[indigo]

Here in New Hampshire I'm at sea level but can be in the mountains within a short distance. If I set up my carb at sea level (or just above) how high of an elevation will this take me before my bike experiences performance issues? I'd rather keep my bike tuned to get good gas mileage than be a performance oriented machine ... doh, TW200? If it is tuned for handling the elevation changes I can set up the sprockets to bring the gas mileage into line with what I'd like to get. How about some feed back? ... Thanks

 

[jbfla]

At sea level the stock US TW is slightly lean. As you rise in elevation there is less oxygen, so the mixture becomes richer.



Other than opening the idle screw a 1/4 to half turn (depending on what it is set at now), I would leave it as it is.



jb

 

[motorfish]

I have a 2009 TW that has stock sprockets and carb settings from the factory. We spend the winters in Arizona (1000ft elev) and the summers in Colorado (8500ft elev). I have ridden from 500ft to over 12000ft (Cottonwood pass 12100ft, Monarch pass 11300 and Trailridge Road in Rocky Mountain National Park 12100ft) and have experienced a 10-20% drop in power climbing in elevation, but did not experience a "miss" until passing above 11000ft and that was only while wide open. I would take a ride into the mountains, as they seem close by your location, and see how the TW performs before I would change much.

 

[indigo]

OK, then the 0 to 6000 foot elevation change here should only affect the carbed engine very little. I'm told there are some awesome fire roads a hour or so's ride out into the White Mountain region. I was concerned to what degree the carbed bike would be affected as compared to an injected one. The sprocket change up would only be a concern if the fuel mileage factor became an issue.

 

[admiral]

Thought I'd throw out my experience in regards to elevation. Where I live and purchased my TW, the elevation is around 2,500ft. A couple of years back I went on a camping/riding trip where the elevation was around 7,000ft +. I noticed a huge drop in power and idle rpm. Looking back, prior to this trip, I had the same idle and power loss on other rides when I was at higher elevations as well. It just didn't dawn on me what the problem was. My solution at the time was as jbfl stated, I adjusted my idle screw to increase rpm which seemed to help some. Didn't think to do anything more as it wasn't really a big issue at lower elevations.



Then I read somewhere in this forum, when it was hosted by the old forum host (commonly referred to as the old forum), about drilling some holes into the side of the plastic air box cover. So I drilled 4 holes about 1/4 inch diameter in the cover and placed tape over them when at my normal lower riding elevation.



So, last summer on my first ride at a higher elevation at Buck Park Cabin area, which is over 7,000ft, I again noticed the power and idle loss. I then removed the tape from the 4 holes, and without having to adjust the idle screw as before, got the power and idle speed back to near normal. I was really surprised by how much power I got back, not just idle rpm. I'm not really recommending drilling holes in the air box cover per se', but it worked for me. Proceed with caution and do a lot of investigation prior to trying this.



Also of note, I replaced the tape over the air box holes with rubber grommet plugs, which are easier to remove and insert back in.

 

[qwerty]

I like the rubber grommet idea. Less mess than tape.



An engine tuned for maximum fuel efficiency is also tuned for burning valves and pistons. Pick your priorities with care.



The 49-state TW carb tune is perfect for absolutely nowhere under 6000 feet altitude. Every stock TW I've ridden is hard to cold start, takes forever to warm up and run right, has poor off-idle throttle response, has a lean surge in 5th gear at a steady cruise of 35-37mph in cool weather, and the engine runs hot. If this sounds good to you, keep the stock tune. If you'd like easier cold starts, faster warmups, better off-idle throttle response, smoother mid-range cruise, a cooler running engine, and more power, go one size bigger on the main, put a thin flat washer under the needle circlip, and open up the pilot screw. Of course, you'll lose about 2.145678901mpg of fuel efficiency. The bike will still be a bit lean at sea level and return good efficiency, but should be spot on heading up the mountains where the grade can cause over-heating with a lean tune, to slightly rich at 6,000 feet, where you pop the grommets.



Barring major changes of 10 teeth or more, changing sprockets isn't going to affect fuel efficiency too much. 14/50, 14/47, 15/50, and 15/54 yielded about the same efficiency for me. 14/54 and 15/47 both saw efficiency slip a bit. I'd stick with the stock sprockets or 15/54 if my mountain roads were paved, 14/54 if dirt.

 

[lonedave]

"Every stock TW I've ridden is hard to cold start, takes forever to warm up and run right, has poor off-idle throttle response, has a lean surge in 5th gear at a steady cruise of 35-37mph in cool weather, and the engine runs hot."



Boy that almost fits my bike to a tee! My new to me 2000 had 98 miles on it when I got it about 2 months ago and now has about 450. I'm at around 400' and though it starts just fine in 30+ degree weather, the other symptoms are spot on. I saw another post of yours with the part numbers from Stadium Yamaha for the pre-2001 main jets and have a 116, 118, and 120 on the way. As soon as I get them, I'll be pulling the carb to do your 3 step mod from another of your posts. After not riding a bike since about 1990, it feels good just to be on one again, but that 35 - 40 mph surging on the street is pretty annoying. I know the running hotter can't be a good thing, but it is kind of a nice foot warmer in the winter! I also like the 72 - 77mpg I'm getting now, but I think I can live with a little drop if I can lose the surging.

 

[TW2007]

I have spent much time in Utah and Colorado with my TW200 and the carb is stock and so was the gearing.



I have had no problems with performance from sea level up to 10,000. The bike runs just fine.



If I was regularly riding above 10,000 feet I would probably re-jet to a 118.



But as was recommended above test things out before changing anything.

Mike