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Re:How FULL do you fill your tank & what kind of MPG?
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TOPIC: Re:How FULL do you fill your tank & what kind of MPG?
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Agpilot (User)
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Re:How FULL do you fill your tank & what kind of MPG? 1 Week, 6 Days ago  
Sorry guys you get a leaner fuel mixture at higher altitudes with the CV! If you are running a slide type carb you will get richer. Wind resistance has nothing to do with it. There is not any need to start re-jetting when you change altitudes. Just leave it alone and it will take care of itself with a constant velocity!
 
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Last Edit: 2017/08/09 05:53 By Agpilot.
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#1019376
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Re:How FULL do you fill your tank & what kind of MPG? 1 Week, 5 Days ago  
Agpilot wrote:
Sorry guys you get a leaner fuel mixture at higher altitudes with the CV! If you are running a slide type carb you will get richer. Wind resistance has nothing to do with it. There is not any need to start re-jetting when you change altitudes. Just leave it alone and it will take care of itself with a constant velocity!

I remember a thread with a member that was getting well over 50 mpg, and everyone jumped in stating he was running too lean.

Turned out that he was running at high altitude.

He did have less gas running though his carb, but he also had less air running though also due to the thinner air.
And was making way less power than someone at sea-level, which is why he was burning less gas and getting better MPG,
but the bike was also "jetted right", nothing needed to be changed.
 
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#1019388
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Re:How FULL do you fill your tank & what kind of MPG? 1 Week, 5 Days ago  
MidwestMike wrote:
Agpilot wrote:
Sorry guys you get a leaner fuel mixture at higher altitudes with the CV! If you are running a slide type carb you will get richer. Wind resistance has nothing to do with it. There is not any need to start re-jetting when you change altitudes. Just leave it alone and it will take care of itself with a constant velocity!

I remember a thread with a member that was getting well over 50 mpg, and everyone jumped in stating he was running too lean.

Turned out that he was running at high altitude.

He did have less gas running though his carb, but he also had less air running though also due to the thinner air. And was making way less power than someone at sea-level, which is why he was burning less gas and getting better MPG,
but the bike was also "jetted right", nothing needed to be changed.


Ah, the latter statement makes total sense. Starve the carb, putt down the road, get better mileage.

A 'CV' carb is above my pay grade. Didn't even know we had them and since there's a slide inside my carb I assumed that's what I had (a slide carb, and maybe I DO?). I'm just an old school slide carb kind of guy which is why I made the statement about a richer mix (which was correct).

Interesting. Are all the Roadie carbs CV?
 
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Last Edit: 2017/08/09 11:36 By MidnightRide.
 
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#1019390
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Re:How FULL do you fill your tank & what kind of MPG? 1 Week, 5 Days ago  
MidnightRide wrote:
MidwestMike wrote:
Agpilot wrote:
Sorry guys you get a leaner fuel mixture at higher altitudes with the CV! If you are running a slide type carb you will get richer. Wind resistance has nothing to do with it. There is not any need to start re-jetting when you change altitudes. Just leave it alone and it will take care of itself with a constant velocity!

I remember a thread with a member that was getting well over 50 mpg, and everyone jumped in stating he was running too lean.

Turned out that he was running at high altitude.

He did have less gas running though his carb, but he also had less air running though also due to the thinner air. And was making way less power than someone at sea-level, which is why he was burning less gas and getting better MPG,
but the bike was also "jetted right", nothing needed to be changed.


Ah, the latter statement makes total sense. Starve the carb, putt down the road, get better mileage.

A 'CV' carb is above my pay grade. Didn't even know we had them and since there's a slide inside my carb I assumed that's what I had (a slide carb, and maybe I DO?). I'm just an old school slide carb kind of guy which is why I made the statement about a richer mix (which was correct).

Interesting. Are all the Roadie carbs CV?




All Roadstars before 08 are factory delivered with constant velocity carbs. They have been around for years... I knew the difference 50 years ago. You are not putting around and starving the engine. You are running the mixture necessary to get max performance at altitude. You lose 3% of HP every 1k of altitude you gain in a normally aspirated engine no matter what carb/fuel injection you run. If you have a round vacuum operated slide it is CV.
 
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#1019394
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Re:How FULL do you fill your tank & what kind of MPG? 1 Week, 5 Days ago  
Agpilot wrote:

All Roadstars before 08 are factory delivered with constant velocity carbs. They have been around for years... I knew the difference 50 years ago. You are not putting around and starving the engine. You are running the mixture necessary to get max performance at altitude. You lose 3% of HP every 1k of altitude you gain in a normally aspirated engine no matter what carb/fuel injection you run. If you have a round vacuum operated slide it is CV.


I didn't know that. I grew up a two stroke guy and have always had bikes with regular slide type carbs, with the possible exception of a few street bikes including my Suzuki RF900R. A CV carb seems like it could invite problems once its ages a bit. Great for the auto adjustments at elevation though.

This makes me wonder about the problem I had a few days ago when climbing a mountain in 5th gear and having the bike crap out a bit or seem to be losing a cylinder like it was fouling a plug, losing spark, had water in the fuel, or starving for fuel.

As soon as I downshifted and raised the revs everything seemed normal. On the way down the other side and back home no other issues. We live at about 2200 feet here in Las Vegas, the mountain pass peaked at 5500 feet.

