1982 Yamaha XS400J Maxim cold start trouble

[ponchoboy]

Hi, I have an '82 Yamaha XS400J Maxim and am having some serious cold start issues. The bike was given to me in non-running condition, but after getting a pair of new needle valves, cleaning a mouse's house out of the airbox, and rebuilding the petcock, the bike ran. However, the bike refuses to start cold. The bike runs pretty well once started with some 2+2 carb cleaner sprayed in the airbox, and will start after it is warm. This is really the first time I've worked with a carb, so I am not too familiar with things in there... could it be something with the starting jet? Something with the choke? Any help would be greatly appreciated. Thanks in advance!

[John]

There should be a long slender brass tube that protrudes down into the bowl area when you have the bowls off. This is the pick up tubes for the choke or enrichener circuit. They actually sit in a small well in the side of the bowl when assembled. This is the enrichener jet . It sounds like the E jet is plugged. Soak this well in carb cleaner, and clean it with a very thin wire. Do not hog it out with a drill, unless you have some small number bits. Not the fractional bit i.e. 1/16, 1/8 etc, but the bits that are numbered will work. Just don't go after it very hard, just clean the jet. You will know when it is clear, by using the nozzle on a can of carb spray, and spray it into the well, and watch for it to come spraying out. Make sure to wear some goggles.

[ponchoboy]

That did the trick! Took the carbs off and cleaned out the enrichener jets like you said... the one wasn't really gummed up that bad, but the area of the bowl that lets fuel to the them was clogged on both. The bike fired right up once the bowls filled with fuel. Thanks again!

[ponchoboy]

One more question about the bike... Does it usually take it a while to get warmed up? Until the bike warms up (about 5 mins of running), the bike wants to shut off when given any gas. I know opening the throttle reduces vacuum, and therefore reduces the enrichener jet flow, but isnt there an accelerator pump that is supposed to shoot an extra shot of gas when the throttle opens?

[DiverRay]

You probably need to pull both carbs and clean them completely. DO NOT soack the body in carb cleaner, as it will swell the rubber shaft seals. Use a spray cleaner and make sure any passage you see is clean. Also, when you pull the top off the carb, check the rubber around the slide fore pin holes. If you look to the left in the Tech Tips, you will find directions for rebuilding carbs. Most Yamaha carbs are just about the same.
Ray

[xs650mike]

My experience with Yammies equipped with "EPA" carbs is that they are very cold blooded and don't run right until warmed up for while. My XJ750RH, XS650SJ, XS650H, XS1100SF and XS400SJ are all like that. Still, like Ray says, it's a good idea to clean the carbs thoroughly. One thing short of tearing into the carbs that I've found oftentimes helps with slightly gooky carbs is to buy a bottle of Techron and put a little in the gas tank in the proportion recommended on the bottle. Your bike just might smile like those cartoon cars in the Chevron commercials. Also remember if you've got the bike on full choke and you open the throttle at all it won't start. Leave the throttle closed until after the engine is running a bit and the choke setting is reduced a bit. Most of these bikes die if you open the throttle at full choke.