2-Stroke Engine Braking

[LewieBike]

Suzuki oil injecting systems were ultra reliable. Yamaha injecting systems were known for failing.

I wish someone would have told me that earlier as I've owned a Yamaha Trailmaster 80, 2 L5T-A 100cc Trailmasters and a Twin-Jet 100, all with injection and none of them ever failed. I put over 40K on the yellow 1970 L5T. The other bikes were used for a lot of road and trail bike exploring also. All of these were used bikes and other than making sure the injector pump cable was aligned with the carb's piston mark, I just filled their oil tanks with Belray or Yamalube and rode the heck out of them.

 

[Build-Break-Fix]

Its NOT recommended to compression-brake in a 2-stroke setup, this is because engine lubrication is delivered along with the fuel and you're essentially applying stress to the engine in the form of compression braking minus the lubrication factor due to the close throttle.

Just a thought! I'm sure there will be 20 haters on everything I'm about to say! Now think about this! From this point of view! Well known compression braking of a 2 stroke is bad for the engine! Right? Or is it? Where exactly does this fact come from? Is there testing data you can toss down and go see? I never actually seen it nor has anyone ever provided test data other then he said she said right? this fact also comes from a time where people only had Organic oils running in there 2 strokes. People says the motor is damaged because oil can not lubricate the piston as you let off the throttle? Does everyone think the oil and gas mix just magically stops flowing the second you let off the throttle? Just based on how a 2 stroke pulls in air fuel mix to the case, makes no sense to come to that conclusion. Even if the carb is closed it's still open to some degree and the high speed of the piston will draw in air fuel mix faster then if it's at a lower RPM through the smaller opening due to the properties of a venturi effect of how a carb works. It actually would suck harder drawing more fuel into the carb body as the air flow is cut off. Paired with the fact Most synthetic oils now really can be run at almost half what the engine is rated to use and protects better would it really damage a 2 stroke engine to compression stop in the end...? With that said I wont try it on any of my builds lol! But Just saying 50 years ago maybe! today with new oils and better carb systems? Just to say this one last thing! Most new carbs with Enrichment valves bypass the main gate in the even the motor is at high rpm and the gates closed dumping more fuel into the system for this whole reason to make sure oil mix still flowing whole time! Meh....

 

[Karl Snarl]

Just a thought! I'm sure there will be 20 haters on everything I'm about to say! Now think about this! From this point of view! Well known compression braking of a 2 stroke is bad for the engine! Right? Or is it? Where exactly does this fact come from? Is there testing data you can toss down and go see? I never actually seen it nor has anyone ever provided test data other then he said she said right? this fact also comes from a time where people only had Organic oils running in there 2 strokes. People says the motor is damaged because oil can not lubricate the piston as you let off the throttle? Does everyone think the oil and gas mix just magically stops flowing the second you let off the throttle? Just based on how a 2 stroke pulls in air fuel mix to the case, makes no sense to come to that conclusion. Even if the carb is closed it's still open to some degree and the high speed of the piston will draw in air fuel mix faster then if it's at a lower RPM through the smaller opening due to the properties of a venturi effect of how a carb works. It actually would suck harder drawing more fuel into the carb body as the air flow is cut off. Paired with the fact Most synthetic oils now really can be run at almost half what the engine is rated to use and protects better would it really damage a 2 stroke engine to compression stop in the end...? With that said I wont try it on any of my builds lol! But Just saying 50 years ago maybe! today with new oils and better carb systems? Just to say this one last thing! Most new carbs with Enrichment valves bypass the main gate in the even the motor is at high rpm and the gates closed dumping more fuel into the system for this whole reason to make sure oil mix still flowing whole time! Meh....

Ya but you gotta remember most of these engines being ran are crappy quality metal and plating. A real engine, should have no prob. Thing is our engines are soft crap with thin chrome lining and our carbs have no bypass( kit carbs). Besides, arent brake pads cheaper than scuffing the cylinder wall? Some engine brake would be fine, but a long hill and you just may do some damage to the liner. I do a little engine braking and its fine, but a whole down hill would not be on my list. All because, these engines are not up to par in the quality area. I actually use organic oil, works way better to save an engine that synthetic in my opinion. That castor layer built up can do some amazing things, even adds a little power. Syn doesnt do that.

