & '82 850L. So when the wife said get yourself a scooter, I knew what I wanted and found it. :D

Mileage has been in the low 30's for a daily 20 mile commute down the interstate. I found the forum and have looked and checked a few things & will keep at it.

The carb boots are still flexible & will look at changing them at the end of the season. Plug porcelains are white to tan. However, I'm interested and knowing what the cylinder compressions should be. From the left side I've pulled a 93 on the left outboard and 80 psi on the others.

Is this within reason? I suspect the valves need shimming, but have never done it. I should probably get the carbs synced as well and adjust the mixtures. What is the priority for the work?
 
Welcome from another 850 owner. I have one just like yours.Sit down and stay awhile.The people here are very helpful.
 
First off Go back & recheck them. This time open the throdle wide when cranking and run the compression test again GOOD LUCK
I love my 850
 
...make sure the engine is warm as well.
 
Was the engine at operating temp (you just drove 10 minutes or so) when you checked the compression? I made the mistake of checking cold---manual says warm her up.

Good luck and welcome!

Rick
 
and the winning numbers are...

and the winning numbers are...

120-160psi factory spec
100psi serviceable limit
80psi still runs like a champ :D
 
Hee Haw Howdy!

Hee Haw Howdy!

Hi Mr. Riding Again,

Yep, great bike! I've got a manual for you on my site too. Here's your new and improved mega-welcome! :dancing:

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


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)
walmart_greeter2.jpg
 
I'll need to warm it up to check. I checked it cold. I'll post when finished.:-k
 
Yeah. Get it nice and hot (this is what the expert GSers told me). Shuter down. Pop out the plugs. Put in your compression gauge. Pull throttle wide open. Turn over engine until the needle stops.

This is also basically what my Clymers says.

Good luck!

Rick
 
Kind of a waste of time to check compression when the valves haven't been adjusted yet. Even if the compression is good, the valves still need to be checked so why not do that first?
 
You're right. I'll be ordering gaskets to do that. I don't think it's ever been done.
 
I just bought a garage queen like yours. Poor neglected thing.
Ran a comp check and got 120, 85, 90, 125.
Checked valve clearances and guess what? Both valves on 2 and 3 were less than .0015!
Only ONE valve was well within spec. The rest were too wide.
Check dem valves and then retest if they are okay.
Meanwhile I'll be buying a lifter tool.....
 
Just completed the valve clearance checks. Yep, all but one was less than the smallest gauge (0.038mm). Got the new Real Gaskets to replace the others. Thanks Steve for the spreadsheet. Saves me the trouble. Great job Bikecliff materials on the tutorial regarding checking the clearances. I especially liked the vinyl tie addendum, by making several, I was able to get 3-4 valves open to check the shims!

I've PM's Ghostgs1 about the shim club and trading shims. This is a great resource site!!!!!
 
One more thing, Utah is mostly high elevation, don't know where you are at but I bet it's up there.
There will be a lot lower reading on the compression gauge at these elevations, there's just less air available to compress in the cylinders.
Same reason a perfectly running engine will be a lot less powerful in the mountains than it is down low.
What's important is that the cylinders are all in the same ballpark, none way higher or lower than the rest.
Thanks for the reminder, I have to send a few shims back to him.
 
Last edited:
You're right. Valley floor averages 4500 ft. All cylinders were checked properly (hot) :rolleyes: and were a consistent 115 psi.
 
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