Weak Engine, Not using the gears! A little help or advise!

Discussion in '2-Stroke Engines' started by StrontiumEthics, Apr 6, 2009.

  1. StrontiumEthics

    StrontiumEthics Motored Bikes Sponsor

    For some reason the power of my engine is weak. Im not to sure of the cc's because I got it from Revolutioncycles.us and it was kind of a replacement. Supposingly it was a 80cc (well 69.9cc) or something around that range. I also have a SBP Jackshaft kit connected as well. What I realize is that the engine is not using the gears as I hoped it will. The power is weak. I dont really have a speedometer, but I can guess that my max is about 30-34 mph. It is suppost to be way more. In addition the take off and acceleration is pretty bad to, it takes to long to get to my top speed. Basically, I am comparing the engine I have now to a Dax 80cc. In the dax things felt alot better and smoother, this engine is kinda slow I dont really like the way it feels. Is there any things you guys recommend that I check? I was thinking to drill a hole on the exhaust according to some of the people on the forum. This might work because when I ran the engine without the exhaust the takeoff was beautiful. But im not to sure what I should do. Any recommendations/ things I should check? I prefer not to actually do any engine work (taking off heads).

  2. Pablo

    Pablo Motored Bikes Sponsor

    There aren't a ton of easy bolt on items. But an expansion chamber qualifies and will give you a lot of bang for the buck.

    I say get all the "tune up" things done. New BP5HS or BP6HS plug, new good wire. Make sure no leaks on the intake.

    Taking the head off is easy as are the manifolds. For sure port match the intake mani and the exhaust manifolds. Consider a new smalller main jet. .65-.67mm.

    EDIT: Make sure the gaskets match as well. The small stock exhaust gasket on many engines is a real power killer.
    Last edited: Apr 6, 2009
  3. StrontiumEthics

    StrontiumEthics Motored Bikes Sponsor

    Oh ok, as of now I am running a NGK B6HS plug. Is the BP5HS or BP6HS plug better than mine? What spark plug wire should I get? How can I port match the intake mani and the exhaust mani? If they are off what do I do? And where can I get a new smaller jet? .65-.67mm? I was considering drilling a small hole in the exhaust to release some back pressure? I have 1 exhausts to play around with.. When I ran the engine without an exhaust for about 25 secs it felt really nice and powerful, I thought maybe I can simulate that effect.
  4. Pablo

    Pablo Motored Bikes Sponsor

    1)Yes. Not by a lot, but the extened tip is less prone to foul and gives just a tiny bit better performance.
    2)Any 7mm wire will work, but a carbon one is not ideal for perfomance but will allow the use of a electronic speedo. A solid metal conductor is good for perf but messes with speedo. A metalic spiral wire is good for both. Silicone insulation of course.
    3/4) Do you have a dremel tool? Easiest is to make a dummy gasket the size of the intake and the exhaust ports, then Dremel the pipe/intake mani to that size with a series of the little sanding drums.
    5) You can get jets of that size at dellorto direct.
    6) Nothing beats an expansion chamber for a 2 stroke. I didn't find messing with the stock pipe helped at all.

    Wires and plugs and stuff

    HERPER Member

    i wasn't even in need of any of that info... but figured id read.. that was pretty educational haha congrats pablo.
  6. StrontiumEthics

    StrontiumEthics Motored Bikes Sponsor

    So basically I widen the diameter of the intake mani? with a rotary tool? How do I know when to stop? I was reading some posting but it wasnt really clear. And what about the exhaust? Do I actually sand the exhaust pipe, or the port on the engine?? That goes for the intake as well?
  7. Pablo

    Pablo Motored Bikes Sponsor

    No need to touch the engine, just the manifolds as they are smaller than the engine ports. Just make a template that fits the engine, then grind/sand the manifolds to match.
  8. A friend of mine put on the performance carb from spookytooth and past me in a race with my stock configuration. So I ported and polished the intake tossed the restrictive gasket and used black silicone then gasket matched exhaust ,hogged out the air cleaner for a straight shot into carb,bh5 plug, 7 mm wire, put needle on 3rd setting, took apart exhaust and cut tip off even with the end instead of drilling holes in the tube. Man the difference was like night and day.. I also bought a 36 tooth sprocket but didnt need it to beat him lol. Since then ive bought the performance carb and boost bottle and sbp shifter kit for the other bike im building,its gonna be a screamer.
  9. 247Jude

    247Jude Member

    I was running a stock muffler without the cap, used a huge washer that covered the end and drilled a couple of 5/8 inch holes, it ran like a goat untill my exhaust manifold gasket blew into two. I used a moose hide to repace the gasket, and broke my clutch cable. As it sits in my basement now.