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Author Topic: Best Silencer for Duncan Pipe?  (Read 1698 times)

Offline laddbg

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Best Silencer for Duncan Pipe?
« on: January 19, 2016, 12:56:44 pm »
Working on reviving my 87 LT500 and looking for suggestions on a good silencer to fit the Duncan pipe. The silencer that is on the machine now is a cobra and does not fit right at all. Love this sight tons of great information!

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Offline Q2W

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Re: Best Silencer for Duncan Pipe?
« Reply #1 on: January 19, 2016, 01:03:44 pm »
I reckon you mean the Paul Turner pipe?  Duncan should sell you the silencer for that pipe.

Or maybe one of the members here has one laying around.

Lots of part hoarders here. lol

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Offline laddbg

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Re: Best Silencer for Duncan Pipe?
« Reply #2 on: January 19, 2016, 01:34:02 pm »
That's what is was wondering do I have to use the turner silencer? That may be why the one that is on it now is jacked up.

Offline Q2W

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Re: Best Silencer for Duncan Pipe?
« Reply #3 on: January 20, 2016, 08:01:03 am »
If i remember right, the PT tailpipes are very restrictive and cause excess piston heat.  Maybe why they went with a different one.

Offline MotorGeek - Jerry Hall

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Re: Best Silencer for Duncan Pipe?
« Reply #4 on: January 20, 2016, 07:50:09 pm »
I would not use the aluminum Fat Boy silencer on anything other than a stock engine that is making 50 hp to 55 hp and then I would limit the time of full throttle blast to only a few seconds at a time. 

The piston overheating problem with the over restricted Paul Turner pipe and Fat Boy silencer will not show its ugly head when making 3 second or less long dyno runs even if you are making 10 back to back runs lasting less than 3 seconds each.  It will not usually show a problem running 100 yard long drag races unless the engine has some serious porting and big carb.  If you are running up long sand hills or riding where the throttle is held open for 10 seconds or more you should modify the stinger and silencer to have at least 1.25" ID from the tail cone to the atmosphere. 

It has been my experience that Lt 500s that are surviving when ridden hard that have the small stinger and Fat Boy silencer are not tuned to make good power and or the porting is screwed up. 

Offline Glamisrider

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Re: Best Silencer for Duncan Pipe?
« Reply #5 on: January 20, 2016, 08:59:51 pm »
Jerry, do you have a suggestion for a Silencer that will work with the PT pipe?

Say like a FMF turbo core or a JH special made or something?


Offline laddbg

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Re: Best Silencer for Duncan Pipe?
« Reply #6 on: January 21, 2016, 07:25:58 am »
Thanks for the responses. Little more info on the bike. The entire engine was sent out to CT in the mid to early 90's, they did the head studs and mild port work it was supposed to be set up for trail riding, fast fire roads. The factory carb was worked over by CT also it is a 43B00. I do run full throttle on the flats and gravel roads. So that being said is the Paul Turner pipe good with the right silencer or should I start over? Kind of on a budget, this thing needs a lot of parts.

Offline MotorGeek - Jerry Hall

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Re: Best Silencer for Duncan Pipe?
« Reply #7 on: January 21, 2016, 10:26:51 am »
Jerry, do you have a suggestion for a Silencer that will work with the PT pipe?

Say like a FMF turbo core or a JH special made or something?



I would not use the FMF spark arrestor model unless you absolutely have to.  The spark arrestor insert adds considerable back pressure  The FMF straight through silencer with the 1 3/8" OD mid pipe works good up to 60 to 65 hp then you need to cut off and replace the small short stinger that connects the tail cone with the mid pipe with 1 3/8" OD 18ga tubing.

Offline Glamisrider

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Re: Best Silencer for Duncan Pipe?
« Reply #8 on: January 21, 2016, 11:41:11 am »
I would not use the FMF spark arrestor model unless you absolutely have to.  The spark arrestor insert adds considerable back pressure  The FMF straight through silencer with the 1 3/8" OD mid pipe works good up to 60 to 65 hp then you need to cut off and replace the small short stinger that connects the tail cone with the mid pipe with 1 3/8" OD 18ga tubing.

Laddbg,
The PT pipe is a great all around pipe especially for the money.  Jerry is saying to use the regular FMF silencer with NO spark arrestor unless you have over 60hp then you'll need to modify the end of the PT expansion chamber where the little 1" diameter piece of pipe is that the silencer pipe (mid pipe) plugs in to.  above 60hp you'd replace it with a 18ga 1.375" pipe instead of the 1" pipe it has from the factory.  But up to 60hp the regular PT pipe with a standard FMF silencer will work good.


Hope this helps clarify it for you.





 

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