WR450 revlimiter


38 replies to this topic
  • boer

Posted February 05, 2006 - 07:09 AM

#1

I have noticed that the revlimiter is very "soft" and not very noticeable on my bike.

Sometimes I don't know if I am close or not, especially when the going gets tough in thick sand up dunes when I'm giving it full throtlle. Will riding close to the limiter adversly effect my engine or can it take the punch day in and day out?? :thumbsup:

Will the free mods and different exhaust make the limiter more noticeable?? :thumbsup:

  • Indy_WR450

Posted February 05, 2006 - 08:11 AM

#2

I dont think the rev limiter is very effective on our high compression motors.
I can push my kill switch in and hold it and if I am under full throttle my bike continues to rip as it diesels with no spark! :thumbsup:

  • CycleWriter

Posted February 05, 2006 - 10:03 AM

#3

I dont think the rev limiter is very effective on our high compression motors.
I can push my kill switch in and hold it and if I am under full throttle my bike continues to rip as it diesels with no spark! :thumbsup:

That's because it's not a rev limiter in the traditional sense. It doesn't cut off spark completely, as in a normal rev limiter. Instead, it retards the spark to prevent the engine from exceeding the rev limit too long which could result in valve float and serious engine damage. This design came about so that you don't lose all power or forward motion in a dangerous riding situation.

On the other question, yes, continually bumping up against the rev limiter will shorten the life of your engine and could lead to mechanical damage. The rev limiter is not an indicator of when to shift or back off the throttle, it's a safety mechanism to prevent you from over revving the engine past design limits. Frequent sand riding will definitely stress a dirt bike more, especially if you do it with a knobby and have to spin the tire a lot. If you regularly ride sand you should step up your maintenance intervals since that would be considered extreme usage. Any engine that is constantly being operated in extreme conditions and/or at the upper range of its rev limit will wear faster and be more prone to mechanical failure.

  • Dodjy

Posted February 05, 2006 - 05:33 PM

#4

I dont think the rev limiter is very effective on our high compression motors.
I can push my kill switch in and hold it and if I am under full throttle my bike continues to rip as it diesels with no spark! :thumbsup:


I'd be a bit worried about being able to do that. You never want uncontrolled ignition in a high performance engine. I'd be using a higher octane fuel - you must be detonating the motor to death.

  • Matty05

Posted February 06, 2006 - 03:14 AM

#5

I dont think the rev limiter is very effective on our high compression motors.
I can push my kill switch in and hold it and if I am under full throttle my bike continues to rip as it diesels with no spark! :thumbsup:

I can do that too, not because of any of the reasons that everyone else gives though!

It is a fault with the kill button. I just have to push it in a bit, not all the way to kill it. If I push it in all the way, it won't die. In motion or stand still.

  • Matty05

Posted February 06, 2006 - 03:24 AM

#6

On the other question, yes, continually bumping up against the rev limiter will shorten the life of your engine and could lead to mechanical damage. The rev limiter is not an indicator of when to shift or back off the throttle, it's a safety mechanism to prevent you from over revving the engine past design limits. Frequent sand riding will definitely stress a dirt bike more, especially if you do it with a knobby and have to spin the tire a lot. If you regularly ride sand you should step up your maintenance intervals since that would be considered extreme usage. Any engine that is constantly being operated in extreme conditions and/or at the upper range of its rev limit will wear faster and be more prone to mechanical failure.

Bullshit!

Yes the rev limiter is there for a reason - continually hitting it won't do shit.
This is why it is an ignition cut as opposed to a fuel cut. Big difference.

As for sand - it places greater load on your engine. More load = more heat. More heat = bad. Everything suffers from load. Load your gearbox up all the time, it will break. Load your clutch up all the time, it will burn out. As for spinning the tyre, how much worse would that make it besides not bogging your engine down which is the bad thing about sand riding anyway?

  • Matty05

Posted February 06, 2006 - 03:32 AM

#7

I have noticed that the revlimiter is very "soft" and not very noticeable on my bike.

Sometimes I don't know if I am close or not, especially when the going gets tough in thick sand up dunes when I'm giving it full throtlle. Will riding close to the limiter adversly effect my engine or can it take the punch day in and day out?? :thumbsup:

Will the free mods and different exhaust make the limiter more noticeable?? :thumbsup:

All you need to do is get a pipe. It won't really make the limiter more noticable, probably less as you won't have to flog the shit out of it to get power. The WR's gain a crap load of bottom back with just a pipe change, not to mention mid and top!

