Need suggestion for ATC70 carb jet

[GIJoeBob]

I am working on a 1985 ATC 70 and I have it running but not well. It idles well but bogs when you push the throttle.

It has one of the K&N style air filters from dratv.com and I am thinking that I need to use a different size primary jet in the carb.

Has anyone else had this experience and what size jet do you recommend?

Thanks for your help.

[TravEX]

One of mine does that. I put the clamp on filter from dratv on it and a 60 main jet. I need to go up another jet size or 2.

If you run it with the choke on, it will run fine, won't it. That's the way mine is at least.

[The Goat]

yeah, it does, we'll be putting a 65 in it in the next few days, so i'll let you know how that works.

also probably going to be taking the stock exhaust off and moving to a different pipe.

[GIJoeBob]

I'll try running it with the choke on or at least partially on. That's a good idea.

I wasn't planning on changing the exhaust. That isn't a requirement is it? I'll be looking for your post regarding the jet.

Thanks for the suggestions.

[GIJoeBob]

I went out to look. The jet I have in there now is the one that came in the rebuild kit from the local honda dealership. Its' a 58. Both the Honda Parts List book and the Clymer book say that a 60 is the stock jet. Strange.

So, I'll work my way up. I'll try a 60 first just for grins and then perhaps a 62 and then 65 if need be.

I wonder why the rebuild kit would have a smaller jet size?

[TravEX]

The TRX's had a 60, the ATC's were 58. Your kit may have been for a TRX.

Goat, let us know what jet you use, before the exhaust change isf you change it. The jets run, 58, 60, 62, 64, 68, 70.... Surely a 64 would be about right, cause 64 to 68 would be a big jump.

[GIJoeBob]

The TRX's had a 60, the ATC's were 58. Your kit may have been for a TRX.

Goat, let us know what jet you use, before the exhaust change isf you change it. The jets run, 58, 60, 62, 64, 68, 70.... Surely a 64 would be about right, cause 64 to 68 would be a big jump.

The kit has a 58 in it, but the books say 60. I'll post my results as well providing I have the proper size jets in my carb bucket.

[TravEX]

ok,thanks...

[TravEX]

Any update on jet size?

[The Goat]

we have 65s in both of the 70s now. that's with the stock airbox and exhaust. on one it seems to have helped performance, on the other it seems to have hurt.

personally i think with the K&N and a less restrictive exhaust a 68/72 would give the best performance. the 65 should be perfect for just the K&N