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Another CARB set up thread

Old 03-27-2013, 11:34 AM
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Another CARB set up thread

So Im doing this partly as a method of tracking my setup and changes I make.. but as well as another thread for others to search for and read that may provide that one visual or textual clue they need to get there bike running well.

BIKE: 1998 Honda VTR1000F
ENGINE: Internally stock,31k miles, MCCT's, Previously had a head gasket coolant leak, fixed with just a new head gasket. Valves checked and no adjustment needed at 15k, 22k, 30k.
EXHAUST: OEM cans with baffle-ectomy
AIRCLEANER: Currently OEM paper, have used K&N and BMC. OEM short / long stacks in OEM locations.

LOCATION: Central Texas .. ALT; 1000ft

Last carb set up and rideability report before this carb clean and MOD cycle:

K&N Jet kit needles, clip 4, 175/180 DJ mains, Keihin 45 pilots, 2 1/2 turns out on fuel screws.

Bike has small bog mid throttle, overall seems low on power.
As seen in the Dyno charts.
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Max HP 95.6 Max TQ 62.2

Disassemble showed only a couple of concern areas.
Vac line starting to show signs of age cracking.
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Old jets were buggered just a bit at the slot. This will be self correcting as I install new Keihin 175/178 mains.

Cleaned up all..
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Installed new Keihin 48 pilots
New Keihin Mains 175/178
Installed new O rings on the fuel screws.
Plugged one factory slide hole and the one drilled for the DJ kit install in the front slide. On the rear slide, I plugged just the DJ kit drilled hole, leaving the OEM ones.
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That is after just the first rough clean up and polish.

OEM needles brought out of the jet box storage, checked for wear and damage, and shimmed for re-install...
OEM thin shims mic'ed at .0195".
#4 Stainless washers I picked up MIC'ed in at .030 (once I picked though 10 or so and found two the same thickness).
So my starting point will be.
Front needle OEM thin shim (.0195) and one SS shim (.030)
Rear needle TWO each OEM shims (.0195 + .0195) and one SS shim (.030)

Front Fuel screw turned out 2.25 turns, Rear screw 2.50 turns.

DJ springs set aside and the Loooooong OEM slide springs re installed.

Thats it for now, as soon as I find some silicone vac line to replace the cracks OEM rubber piece we will be ready to re install the carbs, check the TPS and make sure it is still set correctly and synchronize the carbs..

I'll do some seat of the pants checks and decide if anything else gets tweaked before another dyno run.

Last edited by E.Marquez; 04-17-2013 at 12:47 PM.
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Old 03-27-2013, 11:41 AM
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OK, I know just a little about these carbs, and by looking at all your dyno runs & AFR graphs. Looks like you are running too rich!!!!. Did the dyno operator not mention this also???
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Old 03-27-2013, 11:44 AM
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Also, you need a new carb slide!!! for sure. I'm very interested to see what some of our forum experts have to say? Power looks about right for a healthly superhawk.
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Old 03-27-2013, 11:51 AM
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Originally Posted by [email protected] View Post
OK, I know just a little about these carbs, and by looking at all your dyno runs & AFR graphs. Looks like you are running too rich!!!!. Did the dyno operator not mention this also???

Yes I know it was running rich thanks... I've run my own dyno a time or 2..
As I no longer have access to that machine, i have to use a local shops now and pay to play..

That run seen on the charts was with DJ 180/185 mains, all others things as listed above the same...

I decided with this round of carb set up.. to get away from the DJ needles all together and try the OEM needles and tips 8541Hawk suggested in his thread.

I've been chasing a good set up with the DJ needles and K&N for some time now, had it good, but never great...
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Old 03-27-2013, 11:52 AM
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Originally Posted by [email protected] View Post
Also, you need a new carb slide!!! for sure. I'm very interested to see what some of our forum experts have to say? Power looks about right for a healthly superhawk.
LOL, really? Why do you think that.

