Wilsons Sandbox

On Sat, 1 Jul 2006, truette0108 wrote:

> Any other riders out there from Phoenix? Or the South West US? Anyway, > Im interested to see what jetting you use for summer HEAT. My jetting > is stock and I am experiencing a slight "flat" spot just above idle. I > am thinking about leaning the idle circuit slightly but am concerned > with operating temperatures since air temperature is between 104 and > 108 consistantly.

I don't think anybody replied to you (at least not in the group). So, I will drop this down to a more basic question: Do you need to change jetting for extreme heat? I thought you only changed jetting for altitude change or change in air filter/exhaust restriction. -- Doug Herr doug@...

I was under the impression that CV carbs compensate for altitude adjustments on their own...something to do with the diaphram. So, rejetting is unneccessary unless you modify the intake or exhaust. __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com

On Fri, 21 Jul 2006, john andruszka wrote:

> I was under the impression that CV carbs compensate > for altitude adjustments on their own...something to > do with the diaphram. So, rejetting is unneccessary > unless you modify the intake or exhaust.

Yup, I think I read that here also. Unless anybody chimes in to correct this, then as you say, we are down to intake/exhaust as the short list. -- Doug Herr doug@...

> > do with the diaphram. So, rejetting is unneccessary > > unless you modify the intake or exhaust.

Guys, All the diaphram does is only give as much air as the engine can handle without stumbling being is it's controlled by vacuum passage to the carb throat thru a hole in the slide. You can make the bike run better by jetting it according to your area. Hot air means less oxygen so need a leaner mixture, same as altitude. Most bikes come so lean on the idle circuit they hesitate and stumpble when opening the throttle fast anyway. ( Just think of what it would be like with a straight slide action carb which is why most all street carbs are VC's (vacuum controlled) ) What most do is just drill out the little brass plug hiding the air/fuel mixture screw at the bottom of the carb. Adjust this out to about 2 to 2.5 turns and get much better response out of the engine. Can also shim the needle up with a washer for some more good action. But, this will genearlly bring your fuel mileage down just a bit. I'm sure there are people in here that will get much further into it than I care too. My days of fighting the perfect jetting for a race bike was over 25 years ago. There have been many articles thru the years on proper jetting and how to achieve it. That being said, a stock KLR will run most any place just as it comeing frm the factory. .. '43 Andy in Jennings,La. '00 KLR650 w/ adjustable air/fuel needle. '02 R1150GSA 49,000 mils > for sale '03 Chevy Truck

> > I was under the impression that CV carbs > compensate > > for altitude adjustments on their own...something > to > > do with the diaphram.

I can't see how that would be... the diaphragm responds to the amount of air rushing through the venturi (the throat of the carb, so to speak) but it has no way of knowing how much OXYGEN is in that air, which is really what we're trying to adjust for when we jet for altitude. In the same way you get "out of breath" in Denver even though you're taking the same number/size of breath, the KLR gets rich even though it's sucking in the same rush of air because there's less oxygen in that air. I've never been in the mountains on the KLR, but I'd think it's probably fine up there--the thing is pretty lean from the factory, richening it up a bit (which we often do by shimming the needle and backing out the little screw) isn't a bad thing. --Luke __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com

On Fri, 21 Jul 2006, Analog Aardvark wrote:

> I can't see how that would be... the diaphragm > responds to the amount of air rushing through the > venturi (the throat of the carb, so to speak) but it > has no way of knowing how much OXYGEN is in that air, > which is really what we're trying to adjust for when > we jet for altitude. In the same way you get "out of > breath" in Denver even though you're taking the same > number/size of breath, the KLR gets rich even though > it's sucking in the same rush of air because there's > less oxygen in that air.

No clue, just repeating what I read on this group. A quick google check shows: "While riding, there are no needles to turn. Because these are CV carbs which meter fuel based on flow, they are somewhat altitude compensating. As you go up in elevation the air thins out, the flow through the carb slows, and the needle doesn't rise as high yielding the necessary leaner mixture." So, it is a bit better then a non-CV, but not perfect. -- Doug Herr doug@...

