engine tweeks to increase hp

Discussion in 'Performance Mods' started by vcain, Jul 5, 2008.

  1. vcain

    vcain New Member

    if anyone has anymore that they have done let me know and i will try them out too always up for making my bike go even faster lol

    ok i know is said a month or two ago i would post this the next day but i had other things get in the way and i will admit i forgot (you memery is always the second thing to go with age)

    ok the things i did to increase the speed to my motor are:
    bored out the exost port on the cylender and the muffler
    also in the baffle i cut the tube inside to about a half an inch long
    bored out the intake tube that the carb mounts to to the same size as the whole in the cylinder to maximize gas/air also changed the stock filter to a sock filter it allows more airflow and it is so much easyer to take off and wash
    went from a stock 44 tooth sprocket to a 38 tooth sprocket
    this is on an 80 cc engine if you have a 40 or 45 cc i only recommend going to a 40 tooth anything lower than that will take away from your power band

    top speed after breakin of a new motor is about 48 to 53 mph depending on the wind but 53 is a bit scarry on a bike lol
    you loose a little on the take off so you have to peddle a little more from a dead stop but i think the top speed is worth it

  2. Zev0

    Zev0 Member

    Moved to 2 stroke section as that what the OP is talking about. It was found in the bicycle repair section where it does not belong.
  3. BSA

    BSA Guest

    It sounds like you've done most of the mods. The others would be rejetting the carb and expansion chamber. Look in wild in the streets for even more modifications.

  4. badmoon

    badmoon Member

    First im french and dont understand all if you can explain me some tips i will be happy :)

    when you say "bored out the intake" do you cut the intake put it out or just buff the inside ??? cause me i have a 27 tooth sprocket and have modified the muffler with some new hole and ive reduce the baffle inside so my speed on flat is arround 34 mph max and when i climb
    i need to pedle so give me some help i want to reach 40 mph in flat road .
    Last edited: Jul 5, 2008
  5. Maxx Ported

    Maxx Ported Member

    Have you reduced the head chamber size, to increase compression and polished it?

    Attached Files:

  6. badmoon

    badmoon Member

    i want more info about the head chamber .
    Last edited: Aug 2, 2008
  7. Bikeuser

    Bikeuser Member

    You can't reduce chamber size without affecting the integrity. You show me a guy who has a 9:1 compression HT and i'll buy you a harley davidson
  8. Maxx Ported

    Maxx Ported Member

    I'll post the cc"s when I get the other engines, to compare stock to my Reduced Volume head,

    Attached Files:

  9. Maxx Ported

    Maxx Ported Member

    rainy day today so I pulled the heads off three engines. comp on 2 stock engines is 55lbs. the moded engine is 100lbs.
    stock head is 12.1 and the shaved head is 5.8. I cut .075 off:shock: have over 137 miles on the engine runs great will pull the front wheel about 2 inches off the ground if the throttle is open, when first started.

    Attached Files:

  10. HI,

    SWEET!....So .075 is the "magic" number....good to know...Does it still run well with regular or at the higher compression did you have to step up to plus or premium fuel?

    Thanks.....I can hardly wait to try it out on mine!

  11. Maxx Ported

    Maxx Ported Member

    I don't know IF .075" is a good number, as each head I have done is a different measurement depending on the spark plug to piston clearance. I use a modeling clay to check the clearance.

    I only noticed this, when buying multiple kits???????

    Attached Files:

  12. dave1490

    dave1490 Guest

    nice mod,but i,d watch the bronze bushing.i moded my engine and after time the bushing compresses{soft metal}and creates a gap,after that it,s only a matter of time befor it dissintergrates.watch for a tick,tick sound that matches the rpm of the engine.
    Last edited by a moderator: Aug 31, 2008
  13. ZnsaneRyder

    ZnsaneRyder Member

    I'd recommend premium fuel anyway for any performance mods. Compared to a car, the cost difference is minor to get the premium. Ever since I raised my engine RPM, I run premium now. It runs smoother and quieter with 93 octane, and doesn't ping like the 87 octane does when over the stock 3600 RPM. I'd rather pay a few more cents on good premium for a performance engine, than risk blowing the engine on cheaper gas.
    Last edited: Oct 9, 2008
  14. fourfeathers

    fourfeathers Member

    Hey guys.
    Heres a simple mod that adds more umph. It's the bottom jug gasket. Its' thicknes as stock is around 1.50mms. I replaced it with a proper oil imperveous compressed cardboard gasket that's only .75mms thick. This not only raises compression it also alters both ports timing and increases HP and performance no end. I've been running this on a 70cc HT for 2000ks and couldn't by more happy with it. I've also done all the usual mods on exhaust and carby and juice bottle and have reached 57.4kph on a 44t sprocket.

    Happy riding.
  15. I have a 48cc engine and all is stock and i have reached 57kph(35mph) on a 44t sprocket.
  16. fourfeathers

    fourfeathers Member

    Hey cabinfever1977.
    I also have a 48cc running on a 44t and have had it up to 62kph. Don't get me wrong, I'm not skietting but I reacon the 48t's rev a whole lot more than the 70t's, a lighter piston may be the culprit, but I've never been able to get it to go up steep hills without having to peddle. All the mods I've done on the 70ty has given me a huge increase in tourqe. There ain't been a hill I've come across yet that I can't go up at atleest 43kph, in fact the harder the hill, the harder it seems to accelerate. These little engines may at first glance appeare to be somewhat fragile and poorly finished but with the right amout of attention in the right areas offer enormous potential.

    happy rides
  17. Hawaii_Ed

    Hawaii_Ed Member

    Shift kit is the best mod you'll ever do for these things. Keeps you in the sweet spot of the RPM band, and is nice to cruise without screaming the engine all the time.
  18. i never have to peddal even up hills,my engine and bike actually runs smoother going up hills.
  19. Hawaii_Ed

    Hawaii_Ed Member

    Sounds like a great motor cabin, can you hold 35 MPH uphill?
  20. Mike Hunt

    Mike Hunt Member

    i have a gutted pipe, no head gasket, drilled holes in the plastic intake cover, needle clip on the highest notch. engine runs really well, does a little wheelie when taking off under certain conditions, top speed around 60km/h. some of these mods like the pipe and removed head gasket might reduce engine life, but the motor's are cheap and i care more about going fast than i do about going far, so its all good.