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When my brother passed away, I kept two things...his dog and his motorcycle. The dog is another story. The motorcycle is a 2007 Triumph Bonneville Black. Of course, he had swapped the stock mufflers for so-called TORS (Triumph Off Road). Living in Denver, the “Mile High City", he had wisely not installed the larger 115 main jets that came with the mufflers. So...carburation was stone stock.
Once home in Oregon, I rode it to the local DMV to register the bike in my name and discovered a bit of a lean hiccup in the mid-range running. Then, I tried removing the snorkel from the air box, like conventional wisdom dictates. Trick “performance" exhaust pipes and chopped up air-boxes (or pod air filters) to compliment....should make the beast run better. Yet, the mid-range hiccup became a mid-range stumble. Almost no “pull" when the throttle’s whacked open...unacceptable! Trying to flatten my learning curve on this new (to me) machine and it’s issue, I was surprised to find practically everything I read online, advocated doing exactly the wrong things! Jet richer, shim the stock needle, throw away the air-box altogether, install a jet kit, etc.

I realize that hiring tuning work ain’t gonna be cheap and might not be done right the first time around. After all, re-jetting carbs, besides being a fiddley task at best, is not an exact science. Matching the mixture to the hardware can be fraught with potential error. Getting it precisely correct was something the factories with all their resources, couldn’t quite manage back in the days of carburetors. I don’t claim to be a mechanic, so how could I do better? Well first, identify the problem.

The EPA (And CARB) put the lid on motorcycle emissions (including noise) back in the late 70's. That’s 40-years of incremental engine strangulation. To meet these ever-tightening regulations, meant manufacturers had to make motorcycles that run “lean”...for the sake of cleaner air and at the expense of mid-range power. The simple fact is, a motorcycle cannot be ridden at full throttle for more than a few seconds at a time. Whereas, they idle a lot and are ridden at part throttle (cruise) most of the time. No prize then, for guessing that efforts at lowering emissions appear in the carb circuits that supply air/fuel mixture to the engine at part throttle. Namely, the jet needle. It dominates from just off idle to almost full throttle.
In a nutshell, you could ignore the low speed jet and the main jet because they are not “smog” lean...if you could only get the right needle. Good luck!

Hybrid CV (constant velocity) carbs should be referred to as “constant vacuum" because unlike the other carbs, the diaphragm in the top controls things, based on vacuum, not your right wrist. The so-called “nail-head” needles in these carbs are only adjustable by means of shims and even then still have a “lean” taper. Good for emissions, not so good for performance.

Air, as we know, moves faster than fuel. No trouble when you are just cruising, but when you yank the throttle open, the worst problem a lean midrange presents to the rider...is the dreaded, gutless, lean bog! In a carb with emissions-legal needles the mixture goes too lean and the engine won’t run on thin air alone. CV carbs work around the problem (somewhat sluggishly)...unless you remove or cut up the air box...which is where the vacuum is generated.

Of course, the aftermarket has jet-kits. Usually, including a different, adjustable clip-type needle, but prone to going too far the other way, resulting in marginal improvement at the expense of lousy mileage and potentially fussy ride-ability. Leaving (seemingly) that internet advice about installing huge main jets and pilot jets in vain attempts to work around this lean mid-range issue. Not an ideal solution for improving performance in daily riding.

Bottom line, manufacturers have nearly shut us out, when it comes to proper “performance" tuning of the midrange with emissions-legal, carbureted motorcycles. A virtual guarantee that in any attempt to “improve" performance, the circuit ridden on most, will be compromised. One way or another.

So, short of tossing stock carbs in the trash and coughing up a fortune for tunable “performance” (illegal) replacements... there’s really only one way to solve the mid-range muddle and it’s been hiding in plain sight for decades. So, how about we leave the jets and needles alone and add another circuit instead?

Pic 1 - This instructive graphic shows the basics of carburetor functionality. Stock emissions-controlled carbs are set-up to run at legal air/fuel ratios at partial (cruise) throttle openings. For the record, this means “on the needle” 90% of the time. Idle and WFO air/fuel is usually left at best performance ratios, because you simply cannot street ride at either extreme for more than very short periods of time. (In other words...not...an emissions problem.) The trouble comes when we amateurs try to outsmart the system by messing with circuits that were correct in the first place!

