poor MPG
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Road Captain
Joined: Mar 2005
Posts: 567
Likes: 11
From: San Diego
poor MPG
I have a 2003 Lowrider. I had it bored out to a 95, it has 510 cams and was dyno tuned after the rebuild Problem is I'm only getting 27 mpg. I figured I'd lose some gas mileage but nothing that bad. Right now I'd be happy with mid 30's mpg. It has a 46 slow jet and a 200 main jet and I'm not sure where to look. Any suggestions would be appreciated. I don't ride it hard, just easy cruising.
Stellar HDF Member
Joined: Feb 2013
Posts: 3,072
Likes: 1,726
From: Dallas, Texas
I've got a simple effective fix. Replace the CV-40 with a Mikuni HSR42. So, did it work on my 2007 Dyna (AMS 105"kit, SE-255 cams, Thunder Heart stand alone ignition, V&H Big Shots, solid motor sprocket) HELL YES! 25 mpg went to 46 mpg. Follow the setup instruction and make a few small changes to get it right. DO NOT USE supplied intermediate jets, they are all too rich. Get a 17.5 jet. Same with the main jet, get a 155 jet. Use the 50 accel needle, not the 70. Accel pump shot calls for .080 gap before the pump shot starts, that's wrong. Dial it down so pump shot has no gap.
Supporter
Joined: Jan 2007
Posts: 15,787
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From: along the shore of Mishigami
What do your plugs tell you? When your bike was "tuned", was a Dyno-Tune put in the carb? I've read about more failures on these kits than success's.
Last edited by seniorsuperglideE8; Nov 12, 2022 at 08:31 PM.
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Road Captain
Joined: Mar 2005
Posts: 567
Likes: 11
From: San Diego
So I went thru the carb and cleaned it up but it was pretty clean. I installed a new float switch just to be safe since it was the original from the factory. Just got everything put back together so I will be riding to work all week and taking the long way home to check the mileage. I will pull the plugs in the morning and see whats going on there. If it doesn't get better, I might end up with a mikuni carb, although that sounds a little in depth.
Seasoned HDF Member
Joined: Sep 2008
Posts: 14,077
Likes: 11,099
From: San Diego, CA
Pretty sure it's the tune....
Do you have an aftermarket ICM and were the timing tables changed during the dyno tune....?
The CV40 carb is underrated IMHO... It suffers from the bad reputation of it's predecessor the Keihin Butterfly carb...
A well tuned CV40 will handle up to about 110hp with no problem. They are pretty easy to clean, rebuild, and tune... There is a process for tuning them that is pretty easy to follow. I believe CV Performance has it in a tutorial on their web site...
https://cv-performance.com/instructions-guides
I switched out my old Keihin butterfly carbs, but haven't felt the need to switch out any of my CV40 carbs.... Obviously a Mikuni is a great carb, as is an S&S Super E... But it would be a bigger expense than properly tuning the CV40...
Good luck with your decision and tune....
FWIW... I track the mileage of my vehicles on Fuelly.com
Here is my '01 Springer with a Stage I and CV40 carb:
Here is my '03 Heritage with 95" big bore kit, but with FI:
Do you have an aftermarket ICM and were the timing tables changed during the dyno tune....?
The CV40 carb is underrated IMHO... It suffers from the bad reputation of it's predecessor the Keihin Butterfly carb...
A well tuned CV40 will handle up to about 110hp with no problem. They are pretty easy to clean, rebuild, and tune... There is a process for tuning them that is pretty easy to follow. I believe CV Performance has it in a tutorial on their web site...
https://cv-performance.com/instructions-guides
I switched out my old Keihin butterfly carbs, but haven't felt the need to switch out any of my CV40 carbs.... Obviously a Mikuni is a great carb, as is an S&S Super E... But it would be a bigger expense than properly tuning the CV40...
Good luck with your decision and tune....
FWIW... I track the mileage of my vehicles on Fuelly.com
Here is my '01 Springer with a Stage I and CV40 carb:
Here is my '03 Heritage with 95" big bore kit, but with FI:
Last edited by hattitude; Nov 13, 2022 at 11:24 AM.
Seasoned HDF Member
Joined: Nov 2016
Posts: 5,801
Likes: 809
From: South Carolina
I have to get ready for the bashing....
Try E3 plugs, I'm getting high 45's plus and seems like better mpgs 2 up?
Have mild work done cams Andrew's 37 heads 06 and mikuni 42 carburetor on an 01 Dyna.. Regular plugs I drop an easy 5 miles per gallon
Try E3 plugs, I'm getting high 45's plus and seems like better mpgs 2 up?
Have mild work done cams Andrew's 37 heads 06 and mikuni 42 carburetor on an 01 Dyna.. Regular plugs I drop an easy 5 miles per gallon
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Road Captain
Joined: Mar 2005
Posts: 567
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From: San Diego
It's good to know that a 88 built to a 95 should be getting way better mileage. She seems to be running a little better after replacing the float switch. I was trying to stay away from tuning the carb since it was dyno tuned after the rebuild and that was only 5,000 miles ago. I will take a look at the plugs, I forgot to check the plugs. I will do that tomorrow.
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Joined: Jan 2015
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From: Sandy Eggo's North County
I have a 2003 Lowrider. I had it bored out to a 95, it has 510 cams and was dyno tuned after the rebuild Problem is I'm only getting 27 mpg. I figured I'd lose some gas mileage but nothing that bad. Right now I'd be happy with mid 30's mpg. It has a 46 slow jet and a 200 main jet and I'm not sure where to look. Any suggestions would be appreciated. I don't ride it hard, just easy cruising.
Don't forget the go-juice your using is 10-15% whisky. That's gonna kill yer range by 35+ miles.