May not have been a CV issue but interesting to know and consider; more vacuum at higher revs hence a better balance.

Thanks Ag--
 
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#1019406
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Re:How FULL do you fill your tank & what kind of MPG? 1 Week, 5 Days ago  
OK so I rounded up a good hole punch, sharpened the tip a bit, and gently tapped into the soft neck metal. I was surprised at how soft it actually was and how easy it was to pierce. Poked three holes in about a minute. Super easy fix!

I'm only about a gallon down but will fill it up to the holes, run a couple of gallons out of it, then fill it back to the holes and check the mileage. After that I'll do what I can to run it dry and see how much gas I can squeeze back into it for my own data purposes.

Your actual holes and mileage may vary.

And FYI, if you blow up your bike, toast your britches, and burn your house down (or your whole neighborhood) because you tried this, it wasn't my idea. Read further up the post before you start sending lawyers my way!



And here's looking down into the neck sleeve after the holes were punched:

 
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#1019407
G_Conway (User)
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Re:How FULL do you fill your tank & what kind of MPG? 1 Week, 5 Days ago  
neck line + about 5 pulls
 
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Gerry
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#1019433
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Re:How FULL do you fill your tank & what kind of MPG? 1 Week, 5 Days ago  
Thanks for the pics MidnightRide! I look forward to hearing about your results
 
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#1019436
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Re:How FULL do you fill your tank & what kind of MPG? 1 Week, 5 Days ago  
I have no problem filling my tank up the neck and I have not spiked it. What is the purpose of spiking when we have a fuel vent tube? I'll have to watch closer on my next fill. maybe I'm missing something.

Update: I wasn't filling it up higher than the bottom of the neck! I thought I was but filled up today and realized I wasn't
 
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Last Edit: 2017/08/10 13:13 By Ctkog.
 


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#1019438
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Re:How FULL do you fill your tank & what kind of MPG? 1 Week, 5 Days ago  
Ctkog wrote:
I have no problem filling my tank up the neck and I have not spiked it. What is the purpose of spiking when we have a fuel vent tube? I'll have to watch closer on my next fill. maybe I'm missing something.

FYI I found a really cool elevation map HERE: http://elevation.maplogs.com/

You know, you make a good point.

For me, once the fuel hit the bottom of the filler neck the neck would fill up quickly, then it would sink down into the tank, and then fill up again, down into the tank, and so on SEVERAL TIMES until I'd finally give up on it LOL. Apparently it just doesn't vent quick enough and maybe the long rubber vent tube under the tank has a sharp bend or kink in it. I have to pull the tank off again when my new cables get in so I'll check a little better next time I pull it off.

So here's what happened today with the new holes. I was down about a gallon so before heading out on this trip so I started filling it. Instead of stopping and then filling only the neck when it hit the bottom of the filler neck, it just kept rising. I was suspicious so I stopped to see if it was going to go back down into the tank, AND IT DIDN'T. It was continuing to fill as it probably should have been doing all along.

So I tried to take it up to the holes and that hose was running so fast that it overflowed the tank a bit. I couldn't get that nozzle to trickle. So I stopped at about 1/4" below the holes and went for a ride.

THIS SAVED SO MUCH TIME AT THE PUMP!! It was super fast compared to before.

We planned a 127 mile afternoon loop which took us through the town of Nipton, CA, elevation 3000', which was just in the news because someone bought the entire town to turn it into a marijuana empire (about 50 miles south of Las Vegas).

We ran south down I-15 into an irritating headwind, riding 2-up, at about 80 MPH. Hit the Nipton turnoff 44 miles down the freeway and putted east at about 60 to Nipton. Took some pics, hydrated (temps were about 100*), and continued east back into Nevada, crossing a mountain pass at 4900' elevation.

Hit the remote Nevada desert town of Searchlight, elevation 3500' (former Senator Harry Reid's hometown, LOL) and opted to take a side leg further east down to an isolated Lake Mohave Cottonwood Cove Marina, elevation 650', where we'd never been. That was about a 30 mile leg down and back, way downhill to the river and straight back up to the highway, a 2850' elevation change each way.

Headed north back toward Boulder City, east of Vegas, averaging around 90 MPH for 35 miles while trailing a BMW up a desolate back highway as the sun set over the mountains. Hit the freeway west and ran freeway speeds the rest of the 20 mile ride home, elevation 2250'.

Filled up after getting home, this time at a Chevron station with a slower running gas pump. Odometer read 164 miles at that point. Filled back to the same level and put in just under 3.5 gallons. Mileage came in at 47 MPG for this run, not bad for 2-up at speed, changing elevations, and into the wind. And the fuel gauge still read above 1/4 tank when I gassed up.

Next I'll see how low I can run the tank to see how much fuel I can actually squeeze into it overall.

Once again, it is SO MUCH FASTER to try to get to the top of the filler neck now and frankly I've never taken the needed time to get it up to the levels I ran today. Now it's just like filling a car or anything else; no waiting.

Didn't detect any overflow or leakage issues as a result of the extended fill. But splashing on the tank is clearly something I have to deal with now when trying to really top it off.


 
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Last Edit: 2017/08/10 11:07 By MidnightRide.
 
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