And no.. that is down on measured TQ and HP of a well running SH, as well as felt rideability, throttle response (something that does not show well on a dyno graph unless Way off) is not right currently.

Last edited by E.Marquez; 03-27-2013 at 11:55 AM.
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Old 03-27-2013, 01:14 PM
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Well I'll be interested to see how this works out for you....kind of wonder how you got all those Mikuni parts to fit.....

I could never get the DJ and K&N to work the way I wanted either.
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Old 03-27-2013, 02:53 PM
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Ehh, thats what happens when you type a post on one site about the Mikuni BSR36 carb your working on, then Post in Super hawk forum about the carbs on your SH which are not Mikuni's
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Old 03-27-2013, 03:05 PM
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Happens to all of us.... you know I was just messing with you.

So when is the next dyno run?
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Old 03-27-2013, 04:37 PM
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Originally Posted by 8541Hawk View Post
Happens to all of us.... you know I was just messing with you.

So when is the next dyno run?
It'll be a few weeks I think.

Carbs will be back together tonight.
Forks are apart waiting on a Honda seal.... Friday i hope.
Ordered custom Galfer front brake lines this morning, should ship today.. get then by SAT.

THEN get to ride it by mid next week....
Want to see what issues come up if any, see what seat of the pants improvements i can make. Then once I have it as best i can make it feel.. I'll put it back on the rollers and see what the A/F , HP and TQ numbers show.
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Old 03-28-2013, 06:43 AM
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By "New Keihin needle jets" do you mean "needle jet holders", part #26 on the carburettor component parts diagram on the Ron Ayres site? I didn't know that the jet which is visible in the carb throat in the photo which follows "cleaned all up" was available as a separate part.
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Old 03-28-2013, 08:51 AM
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Originally Posted by comedo View Post
By "New Keihin needle jets" do you mean "needle jet holders", part #26 on the carburettor component parts diagram on the Ron Ayres site? I didn't know that the jet which is visible in the carb throat in the photo which follows "cleaned all up" was available as a separate part.
Correct, not available from a OEM dealer. Yes they can be replaced.. Can be ordered from SUDCO I believe.

Not normally replaced... in this style carb..... but can be. A friend of mine does a lot of custom work on carbs.. boring the throat, creating new air leak passages..., blocking other passages...ect... I asked him to provide all my service parts... two weeks later they show up on my door step.... Im not complaining.

The needle guide is pulled out with a slide hammer and pressed in with a guide rod machined fit to the ID.

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Old 04-17-2013, 12:52 PM
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3 days of riding now on the new carb set up.

The Bog is GONE
It pulls cleanly from 4k on up.
Power has not seemingly changed, but response and smoothness has for sure.

Other than not enough power (I know it's a pig of a bike, 14 years old, 30k miles and never was a brute) I think Im very close to the best its going to get.. and with no glaring issues, not sure what to change,,,, so I think it's off to the dyno.. Which is convenient, mas my wife just took a job as service advisor at our local Honda dealership,, where I've been going to use a Dyno.

Wounder how long she has to work there before we get employee discounts
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Old 04-17-2013, 06:49 PM
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Glad to hear it worked for you
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Old 04-18-2013, 02:36 PM
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Ohh....you fixed your carbs....Ohh 3 days only??....AND..you have a DYNO available....I am jealous / envious and encourage you to: GO FLY A KITE.....



<pouts in corner>
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Old 04-24-2013, 06:20 AM
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Oh my a very thirsty set of carbs....

She is running great, pulling strong, but thirsty as all get out.
88 miles to ROFL comes on... that is consistent over 8 tanks of fuel.
Now I admit, I've been playing with the throttle a bunch, and my gearing is lower then stock, and we did a bunch of freeway miles at 80-95 mph in those 8 tanks which is part of the dismal gas milage.
But damn,, from 135 miles till ROFL when I first got the bike to 120 miles at last carb set up to 88 miles with the current set up.

