400 EX Spark Plug Info?

[CEC]

I Have 2 400s. Have Had Them Since They Were New. After 3 Or 4 Rides The Spark Plugs Are Black And Carbined Real Bad. Is This A Jetting Issue With The Carb? They Are Hard To Start When Cold If You Do Not Know How To Start Them. Eny Info Apper.

[exrider]

Put a #42 pilot jet in your bikes and they will start without the choke. In fact I remove the choke to get better air flow thru the carb. As for the spark plug do you have any mods? The only reason for a four stroke plug to look like that is if you are runnign very rich or have bad rings. How often do you clean your air filter?

[CEC]

No Mods. Complete Stock. I Keep Air Filters Clean And Lightly Oiled

[dynodon]

You shouldnt have to rejet for a stock bike. Sounds to me like your air screw on the carb needs to be opened up some.

[exrider]

How do the bikes run once the warm up? Do they both act the same?

[CEC]

After Warm Up They Run Fine. They Don't Take Long To Warm Up.

[exrider]

change the pilot jet and don't worry about the plug. This is my third 400 ex and I have never had to change a plug. I just put a new one in every year when I tear the bike down if it needs it or not.

[dynodon]

I still recomend to adjust the air screw on the carb ( turn it out 1/2 turn to start with) check the plug and go from there.
A "rejet" on a stock bike shouldnt be neccesary.

FYI, this isnt my first rodeo either

[exrider]

A #42 pilot jet will fix the hard start problem on a 400 ex. Won't help the spark plug issue though. Can't think of anything that will make a stock bike run that rich except for an air restriction or a dirty carb, but a dirty carb will more than likely make it run lean. Does it bog off idle during acceleration. Are you sure the carb jets are stock. If not take out the main. Off the top of my head I THINK stock should be a #148. I can check if you go this far.

[UncleRico]

That black on the tip of your plugs is excess oil burned on due to a rich condition.

Try running it without oil for the next few rides. Make sure you get up into 5th gear and really put it through the paces.

That should keep you from having to deal with spark plug issues.

[CEC]

Carb Jets Are Stock. I've Owned Both Since New. I Don't Think They Bog On Acceleration. I Do Not Ride Them Real Hard Alot, Due To I Mostly Ride With My 7 Year Old On His 90. The 2 400s Have Had This Problem Since Brand New. I Only Ride 3 Or 4 Times A Year So I've Just Been Buying A New Plug Every Time A Ride. It's Like Owning 2 Strokes, Just Have A Extra Plug In Your Pocket

[KB]

They might adjust them carbs. like that from the factory on purpose so you won't burn it up under warranty, kinda like they tell you to on a 2 stroke to mix your oil at 32:1 but I don't think you need that much oil, especially if your running a good quality or synthetic oil.

I would do what Dynodon said first, I'm not sayin exrider is wrong, I could be wrong.
Either way you got 2 good people there than can help you out.

[exrider]

Why do you change the plug? Does it stop running or just not start. Where do you ride at?

[KB]

That black on the tip of your plugs is excess oil burned on due to a rich condition.

Try running it without oil for the next few rides. Make sure you get up into 5th gear and really put it through the paces.

That should keep you from having to deal with spark plug issues.

Ya, that will definetly fix the problem, or take off the air filter & leave it off, either way.              J/K   dont do dat

[Chevy1500z71]

choke just makes it richer, so a biger pilot will alow you not to have to choke it but once its warm the jet is going to be to big.

[CEC]

I Ride At Croom. I Change The Plugs When They Get Real Black, If I Let Them Go They Will Fowl Out.          Thanks exrider And dynodon For The Info

[exrider]

If you want next time you go to croom PM me and I will come and take a look at your bikes

[CEC]

If The Weather Is Not Real Bad I'm Going In The Morning. It's Going To Rain

[exrider]

can't make it on sunday.Save the plug.