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Discussion Starter #1
So I changed the main jet to a 122 and adjusted the idle air screw to 2 turns out. Bike runs decent except for stumbling off of idle. I can leave the choke on and it cures that, but then runs crappy till I push the choke in. One thread I read talked about changing the pilot jet, which I've done on my 70s bikes, going leaner. Would this fix my idle stumble? Don't really want to drill holes in the airbox, but might look at the TPI valve I saw in another thread. Also not too interested in swapping the carb to a Chinese knockoff, at least not while the bloody bike's brand new.

What say you?:D
 

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If your looking for more air the TPI valve is great. I have it wide open at 7000ft and above. Half open for my local riding of 3000 - 7000ft and closed when at sea level to 3000ft. Closes tight, slick design. You may want to try 1 1/2 turns out as well if you are riding at 9000ft regularly. Good luck with getting it optimal!
 

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Bike runs decent except for stumbling off of idle. I can leave the choke on and it cures that, but then runs crappy till I push the choke in.
One thread I read talked about changing the pilot jet, which I've done on my 70s bikes, going leaner.

Are you asking if you should go leaner on the pilot jet - or just saying in the 70s you've changed those jets going leaner?
Not a mechanic; but you said leaving the choke "on" (making it a more gas to fuel mixture) cures the stumble off of idle.
Wouldn't that indicate that you need to be richer off idle (not leaner).
Hopefully a carb master will chime in!
 

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...You may want to try 1 1/2 turns out as well if you are riding at 9000ft regularly...
What is your mixture screw setting, now?
 
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I believe 2 turns was stated in post #1 for the current setting of mixture screw.
A year ago I would have said a 122 main seems a bit too lean.
Then elime, who really know his TWs, has reported success with even smaller jets. No single solution fits everyone’s bike.
However post #1 was a bit confusing as to seeming conflicting reported effects of the choke. For clarification does the “runs crappy trill I push the choke in” mean the bike runs acceptably once warmed up and the choke is turned off?
 
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I believe 2 turns was stated in post #1 for the current setting of mixture screw.
Thanks, Fred.
Guess I did not fully absorb that post!
 
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I read it as stumbling off idle (pulling away from a stop) - then runs fine. But if he starts with the choke out (on) it does not stumble off idle (pulling away from a stop); but then runs crappy at speed - unless he then pushes the choke in (off).

He needs a bar mounted, thumb activated choke so he can turn it on every time he comes to a stop; and flip it off once he gets going. ;) Sorry DtN; folks here will get it figured out .
 

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If you need to start off from idle with your choke on, you need to go up one size on your pilot jet. You obviously need more fuel down low. I think the rule of thumb is if you need to turn out the idle mixture (air/fuel) screw more than 2 turns, go up one size on the pilot jet.
 

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The choke is an enricher valve. He has tuned the bike to be leaner so what is happening is normal if not at altitude. Is it running like this at 9000 ft? What year bike too?
 
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Discussion Starter #10
Sorry for the delay, been off-planet the last few days. I live at 9000'. I ride at 9000', down to maybe 8000, as high as 9500. Bike is not leaving the mountains so trying to optimize it for up here. I'm also confused that it idles better with the choke on until it's off idle and revving, but not sure where to go from here. It ran the same before I changed the main jet down to 122 from 126. Also when I removed the plug to adjust the pilot air screw, I found the thing seated all the way in; I could only turn it out.

I've got some time off now to look into this further. I think I'll put a TTO tach and temp gauge on it, would like to know what rpm it's running and how long it takes to warm up. Thanks for all the responses and I apologize for not getting back sooner.
 
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So I'm new to the TW, but not new to motorcycles.. My question is.. What is the stock Main jet size? 126? Just bought my bike today and dealers closed.. I have no problem changing Jets, for evelation.. Done it before. I reside in Phx, desert rides under 3500' but moving to white mountains.. 5000- 9500' riding.. if stock is a 126, then a 122 should be fine... rite? I had a Yamaha Rhino.. stock was a 145 main.. went to ride co. 9000- 11000' and I jetted down to a 137.5 to run decent.
 

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Stock jet is 126 after the change to a Teikei carb years ago. I'm at 5,500 and ride to 9,000 routinely. I change my jet to a 122 only when I'm going to be riding above 9,000 for several days, and if it was installed I would not ride below 8,000 unless it was all at lower RPMs and mostly level. I ride the stock to 10,000 with no problems except going up a long hill in fifth. Probably 2 turns out on the pilot jet would be ballpark.
 

