I had a similar problem on a DG800B Solo 2625-01. Engine would start, but
upon throttle advance, after reaching 4000 rpm, the revs and the EGT would
decrease. The engine would nearly die at full throttle. Turned out to be a
small leak in the fuel line near the carburetor that was sucking air, but
not leaking fuel. Took 1 month to find it-only found as the leak got bigger,
and started leaking fuel!

Running the engine without a air filter may not be a good idea depending on
location. If it is a K&N filter, properly lubed, and new, it should not be
the problem.

Good luck

--
Hartley Falbaum


"bagmaker" wrote in message
...

Rob,

some thoughts

any airfilter debris sucked in the carb MAY still be there, and WILL
cause a problem if they are, however the effect shouldnt be at full
RPM, more so, it will not start or will idle rough.
Take a look in the throats, if debris is there, do a full pull-down and
inspect. Assuming the engine ran fine last time you flew, expect it to
do so again or look for changes SINCE then.

first theory,
sounds too lean. Removing the filters will do that, improving airflow
to the motor. If it was run too hard when lean you may have internal
damage, scored bores or broken rings from overheating in the upper
cylinder area.
Does the RPM increase or decrease as you get higher?
The higher you go the less oxygen, meaning the engine runs richer. As
you get high with a lean engine, it will rev faster, to a point. As you
get high with a rich engine it progressively decreases RPM.

so,

#1, GET new fuel, dont use the stale stuff in the tank
#2 remove the new filters (you do have new filters yet??) and run up to
full power on ground, check all settings including EGT if possible. Run
for some time, there may be thick, old oil within the motor that needs
blasting out.
There may be an issue with piston ring, main or big end bearing due to
debris from the filter, also a clogged exhaust will do the same.
#3 put filters back and repeat process, note any changes.
#4 if there is a difference you have a filter issue, if not, an engine
issue.

2 stroke engines never run quite as well as they did just before they
seize, so too rich is the best option.

disclaimer: I know nothing, dont listen to me
Its is completely possible following the above will cause you to ditch
head first into a line of school buses, killing hundreds and leaving
you in a chair. Get expert help and sue them-
Blasted American law system.


bagger




--
bagmaker