Is re-jetting necessary?
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Thread: Is re-jetting necessary?

  1. #1
    Senior Member DARIVS ARCHITECTVS's Avatar
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    Is re-jetting necessary?

    Hi!

    I'm in Minnesota at 930' above sea level, and my 2010 T-Dub runs just fine on stock jets. If I took this lil' beast up to Imogene or Engineer's Pass in Colorado (9,500'-10,500'), do I have to re-jet? And, if so, please tell me what I need to buy to modify my T-Dub and where I can buy it.

    Thanks guys!

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    DARIVS ARCHITECTVS
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  2. #2
    Senior Member RockyTFS's Avatar
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    It will still run at that altitude, but not well. 4th and 5th will be useless which is not a big deal because you can't go that fast on either pass and live to tell about it. The problem will be that you will have no power to climb a steep hill in any gear and there are several near the top. I went up Cinnamon and back down Engineer a year and a half ago with my TW on a 122 main jet and 13/50 gearing. I made it up the bad rutted steep section just before the top of Engineer but my buddy's TW with stock jet and gearing did not. I could only use first gear on the last 1,500 feet of either pass. You would be well advised to go down to a 118 or 120 as long as you did not try to ride below 8,000 feet before switching back. I would suggest putting a 55 on the back sprocket as well. These passes are in bad shape in places from so much ATV traffic.

    You can get these jets from Yamaha and your dealer. Changing out the jet is not difficult, but you will need a JIS screwdriver to get the bowl screws out, then you can replace them with SS Allen M4 x10 bolts which makes the job much easier in the field. It's a bit easier if you take the tank off, but with Allens you don't have to. Look at the parts photos in the Write-ups. You need to hold the jet holder with one wrench while undoing the jet with another. The holder is 8mm and the jet is 7mm.

    You probably should wait until next summer as both are now closed by snow.
    jbfla, MtnMan75, SanDue and 2 others like this.
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  3. #3
    Senior Member Fred's Avatar
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    Was recently summiting some 11,600+ peaks with no jetting changes, just a freshly cleaned air filter and a few 9/16ths holes drilled in the airbox cover running 13 x 55 sprockets. Bike wasn't "frisky" but accelerated nicely up steep, loose slopes and churned through steep, icy patches of snow OK.
    As Rocky points out you will want a first gear low enough to be usable at elevation.

    If you make changes before doing them make note of those initial good running settings. When you get back home you'll want to readily get the old good running bike restored again.
    Masking tape on the inside of a cover panel is a good place to mark everything from valve clearances, spark plug gap, common torque values (if your'e into that sort of thing) to the jets and mixture screw settings alluded to above. Same painter's tape can also be used to label & secure anything removed someplace where they can be found again. More labeled tape under cover can remind you of jet storage location.

    Tri-Ox.jpg

    Reduced partial pressure of oxygen up there may have you struggling a bit too. While we don't have Doctor McCoy's magic Tri-Ox Compound you can prepare yourself somewhat by packing light, staying well hydrated and doing a bit of cardio back home to be as fit as possible since this will be significantly higher. for you. Acclimate in stages if possible, spending a night or more at mid-elevations in Colorado should be easily done. Headaches may be common.

    Some conservative health tips from a ski resort purloined off the internet:
    "