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Discussion Starter #13
Went for a 20-miler yesterday, 1st time in over a month I've had a chance to ride. Took the 78 DT175 out first then the TW. Both are jetted down for the 9000' area I ride in, and both did very well. It was pretty nice yesterday, all around us were in the 20s but the cold air had pushed warmer air up the slopes, so it was in the 40s.

The TW performed nicely with the 122 jet and 2 turns on the pilot jet, just a little slow acceleration in 5th gear and slowing on steeper grades, like Rocky said. I guess I never noticed that Yamaha redlines the speedo at 55, that was a little surprising, but as I rode I realized the gearing and tires would naturally keep the speed down.

I'm pretty happy with this tune, not gonna futz with it much, even if I take down to Alamo, which is about 4300' MSL. I forgot I was supposed to be ordering a TTO temp gage for it, guess I'll do that after I check the diameter of the spark plug for the correct probe. I'll take the 126 with me when I go down in case the temps start to get way up there on the ride back.

One other note, I'm really happy with the Pirelli MT43 I put on the front; bike tracks very straight in gravel, mud and snow. Now I notice the rear Trail Wing fishing around so that's gotta go next, or soon. Took the bike up a local canyon trail that 4-wheelers have turned into a scree slope, fist- and butt-sized rocks everywhere, and the bike soldiered through. Man, what a workout! Made me forget all about the cold! Stalled one time coming back down using engine braking (got too slow) but never once dumped the bike. But the Pirelli and the carb tuning were a good fit for the ride. That was fun!;)
 

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Redline isn't at 55 mph. When the TW was designed, our national top speed was 55.
Went for a 20-miler yesterday, 1st time in over a month I've had a chance to ride. Took the 78 DT175 out first then the TW. Both are jetted down for the 9000' area I ride in, and both did very well. It was pretty nice yesterday, all around us were in the 20s but the cold air had pushed warmer air up the slopes, so it was in the 40s.

The TW performed nicely with the 122 jet and 2 turns on the pilot jet, just a little slow acceleration in 5th gear and slowing on steeper grades, like Rocky said. I guess I never noticed that Yamaha redlines the speedo at 55, that was a little surprising, but as I rode I realized the gearing and tires would naturally keep the speed down.

I'm pretty happy with this tune, not gonna futz with it much, even if I take down to Alamo, which is about 4300' MSL. I forgot I was supposed to be ordering a TTO temp gage for it, guess I'll do that after I check the diameter of the spark plug for the correct probe. I'll take the 126 with me when I go down in case the temps start to get way up there on the ride back.

One other note, I'm really happy with the Pirelli MT43 I put on the front; bike tracks very straight in gravel, mud and snow. Now I notice the rear Trail Wing fishing around so that's gotta go next, or soon. Took the bike up a local canyon trail that 4-wheelers have turned into a scree slope, fist- and butt-sized rocks everywhere, and the bike soldiered through. Man, what a workout! Made me forget all about the cold! Stalled one time coming back down using engine braking (got too slow) but never once dumped the bike. But the Pirelli and the carb tuning were a good fit for the ride. That was fun!;)
 
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You can forgive some for not knowing that.....they weren't born yet. :p
Redline on a stock bike is close to 75 mph indicated.....good luck getting it there except down a hill!
 

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"Now I notice the rear Trail Wing fishing around so that's gotta go next, or soon". -unfortunately the stock TrailWing is a dual sport compromise tire that is not optimized for aggressive off-road riding. Not enough of us around the world ride extreme off-road to demand nor justify the manufacturing a better motorcycle tire one can simply have a tire shop spoon on. ATV tires thus remain the only reasonable alternative.
 

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Discussion Starter #17
April 2, 1958, so yeah L'il T, I'm down with that, and it was the first thing I thought of. But then, "Nah, big interglobal company like Yamaha would surely know we've moved beyond the oil crisis times of the 70s and 80s..." I guess not!! Too funny. I remember driving my dad's 68 Pontiac Ventura from Tallahassee back to Biloxi back then, wondering how 55 mph could take so much longer than 75 or 80.

Everything up here is loose gravel so getting aggressive sends the rear fishing around pretty easily. I'm hoping the Pirelli will alleviate some of that compared to the Trail Wing.

And now, back to talking about jetting at higher altitudes...:tard:
 
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