(by the way, you win. We pretty much stole this guy's thread. I'll stop and give it back to him)

 

As an expert in the industry, I know of no hard data that shows an aftermarket 'REV box' in general will decrease engine life. If you care to be more specific by posting what rev box, used in conjuction with other mods, I'd be happy to give you my opinion. For example, an advanced timed REV box (say 10 degrees or more) with a 30 shot of nitrous in a 400EX, with a 13:1 piston running regular gas at 93 octane or less, at sea level will indeed shorten your engine life. However, the same mods while running the corrected (retarded timing) ignition (found only in aftermarket Rev Boxes) can indeed increase engine life - I just depends on the motor mods. So you see, my point is that one single element or mod is not enough to base a true comparison. Besides, this thread is about increasing performance with such things as an aftermarket exhaust. Its not about whether such aftermarket parts should be used at all. In a court of law, your argument is out of context, and your YES or NO question would be denied on those grounds.

 

This is freakin' impossible. I give. Listen to that guy^

 

Haha don't worry Jimmy. It was great reading the whole thread as I have learned more about the ex's rev limit. However, my friend told me that it wasn't really worth it because the HP gains are small because energy is lost to friction and heat. But I guess if a 400ex can rev up to 9500 RPM in 1st, then the revs will already be higher in 2nd. So originally, you'd shift at say 8500 RPM in 1st and then the revs would be at 4000 in 2nd, but with the new limit of 9500, you could probably be at around 5000 already (just example numbers) which would allow you to beat a stock 400ex off the line (which would be cool).

OregonDunePatrol:

Tell me more of this Edelbrock 38MM "Doug Eichner" Carburetor. What is the stock size Carb on a 400ex? Does this carb add a signifficant bit of power? And what about your "lightened" flywheel? I suppose it would help in racing, but what about for wheelying and hitting jumps? What would these things cost me?

-Jed

 

jed250,

A good list of mods to start off with is listed below if you dont want to go big bore ....


1) Exhaust. There are lots of good ones. If you are concerned about noise, the LTE is good, but is also about twice as much. The CT one is nice and might be in your price range.
2) CDI Box. For low level mods, the Big Gun rev box is good. WHen you move up in your list of mods, you might think about a Rev box that is more flexible such as the Vortex.
3) Larger Carb. There are some good ones out there. Mine is pretty expensive. The Keihn carbs are pretty good, I had one for a while and I liked it.

I doubt these mods will help enough to stay with the 450s, but they are a start. If you want to keep up with the 450s, you are gonna have to consider big bore at some point.

 

Speakin of... So say I had a 300ex with the stock ignition. If I'm continually holding it at the line, would I actually be doing my engine good by installing a decent aftermarket ignition? Does a stock limiter limit by simply dumping every other spark? (My dealer told me that, but it doesn't really feel like it when it hits the top.) If it does, would it not be better to allow me engine to effectively burn all the extra fuel that would be otherwise left when my stock ingition didn't fire?

 

...and say my 300 was rediculously slow and I wanted to get a 400 and a big bore kit. what do you like best?

 

The stock size is now indeed 38mm. However, the carbs were smaller back in the beginning of 2001 and earlier. I did notice improvement - probably around 5-8hp at the most. But the main reason I got mine was because its a needle carb and throttle response was much higher, and elevation adjustments are with one screw - there are no jets! Larger carbs for larger bores are something to consider. Right now my carb empties its bowl in about 45 seconds of full throttle - thats because the demand from the 460 engine is higher. I could fuel pump it or simply get a bigger carb. Fuel pumps are cheaper.

The lightened fly wheel also helps only throttle response. You will sacrifice smooth idleing, but thats about it. By lightening up the flywheel, you are allowing the engine to rev up quicker. I have to set my idle higher to keep it from dying while sitting. I dont believe there is any significant HP increase with a lightened flywheel, she simply revs quicker.

As far as jumps and wheelying: The stock EX wheelies awesomely! Its got a lot of torque and a short swingarm. When I bored mine out to a 440, it was unridable because it would simply go over anytime I hit the throttle. I've done a lot of things to keep that from happening - wheelies are not always a good thing when it comes to duning - which is where I ride. For jumping, well im no expert in that area, so I'll just mention that good shocks would be important. I use the Elka Dune Edition tripples all the way around. They work well for the jumps on the dunes, but those are not anything like jumping like what you are talking about. So I'll admit my lack of knowlege on that.

 

The rev limit works by holding back spark at timed intervals. So, what you have is fuel and air going in, but not igniting and being tossed out the pipe. A very rich condition. In the short term, rich conditions on a 4 stroke are not a problem. However, long term, you'll get soot build up on spark plugs, valve stems and even the inside of your exhaust. Soot build up on valve stems (over the very long term) can cause them to stick, even stick open if there is enough soot on the stems. Open valves can crash into the piston - just depends on more factors such as how agressive the cam is and the clearance to the piston.

 

Ive had friends that got the 300 and later realized it wasnt enough power. Im no expert on the 300EX. But I am very familiar with the 400EX. So its going to be hard for me to tell you wich one is best in your situation. However, speaking from that perspective, I feel the 400EX has a lot of potential for the money. The EX's bottom end has a limit of about 60hp. If you go beyond that, you'll have tranny issues. Right now, thats about where Im at with NOS.

By the way, NOS works pretty good as long as the correct "air to fuel" ratio is maintained. But, for most of the nitrous systems out there, thats impossible. The reason why people fry thier motor with NOS is because they tune it, and the outside temp goes up, creating more nitrous pressure in the bottle, thus feeding more nitrous, which turns into oxygen in the combustion chamber. A higher level of oxygen will cause a lean condition, pre-ignition and even detonation. All are serious problems for an engine. Several companies have developed regulators that keep the nitrous constant. That takes all the guess work out of nitrous.