Pic 2 - Most of the time, “outsmart” results from “open” exhausts and air filters. Installing either... affects mid range air/fuel ratios. Of the two, the air filter/air box choices make the most difference. (Since they rely on the strong vacuum provided by the air box, open air filters and richer jetting can actually cripple performance on CV carbs!)
Conventional thinking involves changing the jets. This is inherently flawed! Especially if you cannot match jetting to the factory needle...often the only needle available...particularly in CV carbs. As you see here, increasing jet sizes, results in too much fuel to atomize well. Resulting in lots of reversion (fuel spit back), potential surging at “steady state” cruising, and crap throttle response! If you’ve messed up this badly...nothing will help except to revert to stock specs and try again... the right way!

Pic 3 - In other words, we’re not talking about simply adding yet more fuel. Rapid response to snap throttle, is virtually impossible to achieve with bigger jets and the factory needle...shimmed or not. To deal effectively with the situation, you need an atomized mixture, instantly applied at precisely the right time, in precisely the right amount. Since factory carbs don’t have a way to do that, you add it! Using Thunder Products Dial-A-Jet or Intelajet is the ticket, because it provides both air and fuel in a pre-atomized mixture, on demand and correctly balanced, with no need to disassemble or re-jet the carburetor. The outcome feels like this graph looks! Smooth, rapid response to the throttle, good fuel efficiency, no flat-spots in the mid-range...right...everywhere it needs to be right. Visit thunderproducts.com or call Lonn (320-587-2700) for applications,advice, details and prices.

Pic 4 - My brother would be proud! Installing Dial-A-Jets on his Bonnie took just about the same amount of time as he spent putting on the TORS. No disassembly required! Put the side panels back on and the only visible clue is the thin blue hoses. Two short rides to “dial-in” the Dial-A-Jets setting and problem solved! Mid-range is now an arm-yanker and adjusts automatically for virtually all riding conditions.
 

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That's about the best year Bonnie, in the best color. Nice one :)

Nice write up. My bike runs fine for my purposes, but when I nail the throttle I do have to wait a couple seconds, then the afterburner kicks in. Honestly not sure if it's fuel starved at that point, or too rich, but it takes a second for the carb to adjust. Maybe this would help.

Found this interesting write-up https://thunderpress.net/editorial/columnists/motorhead-memo-intelajet/2018/03/21.htm
 

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I run 3 old carburetted Triumphs. Get them set up right and you have no flat spots. Mine don't. IMHO Someone will always be willimg to sell you one silly thing or another that the college educated, highly paid engineers at Triumph were just too dumb to figure out, right ? Don't think so myself. ...J.D.
 

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Discussion Starter #4
What "old" Triumphs would those be...specifically? And just how did you get yours "set up right"...specifically? Simply "sniping" with no specifics doesn't help anyone,
Also, if you read the article thoroughly, the point of the "silly thing" is to keep NOT set up right modifed motorcycles using stock carbs from having flat spots. Also, a "flat spot" doesn't always show up on a butt dyno. You practically have to ride yours back-to-back with another that is carbureted correctly, (preferably with an on-board A/F meter) to be certain. Lastly, those "college educated, highly paid engineers" deserve full credit for being bright enough to get it as right as they did (TPS and heaters notwithstanding) and still meet emissions standards Doesn't mean it's perfect and doesn't mean there's no room for improvement.
PS - For the record...the "silly thing" was invented by a PHD. Just sayin'!
 

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Pages apon pages have been written on the subject (probably wrote some myself) on this site alone. No sense in taking up more space on the subject. Use the search feature. Carburettors were invented by pre-historic man. How hard can it be ? He didn't even have a computer.

As for my bikes (ONLY because you asked):

2002 America (Keihin carbs, pipes, and jetting mods)
2000 Legend 900 3 cylinder (Keihin carbs, jetting and airbox mods)
1995 Sprint 900 3 cylinder (Mikuni carbs, jetting mods, air box mods, big exhaust, ignition mods).

But, on the other hand, I don't have a PHD, and I cannot play the guitar :D
...J.D.
 

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The Thunder Products web site would inspire more confidence and credibility if it explained how this wonder gadget works.
 

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The Thunder Products web site would inspire more confidence and credibility if it explained how this wonder gadget works.
I DID look at thier website. I have been working on carburetors since the late 1950's. I was a professional mechanic for some years. I have 5 years of engineering at L.A. Trade Tech. In my now retired years I play with motorcycles and sports cars. All I can say is what a LOAD of cow excrement THAT site is ! Just my ignorant, uneducated opinion of course. ...J.D.
 

