Help!! Compression test questions

[regal7point5]

Hello everyone...I have been lurking for a while but never posted. I bought a 1980 GS550E about 6 months ago and have been verrrry slowly tinkering with it. To my knowledge the bike ran probably 8-10 years ago and then just sat in storage. The bike is in fairly good shape and the engine turns over freely.

The bike is pretty well torn apart at the moment with the engine still in the frame (no carbs on it, starter, exhaust, etc). I tried to do a compression test just by using a ratchet and turning the engine over. I can get about 50-60 psi just by turning it by hand fairly slowly. The numbers seem to creep ever so slowly up the more I crank by hand but I just feel I cant crank it fast enough to get an accurate read. Is this correct????

I dropped some oil in the spark plug holes and can get well upwards of 150 psi. This almost leads me to believe the rings may be somewhat stuck to the piston.

I guess my real question is, would there be any harm in rebuilding the carbs and trying to get it running??? Will the rings seat better once it starts running and getting some heat in it? I have a verrrry limited budget and all I have money for is to get the carbs and petcock rebuilt to even see if this thing is worth messing with. I don't really have the funds or desire to pull the engine apart. Any help is greatly appreciated.

Thanks,
Aaron

[psyguy]

put the carbs back on and ride it as it is, say a few hundred miles, including pushing the engine to the redline
after that check your compression again, the engine warm and the throttle wide open
only then will you get meaningful readings
adjust the valves beforehand

[hikermikem]

Ditto what the pysguy sez...

150 lbs sounds quite good actually, the oil introduced into the spark plug holes helps to seal those dry rings; and the valves may not be seating well either if they were neglected.

good luck

[Nessism]

I suggest some Marvel Mystery Oil in the cylinders while you get the rest of the bike together - it helps loosen up the rings if carbon is hanging them up. Also, don't forget to check the valves.

Good luck.

[spyug]

My 750 had sat for 7 years. The PO had fogged the cylinders once and had it covered and sitting on the center stand. It had just around 19000 Km on the clock. I couldn't test fire the bike as the battery was dead and I couldn't therefor get a feel for compression but looking at the bike it felt like it would be solid.

Once I got it home I shot some WD40 and engine oil into each cylinder and let it sit for a couple of days. Cranked it over by hand to make sure it was free.Put in new plugs and battery and connected my "I/V" tank with a pint or so of gas. Choke hard on, stab the button and she fired right up.
It wouldn't idle all that well so I pulled and cleaned the carbs and replaced the o-rings and that sorted it ( for awhile, it never did idle quite right and i couldn't balance the carbs as one airscrew was frozen...i ended up chnaging them out for a set from King of Venus).

After getting it on the road I ran it for a couple of weeks before testing the compression. It tested mid to high 140s across the board so good enough.

Its been a solid runner with bags of power so if you take your time you can bring back these old "sleepers" with little effort.

Good luck with your project and keep us informed of how it goes.

Welcome aboard too.

Cheers,
Spyug

[BassCliff]

Greetings and Salutations!

Hi Mr. regal7point5,

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 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 visit BikeCliff's website.

[regal7point5]

Thanks for the help guys...and thanks for the reassurance. Sometimes thats all you need to keep a project going.