Ahha! Maxx 3.3 (Was 3.3 lost it's wheelies)

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Bradley V. Stone - 20 Sep 2006 03:38 GMT

So, I'm out banging my head on the wall trying to figure out what is the
problem and why my 3.3 won't wheelie anymore.

After WOT runs the idle seemed to stay up until I stopped completely.
Over and over.. thinking somethingn was hanging up on the clutch or
something. Or to lean causing a hanging idle. But no adjustments fix
it. And 15 seconds at idle and WOT it still is sluggish.. RPMs even
drop a little right after takeoff then pick up. Nothing makes a
difference though with tuning!

I get mad and pick it up.. all of a sudden the wheels start moving..
faster.. faster.. faster... Ahah!

Idle was too high.. duh! After High speed run it would get cleaned out
and idle where it "should"... applying breaks stopped it. I looked
again and sure enough it was surging... could just barley see the spur
start to move, then stop.. over and over. Not quite enough to get it to
move, but when off the ground, enough to start spinnin them wheels!

I put it up on blocks to adjust idle until it wheels don't move.
Thinking it's gonna die when I stop, I take off for a high speed run...
it stays running!

A couple more runs and a pinch test... WAYY rich.. lol..

I do the idle thing a few more times and adjust LSN.. getting there. A
little more to go. Wow... interesting. Starting to understand more
why they say adjust idle first, then LSN.. repeat until perfect.

Wheelies aren't quite there yet.. but, I noticed if I do a quick On, Off
On, Off, On it might wheelie. (probably a mix of preloading the front
shocks and leaning out the low end).

And if I go around a corner and hammer it when straightening it did a
couple nice long riding wheelies too. Didn't I hear somewhere these
things lean out around corners?

I also am starting to notice at 1/2 tank it is leaner than full (I tune
with 1/2 tank). But the lower it gets, the leaner it seems to get (and
more peppy).

So, tommorow I'll burn through a few more 1/2 tanks to tune.. :)

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Dre - 20 Sep 2006 04:01 GMT

> So, I'm out banging my head on the wall trying to figure out what is the
> problem and why my 3.3 won't wheelie anymore.
[quoted text clipped - 38 lines]
>
> So, tommorow I'll burn through a few more 1/2 tanks to tune.. :)

Good to hear your finally sorting it, its a great feeling when you have
nailed the tune on a problomatic engine :)

Can you please explain this pinch test you keep talking about?

I've never heard of it before and I'm curious...

Cheers Dre

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Bradley V. Stone - 20 Sep 2006 04:20 GMT

>>So, tommorow I'll burn through a few more 1/2 tanks to tune.. :)
>
[quoted text clipped - 6 lines]
>
> Cheers Dre

Pinch test, from what I have learned, is the most misunderstood thing
around.. lol. It's supposed to help you determine if your LSN is jetted
properly, or in the ballpark.

In a nutshell, here's how I understand it to work.

1. Get engine up to operating temp
2. Do a couple high speed passes to "clean it out"
3. Bring the truck in.
4. Pinch the fuel line close to the carb and listen as the engine dies.

The engine "should" raise in RPMs slightly, then die. If it doesn't
raise at all, you're too lean. If it raises a lot, then you're too rich.

Now here comes the fun part.

Some also add that it should take 3-5 seconds to die and make no mention
of the RPMs increasing or not.

Others say 3-5 seconds and RPMs should raise a little right before it
dies. (this is the one I try to go by as it's middle ground...lol)

But, through in variables like how far you have pinched it from the
carb, if you're idle is too high (like mine was), and it really won't
help much at all. What if it takes 2 seconds to die and RPMs go up
slightly and richening it makes it die in 3 seconds but RPMs go up too
much. Stuff like that makes it confusing.

I personally err towards getting the RPM raise more than the time.

After I get the pinch test done, I then tune the LSN using the idle/WOT
method.

Up to temp, a couple high speed runs. Let idle for 15-30 seconds (I've
heard anywhere from 10 up to 30... 15-20 is a nice middle of the road
time). Should be a smooth idle.

Then punch it WOT. Should take off nice and fast without hesitation or
bogging.

Whew... I think I need a Jato 3.3.

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Dre - 20 Sep 2006 05:45 GMT

>>>So, tommorow I'll burn through a few more 1/2 tanks to tune.. :)
>>
[quoted text clipped - 48 lines]
>
> Whew... I think I need a Jato 3.3.

Nice, thanks for the info, thats what I thought, but wasn't sure.

I'd also be inclined to say that pinching the fuel line *should* raise the
RPM before the engine dies as you are limiting fuel flow just like when the
engine runs out of fuel (cept in that situ you get air in the fuel line)..

Cheers Dre

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GTD - 20 Sep 2006 06:11 GMT

>I'd also be inclined to say that pinching the fuel line *should* raise the
>RPM before the engine dies as you are limiting fuel flow just like when the
>engine runs out of fuel (cept in that situ you get air in the fuel line)..
>
>Cheers Dre

I agree, , ,If it's already too lean, pinching the line shouldn't
raise the revs any, since a lean tune coupled with the pinch should
put it leaner than optimum. If it's too fat, then pinching should
bring it closer to optimum, making the revs come up quite drastically
(If it's fat on the low end, it probably has more carb opened to keep
a decent idle, which is too much for a correct tune). This is more of
a question than a statement, does this all sound correct?
L8r

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Dre - 20 Sep 2006 06:33 GMT

>>I'd also be inclined to say that pinching the fuel line *should* raise the
>>RPM before the engine dies as you are limiting fuel flow just like when
[quoted text clipped - 11 lines]
> a question than a statement, does this all sound correct?
> L8r

Sounds about what I've experienced. Except for the first line, "If it's
already too lean, pinching the line shouldn't raise the revs any". I'd be
inclined to say the revs would still increase but if it is WAY to lean it'll
cut out and stall...

Cheers Dre

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Model Forum / Radio Controlled / Land Models / September 2006

Ahha! Maxx 3.3 (Was 3.3 lost it's wheelies)