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Looks like it's gonna grab some fuel from the bowls and spray it into the air entering the carbs, so enriching the mixture. Works by vacuum, with the little dial controlling at which vacuum pressures the thing opens and closes? That it, am I close?

Seems to be about $200 for a pair of CVK 36's ... you can get a Bonnie pretty damn close with jets, needles and shims. That's a lot of jets, needles and shims to experiment with. I mean, it's still gonna ride like a stock Bonnie with TORS either way, not a bored out motor with open pipes and a hot cam, which would require something more than a CVK to run fast anyways.

I get why someone would drop the money to play with something like this. I get why folks spend time and cash to get their 50HP Bonnie up to 55 or 60. I mean, it's still a Bonnie and not a sport bike, but the tinkering is fun. Personally, me, I like my performance modifications like I like my women: Cheap.

Plus, when I just asked daughter if I should buy a Dial-a-Jet she asked if it would allow me to make phone calls to airplanes, and when I said no, she said why would you buy one then. :)
 

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Probably pretty close. Still kind of a stupid idea in my book. Jets are cheap. I used to have an adjustable main jet for the old VW Solex carbs laying around the shop. I ran it years ago on an engine, but I found that once you set the mixture, you were done. Never touched it again. Would have been just as easy AND cheaper to just put a bigger jet in it in the first place. Took it off an threw it in the junk when I rebuilt the carburetor. It layed around in the junk box in my shop for years. Don't know if it is still out there or not. Expensive scrap brass. ...J.D.
 

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I DID look at thier website. I have been working on carburetors since the late 1950's. I was a professional mechanic for some years. I have 5 years of engineering at L.A. Trade Tech. In my now retired years I play with motorcycles and sports cars. All I can say is what a LOAD of cow excrement THAT site is ! Just my ignorant, uneducated opinion of course. ...J.D.
Yep, it doesn't explain anything. The reader is just expected to take it on faith. If the product were as good as they claim, we'd all be using it already, I think.
 
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Discussion Starter #11
"Jetting mods" is NOT specific! "Pretty damn close" is not a solution. It's not about more peak power. Just a broad power band...best performance at all revs. Explaining how sophisticated technology works is not as important (or apparently as easy) as verifying that it works... ask any kid with a smart phone.

Yes, it's possible to correctly tune any carb that offers a full array of options (needles, jets, slides and more)... to that end and for that purpose. Go for it!

Emissions CV's are not on that list...period!

But as long as prejudices in favor of sloppy work-arounds prevail over proper solutions...well intentioned posts like this are wasted. The point is lost!

If you don't "get" it...then don't get it! Just don't diss what you haven't tried. That puts you in the George Carlin school of criticism..."Criticize most, that which you know least about".
 

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"Pretty damn close" is not a solution.
It most certainly is. I have "gone for it", and did quite well. I got a lot of miles on my bike, and had a lot of fun on it going to a lot of cool place. Pretty damn close has been a fine solution. And $200 cheaper than the stuff you are peddling. I ran with a A/F meter installed for years, and learned there is no magic jetting anyways, the mixture you get varies quite a bit with weather and elevation. (I know, your gadget magically compensates for weather, right?)

That may be a better sales pitch for you now that I think of it. Forget the "emissions laws mean it is impossible to jet a carb correctly" stuff. Go with "the appropriate jetting depends on air pressure, humidity and elevation. Don't you wish you could adjust your A/F mixture with the turn of a screwdriver instead of rejetting on the side of the road? Then Dial-A-Jet is for you. My brother's dog is glad I have one!"

You are going to need a tougher skin to survive the online forums, it was unreasonable for you to expect compliant praise in response your first post here, despite the cute dog tack. Folks have a right to be skeptical, and if you have nothing expect "but I'm right" assertions to defend yourself, you're not going to change a lot of minds.
 

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Discussion Starter #13 (Edited)
NOT..."peddling"...no "sales pitch"...just informing.

All I "expected" was open minds... instead I got you two!

Keep your $200 and stay "close enough", if that suits your ego. After 40-years in the industry, 10-years as service manager at a H-D franchise, 25-years as Tech Editor for a monthly motorcycle publication, many free-lance articles, and two books on subjects just like this, my "tougher skin" can take it just fine.

Although, it seems to me, since no one said in detail what they did to their carbs...you might be the ones "asserting" rather than proving anything.

Please leave my brother and his dog out of it!
 

