Puch high compression head...

Discussion in 'Performance Mods' started by haddenboy, May 9, 2011.

  1. haddenboy

    haddenboy New Member


    Just thought I'd share my latest find for a cheap performance upgrade. This is a puch 70cc high compression head for a moped, but bolts up perfectly with my starfire 66cc engine. I also have a skyhawk super rat that this will eventually be mounted on however i have to drill out the holes on the new head about a millimeter and want to wait til I can use my friends drill press for precision. Anyways, the head adds a noticable increase in top end power, and let the rpms run much higher than a stock HT motor. After I put this head on my superrat as well, I will post more info on results of that upgrade as well.

    Attached Files:

  2. Motocruiser

    Motocruiser Member

    My buddy has a Puch. I always wondered if our jugs or heads would interchange. Let us know what you find.
  3. geebt48cc

    geebt48cc Member

    Nice there Hadden...............

    What kind of temp are you running now? Have you checked to see what your compression is now?

    Thanks Glen
  4. Fabian

    Fabian Well-Known Member

    That's what we all want: a cylinder made out of more thermally stable alloy. There are enough after market cylinder heads for the 66cc Chinese bicycle engines so it's no longer a concern these days, but a high quality cylinder is definitely needed.

    The ideal situation is for someone to manufacture a case reed valve bottom end with the same external dimensions as the current engine; allowing after market hardware (like a SickBikeParts shift kit) to be attached to the original mounting locations.

    I am on record for espousing the idea of a full billet CNC machined engine, designed to optimal 2-stroke theory, and i am also on record for saying that if someone makes this engine, i'll be the first person to have my credit card on the table.

    Now if only SickBikeParts could make a reproduction GT LTS frame in heavy wall steel, with disk brake mounts and integrate their shift kit as a permanent attachment, as well as designing and manufacturing this engine with a torque biased power curve, it would be the ultimate bike,


    to paraphrase Taylor Swift: "like ever" !!!
  5. zwebx

    zwebx Member

    High compression is not always the solution... better port timing and better sealing surfaces are the go for better torque also the best crank seals you can get are also the go
  6. Fabian

    Fabian Well-Known Member

    @ zwebx

    Have you got your longitudinally mounted 4-stroke and right angled gearbox organised yet, in a disk brake frame?

    I'll be heading to Mt Baw Baw on Friday for a filthy steep hill climb; having a reputation of separating the men from the boys...
  7. zwebx

    zwebx Member

    im waiting on a longer crank.... yeah i got disks front and rear... front suspension and a relaxed riding position
    i think i need a +30 mm crank and i dont know a local store that stocks them..
    i might be able to get it done by friday if the parts come in quick or if i can source them locally
    Last edited: Mar 16, 2013
  8. Fabian

    Fabian Well-Known Member

    You must understand that Mt Baw Baw is a total ball breaker of a hill climb; in fact it's so steep that people who do manage to ride up, won't go down if they have rim brakes because the rim gets so hot that it expands the air inside the tyres to such a degree that they blow out.

    It's the second steepest continuous (bitumized) hill climb in the world with a maximum gradient of 22% and a minimum gradient of over 10% with the average being around 14% and it's a full 6 kilometers of beating your engine to death.

    I crunched the numbers the other day and i'll need to use low range first gear which works out to 5.5 k/ph (3.4 mph) for most of the climb (with trailer in tow) meaning that it will take me over an hour of "revving it's guts out" rpm with next to no airflow over the cooling surfaces for the entire period, and i'm not stopping for a rest break.

    The last time such a feat was attempted, the cylinder head temperature went off the scale at 300+ degrees Celsius (572 Fahrenheit) and 600 degrees Celsius Exhaust Gas temperature (1112 Fahrenheit) with a column of smoke rising from the cylinder head, be it on a 38 degree day (100 Fahrenheit), but only for half an hour.

    This time it will be double that with a full hour of spewing oil and piston rings out the exhaust !!!
    Is your bike capable of such severe duty punishment?
  9. zwebx

    zwebx Member

    the motor will be able to take it.. its a industrial motor so its got a fan installed... the only thing i would worry about it how my gearbox holds up (it is beta afterall) and how my ratio is...
    but your right i wont be able to make it friday as because i want to test the thing for about 500 k's atleast to break in all my chains
  10. Fabian

    Fabian Well-Known Member

    Trust me, after 2 minutes of the Mt Baw Baw hill climb your chains will not be broken in, but on the verge of breaking.

    The last time i rode up Mt Donna Buang with an ex-girlfriend using my high-tech speed equalisation device (bungee cord tow rope), the chain measured up at 80% stretch after only 17 kilometers (10.6 miles) with 20% stretch at the start of the climb.
    Must be remembered that Mt Donna Buang only has an average gradient of 6.4% and Mt Baw Baw is around 14%, so your chains will be well and truly trashed in the 6 kilometers (3.75 miles) to the summit.

    I wouldn't mind betting your 4-stroke engine will most likely forcibly eject it's internal components, battling against a 22% gradient; causing an environmental catastrophe as shrapnel pierces the fuel tank, engulfing bike and rider in a fireball that endangers all and sundry, not to mention species listed under "critical stress" by the World Wildlife Foundation, i.e. tasty indigenous animals that go nicely with BBQ sauce.