83 GS650 - Fuel or Spark Problem

[gaillarry]

My 83 has been running great all summer until yesterday I noticed the engine wasn't running on all 4 cylinders. With the engine running I removed the spark plug cap on each cylinder and found #4 had no affect on the engine idle.

Spark on #4 is very good. Changed the spark plug and same problem. Did a compression check and 155 lbs is great.

I'm thinking #4 isn't getting fuel. Whats the best way to verify this?

[Seana23]

Hi babes. With the air box off, hold ya palm over the carb mouth to create a vacume and suck more fuel into the carb... If this doesnt happen, i think you have a blockage...
Do you have an inline filter? If yes, remove it and try again...
try those and repost what happens...good luck.
Xxx

[gaillarry]

Thanks, I'll try that this morning.

[AJ]

To verify that there is fuel in the carb: unscrew the drain on the bottom of the bowl. Put a cup or rag down there to catch the fuel. Put your petcock on prime and let it run to clean out the bottom of the bowl. You can carefully pour fuel back into the tank to keep any dirt out. Note that it is pretty rare for a bowl to go dry. Usually it's too much fuel from dirt in the fuel level needle valve or a bad float, but this is an easy test and usually cleans some dirt out of the float bowl.

Test exhaust pipe temp: use a rag to gently touch the exhaust header pipe. Is then number four pipe noticibly colder than the other three pipes? If it is, put on a little choke (starter enrichener). Does the number 4 pipe now get hot? If so, you probably have a plugged pilot jet or the rubber plug on the bottom of the pilot jet tube is seriously deteriorated.

I'd guess you will need to pull and clean these carbs, at least the pilot jets. If the bike had been running well before, that's probably all you'll need to do, so don't go adjusting idle mixture screws, bench synch or any of that unless you are prepared for a full carb rebuild and adjustment process.

[5150/gs]

My bike did the same thing when i bought it, i rebuilt the carbs and had the same issue until i sync'd em.all was well after.

[tom203]

Switch plug wires on 1 and 4 and see if problem moves to #1.