HEADS UP!!!

Site upgrade in progress... Core site functions are working, but some non-critical features/functions will be temporarily unavailable while we work to restore them over the next couple of weeks.

Please post any bugs you encounter, but before you do, check to see if it's already listed.

Thanks for your patience while we work to improve the community.

Sign in to follow this  
Followers 0
bikefrk

O-Ring for fuel screw and MSR fuel screw 1999 YZ400f

13 posts in this topic

So I have been having a lot of popping on decel on a 1999 YZ400f that I just bought a month ago. Won't idle either, with the idle adjuster all the way buried.

I purchased a MSR red fuel screw for easier adjusting, on the recommendation of the local mechanic.

When I dropped the stock fuel screw out, I got the spring and washer but not the o-ring. I got the remainder of it though. About 1/4 of it.

Hmmmm, no o-ring with the MSR screw. Dammmit!!! :ride:

I already know my local dealer doesn't have the o-ring, because I asked for one when I bought the MSR screw.

The parts fiche looks like you have to buy the whole screw/spring/washer/o-ring to get just the o-ring. $30. :banghead: :banghead:

So, anyone have any tips on where to source a similar o-ring other than the local Yamaha dealer?

And why won't my new red MSR fuel screw go into the hole in the float bowl so I can thread it into the correct location? It goes in partway but hangs up. If it means anything, so does the stock screw.

Hey, thanks if you can lend any help.

Did I mention I leave Friday morning for a 3 day riding weekend? I might be riding a lawn chair at camp now. :):D:worthy:

Share this post


Link to post
Share on other sites

what is the purpose of the O ring? is it needed? mine didnt have it when i road the other day and found it on the bench and havent road it yet

Share this post


Link to post
Share on other sites

The purpose of the O-ring is first to seal outside air out of the idle mixture. Without the ring, it leaks an uncontrolled, random amount of air into the idle circuit. It also provides the friction that holds the screw in, due to the spring pressure on it.

Share this post


Link to post
Share on other sites

For those interested...Suzuki is the only bike mfg that sells the parts separtely according to their fisches (not including ATV's), at least they did in 2006. My advice is to purchase a couple of springs, washers, and orings to have around as spares. You never know when the fuel screw is going to vibrate out and you lose the parts.....

Share this post


Link to post
Share on other sites
The purpose of the O-ring is first to seal outside air out of the idle mixture. Without the ring, it leaks an uncontrolled, random amount of air into the idle circuit. It also provides the friction that holds the screw in, due to the spring pressure on it.

could that be why it isnt running right down low? it seems like it was rich...wouldnt too much air be lean

Share this post


Link to post
Share on other sites

Unless you found the remaining parts of your o-ring, it could've been forced into the drilled passage. Spray carb. cleaner thru all directions of this circuit to be sure. It could be blocking the fuel or air into the carb.

Share this post


Link to post
Share on other sites

I am almost sure I got all of the o-ring out.

I rode it Friday and most of the day Saturday. It ran great. Still some popping on decel, but I think if I fatten up the pilot jet and mess with the screw, I can make that problem go away. :)

Share this post


Link to post
Share on other sites

On my yz 400 i went up two sizes on the pilot jet and put a power now valve and the bike runs great no popping or bog.

Share this post


Link to post
Share on other sites

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
Sign in to follow this  
Followers 0