The small tank really DOES impact where I can ride now...
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Old 04-24-2013, 07:49 AM
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You gotta be running super rich for that mileage...but before you do anything, go through a tank at sane speeds and normal (for other folks ) throttle rates and engine rpm. Then we go from there.

FWIW, the only time I EVER got RLOD around 90 miles was at Road Atlanta in '98 or '99. That was the first time I was on a track so there wasn't much momentum to be had. Lots of point and shoot.
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Old 04-24-2013, 08:02 AM
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Originally Posted by Hawkrider View Post
You gotta be running super rich for that mileage...
Yup thinking the same thing,,,,, but it sure is running well.

It goes on the rollers 1st week in May so I'll know for sure then what the AF is.
Until then... the question is....

Where in the circuit is it rich.
Pilot
AF screw
Main
OEM shimmed needle position.
Front carb? back carb both?
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Old 04-24-2013, 10:19 AM
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Originally Posted by E.Marquez View Post
Oh my a very thirsty set of carbs....

She is running great, pulling strong, but thirsty as all get out.
88 miles to ROFL comes on... that is consistent over 8 tanks of fuel.
Now I admit, I've been playing with the throttle a bunch, and my gearing is lower then stock, and we did a bunch of freeway miles at 80-95 mph in those 8 tanks which is part of the dismal gas milage.
But damn,, from 135 miles till ROFL when I first got the bike to 120 miles at last carb set up to 88 miles with the current set up.

The small tank really DOES impact where I can ride now...

Well it could be all in your right wrist but this is what I have found with mine.

I do have a little different set up as I do have different needles & ECU and a few exhaust tweaks and I also have 9X,XXX miles on the bike and she does need the valves recut as I started to feel the need for that about 6 months ago but with that.....

First I never tried to tune for economy, just ridability so my set up will burn some fuel.

My record to the RLOD (or Red Light Of Death) was 70 miles but that was at triple digit speeds chasing a CBR1000 & a "Busa on a pretty open road and my light is set to come on early but not the right bike for that day.

My normal MPGs are around 35 with my riding style. That is shifting at 5K and keeping the revs around 4K while cruising.

Start wringing her neck and it will drop to around 30MPG but that is keeping it above 6K all the time.

The best I have gotten is in the low 40s but that was a newbie day and I kept the bike at or below 3K all day.

So IMHO I don't think you are way rich anywhere but the dyno will tell though you didn't say what the plugs look like which would give a good hint.

What I think is happening is you have been a bit throttle happy and twisting it a bit more just because the bike pulls so good now..... been there done that....
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Old 04-24-2013, 05:41 PM
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Though if you feel the need to try something..... try dropping the needles down a little bit
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Old 04-24-2013, 05:55 PM
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Originally Posted by 8541Hawk View Post
Though if you feel the need to try something..... try dropping the needles down a little bit
So the interesting part is, the current setup is 80% OEM stock.

Mains are OEM
Needles are OEM
Needle position is OEM front, 1/2 shim thickness raised in back.
Springs are OEM
Pilots are of course 48's and not OEM 45's
Slides are OEM rear, one less lift hole front.
And the OEM Stock parts get a rider 130-140 miles to light.

My lower fuel milage is like a cumulitive effect of larger pilot, raised rear needle, and a slide lift hole blocked meaning the slide and needle comes up faster and more often. .. That all adds up to more fuel moving
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Old 04-24-2013, 07:15 PM
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Originally Posted by E.Marquez View Post
So the interesting part is, the current setup is 80% OEM stock.

That is also why I say the big problem is your right wrist...... it's hard not to be a bit of a hooligan when the bike pulls so well......
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Old 04-24-2013, 07:19 PM
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Originally Posted by 8541Hawk View Post
That is also why I say the big problem is your right wrist...... it's hard not to be a bit of a hooligan when the bike pulls so well......
Very likely the cause.

