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  Topic Review (Newest First)
11-15-2019 02:15 PM
TuckerHardRide If you do buy a new petcock, buy a used (or new) OEM one not the chinese knock-offs.
11-15-2019 01:24 PM
CFM I've seen a plugged gas cap vent act like this. It's an easy test. When acting up, loosen the cap, and see if the problem changes.

Other than that, I'd be suspicious of a gummed up carb. Pump gas is terrible, and it doesn't take more than a few weeks of sitting to have an issue.

I also don't have much faith in the stock petcock. It has an auto shut off, that has proven unreliable. Beyond that, it's completely unnecessary for the petcock to automatically turn on and off with the engine. A normal petcock from a Raptor 660 is a common swap, and one I recommend.
11-14-2019 08:30 PM
Posingtoast28 Had the same problem on mine ended up being the vacuum lines from the carb to the gas valve were bad. It probably wouldn't hurt to run some seafoam spray trough the carb and pour some of the fuel treatment in the tank since it sat so long.
11-12-2019 01:00 AM
jetmech25 Cleaning out the carb after sitting for a few months is always a good idea. Put some fresh gas in the tank and make sure the cap is venting so fuel isn’t held in the tank in a vacuum.

But, I think your problem is valve clearance. Your manual should explain how to check the clearance and how to shim them within specs. Plenty of info here as well under the maintenance section. If they’re even a little tighter than the limit, it will get harder to start when warm. It will start fine when cold if they are at the bottom of the limit, but once the valves warm up, they stretch enough to be out of limits.
11-11-2019 07:08 PM
Z400 Will not stay running

Hello everyone! I have a 2003 Z400 that I bought last year. I rode all last winter here in Vegas and it sat for a few months over the summer when it was too hot to ride. When I start it with the choke on from a cold start it starts right up. As it's warming up after a minute it then stalls out. After that it will not start at all. I checked the petcock and fuel hoses and fuel is getting into the carb, but it seems like it is not getting gas. After it sits overnight it will start right up and do the same thing again. Maybe the carb needs to be cleaned? What direction should I go in? Thanks!

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