78 xs400 won't run right

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Xsrider333

XS400 Member
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Hey guys I'm new to the site just got a 78xs400 2 months ago and it has been an interesting two months. When I first got the bike it had been sitting since 2001 (15years) so when I got I I did what I see as the usual for bikes, changed the oil cleaned the carbs flushed the fuel tank so on and so fourth. Well none of that helped it run better so then I did the points. I gapped them and timed the points only to find out that was only part of the problem after I did that I found out the vaccume petcock was bad so I bought another one that was not a vaccume petcock it was just a normal one. After I got that the bike still didn't run right so I bought new carb kits for it which came with 2 washers the needle and seat and the main bowl gasket. I put that in today hoping that it would solve the problem to no avail. Basically where I'm at now is that I can get the bike to start. I can get it to run with the choke on and sometimes off if I have the petcock turned 3/4 of the way on. Also I can't get it to idle down it idles around 2000 rpm. When I go ride it the bike seems to sputter and backfire on the way up but once leveling off at speed it runs decent. Then when I come to a stop the bike dies unless I hold it at 4000 with the clutch in. Then once it's hot and it dies like that it doesn't want to start for 5-6 min then I'll kick it and it will start hard and then the process starts over. If anyone can give me some insight into what the hell is going on with this bike that would be much appreciated I have no idea what else to do
Thanks,
Nick
 
The idle screws are at 2.5 turns out now I know they should be at like 1-2 and I checked the boots and didn't get any thing
 
check for leaks around boots and butterfly seals...check floats for holes and make sure they are at he correct height.. figure in the manual was wrong i think its supposed to be around 27mm dont quote me on that. Since you have a manual PC make sure both barbs on the intake boots are capped.. Sync carbs with a manometer
 
So after a while of putsing around I put bigger main jets in now I can start it it idles at 1700 for about 30seconds then it takes off to 5000 rpm and won't come down. Even when I turn it off and start it back up it jumps to 5000. floats don't have holes. How do I check the float height I just put the new needle and seat in it too and I've gotta get a manometer I have the barbs capped and idk what else to do now
Thanks nick
 
Xsrider333 said:
Any particular silicone tape? I was thinking about doing something like that.
Click to expand...
I love silicone tape the stretchy kind that sticks then permanently binds to itself often called emergency tape. Its always a great idea to carry on a boat because you can seal a hydraulic or fuel leak even underwater. I also often use it to waterproof electrical connections.
 
Xsrider333 said:
Gotcha I wonder if they have it at like home depot or ace or something thanks I'll give that a shot
Click to expand...
It can be hard to find and even if a store has it the clerks will have no idea what your talking about. Napa carries it but 20 bucks for a 20' roll. Its much cheaper online than any store. Boating stores pretty much always have it. You have to stretch it as you wrap or it won't seal.
 

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