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Fuel mixture screw o-ring


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It seems every couple of years I tear the o-ring on my fuel mixture screw. I would rather not keep buying screws just because I need an o-ring. I see replacements online but I was planning on riding this weekend and can't wait for shipping. Does anyone know the size of the o-ring on the tip of the screw so I can hopefully run down to the hardware store and pick up a replacement? Any assistance is greatly appreciated. 

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I don't know the size but if I was in a pinch I would take the fuel screw into the store with me and see what they have that fits.

Do you still have the old o-ring? Take that in with you too.

Also I'd probably go to an auto parts store. Not sure if the hardware store o-ring would be rated for gas contact.

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I'm slightly interested to know why the OP is tearing the o-ring every couple of years in the first place.

On my 05 CRF250R I've has an after market fuel mixture screw on for over 4 years and granted I don't adjust it often but its not an issue for me.

Similar to this one.

tus_09_fue_mix_scr.jpg

 

As posted it would help to know what bike = carb but ya take it into any bike shop or in a pinch even taken the damaged one into a good industrial supply place and they may have one.

Then solve the issue of why its getting damaged in the first place or buy a bunch of spares

 

 

Edited by filterx
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On 2/10/2017 at 8:45 AM, highmarker said:

which bike make model and carb

2002 yamaha 426. Carb is a keihin. Probably spelled that wrong. 

O-ring issues might be because I have to mess with the screw and idie more than I should have to. She only runs smoothly with the choke out and idle turned down to compensate. I've been struggling with that thing for years and that seems to be the best bandaid so far. With it like that I can go out and enjoy myself without the idle sticking or the bike stalling on me everytime I let off the gas. 

Edited by markolious
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So you are wearing out the o-ring making adjustments while running with the choke instead of jetting it?  I've had several friends who have had nightmarish stories about jetting and I have watched more than one Yamahammer owner kick the crap out of the bike trying to start it, along with several of my friends joining in (I refuse to kick).  What I will say is that both of these owners would rather take a beating than to spend some time setting up their carbs or even changing oil for that matter.  Might I suggest you start with the pilot jet, then the needle clip setting and so on?  I've owned one WR450 and it was a lean son of a gun.  Running your choke "out" (translation choke on??) should tell you the bike is too lean.  As I recall, my Yamaha jetted properly still created a glowing blue head pipe, so that's not a reliable tell-tale.  But your choke is a clear symptom...............

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This carb has definitely been a nightmare. I've been on thumpertalk a half dozen times about it. I've spoken with very knowledgeable people that have fixed some issues. I've done jetting research. I matched my jets to someone else's that has the exact same bike. This carb has poltergeist is the only explanation. It's definitely in better running condition than how the previous owner had it who had missing seals and a backwards slide plate. Good times. 

Edited by markolious
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Sorry to hear that.  Nothing more frustrating than having just enough time to get io a ride, but then having to work on it.  Good friend LOVES his YZ450.  Doesn't even have to jet it for our home alt of 900ft, then rides it to the top of Colorado.  No jetting required.  Some of these Yamaha's are just head scratchers.  I wish I could help you but it sounds like you've already spent some time researching the jetting procedures here on TT?

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I have, indeed. Working on it right now. Trying to find some happy medium between the idle adjust and fuel screw. I can get it to idle for a minute a good rpm before stalling everytime. It also stalls with sudden throttle twist. Less than sudden and its ok. Still scratching my head. 

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I've got a 2005 Honda CRF250R and luckily never had an issue with the carb BUT dealing with carbs was never something I really want to have to deal with.

Then 3 years ago, I wanted to get my street bike license and was looking for a bike and my neighbour had a 1982 Yamaha XS400 that had been sitting for 10 years. I bugged him for a year to sell it to me and he finely gave up and  just gave it to me.

I'm fairly mechanically inclined so started methodically having at it to get road worthy and to actually start.

So before I dealt with rotted tires etc, I went through the 3 main things you need to start an engine. Air, Spark, Fuel.

Air was ok but new clean air filter

Spark - major electrical issues - Obviously new battery and plugs but the fuse box was toast so fixed  then and one of the pick-up coils needed to be replace.d Now I had air and strong sparks on both cylinders when I turned over but bike would not start.

Fuel - The steel tank was a rusted mess which is a separate topic, so then it was time to have at the carbs. I pulled them, took pics and methodically took them apart. In hind sight if I was to do it again I would have gotten them ultra sonic cleaned but I ended up cleaning, reassembling and repeating 3 times before I got them clean. In the process noticed the jetting sizes were not correct so ordered correct jets. Once the carbs were really clean, jetting etc correct, bike started in 5 seconds for the first time in 10 years. I eventually ended up buying another set that had been ultra sonically cleaned and rebuilt correctly and huge difference.

So after my long post I would make sure your carb is really clean and as posted jetted etc correctly. Worst case buy another GOOD clean jetted carb.

Got my street license that summer and ride this little XS400 around town all summer long since 🙂

20140520_135457.jpg

 

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Yes, I have jetted it to what others on TT have theirs set to as well as someone with the same bike. Carb has been pulled multiple times and cleaned. I think this carb is just different and will need its unique jet settings. I'll continue to play with it. Right now I'm recording all the idle and fuel screw combos/settings for ease of start, idle time and response to throttle inputs. So far idle at 5 turns out, fuel screw at 2.75 turns out and idle @ 4.5 and fuel @ 2.25 seem to have the best results so far. Still won't idle indefinitely and has stalling issues at fast throttle inputs.

 

Cool bike, filterx. I'm a tad jealous.

Edited by markolious
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