The Athena experience???

Im trying to figure out what to expect out of this setup...

70cc Athena

21mm Del

Estoril (modified but healthy)

88 jet

2nd slot from top of needle

16x45 gearing

fully advanced and adj. points accordingly starting small.

Plug chop reveals light light mocha cream at WOT and a thoroughly even brown but not wet after a 30 minute trip. I have never fouled a plug or felt possible soft seizing. I think I am jetted safely.

Here is my problem. I can get to 45 no problem. really fast actually, less than a block. But this only happens at 3/4 throttle. If i am cruising at 45 (my max) and try to full throttle, it kinda makes a bogging or a deep low growl and slows way down until i go back to 3/4 throttle.

I have tried needle adj. and nothing runs better than my current setting.

Does this sound normal???

Is my gearing just to low and torquey to try to get more speed out of this?? Does anybody cruise at Full throttle or does every carb just have a sweet spot?

extra thanks in advance.

Re: The Athena experience???

BootyClap Ninja /

four stroking. downjet by single numbers until it stops.

what kind of filter are you running.

Re: The Athena experience???

um a high flow mini KN. Ive tried taking it off and literally no difference.

Re: The Athena experience???

hey man I am having a similar experience in a similar thread on the main perf tuning page but with a 19 del and 65 metrakit... I think we just gotta down jet slowly...

Re: The Athena experience???

you can 4 stroke with too much air or too much gas

Re: The Athena experience???

4 stroking huh??? I could be a little rich still. When i take off from stops it kinda bogs for a second and then rips. It will also almost die at idle if I dont keep it slightly revved. So... too much fuel.

Im just worried about down jetting because at WOT my plug if fairly clean to light beige. And if my plug looks like that how could i be four stroking?

Re: The Athena experience???

like i just said too much air. try up jetting. make sure your throttle cable isn't snaged on anything

Re: The Athena experience???

wait why would it be a snagged throttle cable? wouldn't that keep it from opening up thus being leaner?

Re: The Athena experience???

you can 4 stroke with too much air or too much gas

Not true. Totally different sensation and engine characteristics if you are lean as compared to rich. You bog down (engine feels like it wants to stall out, not sluggish) if you are lean.


Contrary what some people just told you, you are NOT four-stroking. You are running lean! Upjet if you don't want to seize the kit.

Four-stroking is running rich. You notice this by a rumbling/sputtering engine at full throttle.

You are running lean. You notice this by the bogging down when you go WOT. The last 1/4 of throttle only adds air, no extra fuel. So at 3/4 throttle it runs right and when you give it more throttle, the engine goes BWOAAAAA and feels like it's stalling.

Trust me on this one, upjet. And you don't want to have your plug a light moccha, you want it dark coffee with just a hint of creamer.

Re: The Athena experience???

Agreed. 4-stroking is from being to rich. It is a sputtering choking sound like your engine is drowning. A lean bog sounds and feels completely different. Downjet one or two sizes at a time until it stops. You'll be fine.

Re: The Athena experience???

Unless, like Roald said, its not sputtering/choking but the smooth bwwwooooaaahh sound then thats a lean bog. Try going up to like a 90 or 92 first and see if it gets better or worse. Then you'll know for sure.

Re: The Athena experience???

Roald, your description seems to make more sense. I will upjet again. If this fixes my problems on the top end of things (full throttle) how can I balance out the the low end without being too rich down there. needle adjustment???

oh yah, I do have a choke. If i am at at 3/4 and pull the choke it should run better temporarily correct? thus upjet.

Re: The Athena experience???

^ ?

Re: The Athena experience???

Have you played with the idle air control screw?

Re: The Athena experience???

i have but the differences are so minimal at that speed

Re: The Athena experience???

Also; try putting your needle clip second from bottom. Air/fuel screw two turns out from all the way in. Do this before you change the jet.

Re: The Athena experience???

ok i will try that before. thanks man.

Re: The Athena experience???

-needle has poor performance in that positition. it likes second clip from top.

-I adjusted air fuel screw. got a little better idle one full turn from all the way in.

-I went WOT and listened for that Bwoahhhhhh sound during which the bike slows down and I pulled the choke, no change.

_after that test_

-i then up jetted to 94

ran it again after upjet and i lost 5mph and it sounds kinda gurgley and has a hard time finding that sweet spot and start pulling.

does the air fuel mixture need to be adjusted again? I left the needle second from the top.

Do you guys still think lean bog or four stroking?

because that is a huge spectrum of possibilities on opposite ends.


Re: The Athena experience???

one more thing-

blue tinted smoke while cruising but not really at idle.

and there is definitely wetness on the end of the estoril. blackish oil.

seems rich to me. I just cant imagine down jetting with such a large carb and a cylinder that is 70cc's though

Re: The Athena experience???


Re: The Athena experience???

Sounds rich unless your timing is retarded. Did you advance your timing with the kit?

Re: The Athena experience???

It is fully advanced and I started with a small point gap per Elliot's fancy video.

rich, not rich. upjet, downjet.

what other definite descriptions can I give to make this easier to diagnose?

Re: The Athena experience???

eh, im over it. ill figure it out.


Re: The Athena experience???

Kile, Did you check the spreadsheet that has been posted on a lot of the other modifications?

Re: The Athena experience???

yah i did. it looks im the only athena with a 21 dellorto.

I hear this can be a tricky setup.

Re: The Athena experience???

The setup I gave you was for the 20mm for sealevel to 500 feet.

Re: The Athena experience???

Your too rich. Obviously. If you upjetted and it got worse, then obviously you need to go back down, and then down some more. If you top speed is less than full throttle than that means you are too rich.

Re: The Athena experience???

21mm too big for athena?

Re: The Athena experience???

21mm is not too big for that cylinder, it is tricky to tune tho. 88 to 94 in jets makes a big difference in that carb, so try a 90 or 92 and see how that goes.

For example: My Puch Maxi with 70cc RGD tuned, 21mm Dell'orto PHBG and Proma LowBoy rides good with a 96 jet, but 4-strokes with a 98 and runs lean with a 94. That's how close it can come when you take your carbsize to the edge of what is possible.

About needle settings and such:

The performance in the low to midrevs is set by a different part of the carb than the performance in high revs.

Have a look at this:

This tells you what to alter for what rev range. My suggestion: Get your main jet in order first, then fix your needle and then work on the idle.

Good luck getting it tuned :)

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