xs400 running issue?

witchman1989

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I'm at the tail end of my project.

1979 xs400 cafe
I've changed all the gaskets
plugs
oil
re-wired the hole bike
carb rebuild/clean
sync carbs
etc etc

My issue now is, it will run at idle no issue for 10-15 minutes then start to stall. I then test the battery and its still sitting at the right volt/amp. My big question is...are these issues usually standard charging problems>? Really all I need to know!! Unless say a floats sticking or my fuel tank isn't venting. Just a little insight before I crack open case covers and rip the tank off would be helpful. Thank you:banghead:
 
Hey guys so I got back information from the dealer and wanted to ask some information from you guys....please; the go search for it type need not reply. I've searched and searched!

1979xs400 pod filters and open exhaust.
Jet kit ordered, uni filters ordered. Gonna re-jet it then seal up all the oil leaks and do the swing arm pushings. My question is my bike won't run correctly unless the choke is out all the way....with the re-jetting,needle placement,new filters...will this correct itself? Or what is it? My bike will run as is right now choke out no issues but as soon as the choke is released it will run at idle and slowed chug out and stall. Then it will not fire up for a good 30 minutes! Please any advice would be awesome
 
Sounds to me like there's something a miss in your carbs. You may want to clean them again when you rejet. I was inside mine 4 or 5 times when I found a few tiny little passages still plugged. I hit em with an air needle and got a face full of grum. You may also want to check that your tank is venting properly.
 
et kit ordered, uni filters ordered. Gonna re-jet it then seal up all the oil leaks and do the swing arm pushings. My question is my bike won't run correctly unless the choke is out all the way....with the re-jetting,needle placement,new filters..
--Never done that--, But I am betting, that you need to use the pre-sets dialed into the carb for one, and then the likely hood of the dreaded "not clean enough carb" Every one of us has cleaned the carb 3 times before we got it to the sweet spot.

are these issues usually standard charging problems>? Really all I need to know!! Unless say a floats sticking or my fuel tank isn't venting. Just a little insight before I crack open case covers and rip the tank off would be helpful. Thank you

Yes, charging issues are standard. typically its the 3 wires from under the drive sprocket to the first plug connections. (from the stator) the rest of the time its poor ground. My first summer with it, I spent many an hours banging my head into the garage door, then it was discovered, my float was filling up with fuel. ((I would work on it, till it runs, then by that time, its late, and I would go to bed. next day, I was back at step one.) So check the float height. )) (((I also had the fuel tank not venting))) The bike would drive at high speed for about 3 miles, then it would choke out. (out of gas syndrome) I had plastic koted the tank, and forgotten to clear the vent hole. One season, I had it running really rough, for no apparent reason, I took it onto the freeway, eventually there was some sort of pop? I don't rightly remember, but it clicked, and started to run right. I had hoped the Italian tune ups would work. I advocate the boiling method to clean carbs, with some sort of light weight acid, (lemon/vinegar) its the cheapest, and or you can do the dip, for $10 to 15bucks.

From time to time, we have some really bored people, and they put neat things together, like this next link, From Willem, and his "a bunch of How to's in a thread."
http://www.xs400.com/forum/showthread.php?t=10715

other wise, our standard line is suppose to be, find the manual, on top of the Garage, (sticky'ed so it will allways be number 2, on the top of the list, and above that is the Tech section, which is where Willem's thread should be, to help out people.

An excellent carb guide, http://www.amckayltd.com/carbguide.pdf


PS, before you do too much to the bike, put a inline filter on the fuel line. I recommend paper, but the more you look at others bikes, they are using the brass ones. (has a nice 90degree angle) Brass lets bigger particales though, than paper does.

I hate to say the only thing I am worried about for this year of biking, is the butterfly o-rings. I am going to get that done, now and hope that brings my bike to the fuel economy that others have been teasing me with. (they said to take everything off, before boiling my carbs, I wasn't ready to delve into the butterfly effect. so if that has been affecting my mileage, I have been doing 40mpg. (perhaps if I killed my battery, I will upgrade to the AGM)

Swingarm, mine seems to be fine.

I was just browsing the Carb link, and it does say (XS650) don't worry about that, it says its for the BS34 Carb, (not to be confused with the 38 model) The numbers and everything match up.
http://www.mikesxs.net/product/48-9004.html
http://www.mikesxs.net/products-82.html#products

Somewhere on this site, is a link to a Carb-kit, with everything needed, aftermarket style.
 
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Thanks guys, I will be cleaning the carbs aka soaking them over night this week etc etc. Then re-jetting when I get the jet kit! I will also do the inline fuel filter, I can pick on up at the auto store cheap! But when it comes to the venting hose....how would I check to see if its venting correctly?
 
Had I thought that was my issue when my gascap was sealed shut, I guess I would pop the fuel cap, and that would allow another 3 to 5 miles, till it vacuum locks.

(just curious to make sure) your not talking about that other hose on the fuel petcock are you? That is a vacuum line to the intake, to open up the flow of fuel to the carbs. There are many of us, that have forgotten to put that on right, when we put things back together, and oops :banghead: we finally figure out that a simple mistake has happened. I replaced mine with a clear plastic tube. Its been there for 3 years now.
 
Yeah my question was the line off the petcock but I replaced all my lines! And the fuel line to the carb has a clear line with an inline fuel filter now....so I can see what the fuel is running to it! Making life a world easier lol
 
One other question to anyone that wants to give an opinion. I jump the jet size up on the main. Its getting more fuel and adjusted/sync'd the carbs! It tends to run way better now but still has a stalling issue. The owner before me painted the gas cap all black etcetc. Am I right to assume he painted over the gas cap vent and this could be a cause to the stalling issue after a few minutes of running?
 
The vent hole is under the gas cap. under the middle of the seal zone. As long as the PO didn't spray up and under the gas cap, trying to protect a chrome part from rust, because we all know it wont, The following link, may not say XS400, but it essentially the same as our gas caps. (not recommending to buy it, just to note the hole, and location of the hole.

http://www.ebay.com/itm/1978-1979-1...7887896&pid=100010&rk=3&rkt=5&sd=251445384334
 
So Witchman Have you got fire in your bike now?? Been watching your posts for a while & sounds like you've seen some of the same running issues I've had. Also with the best intentions people can do some of the most ill advised things. Like painting the fuel vent closed. I've done similar when repairing a leaking gas cap with a piece of gasket paper. I'd gotten about 4 miles away with my mini bike & had to push it back home.
 
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