Wed, 29 Apr 1998 16:24:03 +0200 - Message No. 2753
From: Sture Qvarfordt

Subject: More tuning of an AT07


I did some modifications a year ago and a run in a DynoJet testbench.
 
Modifications was done to the air filter housing a la Raymond F(but I had 6x20mm), 
a modified original air filter with washable foam filter on original housing (get rid 
of the paper and net, a slip-on "clear tube" exhaust (type Arrow etc.), main jets 
of 130/132, needle lifted 0.30 extra, increased hole in vacuum slide to same size 
as the bigger one.

The carachteristics I got was in short:
Torque close to 63 Nm from 3500 to 5000 and 61.3 at 3000 and 61.0 at 6000 
(very flat curve!).
This means a quite flat power curve with 51.4 at 6000 and 51.7 at 8000 with a 
maximum 54.1 at 6750  
 
I have not made a new test bench run since, but I have done some modifications 
now and then. 
- I increased air inlet to 8x20 because we thought the drop of torque at high revs 
could be lack of air and I increased pilot jet? to 42. This resulted a to rich mixture 
at low revs and lean on high.
- Back to 40 on pilot jet and up to 140/140  on main jets, via some intermediate 
steps (I'm quite fast on mountind/demonting carbs by now). I lifted the needle 
to +0.50 mm. This has been the best feeling so far. More power on high revs but 
maybe a bit lean on medium revs 4500-5000 (but it's just a feeling).
- I'm now on setting where I increased needle lift to 1.1 mm but thats to rich 
from 3-4000 and possibly onwards to 6000.

I will go back to 40, 140/140 and possibly +0.6-0.7 mm and have a run on the
test bench. I think the test guys has got a lambda sond by then, which will 
improve the rich/lean guessing.

Be back whith a torque/power curve by then.

BTW - I think you understand by now that I'm going for much torque on low revs. 
I think it's nice on gravel roads.

/Sture Qvarfordt, 
Stockholm, 
Sweden

dipper@normans.isd.uni-stuttgart.de