Main Jet Falling Out

[Pacheco_450r]

So I have had this happen to me a few times and wondered if anyone else has this issue. Maybe two or three times a year I'll be riding and all of a sudden I have no top end. I'll pull the cap off the bottom of the carb and once again my main jet is sitting in the bottom of the cap. The threads are not stripped on either the jet or the carb. I use that little motion pro jet tool to screw it in and snug it up. I make sure not to over torque it as I've broken a main jet doing that in the past. So is vibration my problem and it's unscrewing itself out or what else could it be? Anyone else have this problem? I'm glad it's never happened during a race but it's always in the back of my mind that it could happen.

[DnB_racing]

is something is causing excess vibration? can you feel vibration on the soles of your feet while riding on smooth surface? or have you altered the intake with something that doesn't dampen vibration to the carb?

make sure to check your oil filter for metal particles,

only time Ive had things loosen up is when Ive had bearings vibrating shortly before total failure

[Pacheco_450r]

I don't feel any unusual vibration and nothing has been changed on the intake at all. This happens maybe 2 or 3 times a year for maybe the past three years so I would imagine if it was bearings in the motor it would have blown a long time ago. I know some people that have had it happen to them but maybe once ever. It really is strange.

[happyboy]

One of a couple things is happening.

1) You are not tightening it enough. Very hard to say as "tight" is different to everyone.

2) The threads are damaged from excessive force previously and will not hold tight.


If you are sure you are tightening it good then I would throw a little blue loctite on the threads next time. Let it dry for a few hours before running it as the fuel will clean the loctite out if its wet. If the blue does not hold then bump it on up to red. :)

[Pacheco_450r]

I think I will definitely put a little loctite, last thing I want is to lose top end right before a big double during a race! Thanks for the tip!