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Although, it seems to me, since you STILL haven't said in detail what you did to your carbs...you might be the one "asserting" rather than proving anything.
No one asked. I have the TORs silencers as well. I'ts a 2008, but we both have the 865 motor. I cut up my air box leaving the battery box but removing the air filter housing. Kinda a home-brew ARK. Like I said, I like my modifications cheap. I have a pair of UNI NU-3006 pod filters on the carbs. I'm running stock needs, no shims and 140 mains I believe, honestly I may have put 142 in though. Pilot jet screws out 2.5 turns. Like I say, in some conditions the setup is a bit lean, sometimes a bit rich. On average about right. I know 137.5 mains are too lean, noticeably so. I ran 145s for a while and felt it was too rich, but that was before I put in the A/F meter.

Honestly, my note taking wasn't the best on this and it's been years since I've touched my jetting. My notes say I have a shim in, but I'm pretty sure I took it out at one point.

That said, I'm no expert and not asserting that that is perfect. Like I said, I did run an A/F meter for years and know it's close, and the bike is fun to ride.



Which Dial-a-Jets did you get? What did they cost? Any pics of the installation procedure, you need to drill into the carbs to get a place for the fuel to inject into the airstream? Was I close to describing how they work? I am curious about them, not assuming they are snake oil. Do think you're a little pessimistic about the ability to tune the CVK though, for non-racing applications at least.
 

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Discussion Starter #15 (Edited)
Finally...some actual conversation! THANK YOU BonnieBlack! (Details on jetting was actually meant for Wire Wheel BTW)

Anyway, There are differences of opinion on air-boxes, but by and large let's just leave it as needing vacuum...CV do! Since you like "cheap" may I suggest that you duct tape your uni filters within about an inch of the ends...try it...then let me know if mid-range perks up. I'd appreciate your feedback.

Got one of my DAJ's from Lonn ($75), the other off fleabay ($40). Tricky part was the fuel outlets that replace carb bowl drain screws. Turns out there are a couple of versions...Bonnies take the longer ones. (See pic)

DAJs come with a tool to cut the hole in the airbox to carb intake rubbers. If we "clock" the perimeter of the boots, I "drilled" mine at about 11:55 on the left and 12:05 on the right. Near vertical, but angled enough to adjust without removing the side panels. (More pics)

You are in the park on how they work, but gotta tell ya the so-called "acoustic" aspect is the voo-doo one. It sounds weird because it is...yet it triggers the DAJ. (Think intake "honk" on a two-stroke.) Vacuum obviously plays into it as well. IMHO, fundamentally, the nozzle becomes an auxiliary needle jet (without the needle) pre-atomizes fuel/air into a fine mist so it will move super fast when the need arises. (Lonn refers to difference in "mist", as "ping-pong balls among the basket balls".) The "dial" is simply an air-bleed adjuster. I left them on the middle position (of 5) for the first test ride and was a little disappointed. Then I doubled checked and realized I didn't have the nozzles perpendicular to the intake. Fixed that critical item, set the dial to full "lean" and... NICE!

I have to say, I was on the verge of diving into "the Jenks Bolts" tuning pool that lot's of carbed Bonnie riders go with. Even ordered the jets and shims. I knew, for a fact, that the needle was the hassle after decades of messing around with CV's on Harleys. THAT is where the "pessimism" comes from...street bikes! Not racers...(those guys don't care how it runs on the road.) Even ordered older Evo H-D jet kits (by Custom Chrome) just to get needles with adjustable grooves and clips.

Then I stopped and thought about it.

A year or so earler I had done an article on DAJ/Intel-A-Jet, where the test bike was an old Harley Shovelhead with an S&S carb...no mid-range circuit at all. The owner was a friend and straight shooter. He told me he was nervous about crossing lanes of traffic from a dead stop...unless he revved the snot outta the Shovel and slipped the clutch. PITIFUL mid-range! (Those old S&S carbs are light switches.) After the install of the Intelajet the thing acted like a normal motorcycle...docile, tractable, quicker revs in a gear...all good!

The light bulb lit...and I called Lonn.

So, I decided to go that route and I'm glad I did. Side-stepped a ton of hassles and hard work and got EXACTLY the result I was after.

All I might do eventually, is re-install the DAJ's in the venturi portion of the carb ("pro-install" they call it)...rather than in the rubber boots. Just because that way "perpendicular to the intake" is a more permanent proposition. (metal doesn't rot or flex.)

