740 carb review also known as DFT DFTA weber

[slabghost]

I guess you'll need Joe to answer that question. There is no need for such vacuum feeds on our bikes I'm aware of.

 

[mjanderson]

I am using one of those vacuum feeds for the vacuum advance on the ignition (although perhaps it's not necessary).

 

[slabghost]

You need a below plate vacuum feed if memory serves. One that gains vacuum as throttle is opened.

 

[Dusterdude]

I wanted to use a vacuum gauge to set my carb and couldnt find the manifold vacuum nipple,thanks for the info mike

 

[joedrum]

sorry about getting off track on passages ...i did this while working on carb and thinking i was proving it was so ..the reality was my lip seal was leaking making me think i was getting passage through there ..and to top that off the bike ran better ...took dan several days to convince me i was wrong ..i thought i posted that here in this thread ...we will get your carbs right guys just post away....im going to drop lower in idle jet than 45 ...im going to sodder it up and go 35 ...to lean out a bit more on hooch...

i also have a carb balancer air deal ive been running on awhile still working on how to make it competant in hook up ..will be posting soon on it also ... :thanks:

 

[mjanderson]

Thanks again for all your hard work and leadership on this conversion Joe. If we all continue to work together, fine-tuning our knowledge and experience, it will be an advantage for everyone.
Mike

 

[joedrum]

pics :BigGrin:

ok this pic showes a hose connected to the idle mix screw hole ....you can also see above hose is the allen head plug in fuel shutoff hole

this pic show the hose come up through the air box and down the primary barrel...probably dosnt have to go in barrel to be effective ..and ive had it both ways ...but in the airbox for sure

this is a joedrum mod to defeat this epa carb ...been riding a couple days now.... ive held off talking about this much ... but it seems the time is now to say something ...i call this the air balancer ...on my bike the idle has always been to rich on my modded engine oldwing ....done many things to this carb to get leaner...the idle circuit is just big in size in my opinion ..not only that the idle jet on my bike is 45...stock is 35 for oldwing ..so its my opinion ..not only is idle circuit to big the jet size is too ....i dont use the mix screw at all for gas feed of idle ...also i have a plug where the fuel shut off is and have screwed that all the way in hope to cut flow some and it dose....as far as idle gose ..all the gas comes from the three hole feed at thottle plate line ..yes just the 3 hole feeds gas not like i posted wrong before thinking the 2 side holes feed gas too ..i was fool by my leaky lips lol...anyway now that idle mix screw is not used for gas feed ..the idle is all adjusted at idle speed screw on linkage or like mine is ..i adjust idle at bar throttle ..i can adjust while riding this way ....both ways adjust the trottle plate from the close possition..to open it some to get air to pull gas from idle circuit ..well this works to good and the gas is heavy on the rich side ...to counteract that the mix screw is taken out ...and a make do slleeve and hose goes in the hole where mix screw was ..and the motor can draw air here and it dosnt feed any gas ...the hose gose to airbox to its air ...this lean the idle out some ... witch is needed big time ...once the throttle open enough that the air there is more faster than idle circuit air idle circuit shuts off and so dose the air balancer i moded into carb ....this has made huge impact on how my bike runs ..mostly in consistancy and leaner and no gas smell

the peopl ive riding with are new to hooch and there just blown away at the bike as i am too ...to have road gearing as good as anything out there ...and run like a crotch rocket is stunning mix to have in one bike ... im not sure this applies to other dft users ..but at least now you seen what hooch has ....im pleased mpg is still low and may never improve 36mpg ...but im also sure this bike could curise all day at 125mph if it had enough gas ... :hihihi: :thanks:

 

[dan filipi]

Joe and I have chatted many hours about that over rich idle circuit with both of us having the carb right in front of us to dissect.
I have a suspicion the idle circuit sets up a "siphon" of sorts that is uncontrollable with the original mix screw eliminated by design.
It's basically a flaw as I see it, when used on our motor. May be it was fine on the auto it was intended for I have no idea.

The hose mod of Joe's could be breaking that siphon and/or adding air to the gas at that point in the circuit.
We both tried putting a screw into the hole where the original mix screw was intended to be, the screw head shaped in a way to better meter fuel flow. That helped some but was hard to control very accurately.
The 'bleeder hose' seems to solve it well for Joe.
I say whatever works.

 

[joedrum]

i can honestly say ..in my opinion ....ive got the dft carb modded and dial in to the hooched out 1200 engine ....

things ive notice that is in play on a high flow set up .....air box has to have enough filter space to not to impede flow of air motor wants ...if so this can cause rich ..all by itself ...like plumbing capasity has to be right ....this is mostly a high rpm flow deal ..but became obvious it effect idle too ....last night while riding home....played with the secondary barrle on carb...it was flawless taching 8000 is instant ...in lower gears ....cant even play more than 2 gears under 100mph 3rd gear gets you there.....in fifth gear at speed roll power is huge with secondary kick in ..even under its heavyest load ..there is no carb deals acting up ...it grabs the load and makes a joke out of it and your gone ...best running anything ive ever had ...just never misses a lick....sure is stunning to me how much better this induction system is over any bike ive ever dealt with ...there is simply no weak spot anywhere ..not even idle....... fixing to install pusher fan on radiator .... :thanks:

 