These engines are designed to be reved hard, thats why they have 5 valves that are titanuum.

Get a vortex ignition if you like, it will rase the rev limit too, so you can take advantage of extra power on top and increased over rev. Hitting it won't do shit. It is there for that.

  • Indy_WR450

Posted February 06, 2006 - 05:25 AM

#8

EFI will fix this problem in the future they can cut the fuel and retard the ignition as well! Cant wait for real EFI on our dirt bikes! :thumbsup:

  • CycleWriter

Posted February 06, 2006 - 10:48 AM

#9

Bullshit!

Yes the rev limiter is there for a reason - continually hitting it won't do shit.
This is why it is an ignition cut as opposed to a fuel cut. Big difference.

Ahh, Matty, back to your usual courteous nature I see. :thumbsup: Hitting the electronic rev limiter (not the mechanical one as on stock US WRs) means you are approaching the red line of the engine. A bike that is continuously operated at or near red line will not last as long as one that is operated more conservatively. The potential for catastrophic engine damage from valve float is higher the more you operate at red line. That is a fact, not bullshit. As for a fuel cut off, how would you do that on a carbureted bike? There is no way to instantly stop fuel flow on a carbureted bike to prevent over revving. That's why the rev limiter is built into the ignition module on these bikes. If you're going to try and discredit me in here, at least do it with good info. :thumbsup:

  • MotoGoalie

Posted February 06, 2006 - 10:55 AM

#10

I like it when people just yell bullshit.

At random threads on the internet.

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • CycleWriter

Posted February 06, 2006 - 11:01 AM

#11

All you need to do is get a pipe. It won't really make the limiter more noticable, probably less as you won't have to flog the shit out of it to get power. The WR's gain a crap load of bottom back with just a pipe change, not to mention mid and top!

That's about the only accurate thing you've said in this thread. A good pipe will give you more bottom and mid range power so that you don't need to rev the piss out of the engine to accomplish the same thing.

These engines are designed to be reved hard, thats why they have 5 valves that are titanuum.

The 5-valve design of the Yamaha isn't expressly for allowing you to abuse the engine. By lightening the valvetrain you can build an engine with a higher red line. More rpm range means a broader powerband, but it doesn't make the engine any less susceptible to abuse.

Get a vortex ignition if you like, it will rase the rev limit too, so you can take advantage of extra power on top and increased over rev. Hitting it won't do shit. It is there for that.

The rev limiter is there as a safety to prevent damage from over revving, period. While the rev limiter may be on the conservative side for a stock bike, raising it can result in reduced reliability if you are the type of rider who continually hits it when riding. Advising someone to do this on the basis that it is safe is reckless and irresponsible, both of which you have shown yourself to be in here. I hope no one takes your advice on this. :thumbsup:

  • Matty05

Posted February 06, 2006 - 04:13 PM

#12

Ahh, Matty, back to your usual courteous nature I see. :bonk: Hitting the electronic rev limiter (not the mechanical one as on stock US WRs) means you are approaching the red line of the engine.

No shit!

A bike that is continuously operated at or near red line will not last as long as one that is operated more conservatively.

It is load that does the damage, not rpm's. They are designed to do the rpm's, pure and simple.

The potential for catastrophic engine damage from valve float is higher the more you operate at red line. That is a fact, not bullshit.

Ummmm, this is why they have a rev limiter!

As for a fuel cut off, how would you do that on a carbureted bike? There is no way to instantly stop fuel flow on a carbureted bike to prevent over revving.

Easily done with solenoids.

A fuel cut limiter leans off the mixture which causes damage to the engine, a ignition cut limiter just retards the ignition to prevent engine spinning past the limiter rpms. No damage done to the engine.


Your rev limiter is there to prevent damage, not cause damage! :thumbsup:

Stock rev limiters are set very conservedly, performance gains are there to be had. The WR's rev limiter is much lower than the YZ's, no problem increasing it. :thumbsup:

  • Drunken Monkey

Posted February 06, 2006 - 04:41 PM

#13

That's because it's not a rev limiter in the traditional sense. It doesn't cut off spark completely, as in a normal rev limiter. Instead, it retards the spark to prevent the engine from exceeding the rev limit too long which could result in valve float and serious engine damage. This design came about so that you don't lose all power or forward motion in a dangerous riding situation.

