HF 2.5HP is a killer engine! New Speed Record!

[chrisnbush]

Oh man, that is wicked cool.

Can you tell me what the ratio is on the CVT and what the wheel tooth count is - where the CVT came from ? I am gonna build one for sure.

New exhaust mods in progress!

 

[Nitropeewee]

yes for sure, NEED THAT CVT!!

 

[lowracer]

I've got a similar engine but mine is the flathead 98cc Lifan 2.5hp that I paid $89 for brand new.
I always hit 50mph @ WOT in aero tuck the way I have it geared (front rack mount)
I too bypassed the governor.
I can cruise in the 40's without getting aero (gobs of torque).
It is definitely a porker of an engine weighing way more than a pocketbike 2 stroker, but torque is king & I can pull the throttle at any speed & it pulls hard + not oil & gas to mix.
It starts on the very 1st pull everytime too.
I just sent my 5/8" Max-Torque centrifugal V-Belt pulley clutch to Jim@Max-Torque for a precision bearing retrofit upgrade ($46). The oillite bushings in the Std clutches are garbage & this change should be pretty slick...I will post a new thread once I get it back & test it out.
-Lowracer-

 

[MikeJ]

Lowracer -

I fired up my HF 79cc for the first time today for testing without a drive chain to the real wheel. Like you, I have the original bushing in the 3 inch belt centrifugal clutch, and I see the bushing as the area I want to improve, even if it does last for a long time for some users. I will be looking forward to your post on the improvement the upgrade has.

MikeJ

 

[HeadSmess]

awwww, this threads too long...

right. a 142 f. today i topped 62.5 km/h. 20 inch wheels. with 15:1 reduction. lower gearing it would get higher but some hills around here are killers...

62,500/60/1.59*15 = 9800 rpm approx... not bad for a lil 4 stroker thats meant to do 7.8 max...

 

[Elmo]

I have reached 39.4 mph on mine with a 12-1 reduction at 6000rpm +

 

[MikeJ]

Hi Everyone, and to Lowracer -

I just ran my engine up to 73 miles on the odometer. It has about 5 hours on it. Been motoring around on common streets, about 5500 feet above sea level. This altitude and the fact the engine is still breaking in leaves me thinking there is power unavailable to me at this time.

How long would you allow for breaking in, on stop and go streets and stock air filter?

My bike is geared for acceptable acceleration at sea level; it is a bit weaker here (allowing 3% power reduction per 1000 feet). I have reached 32 mph for a brief time at 3700 rpm using a jackshaft and Sick Bike Parts MegaRange cassette 3rd gear in back.

Thanks,
MikeJ

 

[lowracer]

MikeJ,
I dont break my engines in.
As soon as I get them installed, I take them out for a full speed run to test them out & make sure they were built well & dont blow up. Then I know if I got a good one or a dud.
Then I change the oil. I run them a few more hours & do another oil change.
Definitely worth the $40 to send your clutch back to Max-Torque for the upgrades (shoes, springs, billet pulley & cartridge bearing).
-Lowracer-

 

[andyszyd]

Hi Everyone, and to Lowracer -

I just ran my engine up to 73 miles on the odometer. It has about 5 hours on it. Been motoring around on common streets, about 5500 feet above sea level. This altitude and the fact the engine is still breaking in leaves me thinking there is power unavailable to me at this time.

How long would you allow for breaking in, on stop and go streets and stock air filter?

My bike is geared for acceptable acceleration at sea level; it is a bit weaker here (allowing 3% power reduction per 1000 feet). I have reached 32 mph for a brief time at 3700 rpm using a jackshaft and Sick Bike Parts MegaRange cassette 3rd gear in back.

Thanks,
MikeJ

32 MPH with 79cc engine is not bery impressing, something is wrong.

I do 32Mph+ with my 52cc 2 stroke pump engine, roller drive.

And I am 285 lb.

 

[MikeJ]

Andyszyd -

I have to agree with you there. But I am not done yet. I did not push the engine real hard during my testing (which was meant to test the "tire in a tire" configuration). Maybe a smooth-wall exhaust system would improve performance. And I have yet to wind the engine up to 4000rpm yet.

Following Lowracer's philosophy, I intend to start pushing the throttle wide open more often. I was just becoming familiar with how my extra long frame (with front shocks) handles. It is definitely not as rigid as a stock length bike with solid forks up front.

Lowracer - Thanks for the clutch input. Mine needs improvement. It does the "grab and slip" dance in the 2400 rpm range. That makes for a jerky acceleration.

MikeJ