I picked up an 04 ltz400 last week and I need a little help indentifying a few problems. The first of the problems is that it seemed to be leaking gas like crazy when I firt got it. I know these thing use a vacume operated petcock and I kinda figured mine is just broke. As a quick cheap fix, I installed a on/off valve. Is there anything wrong with doing that?

The next problem is carb related I think? I really havn't riddin it much yet so I'll fill ya in the best i can. It starts great, but takes about 3-5 min on half choke to warm up enough to actually continue to idle by itself with out working its throttle. Once this process is done, and I hope on it to take it for a rip, It act like it wants to die when ever I let off the throttle. Especially when I put it in neutral and come to a complete stop. Also, when I'm in the throttle real heavy for a period of time like a straighaway and then let off completely, it kinda sounds like its missing or a real slight backfire or something?

The next problem came yesterday when I had a chance to get away for a couple of hours. After about an hour of somwhat hard riding, the quad started to idle when I came to complete stops and I was pretty excited. My brother and I then went to a wide open field where we could top it out, and easily run through all of the gears. after about 15 min of that, it started to die when I was IN the throttle. It would kind of die, then fire again the die then fire again as I would hold the throttle at about 25% the whole time. Also when it was dieing, it would make a strange sound like it was releasing a large burst of air. My brother said it sounded like it was comming from where the exaust mounts to the motor but that was prtty damn tight. I think it sounded like it was comming from the rear. I plan on cleaning up the carb but thought you guys might have some different ideas. How do you get the throttle cable disconnected from the carb?

Lastly, I didn't get a manual with the quad, but What is the oil change procedure for this thing? How do you check the level, how much does it call for, and what kind of oil should I use. Also what plug and what gap? Thanks in advance for all of your help.

 

ttt

 

The on/off valve won't hurt anything, but it'll just mask the true problem. The problem you describe sounds like your Needle Valve Assembly. If you take your carbs fuel bowl off and looking from the bottom, there is a hinge that the fuel float rides on. You need to remove the screw holding the hinge on and remove it. Be careful to not lose or bend anything as there is a very small plunger attached to the hinge. You'll see another screw that just touches a brass fitting that is sort of pressed into the carb. Remove this screw. Get a pair of needle nose pliers and gently pull the brass fitting out of the carb. This is the needle valve assembly. Check the o-ring at the top and make sure it's not worn. The leaking problem you describe you most likely be caused by this o-ring failing. You can try to replace just the o-ring, but you would be better off just spending the $30 something and getting a new assembly from the dealership. Before you install the new part, make sure to get some carb cleaner and clean out the area that the assembly goes into. This area gets full of garbage since there is a small screen at the top of the needle valve. Hope this cures your problem.

 

Is this the possible solution for the just the leaking issue or do you think that it might be causing some of the running issues?

 

It'll fix the leak, but once you turn the gas on the problem is still there. I'm almost positive it's causing your running problems also. It's not a hard fix at all. If you've never worked on a carb it should take about 45 minutes to an hour to repair.

 

Cool, thanks for the help. Im hoping to pull apart the carb and clean in up this weekend. Do you have any tips on disconecting the throttle from the carb? Last one I did, I disconected at the thumb lever. Taking it off was fine but putting it back on was a real pain!

Also could you help me out on the oil change? How much oil, what kind, and what is the procedure.

 

When I did this on my brothers Z400 I never took the carb out. I just loosened the air hoses and rotated it as much as I could so the bowl was visible. But to take the throttle off the carb you need to take the silver plate off the side of the carb and disconnect the cable from there. As far as oil goes, I have used Mobil 1 in every single ATV, street bike, dirt bike, street car and drag car I own. You just need to get the correct weight for your riding application and riding temps. I can't remember the exact amount but I believe it's 2.1 qts. The way to do it is to let the engine run for 5 mins at idle then sit for 2 mins. Drain the oil tank first, then the crankcase, then take off the oil filter cover on the right side of the engine and remove the filter. Replace the filter with a new one and be SURE that you have it installed the correct way. Fill the tank with the proper amount of oil, start it up and then double check the level.