[joedrum]

ok the results of the 1000 mile road trip and dft set up .....the bike did really well running the interstate ....and the bikes getting 40mpg plus i didnt figure it all the way out to the exact but it was obvious i was getting over 40mpg...id say the average speed i traveled was 75mph ....but 80 plus was easy and instant like when you wanted to ...the dft perform huge here ....mine has a proggressive linkage mod where the secondary come in sooner ...this really turns thr dft into a performace carb as oppose to economy car carb ....and brings secondary power in wider window of the carbs operation ...this was great move as it paved the way for like sling shot passing on the intersate at speed...as for perforance on the road ..it simply lacked nothing .....

ok on the down side of things ..it seems my last carb mod is not quite one good enough yet ....seems after long period of running at speed gas was getting into my carb air balancer deal and would cause highe idle when that happen ...seems it gets warm enough the gas tends to leak in air tube ive got from from carb to air box sending it into a high idle situation ..

so the next move is to improve this ......i am going to take the carb off ..and drill the plug out of the carb base that leads to the gas feed for mix screw and then replug the gas feed above the mix screw so there will be no more leaking there at all .....when the gas is not leaking into the air balancer the bike idles great .....

im very pleased how the carb performed ..now all i have to do is bring my mods up to a competant level of operation :builder: :thanks:

 

[Dusterdude]

Excellent

 

[joedrum]

thanks duster ....i am thrilled how the bike performed......went for a ride this morning for the first ride sence getting to fla from indiana.....bike ran super ... :BigGrin:

 

[Dusterdude]

Groovy

 

[joedrum]

wow went for ride just now ..after doing some wiring work ....this is my hpme and i still know some nice strait roads loney roads through swamp land ...when i was a kid these roads got a lot of my hi speed riding ....anyway i know every bump and ripple in this one road at top speed and acelleration.....it was in 90s here already...no vetter full motor cover lowers on ...felt the the runners on shovelking induction system....for the weber ...32-34..they were still running cool to the touch even though id been out riding at rather high speed for a 1/2 hr. or so ...

so i decided to push the bike a bit .....long story short ..i think i was in forth gear and hooch was approaching 120mph ...it was charging hard there ...i was freaked and begining to break ...all the sudden the bike shut down ....thought maybe i hit reserve ...bike came back sort of choppy at first then fine .....rode a bit ..flip back to main tank ...bike was not out of as there .....truth is carb ran out of gas ....sort of like what the stock carbs did instantly when they were use .....but the weber comes back rather quick where stock carbs wouldnt ....anyway as far running this is one bad ass bike ...i know it hard for most to beleave ...but when this bike takes off its gone ....you have to hang on good ..it hits all gears hard .......theres no telling how fast the bike might go ...it marches past 110 like its 70mph....my my im proud ....got more to post but going to eat something first :thanks:

 

[joedrum]

it appears my bike dose not like heat at all ....my bike likes the 1 1/2"thin wall runners ....if i reach down there and touch them and there cool feeling ..i know the bike is going to run hard if asked to....its finally dawned on me that my full motor cover vetter lowers hurt hooches running ..especially at idle ...bike is fine always with no lowers on ....if there on it ...the idle goes screwy...and it seems to dip in power just a bit....im surprise i havnt put this together before now ....so no lowers for awhile and see if this theory proves out ....

well this is no case for me ...on my bike ..to ever add heat ...lol whatever all others seem to think is manditory i find the opposite for my bike ....time will tell ..lots of riding fixing to happen :thanks:

 

[dan filipi]

Does it seem to be running leaner, or richer when the lowers are on?

 

[joedrum]

richer when hot......it seems dan ....i think like a intercooler dose when cooler ..the air is denser making it leaner charge as more air is there ...is my thoughts ...

 

[slabghost]

Cool air is denser than hot air. The warmer air would vaporize more of the fuel charge and actually lean the mix.

 

[joedrum]

today im going to check plugs ....been lots of hiway miles put on .....plain and simple part is it runs much better with cool runners period ...thats just plain fact as it is now ...trapping the heat inside the full motor cover vetter lowers ...has in no way been a asset at all.....total discount to motor operation ...id like to go smaller on idle jet some its .045 now ...like to .040 or .035 like stock honda carbs are .....i think now my idle is at rich side of being ok ....so im going to work on reducing idle jet ...sheesh maybe today.....when runners are cool to touch i get lean pops on deceleration not bad but there ...

oh by the way so far did lots of riding yesterday ...bike ran great with lowers off and idle was fine ....and i was trying to mess it up ..and get it to load up or what ever ...and couldnt

 

[joedrum]

i never have checked plugs yet ...but i did reduce idle jet in primary barrel on the weber ...this seems to be the last great move so far .....it diffinitly made idle smoother ..tho it was smooth already ...it seems it was the last spot that was on the rich side some.......went for small ride test ....seemed to be just a tad smoother down low and could idle slower on the move ...stop at several stops where idle was less than 1000 and hung in there nice ....with how im set up ...i adjusted the idle on the fly and it really responed to the tweaking well ....i really like this set up as it sets up the idle and gas and air mix for everything just off idle ...the bike dose this work better than any motor i have ever had ...no getting going to it ...just gone before you started is more like it ....im always trying to catch up from my own move with hooch bike .....ive got testing to do but id say i just left the 98% range of dial in to an even higher level ....this is a hard area to improve as there only 2 spots left uphill...and many moves downhill one could make

i had no way to sodder up jet and drill out ...i have no bits here.....so the idle jet has one wire strand going through a .045 weber idle jet.....and the way i did it it is locked in and cant come loose inside carb ...it is actually held in place by the idle jet holder ....where ever your at ..you make do with what have ...and never get stoped ..is my way ....glad i did it ...ill post more after a good long ride test soon to happen :builder: :thanks: