Jetting for crf70

[superdutyscaler]

I just installed a billit end cap on the stock exhaust and a UNI open air filter on my son's 08 crf70. I have stock jetting right now and I used my Dremel to cut a slot in the air mixture screw so I can adjust it (it has the flat d shape screw) the bike fires right up, it idles great and after adjusting the mixture screw it takes throttle nice and easy without any hiccups. It pulls fine at top end with no backfire on de acceleration (I fattened up the mixture screw. In first gear woods riding I feel it has no power right off idle trying to get over a log or up a small hill (I'm 190lbs though) but after that it pulls great with plenty of power. So besides the off idle power which is probably my weight the new plug after adjusting is a little too white for me, whats yous think?

[dirtbkr188]

Try turning the air screw a 1/4-turn IN to richen the mixture a bit, and see if the off-idle hesitation lessens. If so, try another 1/4-turn IN to see if it gets even better. If you get to within a 1/2-turn of the air screw being fully seated, you might have to go to the next size larger pilot jet.

Also consider going down 1 tooth on the front drive sprocket, the stock 15/36 gearing is a bit tall for an adult rider. The 14T sprocket will give you a little bit more low-end grunt.

[superdutyscaler]

So turning the screw in richens the mixture? Wouldn't turning it out fatten it up? Or am I'm thinking fuel mixture and this is only an air screw?

[superdutyscaler]

I'm one turn out from fully seated on the air screw and I feel the low speed bog is completely gone (I'm use to my drz400e and rmz450). Low end grunt isn't gonna get better (I'm am way to big for the bike) and the de acceleration pop I was hearing when my son was driving it around after my first post is almost 100% gone. The plug has gotten a tad blacker it's white on one side and brown on the other here's the pictures. Seems like I need a bigger main yet yes?

[dirtbkr188]

Turning an air screw IN richens, turning a fuel screw IN leans the mixture, the stock XR/CRF70 carb has an air screw.

 

Do you have the UNI pod foam filter properly oiled with air filter oil? If so, you might want to try the next bigger size main jet. If not, oiling the filter uniformly will richen the mixture slightly by lowering the amount of air being drawn through the filter. I usually oil them in a freezer bag after spraying on the PJ1 foam filter oil, and then wringing it repeatedly inside the bag to make sure the filter gets oiled uniformly.

[superdutyscaler]

My bad I was having a brain fart on that screw. And yes the uni pod filter is brand new just got delivered and is factory oiled

[superdutyscaler]

I'll let him ride it this weekend and Monday I'll go to the Honda dealer and get the next bigger main yet. You don't know the factory main yet size do you? It's easy but I don't feel like ripping the carb apart until Monday

[dirtbkr188]

I believe the stock size is a #62, the next size bigger should be a #65 main jet. You can also order them from JetsRus, here is the link:

 

http://www.jetsrus.com/a_jet_kit_dirt/honda_070_CRF70F.htm

[superdutyscaler]

Thankyou

[arthur6]

A lot of others here, including us, have a really hard time getting these small Hondas running without the air box (or with a pod type filter). When we buy a bike with a pod filter we just get an airbox off eBay, problem solved.

We have had success mixing some type of power booster in the gas but the moderators here don't like us posting about that.