740 carb review also known as DFT DFTA weber

joedrum · Sep 25, 2015

gee wizz i just posted here ...must have done something wrong .....went for long ride down coastline near cocoa beach .....hooch did really well on idle jet mod ....smoother even more down low in rpm also idles slower and its hang time is better ....slowly getting the idle circuit whipped down .....im sure to get a mpg increased ...seems the effect was wide as the idle and off idle circuit covers so much of the average curising going on ....

great to have such a smooth running monster of a bike ....going riding with a harley in a bit ...one of the big boys ...looks huge compared to hooch ..... :Egyptian:

Dusterdude · Sep 25, 2015

Good deal joe

joedrum · Sep 26, 2015

ive got enough time in now to know both worlds ....i have had some fast set up oldwings both stock carbed and weber carbed ......ive seen and read all the threads ....

.all it takes is common sense to realize cv carbs are a joke to carburation ......adding all the stuff that totally unneeded in the operation of fuel charge makes for one thing a very non power producing set up and actually is not good for the motor .....who knows how many oldwings died from leaking gas in the oil from the sidestand ....about any oldwing full of gas and parked on sidestand will leak gas in motor..... parts are small springs are weak from small size too and it will leak eventually .....in most cases eventually is here these bikes are 40 yrs old ....the parts available to fix old tired parts dont exist ...if they do they not up to par really and are downgrade from stock witch was not really good enough either ......the oldwing motors by there design brought all the discounts to cv carbs and made them major issues that effected the motors health ....and the carbs have always fallen short on providing decent gas charge through the rpm zone ........

these things i know for sure ive been down the stock carb road to great success ....the angry dresser 1100 i built never was out ran by another oldwing and it was fully dressed .....at the time i did not know i had the early 75 carb rack maxed out in its ability to operate with the 1100 powerplant that i modded up to have the early cams in it .....and i did some created mods to even get that to happen .....but truth is it did perform well and better than any oldwing i had before ....

but this did not carry over to the 1200 build i did .....i could get it to run with no load ok on stock cv carbs ....but when load was added ...the vacumm just didnt line up a all ..the new build would suck the slides up to full throttle and empty the bowls quickly and die so completely bike would stop running before it could recover on a perfect set of 75 carbs ....could put them back on 1100 and they would work .....anyway our member eric has been trying several yrs now to get cv carbs to work on his 1200 witch is a lot like mine and is still trying .......

opps pushed the wrong button wasnt done yet .....ok me iwent to a single carb ....why it was right in front of me .....right off the bat i had some early success followed by a couple yrs to where i am now .....it was very hard for me as i knew nothing about weber licenced carb i had .....took me a long time to figure jetting was not going to right it ....it too is a epa junk tech carb thats impossible to dial in right as epa decided to cripple carbs and make something different and call it a higher tech carb .... they created and force carb manufactures to make junk carbs .....witch is the same thing that made honda adapt to junk tech cv carbs ...before this MC carbs were strait carbs with adjustments....

so there was a long sting of mods ive made to this weber epa carb ......to try and get it to dial in right and stay right .....many things worked some but didnt hang ...had a bad side ....it was as hard as anything ive ever done to figure out ....why....cause info out there to read was just epa like ....WORTHLESS INFO BACKED BY STUPID....and was actually more harm than good .....but me being me .....i finally figured that the info gods were stupid and went my own way with the help of others who were doing the same thing and leard in in oldwings just like music ...if a group works in a compliant mode to each other instead of a defiant mode you can make great music or dial in a non dialable carb in.....thats what happen here right at classic oldwings.....

not sure if anyone cares ..but the truth is the stock carbs in there best day is in no way as good as strait carb dial in ....anyone who wants to challenge that is fine with me ...im around .....to have misinfo out there to a great as mod to a oldwing as a c5 ignition is just crazy....and thats that ...im fearless to anyone who thinks diiferent and can back it up with a bike ....

my bike has power ..big power ...but that seems small in light of all the other things it dose so much better than stock cv carbs :builder: :thanks:

Davemacinnh · Mar 31, 2019

This is awesome! Great write up. I am about to do the 740 conversion myself on my 1000. My question is, where did you end up on jetting? I would like to get it mostly dialed in before I put it in. Any help would be greatly appreciated!

joedrum · Mar 31, 2019

Ok first thing is .... if your 740 carb you have has a fuel shut off solenoid don’t throw it away ...most people do but it’s a essential part of the carb and it needs it ...pass that ...there is the power valve deal on most 740 carbs that richen ups the fuel mix through vacuum ...as the epa carb it is ..is made to operate lean actually to lean ...some keep this feature to me it totally screws up dialing a carb in as there no adjustment to this deal ...there are other things I took off the table also ..I have no choke at all on my carb ..when fully open it still blocked a lot of air ..high revving oldwing motors need air especially my motor ....as far as jetting goes always start with the Jets you have and go from there ...my jetting is way big and motor is 1200 with hot cams ...

Davemacinnh · Mar 31, 2019

The fuel shut off is left on and powered correct?
When removing the electric choke, is that just a “seal the hole sort of deal” or is a plate needed? Same with the power valve? Makes sense with the jetting, I just wasn’t sure how close the stockers were. I’m very mechanically inclined but dialing in carbs always gives me a hard time.
I appreciate your insight

joedrum · Mar 31, 2019

I’m a bit busy at the moment I’ll post some more later ...glad your going to give ut try

joedrum · Apr 7, 2019

Ok sorry it’s been awhile since I’ve been on the forum been traveling and not connected to Internet ...yes I can’t remember much on the choke ..but it’s simple just pull it off I’m thinking ...seems like mine just had a choke plate on the primary barrel and I took that plate and linkage out so both barrels are unabstructive ...the power valve if yours has one can be eliminated with epoxy to block fuel flow or simply block the vacuum channel or both with epoxy putty under the three screw cover on the side of the carb ...mine was factory blocked with a cap on it ...not sure what my carb was on to be made like that ..there are several vacuum holes that need plugged also to get it to be a strait carb ....on my bike the first real big problem was the idle / off idle circuit is a combined unit that no matter how I set the mix screw and fast idle screw on the linkage it was way to rich ..but my motor really pull the gas in ..your motor may just dial in as is ...seems others with 1100s got there’s to do really good so to me this is the starting point I’d start with ..with the epa crap done away with and choke removed ...