I rode today... 84 miles and the light came on

The Dyno run in a few days will tell the story.
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Old 04-25-2013, 08:04 AM
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My lower fuel milage is like a cumulitive effect of larger pilot, raised rear
needle, and a slide lift hole blocked meaning the slide and needle comes up
faster and more often. .. That all adds up to more fuel moving
Hi Guys,

Been following this thread because I am about to dip into my carbs also. My question from Marquez's quote above is in referance to the slide mod. I was under the impression that plugging the slide holes causes the slides to liftslower not faster, therefore preventing any over-richness in the mid range?
I have the Dr. Honda V-stacks so I was planning to plug one front and one rear as Mike has suggested so I was looking for clarification.
Thanks as always and looking forward to seeing the A/F charts from your dyno work.
I borrowed my friend's Innovative wideband LM-2 meter LM-2 Wideband O2 Digital Air/fuel Ratio Meter
So hopefully I can get a decent baseline before and after.
Thanks again!
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Old 04-25-2013, 08:20 AM
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Originally Posted by Upland111 View Post
Hi Guys,

Been following this thread because I am about to dip into my carbs also. My question from Marquez's quote above is in referance to the slide mod. I was under the impression that plugging the slide holes causes the slides to liftslower not faster, therefore preventing any over-richness in the mid range?


Yes, errr no,, Wait I said what?????

It's possible I have the concept wrong...I'll need to look at the carb passage flow chart again..if I can find it.

But my comment was based on a memory of vacuum being applied ABOVE the slide, ie cap side of the diaphragm. What Honda calls the "vacuum chamber".

If so, the hole (s) in the slide are bleed holes,,bleeding off vacuum applied above the slide, or lessening the effect of vacuum applied..

If my memory is correct of the design,, One bleed hole would cause the slide to move up faster than two bleed holes.

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Old 04-25-2013, 12:24 PM
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Well I have a little different take on what is going on but I'm just some guy on the 'net so Name:  idunno.gif
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The way I see it is yes there is a vacuum passage to the "vacuum chamber" which also leads to the "lift holes" in the slide.

Now as there are no valves in the system, it is pretty much an open loop.

The vacuum passage gets it's signal from the air moving through the venturi of the carb. The slide lives in the same venturi and "sees" the same signal.

So what I see happening is the main vacuum port is for "course" tuning or to get the slide speed in the in the "ball park"

Then you "fine" tune the speed by adding or removing "lift holes" by adding holes you are pumping out a fixed volume trough a larger "net" orifice, so the slide will move faster.

Remove holes and the slide will slow down as you are working with a smaller "net" orifice.

This is why if you do the front slide mod (or both with the aftermarket stacks) and you push the slides up the modified slide will return slower than the stock slide.
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Old 04-25-2013, 03:31 PM
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by adding holes you are pumping out a fixed volume trough a larger "net" orifice, so the slide will move faster.
Which is why Dynojet kits say to drill the extra lift hole.

As for your fuelling I average about 85 miles before the light comes on. That's with mostly town riding and I tend to blip the throttle a lot when filtering through heavy traffic jams. I'm also a bit heavy handed on the hrc QA throttle when pulling away from lights and open roads. Do you fill you tank with the bike upright or on the sidestand. You can get a little more in if upright, I tend to just fill up on the sidestand, but this does make a difference when people start quoting figures to how many miles they get.

But as you are already aware the dyno will tell.

(:-})
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Old 04-25-2013, 04:06 PM
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Originally Posted by cybercarl View Post
Which is why Dynojet kits say to drill the extra lift hole.
Do you have a link to the published data Dynojet posts which state that?
I've not seen it before, and it's not in the paperwork that came with my DJ kit.
[QUOTE=cybercarl;353596]As for your fuelling I average about 85 miles before the light comes on. [/quote

Ok, then your carburetor adjustments are as bad as mine... it would seem.

Do you have a Dyno graph from your current carb setup? If so please post, would love to see what the AF looks like on a bike with this rich of a setup.

The Dyno charts at the top of this thread netted me 100 + miles to light, but I did have a flat spot mid throttle at cruising speed,, hence my desire to change the setup.

