IrishEKU

A General PITA.
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Apr 21, 2002
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Could someone please tell me the gap for a plug in a 1999 yz400f. I can't find my service manual at this time.
My bike was back firing a lot and running like crap, so I checked the plug and it had extreme carbon. I was in a hurry this weekend and put in a plug before checking the gap. My BAD.
I hope this will cure the problem.
I really appreciate your help.
 

IrishEKU

A General PITA.
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Apr 21, 2002
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Lou,
That was YZ400 guy posting under me, he has stock jetting as far as I can tell and just replaced the throttle cables due to one of them being frayed. Adams bike is one sweet ride and I like it so much I have been considering buying it off him. However, the guy he bought it off of had tried to set it up to race so the jetting may be different. All I noticed was really stiff suspention and a really responsive throttle before his problems. Any help with this would be appriciated, Adam has been a good friend for years.
Thanks in advance to anyone that can help!
Phillip
 
B

biglou

If he's having problems with it running, there are several things I would go after. Be sure to take the carb out and clean it thoroughly. Be sure the jet and carb body passages are clear. Make sure the gas is fairly fresh. If unsure, drain it and get some new stuff. Set the pilot screw at 1.25-1.5 turns out to start with. If it's backfiring on decell, it's lean. Hmmm, that's about all I can think of offhand. Oh, check the air filter. The big four-strokes suck a lot of air. Be sure not to over oil the filter or excess oil can get sucked into the intake and cause all kinds of squirrelly problems with the carb. I think, but I'm not positive, that the stock jetting on this is a 45 pilot and a 160 main. You might pop those out just to see if you're in the ballpark. Back to your original question, a fresh plug won't hurt, either. FWIW, I have seen plugs cause some crazy problems also.
 

IrishEKU

A General PITA.
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Apr 21, 2002
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Thanks Lou,

I hope this helps some. I've been razzing him for a couple of months now that his ride is going to be in my stable before too long LOL IRISH goes to strokers! Will the wonders never cease!
 

YZ400guy

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Jun 10, 2002
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Hey! Thanks Lou.
Everything was fine a week ago. Prior to that I had my throttle pump worked on, along with the new throttle cables. It was running smooth.
This past weekend, I replaced my plug and the maddness started.
An extemely carb fouled plug, some serious flame throwing back fire, hesitation on the throttle and a crappy idle.
I'll try your tricks of the trade. I hope they work.
Hey Irish, you should head down this weekend. Your expertise will come in handy.
Lou, if your in the Clarksville, TN area please let me know. It would be honor to have you in the garage.
 

IrishEKU

A General PITA.
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Apr 21, 2002
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Adam, I will be there just to turn the wrench and toss a few adult beverages if I can. You know I will I know a good "Bench Racing" session when when I see one! I'll let you know via phone if I can make it. If not check out Duke's for print outs on jetting pages....Midsouth is worried about getting $ for work, so it's closley held info. My personal Favorite in the Clarksville area is Queen City, The guy that owns the place is former military and won't screw you. He works on street more than dirt but knows it too. Try him first, he knows his stuff, I may be able to bend a wrench but this guy has about the same Knowledge as Rich......

Good Luck Adam!
Phillip
 

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