ONE MORE THING: DAJ/Intelajet only works to fill-in lean "flat spots"... IE: for bikes with "open" air-boxes/filters, exhausts and STOCK jetting. Won't do a thing for rich conditions...AKA typical "remedial" fat jetting. That's why I was glad the 115 mains that come with TORS had not been installed. (Fine for Denver, too rich at sea level.)

Slightly off subject: I have another friend (retired race tech at American Honda) who owns a 1200 Sportster Sport. He removed the accelerator pump on the stock CV, installed Intelajet and rode it 900 miles to visit me recently. The ride involved temperature changes, altitude changes and a lot of throttle operation (like all long rides) and no matter what...his A/F guage would only "flicker" for a split second and go right back to dead on...for the whole ride up and back.
 

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There are differences of opinion on air-boxes, but by and large let's just leave it as needing vacuum...CV do! Since you like "cheap" may I suggest that you duct tape your uni filters within about an inch of the ends...try it...then let me know if mid-range perks up. I'd appreciate your feedback.
Yeah, I think the biggest problem with Bonnies off the showroom floor is sound. They are just too damn quiet. Some TORs, or something more open, make it sound like a motorcycle. And removing the airbox gives it some induction noise too, which is welcome. That's kind of why I did it, plus winter is long and I wanted to tinker ;)

My dealer, who I think knows a lot about bikes and performance, really didn't agree with the ARK. He liked the airbox, and would have had me spend some money on some cams instead. There's a lot of conventional wisdom on the forums, but there's a lot of echo chamber stuff where we all parrot the conventional wisdom, which we learned here, to each other. I figure he may be right, but without proper testing I don't know.

I have a second pair of those Unis downstairs, it would take nothing to tape them up and see what happens. I'll do that before the season is over and report back. I see what you're getting at.


I've been looking around, and reading posts from other forums about this. The idea is established, I see people comparing it to Mikuni Powerjets and other variable jetting systems. Read one guy with a KLR who summered in the mountains and wintered in the lowlands who went with this system to avoid rejetting twice a year. Makes sense to me.

Not sure why the idea is any more heretical than the booster plugs the EFI guys, locked out of their ECU's, are dicking with.


Anyways, thanks for bringing this up here. I don't think it's been mentioned before in this forum. There have been many "spirited" debates about jetting here over the years, I've never understood how they were so contentious. But in the days of EFI and WC Bonnies and locked ECUs, they have all waned away. Thanks for bringing the energy back to us carb guys ;)
 

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Discussion Starter #17
BonnieBlack, worthwhile to try... worked well enough to share.

Here's a link (I hope) to Lonn's article on air boxes. He thinks like your dealer...but paints with too broad a brush and tosses a sales pitch in to boot. That's too bad, 'cause basically the physics (first five paragraphs) are hard to argue. Especially regarding CV carbs.

http://thunderproducts.com/your-airbox-friend-or-foe/

Oh...last but not least...his website is pretty bad (as you noted) but on the phone, he's pretty damn good.
 

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Interesting thread. Yes, I'm new to posting, but not to the forum. It appears to me that the DAJ works on the same principle of an air shear orchard sprayer (not an air blast sprayer) which uses air speed to cut the liquid where it exits the nozzle (gas in the case of the CV) creating micronization of the droplet size resulting in better burn characteristics. The volume of A/F mixture (in the case of the CV carb) is regulated by vacuum, which sucks in more fuel from the bowl (through our now new circuit), resulting in a richer mixture across the spectrum of throttle position, which combats lean burn.

Please correct me if I'm wrong...I am not the best with carburetors, although I have been around for a while. This would smooth the flat spots in acceleration, except we would still be pulling the same amount of fuel through the normal jetting in addition to the fuel through the new circuit (DAJ) so I don't see how we would gain any improved economy, except for possibly improving combustion characteristics resulting in more power/stroke?

I run a Thunderjet (I think that's the correct term...been on the bike a long time) on a shorty S&S E, 84" blockhead with heads flowed, cams and exhaust, and never really saw much difference (and I think it is similar in purpose to the DAJ). I would like to try the DAJ on one of my S&S dual throats...might be interesting, which brings me to my question for KipW. The website for the DAJ doesn't list Triumph. Which one did you use, or do I need to call them for additional information? Also, is it correct to assume that changing exhaust systems (higher flow characteristics) will require only adjustment of the DAJ and not the factory jetting? Thanks for the info.
 
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