Thanks
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Old 04-25-2013, 07:36 PM
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I'm trying to decide wether to tweak the carbs or not. My plugs are just about perfect on the front and a little bit rich out back. My carbs are bone stock, I think I'm the first person to open them, 175/45 f, 178/45 r. I don't know how the a/f screw is set since I don't have the tool yet.
I have slip-on exhaust with no baffle and have no popping on decel, PAIR is in place, OEM style filter, no bogs or surges or any hanky-panky from idle to redline.
Wouldn't these adjustments you made just richen it right up? The last thing I want to do is start chasing a setup and have to pull the carbs 10 times when it runs pretty damn good the way it is.
The carbs are on the bench so now is the time if I'm going to screw with it.
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Old 04-26-2013, 06:05 AM
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Do you have a link to the published data Dynojet posts which state that?
Not directly from Dynojet but from what I have read in various articles and forums on CV carbs, this is what creating an extra hole does as the depression at the venturi will travel faster through the lift holes as they are either larger or more of. This lowers the density of the air in the chamber above the diaphram as the air rushes in to equalise the pressure, but there is nowhere for it go so it pushes on the underside of the diaphram where it is flexible which in turn lifts the slide. It's all bloody complicated stuff and I don't know all the ins and outs of it all as it gets into boyles law and charles law territory and starts to go way above my head. I guess this is why they call it carb theory. LOL I believe there is a certain element of trial and error.

Getting back to the fuel economy thing, I have ruled out needle valves, float height, petcock diaphram, timing etc etc and sometimes I feel like I'm just chasing my tail with jetting and making changes trying to get better economy. I also think my modified exhaust has a fair bit to do with it, but I'm having fun tinkering and experimenting with different set ups etc. It's a huge learning curve. It could be just the simple fact that I am a bit too throttle happy and I do mostly town riding in heavy stop go traffic and don't fill the tank to the brim. I've not tried blocking lift holes yet as I'm running two long standard stacks, but I'm just about to put some DR Honda copies I've made in and have two spare slides here with a lift hole blocked in each one to go on shortly.

You can see my current set up and dyno result in the following thread.
https://www.superhawkforum.com/forum...-result-30125/

It's all very interesting stuff and I'm looking forward to seeing where you end up with your set up.

(:-})
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Old 04-26-2013, 11:15 AM
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The CV carbs work on Bernoulli's principal. Air moving faster has less pressure. So when you crack the throttle and open the throttle plate the air starts rushing in under the slide. That air is now a lower pressure and the ports in the bottom of the slide allow that lower pressure above the diaphragm. So those ports ARE the vacuum signal. The bottom of the diaphragm is vented to atmospheric pressure on the bell of the carb on the air box side. Thus the reason for being called a CV or "Constant Velocity" carb is the velocity of the air under the slide controls the slide and keeps the velocity somewhat constant.

Therefore the larger/more holes in the bottom of the slide the faster that vacuum can get above the slide and therefore will lift the slide faster. Close off more ports and it takes longer for the vacuum to get above the slide and it will move slower.

I think your mileage is more a case of you were running way lean before. Which is why you had your flat spot. Now you're running richer, which is actually where it should be so your flat spot went away, however you're mileage is suffering.

I'm running 48 pilots and 175/178 mains. I have a Factory jet kit and IIRC the clip is in the middle position, I don't remember the shimming off the top of my head. I ran on the dyno and he said it was a little rich on the pilots. Suggested going down one size. I did try to lower the needles, I don't recall if it was one shim size or one clip position to try to improve my mileage but all I ended up with was a stutter while cruising and low throttle positions.

In conclusion I think you're just running where it should be and twisting the throttle a lot. On a ride to Montana/Idaho last year when we were doing a lot of 80-90mph runs the RLOD would come on at 80 miles like clockwork. Otherwise I usually get to 90/100 when riding at our 70mph speed limits here in WA. The best I've done was like 40-45mpg once doing a group ride with a bunch of cruisers over the pass where we were doing 35-40mph most of the way.
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