dies under load

I have a 99' 400 and just had a trip down to johnson vally.

Before the trip I changed the oil, airfilter and sparkplug. The whole week down there it run great, until the last two days when I would get into the revs before shifting the engine would sputter and bog. If I rolled the throttle slow and shifted early it would ride ok till it would be under load in the mid to high rpm's.

When climbing hills or sand dunes the power would really disapear and the motor would sputter and die unless I took the load off by pulling the clutch or turning around quick and head downhill.

When in neutral or with the clutch in it would rev fine.

I haven't checked anything besides the air cleaner, which was clean. When I did change the plug out there was alot of carbon buildup on the top of the piston.

I'm planning a new top end and timing chain......am I going in the right direction?



Carb is probably gummed up - float may be sticking on inclines - Try to remove and completely clean carb all jets etc....

check your gas tank's vent hose first, see if you can blow through it.

The bike will do this in the flats too.

Well I took the carb out........and found that my JamesNow mod broke and was free to spin around the intake. Apparently the metal fatigued and two tabs pressed into the grooves I cut into the intake sidewalls broke off and I have yet to find them. Hopefully in the air boot. Besides that the carb was pretty dirty. I pulled it all apart and will clean it tomarrow.

I know the bike runs pretty rich and noticed that the main needle was a #175 and the needle jet was in the #7 clip position so I think I'll put the needle in the #5 position to lean it out some.

The bike was jetted for the high sierras and now I am running it by sealevel so I think what I am doing is right...:naughty:

We'll see

Sounds to me like it might be a Plug Breaking down under load, the fact that it revs in natural and shifts ok at slightly lower revs would cause me to think it is more likely to be a plug breaking down under load than a Carb being dirty...

I take it when you said "When I did change the plug out" that was before the trip? If you haven't changed it since the problem came up, change the plug its quick and easy and it’s a sure way to eliminate one possibility…

Good luck

Well I cleaned it out and left the james now mod out too. I had backfiring with the needle in the #5 position so I put it back to where it was originally(#7) and it runs good and no bog on the mid to top end. Now I wish I had more power as I have to use alot strengh to get the front end up when needed. :naughty:

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now