Hey. My cousin has an '89 Banshee. He says that he regularly runs it with about half of a quart too much oil in the crank case. He says that this decreases the volume of air and creates more vaccum. Supposedly this alters the way the reeds function and allows him to rev faster. I am sceptical, but I don't know enough about our machines to dispute it with him. I know some of you on here are really up on this kind of thing. Is he right or is he full of it? He says that he's done it for 2 years. That means that even if it doesn't make it run better, it seems that it can't hurt it any. Thanks for any comments.

 

JG40178

Air is compressible,most liquids are not so this practice would decrease case volume(vapor)and while not appreciably increasing vacuum during the intake or charge stroke it may(my theory)increase incoming fuel/air mixture velocity thru the carb venturi allowing a sort of "ram-air"effect thru the reed cage. On the possible down side the extra oil displaces the air cushion that does compress during the pressure pulse during the power stroke of the piston. Loss of this cushion (which may have been considered by the Yammy engineers when they decided on oil level)could/maybe/might cause over-pressure in the case and blow oil seals. I'm not an engineer but it does not sound like a good idea to me even tho your cuz has got away with it...my 2cents...

 

oil in the crank case of a 2 stroke now thats a new one! why do you think you put oil in the gas of a 2 storke it is to lube the crank case bearings and rings. the oil you put in the case is for the trans. not the engine.

 

cb2000warrior

I don't believe that oil in the crankcase of a 2 stroke engine is a "new one".There are lots of different types of engines. Two-stroke does not automatically mean pre-mix.There are even two-stroke diesel engines shipboard bigger than a city bus that are shut down and started in opposite rotation to back the ship up.The sump may hold over 500 gallons of lube-oil.There are even two stroke gasoline engines that have blowers feeding airbox's to scavenge and charge combustion cylinders prior to fuel delivery. Lots of weird stuff out in the world. Some of them use pressurized oil suply systems with strategically placed spray nozzles inside the gallery.In my 20 plus years as a heavy marine diesel mechanic and propulsion engineer I have seen All kinds of internal combustion engines and prime movers;from two stroke screamers on swift attack zodiaks to monstrous two stroke diesels that you stand on the piston with an assistant to inspect cylinder liner and crankcase bulk head integrity.I've got a REAL good handle on what the oil is in the gas for.I also know that the banshee has a gear box that requires lubrication. I obviously made the assumption that the gear box and the crank case were connected,sort of like a door being open between two rooms,Meaning that any pressure changes in one would effect the environment in the other. If that is incorrect please let me know. Are they seperate like a big twin Harley or is there some type of seal between crank and mainshaft? I was simply responding to jg40178s post. I don't post/reply very often, but I thought I could help out a fellow atver,not just infer he's a dumba$$ and move on. I'll try to be better informed before my next reply. Thanks........

 

BOGHAMMER, thanks for the reply. cb2000warrior, don't take my closing statement "thanks for any comments" too literally. I meant any replies in which someone is trying to be helpful, not trying to be sarcastic. With your infinite wisdom did you somehow miss the part where I said I didn't know enough about the engine to dispute the thoery? That was an admission that I know very little about how engines operate. But thank you for pointing it out in your own way. It gave BOGHAMMER a chance to show you that you aren't as smart as you thought. I really enjoy it when a smart--- gets burned.

 

jg40178

Like I said in my first reply I aint no engineer but I have sure led a few of them back to the path.I appreciate the old adage "They're aren't any stupid questions, only stupid answers" We are all born into this world ready to learn and I think one of the best things one person can do for another is to show or to teach him something. Pay it forward. Thanks....

cb2000warrior

I wasn't trying to flame you but I think you did reply a bit harshly. jg40178 was simply trying to clarify a question that he had. I have a lot to pay back/forward to this world so any time I feel like I have helped some one I get a good feeling.And trust me on that brother...

 

The gearbox and crankcase are separated therefore the volume of oil in the gearbox would have no impact on the way the engine runs. The oil goes in the gearbox not the crankcase.

 

Lets make it simple..Your Banshee friend should be very careful with his mechanical Knowledge. All Banshees are 2 stroke motors and do not require a crankcase reservoir. Any type of pressure change to any motor with reeds will change performance, but not in this case. In a typical 4 stroke motor changing levels of oil does increase and decrease pressure, changing the stroke performance. It is my recommendation that you stick to your manufacturers recommendations. If you are a motorhead like BOGHAMMER you may want to buy a boat. Theory is relevant only when it applies.

 

He's full of it!

 

sorry i didnt mean to come across as a smart a$$.
next time i'll be more careful as to how i word my posts

i'm very sorry if i offened any one