A very newbie question (Yes I searched first)

[bully_23]

Hi all,
I have had my Rm for a few months now and just do basic riding around and jumping the few jumps I have made, with the biggest being my 30' tabletop. I feel like I'm a pretty good rider and would like to start racing in the not too distant future. My bike is totally stock( n-style sticker kit and Fat tapered bars being delivered from santa) and I know it probably needs a few things to make it a bit more competitive on the track. Now this is my first bike and I don't really know much at all, My knowledge of my bike does not go any further than basic maintenance- chain, controls, air filter, oil and very basic suspension setup - set sag and play with the clickers. My Dad is a farmer and knows how lots of things work and can help me with simple things that I mentioned above. but cannot when it comes to the engine he hasn't had a dirtbike or anything too similar before. Anyway I'm sorry this is going so long :blah: but I'm getting to my point. I have asked and searched around here for what I should get for my bike to improve performance, all the answers have been mostly three things they are, Pipe silencer, bigger rear sprocket and a V-force reed block. I know what a sprocket is and what a pipe and silencer are but can someone explain what are reeds where they are located what they do and what a V-force reed block is and how will it help. Thanks a heap sorry for the long post, and what probably seems to be a stupid question to most of you. BuLly

 

[2strokerfun]

Reeds operate as a one-way valve for the intake fuel mixture. They open when suction pulls the mixture into the cylinder, but let very little back into your intake from the combustion pressure that takes place during the ignition cycle. They are generally located in your cylinder, behind the intake boot between the cylinder and the carburetor. New reeds might help because they can be more efficient, both opening easier to let more fuel mixture in and closing, letting less backpressure back into your intake stream. They are a really simple design and when you remove them and check them out, you will easily understand their function and simplicity.

 

[robwbright]

A few recommendations:

Buy a factory service manual.

http://www.repairmanuals.com

Buy this book:

http://www.amazon.com/Motocross-Off..._bbs_sr_1/103-9499230-6109454?ie=UTF8&s=books

The reed valve is between the carb and the cylinder.

From Eric Gorr:

"REED VALVE

Think of a reed valve like a carburetor, bigger valves with large flow-areas work best for high rpm power bands. In general, reed valves with six or more petals are used for high rpm engines. Reed valves with four petals are used for dirt bikes that need strong low end and mid range power. There are three other factors to consider when choosing a reed valve. The angle of the reed valve, the type of reed material, and the petal thickness. The two common reed valve angles are 30 and 45 degrees. A 30-degree valve is designed for low to mid rpm and a 45 degree valve is designed for high rpm. There are two types of reed petal materials commonly used, carbon fiber and fiberglass. Carbon fiber reeds are lightweight but relatively stiff (spring tension) and designed to resist fluttering at high rpm. Fiberglass reeds have relatively low spring tension so they instantly respond to pressure that changes in the crankcase, however the low spring tension makes them flutter at high rpm thereby limiting the amount of power. Fiberglass reed petals are good for low to mid power bands and carbon fiber reeds are better for high rpm engines.

Boyesen Dual Stage reeds have a large thick base reed with a smaller thinner reed mounted on top. This setup widens the rpm range where the reed valve flows best. The thin reeds respond to low rpm and low frequency pressure pulses. The thick reeds respond to higher-pressure pulses and resist fluttering at high rpm. A Boyesen RAD valve is different than a traditional reed valve. Bikes with single rear shocks have off-set carbs. The RAD valve is designed to redistribute the gas flow to the crankcases evenly. A RAD valve will give an overall improvement to the power band. Polini of Italy makes a reed valve called the Supervalve. It features several mini sets of reeds positioned vertically instead of horizontally like conventional reed valves. These valves are excellent for enduro riding because of improved throttle response. In tests on an inertia chassis dyno show the Supervalve to be superior when power shifting. However these valves don't generate greater peak power than conventional reed valves. Supervalves are imported to America and sold by Moto Italia in Maine."

A pipe and silencer will help a bit. The reed valve you talk about may help, but from what I've read, in some cases they can be difficult to jet properly.

I had my 2002 RM 125 overbored to 144cc's. That gives about a 20% HP increase for $500.00 - and that's amazing compared to stock. However, while more power will help in a few situations on the track, real, actual speed on an MX track is made by YOU - corner speed, how well you "keep it on the pipe", etc. . .

Porting and head work would help more than a pipe and silencer for about $250.00. The porting is included with the $500.00 big bore kit I got.

Finally, suspension work will also make you faster - you can only go as fast as the suspension will allow you. That's what I'm planning to have done this winter.

As Eric says, Speed is 95% rider and 5% bike. Better make that 5% count.

 

[FruDaddy]

While I can understand the desire for more performance from the machine, you are likely not using all that the bike currently has. Focus on getting the suspension dialed in, get a few motos under your boots. Once you are skilled enough to win the beginner classes, then you can start looking at power upgrades. That was my 2 cents.

 

[Badgadjit1]

go with the boyesen valve..not the vforce. they're made better. vforce is made of plastic and has 2 pieces. the boyesen is all aluminum i think, and is all one piece.

 

[Agitator]

Technically, the fuel enters a two stroke's cylinder(s) via the crankcase, which is where the reeds are located.
gas tank>carburetor>reeds>crankcase>cylinder...
I don't mean to sound like a smart mouth, it just ended up that way.

 

[bully_23]

Ok thanks a lot for all the info and advice, Yer I asked around and was reccomend to get my suspension done before spending$$$ on performance mods, and yer I think I might get a manual also.
Thanks again BuLly

 

[bully_23]

I can't seem to find a 2002 owners manual is there a year thats similar I could use?

 

[dezryder]

Listen to the wisdom...

While I can understand the desire for more performance from the machine, you are likely not using all that the bike currently has. Focus on getting the suspension dialed in, get a few motos under your boots. Once you are skilled enough to win the beginner classes, then you can start looking at power upgrades. That was my 2 cents.

And xcracer72: "don't waste any money until you are winning on your stock setup. Racing is 95% rider 5% bike"

My two cents: Don't waste your money on performance mods until your skill level is letting you wring every last performance drop from your bike. Until then, spend your extra bucks on top quality riding gear, (Yeah, that $400 helmet) and good tools to work on your scoot. (Manual first)

All the aftermarket company's would love you to be like so many other sheep. (buy the products, and go faster!)

Develope your skills, and improve your bike as necessary to keep improving them. (In that order)

An aluminum drain plug never won anybody a race! :nod:

Good luck in your racing, and remember to keep it all fun!

 

[02rm250]

Ask Santa for a set of dual stages to go with the bars. Theyre only 30 dollars. If youre not experienced on a track, you could probably use some more bottom end. I'm not too comfortable on a track so I wouldnt want to try to ride a 125 on the pipe the whole time, but thats just my 2 cents.

 

[CHR!S]

what are dual stages? dual stage grips?

 

[FruDaddy]

I think he speaks of reeds.

 

[hot125mod]

you need to start somewhere dont knock yourself for something you dont know about ther is a lot of great people to talk to the only way to become more knowledgeable is being areond it and time dont worry the more you do it the more you will know