HT power


Local time
11:25 PM
May 30, 2008
1.will a happy time engine pull a 200lb man from a dead stop without burning the clutch ?

2.will question 1 work much better if im doing 5mph ?

thanks mike

FWIW I think most people will recommend pedaling the bike to get some speed then let out the clutch (pedaling to 5+ mph would be helpful)....Geared low enough you could just let out the clutch but the gearing would be too low to be practical for reasonable cruise speeds....Of course there is always the shifter kit where you may be able to have gearing low enough as to not require excessive abuse on the clutch from a dead stop and have gearing for the top end as well....

Hope this helps you.

A hole in the HT power story

I want to say that all the mods people have mentioned have done well with my first couple HT motors. At the same time I want to say there is a huge hole in the story of power and speed. Let's put it this way, these motors are meant to run at high rpms. That is the bottom line. My best build yet is a stock 66cc that has had the exhaust and intake manifold as close to port matched as is possible and the stock exhaust drilled out and only $25 plus shipping for a Speed carb and $20 plus shipping for a 48 tooth rear sprocket. I did substitute a used but good quality plug wire that was lying around in my garage and a NGK bp7hs(cooler) plug too. All I am going to say is this thing is nice. It will pull off the line as well as any production scooter and will top out at 35.6mph on a flat stretch of road. I was able to tune the carb so it has a smooth transition through the entire throttle range.

I have gone through all the common mods and performance parts to find that not much at all is needed to pull my 235lb self and a heavy stretch cruiser off the line and up steep bridges and hills without a problem. The motor feels much smoother in its preferred rpm range too. Not only can I make it over the bridges without loosing speed but I can accelerate up them.

My advice, rather than spending more money than the entire kit cost and enough time to carve one of these motors out of a block of aluminum just run them the way they are designed to run.
Normally letting out the clutch without a roll or peddle off will stall the engine no matter the weight of rider.

reach a speed of 5mph or 10kmh before releasing the clutch. That way you don't stall the engine and destroy your clutch pads.
These clutches are way more durable than I thought they would be. I've slipped the clutch all the way up hills with no resultant damage. But these small motors with mid range gearing definitely need you to pedal from a stop.
I have read every entry in this forum and most multiple times. I do not disagree with most of what I have read about power increasing mods but I am telling you: Follow my last post and you will be riding a vehicle that runs neck and neck with a production 50cc scooter or moped. I don't have to pedal assist at all from a stop and I can get a speeding ticket according to the laws of my state(30 mph max on a moped with a moped license)

One last thought on the subject; a set of clutch pads cost $8 and takes all of about 15 mins to replace. Who cares if one "burns them up"? We aren't talking about changing the clutch in a Ferrari.

You don't have to listen to what I am saying but I know what I'm talking about. (This comment is not aimed at you. I use it all the time)
Yes, I very much agree. See, I'm 6' 6",255 and ride a 28" bike. I help some, but if you just use a little common sense, you can pretty much start just about anywhere.

I run a modified GT5R 66cc "Super Rat" china girl engine, shaved stock slant head for a little more compression, a re jetted carb, a hotter ignition, a SPB Expansion pipe and shift kit, a Pirate centrifugal clutch.
(this clutches spinning mass gives the china girl some "fly wheel" effect, its noticeable)
This all feeds through a shimano 11/32-9 speed rear cassette with a 48tooth driven chain ring and a 36 tooth drive chain ring.
The stock clutch is only used to bump start the engine, once running its hands off the stock clutch.
This is a good set up if you like to peddle because that big 48 tooth can really help out the engine.

I always start off in 1st or 2nd gear, peddle it up to like 10mph before I get on the throttle. This also relives undue shock on the bikes derailleur drive train.
Once under way I up shift and peddle, I listen to the engine, I can hear and feel the the sweet spot at about 35 to 40 mph .

Top speed is an observed 57 mph on level ground, it pulls over a 350lb load with me, the weight of the bike its self, my gear and a half gallon of gas, no wind, 2 way average, but i try not to push it that hard.
So its barely breathing hard at 35 mph.

I know im taking strain off the engine by keeping the RPM down, helping it live longer and getting way better gas mileage.

Yes... it could easily pull my fat behind away from a dead stop, but why strain the engine and drive train?

Peddling has also helped me drop 20 lbs so far, down from my usual winter 270lbs... My doctors are congratulating me, my blood pressure is down, and I'm having a ball NOT being stuck on the subway coming home from work at 4 in the morning.
The ride home over the Manhattan bridge to Brooklyn is a treat at that hour, less traffic, fewer cops and you can really get on it!

Theirs a reason these things still have a crank and peddles...ITS STILL A BICYCLE... peddle it!

Have fun, and watch out for Kamikaze cab drivers!
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Normally letting out the clutch without a roll or peddle off will stall the engine no matter the weight of rider.

reach a speed of 5mph or 10kmh before releasing the clutch. That way you don't stall the engine and destroy your clutch pads.

hmmm, i can and do take off with my m.b.'s like a motorcycle and i do not pedal.
I just feather the clutch like on a motorcycle and it pulls me easily from a dead stop.
of corse i only weigh 150 lbs.
one of my bikes is running 20" wheels with a 41 tooth rear sprocket, 66 c.c. h.t. all stock except for an accell 8mm plug wire, ngk b6hs plug, modified baffle and a high flow air filter.
my other bike is also running 20" wheels, 41 tooth sprocket, 49 c.c. h.t. with an expansion chamber with a modofied stock muffler, a high flow air filter. ngk b6hs plug, accell 8 mm plug wire.
I run 32:1 in both of my bikes, and both carbs have been re-jetted.
I don't like to pedal, i just use the pedals for foot rests.