do 2 strokes have a rev limiter??

[crrider491]

do 2 strokes have a rev limiter?? i dont think they do but some people say thay do??

[punkrock MX]

yes they do

[jwriott]

yes they do

I've NEVER ridden one that does.

[x2468]

if they dont have one, how would they keep from like..... exploding?

[cornerspeed]

if they dont have one, how would they keep from like..... exploding?

That's why I've blown many up, nothing to brag about but I've had abunch let go in the 1990's era of 2 smokes.

[Hokie]

do 2 strokes have a rev limiter?? i dont think they do but some people say thay do??

sure they have a rev limiter, it is called "the throttle".

[velosapiens]

if they dont have one, how would they keep from like..... exploding?

4-strokes need a rev limiter because they're valve trains are fragile and if they go to fast, the springs won't be able to close the valves in time and the piston will hit the valves and all hell will break loose. this is why bikes with lighter (ti) valves and stronger springs can have higher rev ceilings (and shorter valve life due to the softer valves and greater force with which they slam into the seats).

2-strokes don't need a rev limiter because they're not depending on the strength and speed of a spring to keep the engine from self-destructing. revs are generally limited by laws of physics

[barch88]

4-strokes need a rev limiter because they're valve trains are fragile and if they go to fast, the springs won't be able to close the valves in time and the piston will hit the valves and all hell will break loose. this is why bikes with lighter (ti) valves and stronger springs can have higher rev ceilings (and shorter valve life due to the softer valves and greater force with which they slam into the seats).

2-strokes don't need a rev limiter because they're not depending on the strength and speed of a spring to keep the engine from self-destructing. revs are generally limited by laws of physics

Would my Yamaha have shorter valve life than lets say a Honda then? Because it has Titianum valves? I thought titianum were better?

[velosapiens]

Would my Yamaha have shorter valve life than lets say a Honda then? Because it has Titianum valves? I thought titianum were better?

honda also has ti valves don't they?

your yamaha will have shorter valve life than an old xr400, but from people's experience, the modern yamaha 4-strokes are among the most durable of modern high-performance 4-strokes. i don't know if this is because of the valve material(quality of ti) or manufacturing tolerances or the 5 valves being slightly smaller and lighter than 4-valves or what.

my observation was only meant as a general rule, to be taken into consideration with many other factors of quality and riding style.

[barch88]

Oh, thanks. Im not sure if the Honda do, I know there trail bikes do, but unsure about the Motocross ones, I know they have "Hot Cam" though.

Yup, Yamaha is great and I suspect this bike should be awesome just like my others.

thanks.

[Skinsfan6]

yes they do

No, they don't. The only two-stroke bike that has even the slightest chance of having a rev-limiter is a PW50 or PW80.

[ttr125smms120]

i thought that at high RPM's on a 2 stroke, the ignition timing slowed down or something?

[gray151]

isnt the ignition shut down at some point?

[ttr125lerider]

wow....no smokers dont have limiters

they go flat when you get too high, and thats when you pull in your left fingers, pull up left foot, and release left fingers, and youll see you can go faster

[crrider491]

i dint think it had one

[jjgixxer]

they don't have one, the power will fall off and the motor will not pull no more rpm..

[floyd128]

Its all in the exhaust port. At the higher RPM's the port will open before the expanding gases get much of a chance to push on the piston. So, no more pushing on the piston, no more increase in RPM's.

[holeshot]

Would my Yamaha have shorter valve life than lets say a Honda then? Because it has Titianum valves? I thought titianum were better?

Ti valves are lighter, but don't last as long as SS valves. Ti is better only if you think it gives you a performance advantage - a lot of people claim that there is no detectable difference.

I'm still waiting to see how long the TI intakes on my Honda will last..

None of the two strokes I've owned had an ignition rev limiter like YZ426F or CR450F. The ignition on the four strokes start to break up or cut out at high rpms - the two stokes just gradually flattened out because they reached the limitations of the motor design.

[motomandan]

WOW, lot's of wanna be mechanics. Basically all OEM bikes, two and four stroke have a rev limiter of sorts. Basically it's built in by design on the average two stroke. Port size as compared to displacement limits how far the bike will rev. there is more to it then that, but that is the basic formula. When grinders go in and enlarge the ports, bore the carbs, and change exhaust port timing, you come up with a higher RPM capability, that can be beyond the crank/rod/pistons ability to stay in one piece. most back yard tuners will build the top end, with no thought of what the bottom is capable of and BOOM, disaster strikes.

Four strokes have the problem of valve float, and when that happens the piston hits the valves, and more carnege. So the manufactures put a rev limiter in the ignition to eliminate valve float, or close to it. Then the back yard tuners put in aftermarket ignition to get more rev's without stiffer valve springs, or cam timing. BOOM again.

[Skrip]

also for whoever asked, the honda valves in the competition crf's are titanium coated. thats why the valves, especially the right intake, go so quickly after the second or third adjustment. The ti coating is worn and they will go out of spec more quickly.