dosomethinggreat Posted April 18, 2007 Share Posted April 18, 2007 Hey every one, I recently got my first motorcycle. It is a 1980 Yamaha XS400SG with 14,000 miles on it. I have a good amount of auto repair know how but carberator work/ motorcycles are new to me. The bike is very hard to start and requires lots of charging and cranking over under full choke. Once it does start it is only running off the Right cylinder. The left cylinder will only start to fire with lots of associated backfiring after being driven around for about 2-10 minutes. Once the left cylinder starts to fire and finally gets hot the bike runs great. It will even start right back up if stopped. It should be noted that my bike has the electronic ignition system (TCI)The air filters are completely dry rotted and most of the filter is missing. I ordered new filters but have not recieved them yet. The rubber boots between the carberators and the cylinders are pretty badly dry rotted and cracked. What are these called? I heard leaks here can cause problems so I want to get new ones. I also think I ran the engine with only one spark plug cap connected during my trouble shooting. I later read that this can damage the ignition coils. Thoughts? -Things I did- 1: Replaced spark plugs with new NGK's I checked for spark and it looked rather weak on the old plugs. The left (problem side) was sparking from a wrong part of the plug (not the tip). I replaced both and it looked better but still a little weak. 2: Gas was about one year old so I added a bunch of gas additives 3: I removed carberator and fallowed the Haynes manual for the bike. Removed floats, pin, and filter for cleaning. Unscrewed main jet,pilot jet, and starter jet for cleaning. Also removed carberator piston and needle for cleaning. I used compressed air to clean everything. I blew air down all the ports and air apeared to blow through everything ok. I have to admit, the space between the carberator housing and the butter fly valves did not look the same for the two carberators so I adjusted them until they looked closer. I hope I did not mess up the syncronization of the carbs. The bike ran better once it got hot but the starting problem was not fixed. Please help me on this one. I am at a loss. Thanks! Link to comment Share on other sites More sharing options...
Moderator drewpy Posted April 18, 2007 Moderator Share Posted April 18, 2007 Hey every one, I recently got my first motorcycle. It is a 1980 Yamaha XS400SG with 14,000 miles on it. I have a good amount of auto repair know how but carberator work/ motorcycles are new to me. The bike is very hard to start and requires lots of charging and cranking over under full choke. Once it does start it is only running off the Right cylinder. The left cylinder will only start to fire with lots of associated backfiring after being driven around for about 2-10 minutes. Once the left cylinder starts to fire and finally gets hot the bike runs great. It will even start right back up if stopped. It should be noted that my bike has the electronic ignition system (TCI)The air filters are completely dry rotted and most of the filter is missing. I ordered new filters but have not recieved them yet. The rubber boots between the carberators and the cylinders are pretty badly dry rotted and cracked. What are these called? I heard leaks here can cause problems so I want to get new ones. I also think I ran the engine with only one spark plug cap connected during my trouble shooting. I later read that this can damage the ignition coils. Thoughts? -Things I did- 1: Replaced spark plugs with new NGK's I checked for spark and it looked rather weak on the old plugs. The left (problem side) was sparking from a wrong part of the plug (not the tip). I replaced both and it looked better but still a little weak. 2: Gas was about one year old so I added a bunch of gas additives 3: I removed carberator and fallowed the Haynes manual for the bike. Removed floats, pin, and filter for cleaning. Unscrewed main jet,pilot jet, and starter jet for cleaning. Also removed carberator piston and needle for cleaning. I used compressed air to clean everything. I blew air down all the ports and air apeared to blow through everything ok. I have to admit, the space between the carberator housing and the butter fly valves did not look the same for the two carberators so I adjusted them until they looked closer. I hope I did not mess up the syncronization of the carbs. The bike ran better once it got hot but the starting problem was not fixed. Please help me on this one. I am at a loss. Thanks! check ignition timing, valves adjustment and change your petrol (gas). if still not right do a search for carb xs400 as I have replied numerous time to this. Drewpy Link to comment Share on other sites More sharing options...
