My 85 dbi has gotten very noisey and revs at idle, is there a muffler needed

Check the Spark Arrester on the muffler. Usually an allen key to take off a section of muffler to get to it. It's a small Screen. They clog with soot and the engine cannot breath.

Have the spark plugs been replaced? Have the plug wires been tested?

Pumping the primer bubble while the engine is running should cause the engine to over fuel and stall (if the tuning is correct). Sounds like its not fueling enough, pumping the primer is forcing fuel through the carb causing the engine to pick up rev's, but this is soon exhausted which is why it wont rev on the throttle.
* Check that the fuel line is not damaged and drawing in air. (if this is intact try the next step)
* Strip and clean the carb. Replace any diaphrams if needed.
* Check gaskets seal between carb, air filter and cylinder.

Just out of curiosity what standard carb settings did you use.?

easy... if the carb adjustments are still factory set the you just need to replace the muffler screen or also called a spark arrester.it covers the muffler exit....

Tony,

Sounds like the exhaust might be restricted, try taking the muffler off and start it then, if it revs freely then the muffler is blocked. I am assuming it was brought to you on a ship, no telling what kind of vernin could have crawled into the pipe and gotten stuck.

There are a few things to check, if the muffler has a spark arrester gauze in the out let this may well be blocked, remove the muffler and the gauze, does the engine now rev? if yes either the park arrester is blocked or the muffler itself is blocked, if this does not cure it, check the flow of fuel from the tank to the new carb, replace the filter in the fuel tank and try again, if this does not help try running the saw with the air filter removed, if it revs normally the filter is blocked.

have you checked for blocked muffler screen or exhuast port/ muffler
2 stroke wil idle sometimes with blocked/ restricted ex port / muffler
then just go burrrrr if try to pull more revs

no exhaust out , no fuel mixture gets in basically not breathing

have you checked fuel filter and fuel lines ?

tried new plug?

try blocked ex port and muffler 1st

cheers

Hi
This can either be a clogged muffler or carb. Take the muffler of and see if it will rev. if not you need to clean and install a carb repair kit. Do not run long with muffler off.
Sam

THEN YOU MAY HAVE A PLUGED UP MUFFLER

Either bad plugs , wires or timing is off, or chain jumped.