Can I run 2 cycle bike without muffler?

Paul w u

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Joined
Sep 27, 2017
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1
I'm kind of new to the 2 stroke bicycle motor thing and I have a slightly pressing question. Is it possible to run the bike (not sure what make or model at this point as I got the bike from my uncle pre assembled) with the muffler. I don't plan to leave it that way for long tho. The bolted keep stripping in the threads and the muffler keeps coming loose, probably bc of all the shaking and lack of a clamp to hold it from doing so. I managed to make it to work but I still have to make the return trip and it is too far to peddle and I have no access to thread tappers till I get home. Wondering if its safe to just take it off for the half hour ride home.
 


crassius

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Jul 23, 2012
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I wouldn't, if you suck cold air back into cylinder, you may damage the piston.
 

Murkle

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Jun 15, 2017
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2-strokes run fine without mufflers, if your muffler pipe is an expansion chamber you might notice a low to medium power loss, but you should be fine.

Here's a little rant, but it's necessary.
Weather or not crassius is 100% right, or wrong for that matter, yes, cold a air on hot parts introduces a chance of heat shock, this chance is very thin, even pulling air back through the exhaust is very unlikely. What I think he's thinking of is the chance of particles, or foreign objects, like dirt or pebbles. These can cause damage, but unless your exhaust port is facing strait forward, and under the frame of your bike, than you should be fine.


Here is an actual rant, but it's helpful.
The glasses are still expanding as they leave the cylinder, meaning return isn't likely. Plus, when freshly fueled air is pulled into the engine from the carb, it's then pressurized by the crankcase pushing it into the cylinder. This air I speak of coming from the carb? It's 'cold', that doesn't damage anything, and the crankcase wouldn't have much of any time to 'warm it up' before it entered the cylinder. Does that damage anything? No. If cold air didn't flow through the crankcase, it would overheat, and s seize. As we all should know, cold air is denser hot air. The denser the air, the more oxygen atoms are present. The more oxygen you have the more fuel you must have mixed in to maintain a proper balence. The more oxygen and fuel you have, the bigger explosion you get. The bigger explosion you get, the more power you have.

Thank you,
Murkle
 
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crassius

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Jul 23, 2012
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4,568
with a 6 inch or so pipe bolted on, air should warm enough in pipe to be OK - no pipe at all means after gas exits, piston is still going down and might pull in cold air (low flying birds or somesuch could also be bad in there)
 

Steve Best

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Sep 22, 2012
Messages
1,269
Crassius, like myself, has some 40 years of 2 stroke experience. He has seen a lot of stuff.
He has seen 2 strokes destroyed from being run with no pipe. He is trying to tell you man!
The cold air that is sucked back into the cylinder between strokes (and it IS sucked in) will lean out the mixture around the exhaust port. This will cause detonation and overheating in that area. This won't happen at idle, it happens as you are working the engine. It will happen without warning.

Another issue is the noise. It irritates the heck out of the average citizen.
I know you don't give 2 flutes about what your neighbors think, but they've complained to John Law and are shutting us down.

Read my sig line below. It applies to anyone not running a muffler.
 
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