I'm looking for a 55 mm for my 103 with stage II heads and cam and I'm currently running the stock throttle body with 4.9 injectors but at hi speeds it seems to be lacking.. Does Harley make a 55 mm throttle body for a cable bike.. All I can find is Screaming Eagle throttle by wire.. I do know HPI makes one but they are a little expensive and thought maybe an HD one would suffice.. Any help or info would be appreciated.. Thanks..

 

lacking meaning what???
you could be shooting yourself in the foot!!
seen this toooo many times especially with carbs, hummm if a 400 cfm will work, a 750 would work twice as good, hardie-har-har!!!
like mowing the grass on a rider with one low tire and the lawn shows it, find the root cause, aka, air the tire up.

 

POWER!!!
​​​​​​ My last test hit I did was great up until about 120 mph after that it really didn't want to go over 125 mph.. It just seemed to lose acceleration.. Not sure if it was my Fuel PE mode making it to rich or the stock throttle body just to small for my build..

 

https://www.horsepowerinc.net/cable-...7-big-twin-twi
HPI is is about as good as it gets.

 

What's your dyno sheet look like?

 

I don't really trust my last dyno sheet, it was done April of 2022.. The shop that I had it tuned at actually decreased the performance of my build. I went back to My tune and manually tweaked it by doing 0-115 mph test hits with data logging.. It's a long process but is worth it in the long run..

 

I don't believe a 55TB is going to gain enough to break the MPH goals you have. You prolly need another 25-30%, and the TB (and retune) may elevate the right side by 3-4%. Engine tips site says 10% increase in speed requires a 33% increase in HP.

 

To answer the question,,,HD SE used to make a 50mm tb for cable, i have one, bought it for my bike. stepped up to the HPI, which is kinda hard to beat especially with the 58 intake plenum behind it, they call it the 55/58 setup.

my opinion on your speed issue,,i dont think the throttle body is going to make the difference,,,,it might help some, but unless you are over 110 hp which your sheet was not,,,i expect you might be running into the limits on weight, wind resistance and gearing.
m

 

I do appreciate the response but the thing is on my 97" Evo Fatboy I've had 5th gear still accelerating at 137 before I let off and still had 6th gear... That bike on the Dyno did a 6th gear pull to 6000rpm/160 mph..I know it's a Dyno and I'm not comparing that run to real world conditions..

I guess the lack of HP up top is my issue and am sure a larger T-body will make some difference and maybe even a cam change.. The TW 5-6 is not known to pull past 5500 rpm.

I have been contemplating a 110" with either the W8 or the 888' but with everything else I'll need it'll be $3k.. We'll see..

 

most mfg test air flow to peak and then figure in at 50% throttle @ 50% flow which works well for the street. a larger TB can increase responsiveness and uncork the top end. however, the ecu with cut back from sensor input unless compensated for, tit for tat, you will gain in one area and lose in others.
mr. marco makes a fine point and you confirmed it. if you do not have the gearing for it, it will stall.
another issue is hd power curve falls like a rock, you need a curve that extends past peak, called after peak power. if you have two engines the same but one can pull the after peak 500 more rpm out, you will win since you have more mph per shift.
trade up

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