Fueling/carb

[phil w]

OK so Im getting on really well with the XT600. I keep thinking its a bit slow, but then I think back to my XTZ660 and re read some of my posts and I rekon Im plonking along at about the same speed... 60/65mph. Thats not so much slower than my new Tenere I had also... as I used to sit on that at 75 on speedo, but a load of people say the electronic speedo on it is always near 10% out
One small annoyance is cropping up, and wondering whether its worth looking into
Say Im driving in built up area, my speed is about 30/40 mph and Im in 3rd/4th gear. It feels as if the bike is just about to go to reserve...i.e the moment just before that happens, it almost feels stuttering but open up the throttle and it pulls fine. Would this be a transition inbetween the 2 carbs ?
wonder if anyone else has this going on ??

[dark_knight87]

Phil,

I could be wrong as I am recent convert to a Thumper but sounds to me like you are in a too higher gear for your speed and the bike is struggling.

Regards,
Russ

[phil w]

No its not the gear Im in. Its when Im travelling at a given speed, especially more noticable at the slower speed roads and the throttle is only open a quarter twist say. It happens if Im in 2nd at 15/20 mph say, but I notice it more for the speed you would travel around town roads

[xtrider]

Mine does that also and on another forum there was four others that had that issue also. I know mine is running rich due to a black sparkplug and it really stumbles at a steady throttle but runs great as soon as I start to give it some throttle. I think the stumble is around where , as you said , the transition point where the secondary is opening up but starving the motor of air(my guess) or fuel. I still have to go through the sinc process to get the two correctly timed ,which should take care of the stumble , otherwise I have a pair of Raptor 660(the atv) carbs that fit right on except for the airbox side. I'm first going to spend some time working on the original carbs , it's just a pain taking the bike apart each time just to turn a screw and then put back together to try.

[dark_knight87]

I was always told to try the simple things first - clean / replace the air filter, clean the carbs, adjust the throttle cables etc...

I have just put a new air filter in mine and once I had fitted it correctly mine is now a little rocket (up to about 70mph!)

Just a thought!

Regards,
Russ

[xtrider]

With mine, all the normal little things have been done, over and over. I even took the boots off and the exhaust endcap out, not even noticeable other than noise. New sparkplugs(several in fact), different grades of gas, new CDI, all electrical connections cleaned and dielectric greased. The fact that so many are complaining about the exact same symptom tells me it is a common thing going out or going out of "tune". If I had the time to throw in those other carbs, or go through the sinc process, it would tell me instantly where the problem is. Since the stumbling goes away the instant any throttle is given, my best guess has to do with those old carbs. And yes I have taken every single part out of mine and cleaned put back together with a bunch of new parts, no real difference other than starting a bit better.

[phil w]

Ive left mine. It is a slight annoyance but like I say only at low speeds. The bike is pulling like a train and is really fantastic fun. Maybe come winter down time it will have the once over

[xtrider]

Tonight it was a rather warm and humid day and mine was do the stumbling pretty bad so I decided to take that cap off the nipple on the left side intake boot to let some more air into the motor. Wow !!!! totally different bike. The stumbling went mostly away except at idle there is some. Crack the throttle and she has more than ever. Now I need to find a way to make my pilot and main jet smaller(since they not available anymore). The needle I'll find a way to drop it.

Sooo, I'm thinking if anyone that also has a stumble/jerking, to maybe try this ( temporary ) to see if it is running rich and causing it , put a hose on the nipple and run it out so you can plug/unplug the hole as your driving to test different rpm ranges. Don't leave it like that though, it's just as a diagnostic procedure.

Anybody know what that nipple is for anyway?????

[ActionManMelb]

Anybody know what that nipple is for anyway?????

It is to connect a vacuum gauge for diagnosis of leaking valves, poor compression, incorrect timing etc.

Warning...before you mess with your jets make sure the float/fuel level is correct.
Yamaha are not total idiots....when the bike left the factory it was running well.
At least you have proved that it is too rich, look for another cause such as an air restriction before you alter the jets.

[xtzrick]

Phil
I think your bike is more more modern than XTriders' & is subject to different emission tests, previous experience would suggest that you are more likely to be running lean.

After you have checked the basics, air leak, blocked jets etc.

Open the throttle 'til you feel the 2nd carb start to open & tippex a dot on the grip & the housing inline with each other so you can see them when you are riding.
Then warm the bike up & ride for a couple of hundred yards in the trouble zone.
If the dot on the grip is above the dot on the housing your problem is before the transition & you might be able to correct the problem by adjusting the mixture screw. If the dots are inline it's at transition, try adjusting the left carb needle &/or get a different pilot jet. Kedo have sizes #46, #48, #50 & #52.

While you are riding in the trouble zone pull the clutch in & kill the engine at the same time & check your plug colour. This will let you know whether to try rich or leaner carb settings.

Then wipe off the tippex, if the FEDs see it they will know you've been testing & fine ya

Rick