A GEBE two stroke experiment...

Discussion in '2-Stroke Engines' started by JemmaUK, Jul 10, 2008.

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  1. JemmaUK

    JemmaUK Guest

    Hi all,

    I have been toying with trying nitromethane fuel on my bike for a while. I've to this point been put off by the messages on here warning dire consequences should this be used alone but I am trying to test different mixtures of petroil/nitromethane.

    I had a 3/4 tankfull on the bike of normal mixture so I thought I would add a little of the NM to it. All in all I added 3 teaspoons of NM to the tank and filled up the rest to make sure it had mixed.

    Effectively that was 15ml of NM in 770ml.

    At this ratio I didnt have any expectations at all - given the amount was so low. I am amazed the difference it has made. The bike is slightly more responsive and it holds speeds better in headwinds (a GEBE weakness) but its in the starting that the real difference is found.

    It used to be that it would need 4-5 pulls on choke to get a cold engine to start (mine is the Tanaka 32), and 2-3 pulls to fire a warm/hot engine. With just that small amount of NM in the fuel mix, its now one pull with choke to start a cold engine and one (choke off) to start a warm one. I actually pulled the starter as hard as I would normally this morning and hurt my arm because the engine fired almost immediately.

    I have checked the plug and it is the same lovely tan colour as it was before I started so I am not running lean. What I will probably do in the next few days is put another 15mls in the tank to see the difference - ie to see if it will help performance without hurting the motor.

    I have added 50mls to my remaining mix in the 1 gallon can that I use which is a little lower than what I have in the bikes tank so I will see if the effect is the same...

    Jemma xx

    WARNING: Nitromethane fuel is Methanol based. Methanol is a metabolic poison and can KILL. It can be absorbed through the skin, and both fuel fumes and exhaust fumes can be dangerous. Use gloves when handling it, and if any area of skin comes in direct contact, rinse IMMEDIATELY.


  2. badmoon

    badmoon Member

    where can we find NM ?
    Last edited: Jul 10, 2008
  3. mcassMB6

    mcassMB6 Member

    You should also be careful too because this added to your gas tank basically "destroys" and breaks down oil. Be sure to keep an eye out! Sounds like your plug checking is keeping this at bay!
  4. duivendyk

    duivendyk Guest

    That is mystifying to say the least, nitro has a lower vapor pressure than petrol and is even difficult to ignite.You had just a 2% ratio,very odd, but not unwelcome though.
  5. fastboy9

    fastboy9 Member

    Nitromethanol is a common remote control car fuel, nitro cars run on it. So your local rc hobby shop will sell it. Another thing to watch out for, when nitromethanol burns its exhaust fumes act as tear gas!! Alot of monster truck's run on it, and if you have ever been to a monster truck show then at the end of the day that is why your eyes are burning!

  6. JemmaUK

    JemmaUK Guest

    It confused the **** out of me as well - but I think I know the answer to it sorta.

    With the old stationary engines and diesel tractors they were sometimes hard to start so you'd squirt ether up their bits as a starting aid - cue large cloud of black smoke, an asthmatic wheezing and there we go..

    The reason ether works like that is because it has lower point of flash ignition than does diesel/parafin or any of the other weird fuels that were used back in the day.

    I think that with straight petroil the engine has to be spun multiple times on the recoil starter to increase the temperature in the combustion chamber and at the right time the conditions are such that the engine fires. Add nitromethane and there is a component in the fuel that will burn alot more readily than straight petroil - which means it flashes and raises the temperature in one shot and the engine fires immediately on the 1st pull - not the 3rd or 4th.

    In fact for the first time since I have had this motor, and I have put 500 miles on it, the engine will fire before the recoil starter is out to its full stroke - I still have the sore shoulder to prove it...

    Jemma xx
  7. crazeehorse

    crazeehorse Member

    have you ever checked the burnt residue from the top of the piston, if it breaks down the oil, as said before, it should make for less lubrication once its burnt, i don't know what you could compare it to, maybe just do the old finger snap test?
  8. duivendyk

    duivendyk Guest

    What exactly transpires in a combustible mixture at the molecular level during an electric discharge, to bring about an explosion is likely to be complex.Ether,with its high volatility certainly helped starting really cold engines,I can attest to that.That makes intuitive sense.But that low concentrations of an admittedly energetic compound would have such a disproportionate effect is puzzling.The stuff carries it's onboard oxygen and so would seem easy prey for energetic electrons to initiate a reaction, raising local temp & igniting the HC's and so on.
    It has puzzled me a lot, why some engines,more notably 2 strokes it seems, are hard to start.By that I mean 5 pulls or more,even at 30 degrees C,that means more than 20 compression cycles,ignition does not change,nor does the mixture,so what's going on?There could well be something to your temp. theory,but that implies at 5 C, forget it!.There's no arguing with results though.It would be interesting to find out what happens at 4%.
  9. Marktur

    Marktur Member

    Nitro fuel has just taken a HUGE jump in price. From what I understand, the mfg shut down temporarily (to raise demand???)...all I know is that RC fuel just went up by close to $10/gal here in South Florida. OUCH!

