ATC 70 jetting with Uni filter

[AlaskanSD]

I have an 1979 ATC 70 and just stuck a straight "UNI" filter onto the carb and did away with the airbox - at least temporarily. Of course now it's not running quite right as it's lean.

What's the stock jet (main) on that little carb, and what should I go to? I assume I need to mess with the Main...

Any and all info would be much appreciated. Also, does anyone know where to find the little shift indicator (white with red ridge for indication)? I don't see any on DR ATV...

Thanks!

[hrc200x]

Where does the motor start running bad? Anything over 1/2 throttle? I've got a similar set up on a 70, clamp on UNI filter plus a cobra pipe, and anything over 1/2 throttle it starts missing, putting the choke on helps alot. Stock main jet according to clymer manual is a 58. I'd suggest going up in main jet sizes until problem goes away. Did it run perfect before the filter swap?

Gear indicator should be available from honda, atleast it was around 2 years ago when I bought one.

[AlaskanSD]

Thanks for the comeback! It wasn't running great before as there was tons of rust chunks blocking the lines and the carb. So I cleaned all the out, put a carb kit in it, and just stick the uni filter on for kicks. I still have the stock box and it's fine. It starts cutt'n out and backfiring through the carb slightly if I punch it over 1/3 throttle. If I ease it up slowly, it'll rev up ok...but not great.

I haven't tried the choke thing yet, but I will. I'm sure it'll be much better w/ the choke on. Where's a good source for jets??

Thanks...

[hrc200x]

For jets try any local ATV/snowmobile repair shop, or www.denniskirk.com

[TimSr]

I would be looking at the points, condensor, and point gap which controls your ignition timing. I doubt that carb adjustments are causing anything that drastic.
Ive taken the airbox completely off an ATC70 for test purposes and it still appeared to run decent.

[AlaskanSD]

I have some jets coming from Dr ATV (62, 64, and 68). The points and ignition are brand new, and the only that changed (to cause this drastic difference) was to completely remove the airbox and stick on the straight filter.

I guess we'll see!! :naughty:

[AlaskanSD]

Just to add some closure. I never did play with the jets, although I have them here if I want to. I cleaned and rebuilt the carb, and put the stock airbox back on, with the needle clip on the middle position (I'm pretty sure that's stock).



And... it runs AWESOME. Smooth, consistent, with the power you would expect a 70 to produce.

When I get some more time, I'll start modding, in the meantime, I'm happy with stock consistency. And I have to get #2 all up and running for the girlfriend. I've got pink fenders on the way for it! :w00t:

[Wickedfinger]

I went up to (I believe) a #64 when I put the K&N and Cobra pipe on my ATC70. I also moved the clip up one position richer.

[hrc200x]

Wicked, did you try running it with the mods with stock jetting? How did it run? Also, raising the clip on the needle makes it leaner, lowering the clip makes it richer right?

[AlaskanSD]

Wicked, where did you find that rear grab bar? Or did you fab that yourself? I'm looking for something along those lines... And might have to whip out the TIG

[Wickedfinger]

Wicked, where did you find that rear grab bar? Or did you fab that yourself? I'm looking for something along those lines... And might have to whip out the TIG
Its a PRM rail ..... you can get it from PRM-ATV.com.

[Wickedfinger]

Wicked, did you try running it with the mods with stock jetting? How did it run? Also, raising the clip on the needle makes it leaner, lowering the clip makes it richer right?
It ran like crap with the stock #58, way lean to the point it wouldn't run past 1/4 throttle from gulping too much air (if thats possible with a little peanut carb) and I cherried the header quick. Richer is down on the clip.

[AlaskanSD]

Thanks Wicked!!

[STiForester]

Ill also be putting on a pipe and a uni filter. Hopefully it will be good with a 64. So clip goes down on needle for richer also? that would raise the needle in the carb which theoretically would make it run richer

[3wheelrider]

Yes clip down brings the needle up= richer