Mr. Aardvark I hate to disappoint you, but there are a couple of points here that you are misinformed about. 1. There is not less oxygen (O2) in the air at higher altitudes. There is approximately 20.9% O2 in the air at any altitude you are going to be able to ride in (at ultra high altitudes with ultra cold temps you will see differences due to some elements "freezing" out of the air. 2. The problem is less pressure to push the O2 molecules. At sea level with standard temperature and pressure (STP) you have one atmosphere of pressure, approximately 14.7 psi. At approximately 18,000 ft. you have 0.5atmospheres, or about 7.4 psi. (of course most of us will never be riding at 18,000 ft, but bear with me) The correlation you made between breathing and carburetion is partially accurate, but the reason has to do with the partial pressures of gasses and how they react. In the body O2 is pushed through the cell membranes in a process called diffusion. You must have a minimal amount of atmospheric pressure to push the O2 molecules. If you do not have enough pressure then you have to compensate by increasing the amount of O2 on the air. In medicine we do this with supplemental O2 by giving a higher % of O2, in some cases we can increase the pressure of the air that is being given, or both. This also correlates to out vehicles because we have to have four components to burn the fuel we are putting into our bikes, fuel, O2, heat, and a chemical reaction. Without a high enough pressure gradient we can not sustain an efficient fire. As in the body we compensate by adding supplemental oxygen, in our vehicles we do it by adjusting the fuel air mixture. Another way to compensate is to turbo-charge the system. This is how airplanes are able to fly at high altitudes. They boost the pressure to much higher than normal pressures. In some of the WW II war planes the boost was around 45 psi. If you know of a turbo for the KLR, please let the list know. (I did not confirm the numbers stated above, so if I am off by a small margin, please bear with me) Don Marr KLR650 in Bahrain K1100LT in Coos Bay, OR

On 7/21/06, Analog Aardvark wrote: > > I was under the impression that CV carbs > compensate > > for altitude adjustments on their own...something > to > > do with the diaphram. I can't see how that would be... the diaphragm responds to the amount of air rushing through the venturi (the throat of the carb, so to speak) but it has no way of knowing how much OXYGEN is in that air, which is really what we're trying to adjust for when we jet for altitude. In the same way you get "out of breath" in Denver even though you're taking the same number/size of breath, the KLR gets rich even though it's sucking in the same rush of air because there's less oxygen in that air. [Non-text portions of this message have been removed]

--- In DSN_KLR650@yahoogroups.com, "truette0108" wrote:

> > Any other riders out there from Phoenix? Or the South West US?

Anyway,

> Im interested to see what jetting you use for summer HEAT. My

jetting

> is stock and I am experiencing a slight "flat" spot just above idle.

I

> am thinking about leaning the idle circuit slightly but am concerned > with operating temperatures since air temperature is between 104 and > 108 consistantly. > Thanks, > Zac >

Zac, I spent several miles on my trip at both altitude and heat. IMHO, the KLR performed very well in both. I met a pair of guys touring on harleys. Odd thing about it was that one was riding a fuel injected newer bike, and the other was riding an older carbed model (carbs nearly the same as on the KLR). The carb guy had no complaints at altitude, while the newer injected Harley rided claimed he lost huge amounts of power. Even in the heat it did well. At 14,100 feet on Pikes Peak summit, I only noticed a slight loss of grunt, but barely. If you're experiencing a flat spot, you might want change out the spark plug and see if that helps. I noticed a flat spot around 3500 when the plug needed changed. It would pull hard again when it hit 4200. My bike uses some oil at highway speeds, I suspect this was the reason for my fouled plug - they don't like oil on 'em. If you've been running at high speeds, or the stock plug is still in there on a fairly new bike that may have oil fouled the plug before the rings completely seated, the plug may be your problem. While I was picking up some parts in Montana, a guy with a new 800 Vulcan had the same problem with only 3000 mile on the bike. He did the first oil change and changed out the plug. It ran fine after. For under $4 and a few minutes, it's a cheap test anyway. Give it a try and let us know how it turns out. Camo Greg