 

[Build-Break-Fix]

Ya but you gotta remember most of these engines being ran are crappy quality metal and plating. A real engine, should have no prob. Thing is our engines are soft crap with thin chrome lining and our carbs have no bypass( kit carbs). Besides, arent brake pads cheaper than scuffing the cylinder wall? Some engine brake would be fine, but a long hill and you just may do some damage to the liner. I do a little engine braking and its fine, but a whole down hill would not be on my list. All because, these engines are not up to par in the quality area. I actually use organic oil, works way better to save an engine that synthetic in my opinion. That castor layer built up can do some amazing things, even adds a little power. Syn doesnt do that.

Funny enough I don't actual own a 50cc 66cc 80cc 100cc kit lol I do have piles of jugs and pistons that are brand new from them, I tossed them for the lower half since get cheaper deals whole motor vs just lowers i want. I just never use them in builds! mine Either have pz20 vm20 or vm22 carbs on all of them. Never used a stock carb except once on my first yd100 build. Even that does not have plated liner or stock carb now after I added a steel sleeve to it and cut the top head off lol! Never really considered the Chinessium in the motors, But never actually owned one Unless you count the two I blew up on purpose to see how long one last with no oil, or hammering new one out of the box show how rings get jacked cause of it. all the rest are cast iron or w/e Sthl chain saw jugs use in them, weird material.

 

[Karl Snarl]

Funny enough I don't actual own a 50cc 66cc 80cc 100cc kit lol I do have piles of jugs and pistons that are brand new from them, I tossed them for the lower half since get cheaper deals whole motor vs just lowers i want. I just never use them in builds! mine Either have pz20 vm20 or vm22 carbs on all of them. Never used a stock carb except once on my first yd100 build. Even that does not have plated liner or stock carb now after I added a steel sleeve to it and cut the top head off lol! Never really considered the Chinessium in the motors, But never actually owned one Unless you count the two I blew up on purpose to see how long one last with no oil, or hammering new one out of the box show how rings get jacked cause of it. all the rest are cast iron or w/e Sthl chain saw jugs use in them, weird material.

See you should have no probs then, quality jug. The nikasil lining in those is far superior to the chrome lines and even steel sleeved jugs. When i get my minirelli jug engine built next year, I wouldn't worry one bit about engine braking. That type liner should handle anything a motorized bike can throw at it. Well long as its tuned proper and a good oil mix in the tank.


Have you tried to destroy a quality jug motor yet? If yes, got any pictures i can study?

 

[Chainlube]

There is two types, braking and breaking, so wtf is this thread about?

 

[DAMIEN1307]

There is two types, braking and breaking, so wtf is this thread about?

I think its probably a combination of both judging by what ive read here lately...lol...DAMIEN

 

[Chop-chop]

Who gives a flying fk ? I've said my piece so just let the professor Build-Break-Fix find out the hard way. I just think he fails to see that we're talking about engines build by the country that has a level of quality control that borderlines non-existent, so let him keep on compression-braking his way to never-never land.. I ain't losing any sleep over his bright intellect....

 

[Member 30571]

Mr Nutcase, Sent me a PM yesterday and started chewing me a new ass for something I had nothing to do with.

 

[Street Ryderz]

BBF doesn't really understand how a 2 stroke works, it's atmospheric pressure that pulls fuel out of the carb body not the vacuum and when the slide is closed the volume is greatly reduced which means so is the amount of air/fuel which carries the oil for protection.
He said, It actually would suck harder drawing more fuel into the carb body as the air flow is cut off.
That's a load of crap, think about it, if more fuel was pulled through into the case the engine wouldn't be slowing down, SMH it's dumb ass logic and false info like this that confuse people into doing dumb things!