studly256 Posted April 24, 2007 Share Posted April 24, 2007 Hey every one, I recently got my first motorcycle. It is a 1980 Yamaha XS400SG with 14,000 miles on it. I have a good amount of auto repair know how but carberator work/ motorcycles are new to me. The bike is very hard to start and requires lots of charging and cranking over under full choke. Once it does start it is only running off the Right cylinder. The left cylinder will only start to fire with lots of associated backfiring after being driven around for about 2-10 minutes. Once the left cylinder starts to fire and finally gets hot the bike runs great. It will even start right back up if stopped. It should be noted that my bike has the electronic ignition system (TCI)The air filters are completely dry rotted and most of the filter is missing. I ordered new filters but have not recieved them yet. The rubber boots between the carberators and the cylinders are pretty badly dry rotted and cracked. What are these called? I heard leaks here can cause problems so I want to get new ones. I also think I ran the engine with only one spark plug cap connected during my trouble shooting. I later read that this can damage the ignition coils. Thoughts? -Things I did- 1: Replaced spark plugs with new NGK's I checked for spark and it looked rather weak on the old plugs. The left (problem side) was sparking from a wrong part of the plug (not the tip). I replaced both and it looked better but still a little weak. 2: Gas was about one year old so I added a bunch of gas additives 3: I removed carberator and fallowed the Haynes manual for the bike. Removed floats, pin, and filter for cleaning. Unscrewed main jet,pilot jet, and starter jet for cleaning. Also removed carberator piston and needle for cleaning. I used compressed air to clean everything. I blew air down all the ports and air apeared to blow through everything ok. I have to admit, the space between the carberator housing and the butter fly valves did not look the same for the two carberators so I adjusted them until they looked closer. I hope I did not mess up the syncronization of the carbs. The bike ran better once it got hot but the starting problem was not fixed. Please help me on this one. I am at a loss. Thanks! Sounds like compression either a ring or valves bent try running a compression test on that cylinder Link to comment Share on other sites More sharing options...
dosomethinggreat Posted April 26, 2007 Author Share Posted April 26, 2007 Thanks for the tips guys! I adjusted the valves and the left intake and exhaust valve gaps were too big so I brought them into spec. I also checked the right sided valves and the exhast side was out some so I adjusted that as well. The right intake was at the high end of the spectrum so I made it a bit tighter. Now the bike fires up after a few cranks and no longer backfires. The left seems to be warming up at the same rate as the right side. FANTASTIC! I drove the bike to my parents place about 180 miles away the other day and added a can of carborator cleaner to the gas that the local motorcycle inspection station recomended I use. After 30 minutes the carberator apeared to run a bit better and it must have clened out some of the jets because it was idling at 4,000 RPM even though I had adjusted it to 1500 previously. I readjusted it to 1200 RPM and it has idled much better ever since. Link to comment Share on other sites More sharing options...
Moderator drewpy Posted April 26, 2007 Moderator Share Posted April 26, 2007 Thanks for the tips guys! I adjusted the valves and the left intake and exhaust valve gaps were too big so I brought them into spec. I also checked the right sided valves and the exhast side was out some so I adjusted that as well. The right intake was at the high end of the spectrum so I made it a bit tighter. Now the bike fires up after a few cranks and no longer backfires. The left seems to be warming up at the same rate as the right side. FANTASTIC! I drove the bike to my parents place about 180 miles away the other day and added a can of carborator cleaner to the gas that the local motorcycle inspection station recomended I use. After 30 minutes the carberator apeared to run a bit better and it must have clened out some of the jets because it was idling at 4,000 RPM even though I had adjusted it to 1500 previously. I readjusted it to 1200 RPM and it has idled much better ever since. glad to hear, well done Link to comment Share on other sites More sharing options...
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