Best 2-Stroke Engines

Discussion in 'Spare Parts & Tools' started by pessen, Feb 21, 2009.

  1. pessen

    pessen New Member

    Hey everyone,

    I am considering building my first motorized bike and have doing some looking around the internet to figure out what would be best.

    So far it appears that Grubee (SkyHawk, SkyFire,...) are some of the most highly rated products. Anyone have any thoughts or recommendations on what engine to buy? What is the biggest difference between these and some of the cheaper kits you can buy?

    I want an engine that mounts in the middle of the frame (like the 2-stokes do), not something that has to be mounted on the back of the bike.

    I live in Albuquerque, NM at an altitude of 5200ft. I have heard that the small 2 strokes don't perform well at high altitudes. I will just be using the bike to commute to/from work mainly, and not doing many intense hills or anything. What engine/setup would you recommend for this type of use.

    I had someone recommend buying the 80cc(really 66cc) engine, as well as a shifter kit, and a Dellorto carb (for better idle, low speed, and transition to high rpm). My question is this, how much will the shifter kit and carb affect the performance of the engine. The carb isn't that expensive, but the shifter kit is like $200. Is it really worth it?

    I am just trying to find out more info before I buy something. I want to be satisfied with what I get, not wishing I had done more research. Any input would be appreciated!



  2. Skyliner70cc

    Skyliner70cc Active Member

    Yes, the shifter kit is well worth it. Without it, I could not climb the steep hills at 6600 foot altitude. You can get away without using a new carb for a while by suffering with a rich low to middle end jetting but adjustable high speed jetting where I do 99% of my riding. One way to deal with the altitude and rich mixture is to blend a very small amount of E-85 fuel into your gas mixture. How much depends on a lot of factors and requires small steps and lots of trial and error because not all e-85 is 85% ethanol (some is 70% ethanol/30% gas). I'm currently running 6 oz of E-85 with gasoline added to make up 1/2 gallon in one of my engines. It is running leaner and stumbles less.

    No engine, 2 stroke, 4 stroke, turbine, jet, work as well at higher altitudes as they do at sea level.
    Last edited: Feb 23, 2009
  3. duivendyk

    duivendyk Guest

    As the airpressure decreases with altitude there is less O2 available for combustion,so the engine will run richer. Blending in ethanol to replace some gasoline, reduces the over-richness and the engine will run better at altitude,but unless there is more oxygen available, power loss is inevitable.Nitro (methane) addition can boost power but is tricky and very expensive.
  4. Skyliner70cc

    Skyliner70cc Active Member

    I didn't want to mention it but I'm also running some nitromethane as liquid turbocharger to regain the lost power at altitude. The nitromethane does its job best when the engine is under heavy load, e.g. climbing up a steep hill at full throttle. I usually don't don't notice the effect of the nitromethane if the engine is not being loaded down pretty good. I don't recommend folks using nitromethane unless they are willing to fry an engine. I've converted to many engiens over the years to nitromethane fuel from gas for model airplane use.
  5. duivendyk

    duivendyk Guest

    Another factor at altitude is that due to the lower air density engine cooling is compromised to a certain extent,esp in engines without forced air cooling.Usually this is counteracted by the lower temp,but not allways. In summer going up steep inclines in low gear and at full throttle at high altitude can put an engine under a lot of strain,2 strokes especially, because the lubrication is supplied by the micture,throttling back after cresting a hill can consequently deprive it of much needed lubrication.Don't employ engine braking with a 2 stroke !!.I ran 2 strokes in the desert and mountains in the Middle East and used low fuel/oil ratios,this also leans out the micture.I also crafted clamp-on aluminum fin extenders to improve cooling which worked out well.Some people have written in this forum on the benfits of acetone in improving engine performance.But it has been reported to be unfriendly to fuel systems.
    Last edited by a moderator: Feb 24, 2009
  6. Mountainman

    Mountainman Active Member

    hi there pessen

    well you mention above that you don't have many hills
    so it seems to be pretty wide open for you there
    using just a standard Happy Time engine should fit your bill
    don't see why you would need a shift kit ?

    you should be able to get to work and plus some fun riding
    for around 150 dollars invested

    have a blast when you ride the motor bike
  7. loquin

    loquin Active Member

    Well, the best 2-strokers are the Mitsubishi & Tanaka, but, they're not going to fit inside the frame very well... You'd be looking at a more expensive rack mount. But, if you don't want to spend what could be a fair amount of time tinkering, then the extra cost may be worth it to you.
  8. pessen

    pessen New Member

    Thanks for all your responses. Mountainman brings up another question I had. BikeBerry and other places sell engine kits for around $160 dollars, while SpookyToothCycles sells their Skyhawk kit for $250 and says that the other cheaper engine kits are junk. Who do I believe?

    Will I regret buying the cheaper kit or is SpookyToothCycles simply charging me for their research and design costs?

  9. duivendyk

    duivendyk Guest

    Could you quantify what an 'intense' hill is, what max grade do you actually encounter on your daily trip?.I used to measure them with a 2ft level& tape measure,hold level horizontally against hill&measure vertical of bottom-end of level to road surface Grade = H/24x100 %. (H in ".) Most people guess that it's steeper than it actually is.I think an HT can cope with a 6% grade with normal gearing.Any opinions? (preferably not based on mere guestimates)
  10. pessen

    pessen New Member 80cc engine?

    I emailed to ask how manufactured their engines. They said they got their 48cc from Grubee but that Grubee doesn't make 80cc engines. They said their 80cc engines were from a different manufacture that was of equal quality.

    However places like sell 80cc(66cc on their site) which are the Skyhawk brand, which in researching I thought that was a Grubee brand? Does anyone know what I am missing here?'s 80cc engine kit (which is probably really a 66cc engine) is on sale for $129. Is this a good deal or are they a lesser quality then other engine kits like the $250 one from SpookyToothCycles?
  11. hillofbeans

    hillofbeans New Member

    Check out in Tucson. Good outfit, good variety, answers.
  12. hello there pessen

    If you want a good ht two stroke of good Qualit,i'm only suggesting here now,you might pay a little more but it's worth it try to get a hold of crhis hill and get your hands on one of his engines ,it's frame mounted and over all it has good perfomance. he also has good service for replacement parts and is very reputble at what he does.Here is his site adress,,hopefully this helps.
  13. jlebh1

    jlebh1 Member

    sounds like some good advice here
  14. maurice terrazas

    maurice terrazas New Member

    what is that best in bike engines and the cost