Motorcycle Repair: 1980 Suzuki GS550ET Low Compression, indoor storage, leak down test

Question
Hi Mark,

Thanks for your help on getting this bike going.  

1980 Suzuki GS550ET with 15k miles.  Bike was running pretty good 2 years ago when it died because of an electrical problem. It always had pretty good power and accelleration. It has been in indoor storage since then.

i just recently fixed the electrical problem, replaced the starter, and rebuilt the carbs.  I have good spark and have taken the carbs apart again to double check them.

The bike starts right up and will run at 1000+ rpm with the choke on part way.  If I try to open the throttle up at all, it bogs down and stalls.  It must also have the choke on to keep running even after it has warmed up.

I checked compression and found 100 psi on #1, 40 on #2, 70 on #3 and 90 on #4  Adding a little oil in the cylinders will only bring each reading up about 10 psi.

I assume my next step is to start looking at the valves and cams?  Any idea for anything special to look for?  What do I need to get for good compression numbers to get running again?

I find it strange that performance went down so much in only 2 years of storage.

Thanks for your help

Biz

Answer
Hi Biz,

Q:  i just recently fixed the electrical problem, replaced the starter, and rebuilt the carbs. I have good spark and have taken the carbs apart again to double check them.

A: Visit: www.thegsresources.com and www.electrexusa.com for more details on Suzukis charging system design flaw and more.


Q:  The bike starts right up and will run at 1000+ rpm with the choke on part way. If I try to open the throttle up at all, it bogs down and stalls. It must also have the choke on to keep running even after it has warmed up.

A:  Pilot circuit is obstructed. Thoroughly clean carburetors per my instruction file.


Q:  I checked compression and found 100 psi on #1, 40 on #2, 70 on #3 and 90 on #4 Adding a little oil in the cylinders will only bring each reading up about 10 psi.

A:  Now perform a leak down test to determine which part(s) are causing the poor combustion chamber seal. You need at least 100 lbs in each cylinder with no more than 10% difference betweens cylinders.


Q:  I assume my next step is to start looking at the valves and cams? Any idea for anything special to look for? What do I need to get for good compression numbers to get running again?

A:  Leak-down will determine what is leaking. You could check and adjust valve clearances. Otherwise, focus on results of leak-down on low cylinders.


Q:  I find it strange that performance went down so much in only 2 years of storage.

A:  Gas goes stale very quickly. Varnishing begins in about three to four weeks.


I'll need your email address to return test and repair files. You gave allExperts the address with your question, but experts do not see that information. All We get is your name, subjet, and the question.

Respectfully,
Mark Shively
mshively1@woh.rr.com