A GEBE two stroke experiment...



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.

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!
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.
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!

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.

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
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?
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%.
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.
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:
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