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tuning for altitude

Old 05-27-2011, 02:41 AM
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Question tuning for altitude

I have two problems, three if you include the wife. -lol-
First of all, two mechanics have looked at my carbs, all clean and now back to factory specs. The second guy tells me this (1st prob) jumping and spurting I feel under acceleration may be due to the lack of maintenance of my valves. He mentioned it should be controled and adjusted after every 24000 Km's. Is this true? If so it needs to be done anyhow I figure.

Secondly, the carbs have been put back to factory specs, so I am now getting the milage I used to get BUT I live in switzerland, already at 400 meters (1200 feet give or take); and when I tried yesterday to do a mountain pass, up to 2100 meters (which I did last year with power all the way) the bike lost all power and started to really STRUGGLE , hell it felt like it was having a seizure. This was at about 16-1700 meters. Is it because the factory specs are for sea level? I thought the bike was just not getting enough fuel, because down around 400 meters it pulls hard, aside from the jumping and spurting. Could it be that I have to dial the carbs up a bit more? Any ideas would be appreciated!!!

This is a huge issue for me as I love to ride from here to heaven and back; having that said, my backside was screaming... what's up with the stock seat? I hear all about these Corbin seats and they do look comfy but they look higher as well. I have recently riden a hawk with a LOWER seat, the foam cut away into a saddle. SUPER SUPER COMFY. Are there any properly made seats like this that I can order?
Also, any ideas on which brake calipers I can switch to, to get this thing to stop BEFORE I run over the neighbors cat? I figured steel lines will also be in the mod list for my bikes future.

Thanks alot for any and all feedback!
Ah no wait... TIRES, I am running pilot power 2ct, BUT they wear out to quickly as I commute with the bike. Any ideas on a good tire for commuting, that won't slip out when having fun!?!
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Old 05-27-2011, 07:57 AM
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The valves should be checked and adjusted, if necessary, every 24,000 km.
The shop manual which can be accessed through the Knowledge Base on this forum sets out jetting changes for riding at higher altitudes. There may be other carburettor issues you have to deal with.
Sargent and Corbin seats are popular but, if you like the stock seat with some foam removed, find out where the other rider had it done. It's probably the cheapest solution.
Brake modifications are dealt with in a number of threads including List of Bolt-On Front Brake Mods??????
There are lots of acceptable tires. Look at what other riders in the Alps are using.
You may have expressed latent aggression toward your spouse. There ought to be a good marriage counsellor in your area. It's a more important issue than problems with your bike.
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Old 05-27-2011, 08:40 AM
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Originally Posted by swiss-storm View Post
Is it because the factory specs are for sea level? I thought the bike was just not getting enough fuel, because down around 400 meters it pulls hard, aside from the jumping and spurting!!!
While checking valves is important, I doubt their performance would be correlated to altitude if they're out of spec. Not fully positive on this though...

If anything, as you gain altitude, your bike runs too rich. As you go up in altitude, you are putting the same amount of fuel into air with less oxygen, so the ratio becomes unbalanced. Popping and spitting at lower altitude indicates a rich mixture too (I think). It's a long shot, but if you had dirty carbs, their passages may have been restricted, and now that they're clean, they're allowing more fuel through, and thus your rich condition. Or maybe factory specs can't handle the elevations that you're running at. It's possible that turning the idle mix screws in will help... maybe others at elevation have tips on what they've done?
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Old 05-27-2011, 08:44 AM
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Originally Posted by comedo View Post
You may have expressed latent aggression toward your spouse. There ought to be a good marriage counsellor in your area. It's a more important issue than problems with your bike.
More important? I'd say it's a tie.

Now that the brakes on my bike are upgraded, I'm looking for upgraded brakes that will fit my wife. So I can stop her from nagging faster.

And to the OP, I would think you need less gas at altitude since there is less oxygen. You'll need to lean out the carbs a little bit, but that might make it run worse at your typical elevation. The manual does list high altitude specs, so maybe start there if it's running good at low altitude with factory specs.
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Old 05-27-2011, 09:46 AM
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Search Flo-commander. This would be the simplest solution to quickly lean the carbs for occasional high elevation rides. Otherwise trade for an injected bike
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Old 05-27-2011, 11:54 AM
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mechanic seems to believe it runs too rich as well, and that maybe MAYBE when another garage had stripped it down last year, they may have inserted the jets backwards; explaining the jumping as the rear is now too rich and burning improperly and the front burning to quickly. Also why in the mountains the things just about floods.
The brake issue I think I can get help with, as it turns out he has experience with that request.
As it is I will look into the carb setting on my own as well as this flo-commander. thank you all for your two cents; it's really great to have a few people pile their ideas on an issue, helps to attack from all angles.
At the same time though, just a quick comment to a certain gent who posted here. I am certain there are many great councellors around but my marriage is fine. Your sense of humour on the other hand could use a boost. I think you can find that in the "learn to take it easy" isle at your local walmart. Aside from that, I have no intention of flamming anyone on this site, I quite appreciate what it has to offer.
thanks again
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Old 05-27-2011, 12:13 PM
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I live at sea level, and with stock main jets, .020" (0.5mm) needle shim, 48 pilot jets and pilot screws out 2 1/2 turns, mine runs strong up to 6,000 feet (over 1800 meters), which I did just a few weeks ago.

I should add that before I got the Yoshimura slip-ons, I ran stock pilot jets (45) with the 0.5mm needle shim. With that set-up and stock mufflers, I ran it at over 1800 meters several times with no problems. You didn't mention if you had stock exhaust or not.

Last edited by VTRsurfer; 05-27-2011 at 05:31 PM.
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Old 05-27-2011, 12:14 PM
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Ask Mike (8541hawk) , he knows everything!
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Old 05-27-2011, 12:16 PM
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Swiss, I'm pretty sure comedo was joking . . .
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Old 05-27-2011, 12:34 PM
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Originally Posted by swiss-storm View Post
mechanic seems to believe it runs too rich as well, and that maybe MAYBE when another garage had stripped it down last year, they may have inserted the jets backwards; explaining the jumping as the rear is now too rich and burning improperly and the front burning to quickly.
The emulsion tubes (part that the main jets screw into) are specific to the front and rear carbs as well. Picture jacked from 8541Hawk:

https://www.superhawkforum.com/forum...sion-tubes-jpg

You may also be interested in this thread:
https://www.superhawkforum.com/forum...-set-up-24769/
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