Motorcycle Repair: 1983 Yamaha 900, vintage honda, yamaha 900

Question
Bill,

Sorry to bother you with a yamaha question but it seems generic. i have a 83 seca 900.  It has electronic ignition but normal vacum sliders.  The bike has sat for years.  I thoroughly cleaned the carbs/jets etc.  Recently I replaced the coils to no luck.  The bike starts with the choke and when warm tries to idle.  The bike will sadly accelerate (no load) without the choke but will shoot up with the choke.  Trying to run the bike, I have to choke it up and then the bike will run at about 3K rpms.  If I try to go above this, the engine goes weak.  The plugs look good and clean and I am getting spark to the caps.  Seems like a timing issue but i get no pops or backfires.  Just gutless, like a cylinder is down.  

Any ideas?  Don't know if there is any timing adjustments on these electronic ignition things?


Thanks Kevin

Any

Answer
Kevin,
Definitely not a vintage Honda question....

I went to http://www.powersportspro.com/partsfish/login.asp

and found your bike listed there. Appears to NOT be one of the YICS models that had a butterfly shaft system inside the head, which is proabably a good thing these days.

You mention the bike sitting for years and only cleaning out the carbs.

Pull the fuel tank, take off the petcock and clean or replace the fuel screen and check the petcock for flow through all the passages. Looks like it all comes apart and parts should be available from K&L if Yamaha doesn't have them.

Second thing to check is the fuel tank gas cap for venting or however the tank is supposed to vent. If the vent system is plugged the tank will get vapor locked and no or little fuel will flow to the carbs. Either of these areas will show up as fuel leaness or starvation.

I don't know anything about the ignition systems. You can generally check the timing with a timing light at idle and at speed to see if the spark advance is working. Check the connections to the ignition pickup at the left dyno end of the crankshaft. Always be sure that there is a fully charged battery in the bike and that the charging system is functioning properly. Low voltage will shut down the electronics.

Check the web for YAMAHA SECA websites, that may have more information for you.

Bill Silver