10k rev limit

[Derno24]

QUOTE

Originally posted by theJeStEr1340
Wow, compairing a quad that is jumped and abused in the woods to a street bike is the worst. Like someone said, landing a jump or downshifting into a corner is **** on a motor, you don't see too many street bikers down shifting into a corner, usually they are easy and let the RPM's drop enough. It is 2 completely different things. Yes, they are motors, but we abuse motors worse than they do. Anyone know how often Street bike Racers (closed course) replace their valve train? It would be a good thing to look into.

No offense here, but you must have never watched ama streetbike racing. Aaron Yates, Matt Mladin and all the reat riders slam their bikes down gears all the time to get the speed to drop faster to get into corners. One image that comes to mind is Aaron Yates winning a 600cc class race heading out for the final lap with all the other racers right on his tail. Comes into a hard 90 degree turn downshifting so fast the bike is popping loud and tire is completely locked up and then bang he is gone. Downshifting is used in every form of racing. If anything it is harder on street bikes due to the fact their tires will not slip as easily as ours will. Remember dirt is forgiving and will allow you to slide as asphalt won't let you slide as easily. especially with tires that act like glue when heated.

[theJeStEr1340]

Up until the Question about how often do the pro's go through their valve train I was talking about regular people who ride their bikes recreationally, maybe taking their bikes to a track once in a while if at all.

[banzairx7]

A guy that I work with wrenches for his son who races a CBR929 locally. I'll ask him what they do for valvetrain maintainence.

[Derno24]

But again isn't that what we do? Ride recreationally and race occasionally?

[wistech]

10,000 rpm? No thanks. I have a speed map in my quad right now with a 10,500 limit on it and that absolutly the minimum I can accept. I now shift at the limiter. Lets get some quality valve springs ,valves and hardened cam lobes and move on. Ived checked a dozen valve springs for pressure and only one outer spring was even close to the 40psi minimum in the manual. All the inner springs were right on. I had to use .030 to .035 shims to get the spring pressures up to 40psi. Hopefully that will reduce the likelyhood of valve float. Im also halving my valve lash because from what Ive read tight clearances are easier on the camshafts.
I am also going to a higher compresion piston and and advancing the camshafts to see if that will boost the midrange so 11,500 is not required for max power.
I would also like to try a map like the one in the fx400(mc500) with all that low end and midrange.

I still think most of our troubles are just low quality and underspeced parts.

[USAMoto00]

Don't forget when comparing to a street bike that the street bikes such as Mladin's and Yates' have a clutch mechanism installed to allow those harsh downshifts to have less of an engine breaking effect on the valvetrain. It's kind of like a slipper clutch. They abuse those bikes in one sesion more than we could in an entire year. If you need info, they are the Formula One technology for motorcycles. If you doubt me, look at Yoshimura. Do you think it was a mistake why Doug Gust's Z400 is so fast? A little hint: Suzuki didn't come up with the power! On a side note, I agree to disagree. The rev limit will have an effect on the motor if you use it. How many of you actually use it though? And how often do you use it? Occasional is no problem, while constant is. I ride my quad very hard, but not rev limit hard. I shift before it gets there because the next gear will do fine. It does me no good to bounce off the limiter unless in dire need. I would rather prolong engine life than blow it up for no reason. I'm sure everyone has their own opinions on this matter, but do you think it's luck that my quad has been so reliable with no problems?:confused: :usa

[JeffQuadShop]

Thats kinda been my rule of thumb....If you've hit the rev limiter, you should have shifted about 500 RPMs ago.

[USAMoto00]

You said it Jeff.:clap:

[cannondale27]

Definitly you want to shift before the rev limiter and the right gearing makes that easier.If a person finds themselves hitting the rev limiter all the time higher gearing would be in order.
In streetbikes I think the valvetrain last longer because they arent subjected to shocks while at high RPM.Think of what a whoops section does to the sound of your motor.You will never hear a streetbike go through that.The stunt rider guys around here run at high rpm all the time and have trouble all the time also.Anytime the tires leave the ground and come down it is a shock to the motor.
As far as hitting the rev limiter in the air.Of course you dont want to do that but it happens.Ever hear of a panic rev?It works and can save some broken bones but it can kill your motor.When the tires are driving your motor such as down shifting or landing or even when going down a hill if you are off the gas you will not hear your rev limiter but your motor could be turning way over the rev limit.All I am saying is that broken valvetrains in our motors is not abnormal put higher quality parts in and it can last longer but until we get pnuematic computer controlled valves the service intervals cautious as they are will not change that much.

[jfarrar]

i run my quad near the rev limit through every gear most of the time.on an mx track its the one of the only advantages a dale has over the yammi and honda.lower the rev limit and you'll be seeing the backside of alot of those machines.when im running my quad up near the limiter my motor is usually under a pretty good load going down a flat straight or out of corners or whatever but i usually will never do it downhill or with not as much load on the engine.then it starts to make scary noises.i have never dropped a valve or had any rpm related malfunctions in my engine and if any one should it is me