I've been having trouble with my '78 XS400 for quite some time now, no matter what I do, nothing makes it run any different.
At an idle, and just off of an idle, I can't get it to run on 2 cylinders. BUT, if you are lucky enough to get it above 3k rpm, it runs great!
-Both cylinders get good spark when tested against the block.
-Both carburators are perfectly clean, and have been fully rebuilt.
-Both cylinders have good compression.
-I replaced both coils with brand new Yamaha coils.
-Points are new and properly gapped (K&S engineering, all Dennis Kirk offered)
-I put new points wires on it.
-Put a new Yamaha condenser on it.
-I installed a MAC 2-1 megaphone (with baffle still in place) to replace the rusty swiss cheesed stock pipes.
-I've tried 3 different sets of new spark plugs, right now it has splitfires in it.
I can turn the ingition timing all the way one way, and then all the way the other, and it only makes a minimal difference.
Messing with the carburators does pretty much nothing, I've tried many different sizes of jets, messed with the needles, nothing.
Right now I've even got it at a shop, and they're doing nothing but scratching their heads the same as I was. I'm thinking of getting it out there this week.
At an idle, and just off of an idle, I can't get it to run on 2 cylinders. BUT, if you are lucky enough to get it above 3k rpm, it runs great!
-Both cylinders get good spark when tested against the block.
-Both carburators are perfectly clean, and have been fully rebuilt.
-Both cylinders have good compression.
-I replaced both coils with brand new Yamaha coils.
-Points are new and properly gapped (K&S engineering, all Dennis Kirk offered)
-I put new points wires on it.
-Put a new Yamaha condenser on it.
-I installed a MAC 2-1 megaphone (with baffle still in place) to replace the rusty swiss cheesed stock pipes.
-I've tried 3 different sets of new spark plugs, right now it has splitfires in it.
I can turn the ingition timing all the way one way, and then all the way the other, and it only makes a minimal difference.
Messing with the carburators does pretty much nothing, I've tried many different sizes of jets, messed with the needles, nothing.
Right now I've even got it at a shop, and they're doing nothing but scratching their heads the same as I was. I'm thinking of getting it out there this week.