Jackshaft Engine max went from 34mph to 25mph? with a jackshaft and tuned pipe

[Fabian]

Petrol (otherwise known as gas) is not designed to have oil mixed with it - Petrol is designed to be used as petrol.

Adding oil to petrol reduces the performance parameters for the fuel as designed by the manufacturer.
To try and compensate for octane reducing effects of adding oil to the fuel, you must use a higher octane fuel to prevent detonation, especially when mixing fuel at 20:1

Alcohol increases the octane rating of the fuel but it attracts water from the moisture in the air.
When the engine cools down the remanants of any water vapour will also cool down and condense into fine water droplets on any of the parts inside your engine, and the potential for light surface rust on precision machined surfaces is a real possibility, roller bearings being the worst possible place you would want any water vapour to condense.

Seems quite simple really.

Fabian

 

[Pablo]

Unfortunately many places in the USA, petrol without EtOH is not to be found. In my state for example. The only thing you can do is mix fresh, and when you store the engine, run a good oil with anti-rust and other preservatives, plus fog the engine.

As far as oil reducing octane rating you are quite correct. However these engines (stock) have a static CR of about 7:1, so the octane reducing effects of oil are not even perceived by the engine, so in the quest to get higher octane fuel - sometimes power is lost because the anti-knock compounds used to make fuel "higher octane" (EtOH for example) don't actually add any energy to the petrol. I know for a fact my engine with stock CR ran much better on regular fuel 87 (R+M/2) (not "premium" 92). My high compression slant head, it's a wash. Either fuel is about equal as far as I can tell in that one.

 

[motorpsycho]

you must use gasoline with as little alcohoal added to it as possible. if you look on the gas pump it will say"X % alcohol") you want to steer away from gas that has alcohol in it.
why not just use regular 2 stroke oil instead of motor oil? it would make things alot easier.
by using motor oil, you may not have enough oil in the fuel/oil mix, and you MIGHT have cause premature ring wear, which would cause you to loose compression, which would cause a big loss in power.
It would be like running a 4 stoke engine low on oil in the crank case. it woudl cause premature brearing and ring failure and a huge loss in power.
when the rings wear, the compression goes down causing "blow-by". in other words, the compression "blows past" the rings. the more compression you have, the more power an engine will make you can never really have too much compression, but if you build a high compression motor you will have to go to a higher octane fuel for it to run right.

 

[Skyliner70cc]

quote: "rust on precision machined surfaces"

Hahahah, I laughed so hard when someone refered precision machined surfaces on the HT engine ...hahahahaha

 

[StrontiumEthics]

Hey guys strange enough I actually got hold of the possible problem. It was my gasoline to oil mix. Previously the only 2 stroke oil that I used was the one from Autozone:
Sta-mix 2 stroke oil. But I decided to pick up some motorcycle 2 stroke oil: Honda GN2 2 stroke oil, and accuratly mixed it at 32:1 ratio adding 120ml of 2 stroke oil to one part of gas. And surprisingly, when I started it up and let it warm up for about 20 mins so I could get all the old fuel out the system, it went back up to about 30-31mph. I didnt really max it out yet, but it felt like before but a better. I learned from the situation that 2 stroke oil quality is very very crucial, and adding motor oil to gas is a recipe for engine malfunction!!!! Im sorry I ever done it.

 

[AussieSteve]

32:1 is still pretty light on. It wouldn't hurt to try a little more oil and see if performance improves even more. (Say, 25:1 or even 20:1) The extra oil will help the rings to seal and possibly bring the compression up a bit, as well as slightly improve cooling.
More compression = better high and low end power.
It certainly won't do any harm. If power is better or the same, the extra oil will ensure a longer engine life.
If it runs better, but the plug gets a bit dark, try going from an NGK B6HS to a B5HS. (Hotter)

... Steve