Motorcycle Repair: choke misuse, head pipes, car parts stores

Question
Hi, I asked you a question a little while back about my 77 suzuki gs750.  you thought it was probably my carbs and you are probably right.  I think in addition to cleaning and all I need to get the fuel and air mixture adjusted correctly.  my question though is this.  I didn't put in my last email that I accidentally rode for maybe a half hour with the choke on and then turned it off when I realized it.  I then rode for a little while longer just fine, and when I tried it the next day, that is when I got a violent backfire and now it doesn't start.  I am still going to try all your suggestions that you tried before but I wanted to know if taking that ride with the choke on could have caused any damage or broken anything.  I hope not but please let me know if anything might have given out under that kind of abuse.  thanks.  Grant

Answer
Grant,

Was the exhaust pipes glowing orange? This is more common with choke left on too long while stationary, but may happen while riding. The heat may have warped the head, damaged the head pipes, gaskets, and valves. Maybe nothing is damaged.

Check the condition of the spark plugs. Describe the colors of the insulators to me. Check the threads for evidence of discoloration and advise.

Check cylinder compression and advise of the readings. If compression is lower than 100 psi or a difference of about 10% between any cylinders, perform a leak-down test. Both tools can be borrowed or rented from most car parts stores.

Try the above before cleaning the carbs.

Backfiring may be ignition related due to fouled plugs.

Reply to my email: mshively1@woh.rr.com

Respectfully,
Mark Shively