jr50 muffler

P

paper racer

~SPONSOR~

Jun 13, 2001

61

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• Mar 22, 2004

• #1

i just bought an 84 jr50 and it does not have a muffler. Will that hurt how the bike works? it isn't that loud. Thanks.

 

Vic

***** freak.

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May 5, 2000

4,008

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• Mar 23, 2004

• #2

When my son had one, the silencer mount broke. I thought I would fix it, but when I heard how quiet it still was, I just left it off. No, it doesn't hurt anything. The only thing is, you lose the spark arrestor. Not a real problem, IMHO.

 

P

paper racer

~SPONSOR~

Jun 13, 2001

61

0

• Mar 23, 2004

• Thread starter
• #3

THANKS, you just saved me 100 bucks.

 

Vic

***** freak.

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May 5, 2000

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• Mar 24, 2004

• #4

paper racer said:

THANKS, you just saved me 100 bucks.

Click to expand...

You could use that toward your lifetime membership. :)

Glad I could help.

 

M

moto2121

Member

Mar 2, 2004

38

0

• Mar 24, 2004

• #5

won't the lack of back pressure hurt low end proformance??

Just wondering cause my son has a 92 jr50, and it was missing the silencer when we bought it

 

Vic

***** freak.

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May 5, 2000

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• Mar 24, 2004

• #6

I don't think the silencer adds much back pressure, anyway.
Potential loss of low end power, due to decreased backpressure, is more of an issue with four-strokes.

 

Jasle

Sponsoring Member

Nov 27, 2001

1,358

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• Mar 25, 2004

• #7

Not so. When racing the pw50 wihich isn the same ballpark as the jr we noticed a huge drop in bottom end performance just taking the silencer out like everyone said we should.
Also on the Cobra CM and PW-3 we changed to a smaller dia core size in the silencer and noticed an imporvment in bottom end performance.
Also you jetting changes a bit without the back pressure. the back pressure helps tune the sonic waves that aid in extrating fuel from the cylinder.

But check E-bay there are usually a good amount of parts there.

 

Vic

***** freak.

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May 5, 2000

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• Mar 26, 2004

• #8

I have no experience with the above mentioned bikes, but I'd bet Travis Pastrana's medical bills you won't notice a difference on the JR.

 

Jasle

Sponsoring Member

Nov 27, 2001

1,358

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• Mar 26, 2004

• #9

so how much do you owe me? :) We have several racers out here running PW50's. they are in the same 2.5hp class as the jr. the difference with or without the silencer is the difference between making it up a hill from a standstill or not being able to get up the hill without the silencer. when your talking about a bike with only 2.5Hp then 1/2 Hp is a huge difference. But yes I would be your or I would not notice the difference but a 40lb kid might.
I know my kid noticed the difference when I switched from a 70 main to a 65 (two steps in the pw's carb). that change is as subtle as the silencer issue.

 

Vic

***** freak.

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May 5, 2000

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• Mar 26, 2004

• #10

Jasle said:

so how much do you owe me?

Click to expand...

As far as I can tell, nothing. :)

PWs and JRs run in the same class, but they're not the same.

 

S

Skitspuce

Member

May 21, 2003

63

0

• Mar 29, 2004

• #11

I removed the silencer on ours, and could tell absolutely no difference in (lack of) speed or noise level. Do the first gear mod and you'll double the acceleration, anyway.

BTW...has anyone tried the FMF pipe for these things? I'm sure it wouldn't add much power, but it'd be cool to have. If I could just find a way to hang with the XR50 guys, I'd trick it out.. :clue:

 

Vic

***** freak.

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May 5, 2000

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• Mar 29, 2004

• #12

Skitspuce said:

If I could just find a way to hang with the XR50 guys, I'd trick it out..

Click to expand...

You may want to have a talk with Eric Gorr. :)

If I remember correctly, Dyno Port makes a pipe for them. I have no idea how well it works.

 

Z

ZOOK250

Member

Oct 5, 2001

270

0

• Mar 29, 2004

• #13

i drilled out the restrictors in littlezook's 2001 jr and it had a noticable drop in low end. if i hadnt done the 1st gear mod it would have a hard time accelerating evan on flat ground. i am going to put the restriction back in.

 

S

Skitspuce

Member

May 21, 2003

63

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• Mar 30, 2004

• #14

I'm glad you said that about the restrictors...I assume you're talking about the baffles inside the pipe itself and not the silencer. I thought about cutting those out, too. Sounds like I oughtta leave them alone. Thought about talking to Eric Gorr about it, but decided that I'd wait until he's a little less busy...plus, I feel a little stupid trying to make power with this thing. But then again - if kids can hop up a 80hp Civic, why can't I do a JR? :)

 

Vic

***** freak.

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May 5, 2000

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• Mar 30, 2004

• #15

The only restictor ours ('97) had was a washer with about a quarter inch hole in it, between the cylinder and headpipe. I tossed it immediately, as the bike ran like it had an exhaust restriction. :)

 

Z

ZOOK250

Member

Oct 5, 2001

270

0

• Mar 30, 2004

• #16

the restrictor in the silencer has to be drilled out. the purpose of it is to redirect the exhaust through the baffles instead of going straight out. kind of resembles a beer cap welded inside to block the diameter of the pipe.

 

S

Skitspuce

Member

May 21, 2003

63

0

• Mar 30, 2004

• #17

I'm talking about the baffles welded inside the pipe itself...if you look at the back side of the pipe towards the silencer you can see a square weld. There has to be something in there, or it'd be super loud with no silencer on it.

 

Jasle

Sponsoring Member

Nov 27, 2001

1,358

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• Mar 30, 2004

• #18

well I cannot tell you the difference between the jr with the pipe but I can tell yo the PW50 with the FMF is totally different. Some port work, the pipe and boring the carb to 14mm and the bike rips. Add the stiff clutch washers and your kid can pull wheelies and lay big roost. I'm sure you could cut a coil off the jr spring to stiffen up the clutch to get better revs before clutch engagment.