    Jemma - there's reasons why they don't run Nitro fuel in gas motors..it has tons more power, but there's definitely reasons why it's not mixed -- I don't know, but I fly RC airplanes for over 20 years now, and I've never heard of anyone doing that with their 50cc-100c gas motors to get more power... I'll ask around tomorrow...we have over 500+ members...someone should know the answer.
  10. augidog

    augidog New Member

    interesting...but i'm not knowledgable about special fuels.

    i did want to remind you that you've barely scratched the surface re: break-in...per dennis, at least 1000mi of MB'ing is needed before the tanakas start to kick-in...man do they ever kick-in when they finally get there. and, the concensus (from tanaka also) seems to be that one shouldn't tweak or experiment until you do get there.

    "augi, this thing is better than ever, what'd you do?"

    "i kept riding it."

    ;) :cool:
    Last edited: Jul 12, 2008
  11. JemmaUK

    JemmaUK Guest

    If the only thing that the NM does is give me easier starting then I will leave it in just for that advantage... I already have tendonitis in my shoulders, the worst its been I couldnt move at all for a half hour. If I had a bigger tank on the bike I would use it more, but mostly its just short journeys at the moment.
    The tanakas do seem hypersensitive to pipes though, 3 miles of one of those and the engine was not happy..
    So I will keep it @ 50ml/gallon and await developments.

    how much does the performance increase when they run in?

    Jemma xx
  12. softride

    softride Member


    Thats a great post
    I can confirm that what you did is validated in my experience as last summer I did exactly that when i had run out of gas for my weedeater ,it had never been hard to start but when i added the dregs of my RC fuel in the tank that baby fired right up and was zinging like a good un I knew straight away that it was different from the revs, being a racer i quickly thought okay what if i used race gas ,so when i ran out of the RC mix I added some of my race gas to the tank Sunoco 110 octane which is what Nascar uses, Results were poor to say the least ran like a dog and was hard to start had to use starting fluid like you mentioned to get it running.
    I guess if your looking for a little extra help it would be usefull but again long term effects are not known NM is used in a lot of top classes of drag racing but those guys are stripping their motors down every run virtually so they are able to keep a handle on whats happening .
  13. augidog

    augidog New Member

    i felt it the day those rings found their seat..."cruzin" was behind me and he said later i just all the sudden "walked away" ...it was awesome! not a real boost in "performance" but shootfire it got tons stronger.

    and it keeps getting better...

    folks who only get an occasional test-ride still comment on the improvement over their last ride :)

    i think a fully-seated tanaka would happily take that pipe, just keep ridin' it 'til you get there :cool:
    Last edited: Jul 12, 2008
  14. Marktur

    Marktur Member

    Just check your plug for lean runs...and maybe throw in an extra teaspoon or 2 of castor? Someone mentioned that the nitro fuel will break down the 2-stroke oil, but I don't know.

    I went out to the flying field, and not one guy has ever put nitro in their gas...so you're breaking new ground.

    I *did* however buy myself a new plane! (Told my wife it was my midlife, and she should be happy I didn't come home with a Vette!) :)
  15. JemmaUK

    JemmaUK Guest


    I just did a run out to see my grandmother - 22 miles round trip - to take my mind off things and try and cheer myself up.

    I had noticed a few performance differences at first - but the difference now is amazing...

    Distance: 21.1 miles (34.1km)
    Max speed: 37.53mph
    Average speed: 25.48mph
    time : 50 minutes

    This is an average of out and back - the max speed even downhill I have seen before is 35mph and the average speed is up by 3.5mph on the same journey.

    While I had a tailwind on the way out, i was fighting a headwind on the way back and even in those conditions in 'racing trim' I was running between 27-30mph - before the bike would have been fighting to hit 26mph. The temperature is somewhere around 18 degrees centigrade.

    The ONLY changes I have made are 2% or so nitromethane fuel and I have also purchased a riding hat/helmet for safety reasons and because I have people depending on me and my continued good health.

    With tailwind - on a very slight upward grade I was hitting 36mph flat out at one point....!

    Jemma xx
  16. badmoon

    badmoon Member

    are you using a 44 t sprocket JemmaUk ?
  17. JemmaUK

    JemmaUK Guest

    I am using the GEBE system with the standard #13 gear.
  18. badmoon

    badmoon Member

    oh ok i see.

    SO before nitromethanol what was the top speed and average one.
    Last edited: Jul 20, 2008
  19. JemmaUK

    JemmaUK Guest

    top speed on the flat without tailwind was 31-32mph

    Average speed from lexden to mersea island was 22mph - the same journey.

    Since I had a headwind/tailwind those would have equalled themselves out so the average speed difference is likely due to the fuel changes.

    Jemma xx
  20. badmoon

    badmoon Member

    so if i have a 27t sprocket and hit 35 - 36 mph on flat without wind i think i would hit near 40 with nitromethanol . i will try thats i thinks it will works fine. my engine is a 2 stroke 67cc(80cc) HT does it will work nice or not ?