On the other question, yes, continually bumping up against the rev limiter will shorten the life of your engine and could lead to mechanical damage. The rev limiter is not an indicator of when to shift or back off the throttle, it's a safety mechanism to prevent you from over revving the engine past design limits. Frequent sand riding will definitely stress a dirt bike more, especially if you do it with a knobby and have to spin the tire a lot. If you regularly ride sand you should step up your maintenance intervals since that would be considered extreme usage. Any engine that is constantly being operated in extreme conditions and/or at the upper range of its rev limit will wear faster and be more prone to mechanical failure.



I read your post, you don't ride in sand, do you?

Hitting rev limiter wont hurt your bike, how would it :thumbsup:

Stock limiter on the wr is lower than YZ, a really great mod here in Australia is to get an '03 YZ ignition module! Makes the bike flat out rip!!!

  • Drunken Monkey

Posted February 06, 2006 - 04:57 PM

#14

The 5-valve design of the Yamaha isn't expressly for allowing you to abuse the engine. By lightening the valvetrain you can build an engine with a higher red line.

It is a race bike, it is made for abuse.
Yes, a lighter valve train you get higher rpms, but you also get quicker engine spin up. 5 valve design is superior to stop valve float, lighter springs can be used, valves don't open as far, less force of valves slamming shut, the list goes on and on.

Get an XR if you wan't to cruize around...............

More rpm range means a broader powerband, but it doesn't make the engine any less susceptible to abuse.

Man you speak some crap! Diesel engines have the broardest power of all, yet don't rev very high at all. 2 strokes scream, but power is anything but broard.

If you want to be credible, don't talk shit.....................

  • Drunken Monkey

Posted February 06, 2006 - 05:02 PM

#15

EFI will fix this problem in the future they can cut the fuel and retard the ignition as well! Cant wait for real EFI on our dirt bikes! :thumbsup:

Only a matter of time................
Too bloody long of a wait if you ask me!

  • moach1

Posted February 06, 2006 - 05:40 PM

#16

come to think of it i never hit mine either. i push it pretty hard sometimes. at supercross you can hear the bikes bouncing of the rev limiter.

  • boer

Posted February 06, 2006 - 08:32 PM

#17

Thanks for the input guys. :thumbsup:

This thread is turning out to be very interesting......... :thumbsup:

  • CycleWriter

Posted February 06, 2006 - 08:49 PM

#18

It is load that does the damage, not rpm's. They are designed to do the rpm's, pure and simple.

Valve float can happen with or without a a load on the engine.

Easily done with solenoids.

A fuel cut limiter leans off the mixture which causes damage to the engine, a ignition cut limiter just retards the ignition to prevent engine spinning past the limiter rpms. No damage done to the engine.

Explain how a solenoid can instantly shut off gas flow in a carbureted motorcycle engine, please.

Your rev limiter is there to prevent damage, not cause damage!

Uhm, isn't that what I've been saying? The rev limiter is your bike's way of saying, "Ease up on the revs before you blow me up."

Stock rev limiters are set very conservedly, performance gains are there to be had. The WR's rev limiter is much lower than the YZ's, no problem increasing it. :thumbsup:

The reason the WR's rev limiter is lower is because the engine has heavier flywheels and therefore greater reciprocating mass. Spinning it as fast as a YZ just puts even more stress on the engine.

  • CycleWriter

Posted February 06, 2006 - 09:06 PM

#19

It is a race bike, it is made for abuse.
Yes, a lighter valve train you get higher rpms, but you also get quicker engine spin up. 5 valve design is superior to stop valve float, lighter springs can be used, valves don't open as far, less force of valves slamming shut, the list goes on and on.

There are still design limitations involved. Treating any bike like a race bike means shorter service intervals, shorter service life of parts and overall shorter engine life.

Man you speak some crap! Diesel engines have the broardest power of all, yet don't rev very high at all. 2 strokes scream, but power is anything but broard.

Diesels use high compression to make gobs of torque at low rpm. That's why they are superior for vehicles like trucks, tractors and anything that needs to pull heavy loads. 2-strokes use revs to generate horsepower, but they suck at pulling loads at low rpm because they generate so little torque. They also have no valvetrain to worry about being over-revved. Either way, what do they have to do with a WR?

If you want to be credible, don't talk shit.....

You mean like you and your Aussie pal, Matty? No thanks, I never want to be that credible. :thumbsup: :thumbsup: :bonk:

  • Matty05

Posted February 06, 2006 - 09:30 PM

#20

Uhm, isn't that what I've been saying? The rev limiter is your bike's way of saying, "Ease up on the revs before you blow me up."

No - you say hitting it will do damage. I say you are wrong. :thumbsup:




 
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