Muffler Clogged Up

alloo66 · Post by **alloo66** » Tue Oct 30, 2012 2:52 am

Does any Stella Dealer Decoke the Muffler? What are the symptoms of a Clogged exhaust?

BuddyRaton · Post by **BuddyRaton** » Tue Oct 30, 2012 3:01 am

They probably would but what makes you think that is the problem?

It is much easier to help you if you give us symptoms.

How many miles?

az_slynch · Post by **az_slynch** » Tue Oct 30, 2012 3:04 am

I don't believe that the dealer would de-coke it. Traditional methods of cleaning two-stroke exhausts use chemicals like Draino or muriatic acid solutions, or thermal methods like throwing the muffler in a fire or burning it out with a torch. All of these methods are a bit risky (some more than others) and could lead to muffler damage and/or personal injury.

There are after market exhausts available that will give you more performance for under $150 and will avoid the risks of cleaning a muffler.

A clogged muffler cause hard starting and reduced performance. There are other issues that can cause similar symptoms (worn rings, carburetor issues, fouled plug) too. Does your muffler have an oily, crusty residue in the exhaust tip? If you pull the muffler and look down the down pipe; is it oily and crusty down in the pipe?

What sort of two-stroke oil do you use in your Stella?

alloo66 · Post by **alloo66** » Tue Oct 30, 2012 5:50 am

Full throttle bog, 4k miles. Just a suspicion. Common with most two strokes, non consistent top speed. If I back off the throttle the bike runs better. I'm holding off on buying a sidecar kit, as I just purchased this bike and am not sure how fast it will go and if it runs like other two strokes. This is my first Stella.

az_slynch · Post by **az_slynch** » Tue Oct 30, 2012 5:59 am

4K is a rather low for a clogged muffler. I have seen it on some 50cc bikes, but I often find weedwhacker oil in the autolube tank of those bikes too.

Have you changed the carburetor jets, changed the air filter or done any tuning to the motor?

alloo66 · Post by **alloo66** » Tue Oct 30, 2012 9:50 am

No no changes.

az_slynch · Post by **az_slynch** » Tue Oct 30, 2012 11:25 pm

alloo66 wrote:No no changes.

I wonder if your mixture screw has worked loose. Either that or your air filter might need a good cleaning.

neotrotsky · Post by **neotrotsky** » Wed Oct 31, 2012 3:41 am

I went 18k without any muffler issue whatsoever... 4k does sound low. But, I agree on the replacement option: For under $150, you can get a Sito+, rejet and you're good to go with a bit more pep

Lokky · Post by **Lokky** » Wed Oct 31, 2012 5:18 am

neotrotsky wrote:I went 18k without any muffler issue whatsoever... 4k does sound low. But, I agree on the replacement option: For under $150, you can get a Sito+, rejet and you're good to go with a bit more pep

Yeah I find it really hard to believe that the pipe needs decoking after 4k... To me it seems like the cylinder would need decocking well before the pipe does, and a cylinder can go without decoking for what, 20k miles if using good oil?

alloo66 · Post by **alloo66** » Wed Oct 31, 2012 4:27 pm

So how do you tune the carburetor? AF mixture screw? I've done it on other vehicles, just not a classic scooter? Any pictures of the carburetor and screws to adjust?

az_slynch · Post by **az_slynch** » Wed Oct 31, 2012 4:44 pm

alloo66 wrote:So how do you tune the carburetor? AF mixture screw? I've done it on other vehicles, just not a classic scooter? Any pictures of the carburetor and screws to adjust?

Start with the Stella Service Manual, found here.

Page 30 is the start of the section on the carburetor; page 36 discusses carburetor tuning. In my experience with Stellas, the sweet spot lies somewhere between 2-4 turns out of fully seated; your experience may vary.

The Spaco/Dell'Orto SI series carburetors are a bit different that most other carburetors. The mixture screw affects fuel delivery for both the idle jet and the main jet, rather than just the idle mixture. The upshot of this is that adjustments to this screw affects the fueling across the engine's entire rev range.

I would recommend starting by counting the numbrt of turns it takes to turn the mixture screw in until it stops. That way, you have a baseline to return to if readjusting the screw doesn't help performance.

Once you have re-tuned the screw, you might want to do a plug chop. I recommend popping a clean sparkplug in first, in order to make it easier to interpret the engine's mixture state. Fire it up, find a long enough road with a safe shoulder and wind it through the gears until you get to the top of third gear . Press and hold the kill switch, while clutching it in and roll to a safe stop. Pull the plug (careful, it'll be HOT) and check the coloration. The plug insulator should be mocha colored. If the insulator is white, the engine is running too lean; add a quarter turn out on the mixture screw and re-test. If the insulator is black and oily, the engine is running to rich; turn the mixture screw in 1/4 turn and re-test.

alloo66 · Post by **alloo66** » Wed Oct 31, 2012 8:32 pm

Thank You. I checked it out today. Fried my positive battery cable after. Waiting for scooter works.

Found a good stella resource www.iheartstella.com