[Flynn's_61]

I'm interested in you guys with different transmissions behind the 45 flatties
and I'm wondering what your most realistic top speeds will be?
Anybody got one they can take on the freeway?
Pics are cool!


sweet.

 

[Scavenger]

realistic 60,,though I'm sure someone will say they cruse all day long at 75

 

[iiggii]

Yup 55 -60

 

[choppercopper1]

60 going down hill with a strong wind on your back. LOL mine tops around 55.

 

[lackluster]

You can have a higher top speed, but it'll cost you a lot of low end torque (which makes them much less fun on the street). It'll also cost you more than a few bucks. Theyre awesome and fun, but they're inherently "slow" so you'll have to throw down some cash and make some compromises if you want it to go faster.

 

[old.wrench]

Those little flatheads are cute as a bugs ear, but they wern't designed to haul ass. The Factory advertised the top speed as 55 m.p.h.

Regards,
Geo.

 

[gearhead1951]

Check with "Panic" at www.victorylibrary.com about what performance is available for these old warriors !

Howbout a 54" stroker using sportster rods and journal !

 

[el diablo]

realistic 60,,though I'm sure someone will say they cruse all day long at 75

mine actualy cruses 75 m/ph

but cilinders and heads are reworked ,linkert M74B ans some more nice goodies and a joe hunt magneto and a '69 ratchet top 4 speed gearbox
also different sprockets and chains ....and more

it runs like a charm and reliable
both at low cruisin speeds and at full throttle

 

[thefrenchowl]

This pretty std one did a pass at 90mph at Bonneville Speed Week in August... And ridden by the lady, Madeline!!!

Patrick

 

[HD48FL]

This pretty std one did a pass at 90mph at Bonneville Speed Week in August... And ridden by the lady!!!
Patrick

Speaking of Bonneville and Flatheads, check out Paul Friebus (American Cycle Fabrication). He hit 98.4 mph on his 45 Flathead.

He certainly knows his Flatheads: http://www.americancyclefab.com/Bonneville_Racing_U1J9.html

 

[wldpilot]

Here is an excellent thread on how to do some simple mods to wake your 45 up:
http://www.jockeyjournal.com/forum/showthread.php?t=22069

 

[dudleysbasement]

i had a 42wla that could do about 100 but it had an offset crank pin added 1/8 stroke , k piston ,gas ported the tops off the cylinders to match k model , ported the cylinders . brazed the outside and bored the intake manifold out for larger linkert , sporty pb+ cams which i added the oil pump drive to i also increased the motor sprocket to next size up from stock

 

[Scavenger]

not on a daily basis ,,and in the end I'm sure that what he's asking,,everyday roadabilty

 

[Bill]

Hi Greaseball, 45 are great bikes around town, but from my experience not much on the freeway.

Patrick, thanks for posting the picture of us with our 45 at Bonneville this year, what a great experience that was. We hope to go again next year. I bought a Sport Scout Basket case and hope to go faster than my wife, so I'm shooting for 100. Hope to see you there.

Bill

 

[HD48FL]

not on a daily basis ,,and in the end I'm sure that what he's asking,,everyday roadabilty

Correct, the thread got a little off topic. My response was to the one above mine. Sorry for taking things off path.

 

[Rubone]

You asked about different trannys behind a 45 for top speed. Keep in mind that the stock transmissions and all Brit options all have the same 1-1 overall final ratio. So your effective gear ratio is in the drive sprockets, not the transmission. therefore your top speed is determined by engine RPM driven through whatever ratio you choose. The extra gear in a Brit 4-speed might give you more in town gear options but once in high its all the same.
My 45 is quite comfortable at 55-60 and will run 75 in bursts. It is completely stock and far heavier than a custom build would be. It also does this at a base elevation of 7000ft. The 45 likes RPM more than Big Twins do so don't be afraid to spin it a little. I originally was runing a 33 tooth engine sprocket but my wife did not like it as when she rode it she tended to stall it on takeoff. I changed to a 31 with no loss of top speed but better take-off and acceleration. Still smooth and happy at 55-60.
Robbie