    1. A quick way to adapt to the elevation is to carry a portable oxygen canister, taking a shot or two whenever you feel winded. You can buy or rent oxygen concentrators in the Breckenridge resort, and the medical stations there will have oxygen on-site for sick skiers.
    2. Take it Easy
      It's understandable that you're eager to hit the slopes, but take it slowly. Over-exerting yourself will only make it harder to adjust to the elevation. Try a low-impact activity on your first day, such as snowmobiling. Breckenridge offers many alternatives to skiing and snowboarding, so you can still enjoy yourself while you get acclimated to the altitude. If you are flying into Denver, consider flying in a day early and staying in Denver the first night. Denver's elevation is 5000ft. Sleeping overnight in Denver will acclimate your body to 5000ft before you make the ascent to 9000ft. This two-step altitude adjustment gives your body more time to adjust.
    3. Stay Hydrated
      Drink plenty of liquids. High elevations can cause fluid loss, so it's important to stay well hydrated. Stick with water or liquids that replace electrolytes. Avoid sugary or caffeinated beverages such as soda-pop. These liquids act as diuretics and can dehydrate you. Drink lots of water! Frequent urinating from consuming so much water is much better than laying in bed with a splitting headache.
    4. Eat Right
      Stop in at Breckenridge's world-class restaurants to recharge. A meal high in carbohydrates will improve your body's ability to absorb oxygen, and will give you the energy needed to adjust to the elevation. Avoid salty foods - the sodium will increase your blood pressure, which can exacerbate the symptoms of altitude sickness. When we arrive in Summit County we like to eat at a place called "Noodles & Company". They have delicious noodles that are high in carbs.
    5. Take Your Vitamins
      It's been shown that taking iron supplements makes it easier to perform aerobic activities (like skiing) at high elevations. Consult a doctor first, though - iron is toxic in high doses. Taking 120 mg of Ginko Biloba in the weeks leading up to your skiing getaway, and maintaining that dosage during your trip, can also reduce the time needed to adjust to the altitude.
    6. Hold the Beer
      Alcohol and tobacco can impact your body's ability to absorb oxygen. Of course, it's hard not to indulge yourself when in beautiful Breckenridge, Colorado! Swing by the famous Breckenridge Brewery and knock-back a cold one once you feel acclimated to the elevation.
    7. Get Medicated
      Drugs such as Diamox (Acetazolamide) can reduce the symptoms and duration of altitude sickness. Ideally, Diamox should be taken a few days prior to your trip, but it can also be used on the spot if you start feeling ill. Keep ibuprofen or acetaminophen on hand to prevent headaches.
    8. Descend to Sleep
      Sleeping at a lower altitude makes it easier to adjust to the rarefied air of Breckenridge. You'll feel better and have more energy after a good night's sleep in a lodge at a lower elevation. Lodging is scattered all up and down the mountains, with some lodges being higher than 10,000 ft. As a matter of fact when olympic ski teams contact us to book a stay the first question is always what elevation we are at. The Ski Silverthorne lodge is at the bottom of Buffalo Mountain at around 8,500 ft.
    9. If All Else Fails
      If you've feeling ill, descend to a lower elevation and work your way back up to the resort gradually. Sometimes the best remedy is simply time. While no one wants to lose out on a day's fun, you'll feel even worse if your whole trip is wrecked due to prolonged illness.
    Last edited by Fred; 10-22-2019 at 07:33 PM.
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  5. #4
    Senior Member MtnMan75's Avatar
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    I'm not sure if it is the displacement combo coupled with the lower compression ratio, but this thing seems capable of running on either extreme of an ideal mixture. Other toys I've had will start sputtering and complaining right away when you stray away from the 12-14:1 range and they are all larger displacement. Usually a smaller engine is more finicky about it, but the TW seems to keep running. Longevity may take a hit if you keep it lean over the long haul, but there are so many people that have put tons of miles on them without messing with it. I like to tune all of my bikes, but I think it's just more that I like to turn a wrench or solder a component as much as I like riding. Just playing with mine, I've had the temps on the cylinder head going colder and the header pipe getting hotter because it was so rich it must have been burning into the header pipe... and STILL the bike kept pulling. Lean rears its ugly head fairly quick with the temperatures if you are monitoring it and it's always a condition that will do more harm than too rich in the same time frame. I like to use one of those Infra-red tools while I am re-jetting and using the butt dyno. Stock mine was running around 350-390 degrees beside the plug (head temp), and header just 6 inches from the exhaust port was mid 500's at 3000', low humidity and ambient outside of 70 degrees. I've brought that temp down a little by getting my mixture richer and the power across the throttle range is a little better, but don't expect any big power leap from it. Currently waiting on a machine shop to fabricate and weld on a bung for a new AFR so I can put some actual numbers to this.
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  6. #5
    Senior Member Fred's Avatar
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    +1 on infra red temperature guns.
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  7. #6
    Senior Member GaryL's Avatar
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    My attitude on this subject remains the same. If it ain't broke then don't fix it! For the occasional trip up into the high country I would expect the TW will not perform as it normally does at your usual elevation. Keep in mind that old truth we have all heard many times before, For every action there is an equal and opposite reaction. Re Jetting for high elevation will have a benefit in the higher elevation but could also be non beneficial at your normal elevation. If you live in the high country then of course you go for it but as a visitor I would leave a good running carb alone. BTW, when you do get up in those high places you will notice your body does not perform as it normally does either and there is no re jetting for it.

    GaryL
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  8. #7
    Senior Member Fred's Avatar
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    Listen to these fairly un-altered machines above 11,000 ft. Mine needed to be downshifted into first gear only for the switchbacks, second gear worked fine for loose gradients approaching 20%. No blubbering I could detect.
    Now my bike has the TTR's 223cc 6-speed with a TW200 carb so was running a bit lean anyways. As such my experience may not be comparable to a stock bike. However Admiral was right behind me ona stock carb TW for the entire ride and he never complained of disappointing performance. Maybe he can share his experience.
    My point is not that it is mandatory that one should, or should not make specific changes for a 10,000 ft ride. These bikes can be fairly versatile. My Mr.Gizmo TW200 has sea level tuning and runs acceptably over local 9,000 ft. Sierra passes with a noticeable, but not crippling loss of power.
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  9. #8
    Senior Member admiral's Avatar
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    When I was in first gear it was because it was steep as shit. I would have been in first gear if I had to ride that steepness at 10 ft. My TW didn't have any problems with the stock jets up here with Fred and ejfranz.

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  10. #9
    Senior Member Fred's Avatar
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    Awesome photo Admiral!
    First time up there where impending thunderstorms didn't make me want to stand a bit further away from that flag waving metal lightning rod.

    Betty Doesn't like getting zapped. Betty Boop.jpg
    Last edited by Fred; 10-23-2019 at 12:18 PM.
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  11. #10
    Senior Member RockyTFS's Avatar
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    Cinnamon Pass is 12,640 feet, Engineer Pass is 12,800 feet, and Imogene is 13,114, NOT 9,500 to 10,500. I stand by my experience of two summers ago. That last 2 or 3,000 feet is a whole 'nother ball game.
    littletommy and Fred like this.
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