2 stroke muffler question

[fetor56]

I'm NOT an engineer and i've done BOTH(drilling and cutting)
I'm at sea level and i've kept a check on my mixture each time cos it's important to me.There's only been a SLIGHT leaning-out of the mixture from standard to fually cut,not enough to even get me mildly concerned about recommending this procedure to other ppl............................the end.

 

[thatsdax]

Yes... This is true..

Yes.. this is True.. I have a Degree in Engineering. It is an Electronics Engineering Technology degree. BSEET. Working on a Masters degree at Denver University., slowly.. I have 2 other degrees as well. Not that it matters.. What does matter is that I have been Working on, Building, and Selling Engines, PTO's, and Power Generators since the 1970's. and.. For the purposes of Engines, I am at 9000 feet, and anywhere you go west from here is up. That means, I am at a low point. I test engines to heights of 12,000 to 14,000 feet almost every year. I also have a location near Kimberling City where I have been able to run and test. That is around 1,000 feet or so. At any rate.. Do not be so shocked that I and others in this forum have College Degrees. It is an integral part of this world. Enjoy the ride...

 

[KanesKustoms]

Muffler Switch

Hi guys
Can anyone show/tell me What other aftermarket mufflers can be used on the 70cc NTJL motor Im looking to reduce the noise but maintain or improve performance. but really performance is not the issue here.
Ive checked out some of these pocket bike muffs and with a few mods I can fit one on this motor easy question remains which one will best reduce the noise and not compromise the normal performance.

 

[andyinchville1]

HI
Heh heh...OK I gotta say it again because I am going to find somebody here who will do this...Car Muffler....;-0 .....Big enough (get one that is normally used for a V8....but if you are not feeling that overkill maybe one for a 4 cyl car..NOT a glass pack tho....one designed to be quiet) so as not to cause any noticeable restriction to exhaust flow in our little engines and definitely quiet....Can I count on you to go for it? ;-)....I think it would work great BUT there are those here that say a fair amount of noise also comes from the intake side of things and the clutch cover needs to be rubberized too to deaden sound...
Hope this helps
Andrew

 

[cooltoy]

Kanes, your question is why I found this place. After a couple of months or so of reading here, I have not been able to come up with an easy answer. Most of the mods I've read about here tend to make the engine run better but tend to be louder. i know that if I put my finger over my tailpipe/baffle, I can stall my engine, that is not a good thing as that tells me that they need a free flow and mufflers tend to block that much needed flow. it's like you can't win.
Andy is thinking car mufflers. I'm thinking that they are so big that it will not help in any way but I don't really know. It's possible that the large size would help to mellow things out but I just do not think so. Could a Ski-doo muffler be an option? I think in the end 4 stroke is the only way to go to get rid of the sounds. Sad but true. I will be trying the pipe insulation wrapped around the baffle trick myself, with a few inches cut off of the end .I guess we are all waiting for that magic post from a member here telling us that "this" worked great and I can not hear my engine idle.......... Anyone???

 

[likearock111]

Baffle Mod --> decreased performance??

Hi all,

I have a Dax 70cc on a Skyliner. I had kept everything completely stock for break-in (first couple of months), and I just decided to do the baffle mod. I took a Dremel to the baffle pipe, but I left about 2-3" of pipe still on the inside of the end cap of the muffler.

After two days of riding, I can notice a couple of things. First of all, I really think I'm getting better HP, especially at lower rpm.

Second, and more importantly, I now notice a weird sort of bogging out that happens when I ride at roughly 75-100% of WOT. It almost seems like the engine isn't getting enough gas or something, but I'm not experienced enough with these things to know. For example, if I run at full throttle, it will have power like normal for 4-5 seconds, then it will bog down to ~70% of expected power for 5-10 seconds, then it will have power like normal again for 4-5 seconds... and so on...

Does anyone know what could be causing this? Does this sound like a carb problem to you? I took apart the air filter, and everything looks fine in that respect. I'm just confused as to what I should be looking at to fix.

Thanks for reading!

Likearock

 

[fetor56]

Hi all,

I have a Dax 70cc on a Skyliner. I had kept everything completely stock for break-in (first couple of months), and I just decided to do the baffle mod. I took a Dremel to the baffle pipe, but I left about 2-3" of pipe still on the inside of the end cap of the muffler.

After two days of riding, I can notice a couple of things. First of all, I really think I'm getting better HP, especially at lower rpm.

Second, and more importantly, I now notice a weird sort of bogging out that happens when I ride at roughly 75-100% of WOT. It almost seems like the engine isn't getting enough gas or something, but I'm not experienced enough with these things to know. For example, if I run at full throttle, it will have power like normal for 4-5 seconds, then it will bog down to ~70% of expected power for 5-10 seconds, then it will have power like normal again for 4-5 seconds... and so on...

Does anyone know what could be causing this? Does this sound like a carb problem to you? I took apart the air filter, and everything looks fine in that respect. I'm just confused as to what I should be looking at to fix.

Thanks for reading!

Likearock

It sounds like with the increased exhaust flow your running the engine too lean.Take your carby's needle UP one notch to increase your fuel flow and see what happens.
I only had a SLIGHT leaning out of my mixture but i only drilled a few holes in the pipe,not cut it off completely.

 

[likearock111]

Gotcha. So needle up = circlip down, right? Another thing I just remembered - When I took the entire exhaust off of the engine, the exhaust gasket was stuck to both pieces of metal, and a little of it tore off. I figured it wouldn't be too big an issue, but I probably should replace it. I think I'm going to go ahead and replace both the intake and exhaust gaskets with cereal box + permatex and see if that might be an issue. Thanks for the help, Fetor!

 

[fetor56]

Yep,circlip down.
I havn't had any trouble with my gaskets but some ppl make them from a dual thickness of aluminium can or sheet copper.....a sheet of good/heat resistant gasket material would last for ages.

 

[fastboy9]

Exhaust Pipe Exploded!!
On returning home from a 10 mile ride the exhaust pipe actually blew off! I had removed the baffle from the exhaust pipe, I'm guessing now the can acted as a basic expansion chamber, I was going about 29mph and the gases built up so much that they couldnt get out the can quick enough. High Pressure + Carp welding = Explosion. I must say though the sound is awesome and the performance is amazing!! But I would not reccomend you do this! It will severely damage the engine, only had to ride home about half a mile though luckily. The muffler can blew off, just leaving me left with a header pipe bolted on to the engine! Now I've got an excuse to upgrade to a pocket bike exhaust pipe, will keep you all informed on my progress.