Question on high altitude jetting/operations
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  1. #1
    Junior Member DaveyM's Avatar
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    Question on high altitude jetting/operations

    I'll be taking my "new" 2000 TW out to the San Juans riding in a couple of weeks along with my son riding an overhauled TTR125. The bike has the stock pre-2001 TW carb, with all the stock jets. I've heard others say they rode the stock jets up to 9000 feet, but we'll be no lower than 6000 and as high as 13,000 feet. I'm not that heavy, so I think the TW will still have the oomph to get me there and back. What I'd like to know from those who know the older carb, is what I should prepare to modify once we arrive at our 6000 foot base camp. Unlike the TTR, Yamaha has no service manual suggestion for high altitude TW modifications. The bike is usually a commuter at 1000 foot elevation, so whatever mods would need to be reversible. I do work with engines a lot, but I have NO experience with the TW save a recent carb cleaning. Any suggestions would be appreciated. I've perused many past threads here, but still don't feel comfortable that I've got a solution for a pre-2001 carb. Any part numbers or sources would be appreciated. Thanks!

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    Senior Member B-dub's Avatar
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    Did you see this post?
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  3. #3
    Junior Member DaveyM's Avatar
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    Quote Originally Posted by B-dub View Post
    Did you see this post?
    Yes, I read that earlier. Although the airbox cover mod should work, the 2001 and newer TW's have a different carb than my bike has, so the results may not be the same. I'm hoping for a mod, perhaps with jetting (such as the size and part number of the jet) will be brought forward by someone who has done the deed and found it worked. Thanks!

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  5. #4
    Junior Member DaveyM's Avatar
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    Let me ask the question another way (I now have the jet part numbers, BTW)--which main jet size worked best between 10,000 and 13,000 feet? There has to be at least one San Juan TW rider that has some experience with this on the forum.... I hope! I know I'll basically be pushing the bike uphill then, but at least the engine will give my hands a little heat to warm up!

  6. #5
    Senior Member Leisure Time Larry's Avatar
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    Davey man, this is a worldwide forum. I know of a San Juan, Puerto Rico. I live near the San Juan Islands, but I had to look up that you probably mean the mountains in sw Colorado. So, welcome to the site! Now let's see if we can help you out. These bikes are generally set up lean stock, and a lot of dubbers have gotten pretty close to the sun with the stock setup. Your stock jet should be a 114. If I was planning to go that high I would probably order the next two smaller jet sizes, the 112 and the 110. I would probably pre-install the 112 and carry the 110 and the stock 114 to rejet in the field if the 112 wasn't getting the job done. For $5/ea, I think keeping a variety of jets in the toolbox for various conditions is a good idea. I'd rather have them, then decide later I want a different one only to have to wait for shipping. I would also carry a small screwdriver, modified if needed, to do on the fly changes of the pilot screw. I have not personally ran this set up nor have I ran that high, but this is my 2 cents until you can get someone else to chime it. Good luck.
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  7. #6
    Junior Member bradcarter's Avatar
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    I was just up in Pagosa Springs, CO two weekends ago and my stock jetted 2013 TW was starting to have a hard time around 8000 feet and above (didn't go above 10,000). Power was still decent but what was getting me was anytime I'd come up to a log, rock whatever and give it some quick throttle to get over the obstacle the engine would hesitate for about a half to full second then take off. According to the carb tuning thread this is a sign of running rich.

    I worked around it fine but since I never go lower then Albuquerque (5300') I'm going to rejet before I head back up there in a couple weeks. I'm 225 pounds and the power was good enough for me, it probably depends on what kind of trails you'll be doing. Steep rocky ATV trails that required slow manoeuvring then a quick acceleration is where it would get me. No problem starting the bike when I was up there either.

  8. #7
    Senior Member lizrdbrth's Avatar
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    Yamaha parts fiche don't tend to show alternative jets for the TW. But they're easily deciphered and cross-referenced by their suffix numbers, which are the jet size, divided by two.

    288-14343-57-00 is the PN for the stock 114. The "57" indicates size. 114/2=57.

    288-14343-56-00 = 112

    288-14343-55-00 = 110 (listed as an '85 BW200 part). And so on.


    I know they all existed at one time but some have recently been declared obsolete. I ran the part numbers for all of the above down to a 108 and a number of online sources CLAIM to have them but if I were you I'd call first and make sure the source checks physical inventory. I've never tried to source smaller ones but my local dealer has some of the obsolete larger ones sitting on his shelves.



    Last edited by lizrdbrth; 07-17-2013 at 04:39 PM.
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  9. #8
    Junior Member DaveyM's Avatar
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    Quote Originally Posted by lizrdbrth View Post
    Yamaha parts fiche don't tend to show alternative jets for the TW. But they're easily deciphered and cross-referenced by their suffix numbers, which are the jet size, divided by two.

    288-14343-57-00 is the PN for the stock 114. The "57" indicates size. 114/2=57.

    288-14343-56-00 = 112

    288-14343-55-00 = 110 (listed as an '85 BW200 part). And so on.


    I know they all existed at one time but some have recently been declared obsolete. I ran the part numbers for all of the above down to a 108 and a number of online sources CLAIM to have them but if I were you I'd call first and make sure the source checks physical inventory. I've never tried to source smaller ones but my local dealer has some of the obsolete larger ones sitting on his shelves.
    Since I asked the question, I took some of the earlier forum posts that gave the P/N for smaller jets and went with it, just in case (and those $5 jets won't make one poor). I found the 112 jet is no longer available in Yamaha distribution, but the 110 was (4 jets in stock in the whole US of A), so I have one coming. I haven't asked Sirius up in Canada, who know how to get jets for about anything (including ancient bikes). Since no one has definitively said "I got such and such a jet and rode the bike successfully up to 12,000 feet with it," I guess I'm the test banana, and will report back after the trip. There are lots of Youtube vids of TW's up in the San Juan high passes, so I know it can be done. Right now my plan is the 110 jet, and trying the airbox cover removal if things really suck on the rich side. GIven that the 114 is considered lean at lower elevations, I figured the 110 should be spot on from 8K up to 13K. Thanks.

  10. #9
    Senior Member trailscout's Avatar
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    I currently have a 105 in my TW. Went up over 11,500 the other day and it ran strong all the way. Lowest elevation in my area is 7,000.

    I'm using Keihin 99101-393-105. It has a round head with a screwdriver slot. The plastic cup won't fit on the smaller round heads. I bought the jets at PJ Motorsports.

    Your Keihin-Mikuni Jets Store-Pjmotorsports.Com

    I realize a 105 sounds kinda lean but a 108 did not clean it up. Fuel level is set using a caliper with the carb upside down. 29mm I think.

  11. #10
    Senior Member lizrdbrth's Avatar
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    FWIW this is the best method of setting float height so that you'll know what you've really got. The ruler method will only be ballpark, at best.

    Early carb shown. The late model carb's fuel level is set at even with the float bowl gasket surfaces.






    Last edited by lizrdbrth; 07-21-2013 at 10:20 AM.
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