crf70 has NO bottom end

[invision]

my cousins crf70 has nothing in the bottom. its ridiculous. i can wring that thing all day long and it just put puts along. i realize its a 70, but it feels like its clogged up or something, even though we've cleaned the air filter, the carbs, changed oil, fresh gas etc etc, but i beleive its always been like this. is there anything, short of buying a new sprocket that we can do?

[WoodButcher]

my cousins crf70 has nothing in the bottom. its ridiculous. i can wring that thing all day long and it just put puts along. i realize its a 70, but it feels like its clogged up or something, even though we've cleaned the air filter, the carbs, changed oil, fresh gas etc etc, but i beleive its always been like this. is there anything, short of buying a new sprocket that we can do?

Pull the air box snorkel and raise the needle one clip.

[invision]

Forgive me for being dumb, but i have no idea what "raising the needle" means. hah. what we did to his bike is about the extent of my mechanical knowledge :p

but hey, im a fast learner.

[Tekisasu DR]

In addition, main jet #68 or #70, and remove core from the muffler helps a bit more.

Ken

[Hemibee]

Forgive me for being dumb, but i have no idea what "raising the needle" means. hah. what we did to his bike is about the extent of my mechanical knowledge :p

but hey, im a fast learner.

I don't know much about carbs and the differences in them but generally the needle will have a clip on it that fits in slot in the needle. To raise the needle means move the the clip one or more notches toward the tip, ie needle point end.

It does sound like the bike is probably starving for air. A simple mod is as Rusty said cut off the snorkle or open it up. Think of it as running a marathon and having to breath thru a straw from the local Dairy Queen. Several bikes could use the entire top of the air box removed. You might want to start by making smaller openings and slowly increase them until you find the correct amount to provide the needed air flow. If I was doing it I'd just remove the entire top to get that thing some air.

[WoodButcher]

Forgot to suggest an aftermarket air filter too. I wasn't thinking real clearly there. I was thinking of my daughter's xr100 when I said to remove the snorkel.

The xr/crf70 is different. It has a little pod on the back of the carb that hold the air filter. It has a small plastic inlet that comes off the cover of the air filter. I just took that over to the band saw and wacked is off close to the main housing. At that point it made the hole bigger. I played with the needle clip position and I think I ended up in stock position. It was the 100 I moved the clip one position down.

Anyway, opening up the airbox will tend to lean out the mixture, so raising the needle helps get more fuel faster in when you accelerate and should be tried. A larger main jet allows more fuel at full throttle. What you need to do is figure out if your lack of low end is because it is lean, or it is bogging because it is rich. Just raising the needle one clip will allow more fuel to flow when you open the throttle and will let you know whether it was lean or rich. ie, if it gets a little better then it was lean. If that made it worse, then you need more air and need to open that pod to allow more air.

I also think UNI makes a pod air filter that replaces the stock air filter and housing. It flows a lot more air. That would definitely require a bigger main jet, but would help on the power side a lot.

I miss that xr70 we had. and the 100. but the kids out grew them and quit riding. oh well.

[invision]

im dumb hah... wheres the needle at? i looked everywhere and cant find anything.

[WoodButcher]

im dumb hah... wheres the needle at? i looked everywhere and cant find anything.

Okay, on the top of the carb there is a cable that comes in. That is the throttle cable. It has a knurled knob that holds it on. When you remove that, the needle is under there. However, at this point I should suggest a manual. Clymer makes one and it will help a lot.

The reason I say that is there is a clip that holds the needle down and it will pop out. If you aren't mechanical, then having a diagram around to know how to put it back together is important.

Oh yeah, you may find it easiest to do this with the tank off and even the carb.