Pro Circuit T-4

I was planning on getting a Pro Circuit T-4 silencer to replace my stocker. I have a few questions that I hope you guys will be able to answer.

1. I noticed that unlike other aftermarket pipes that have allen screws, the T-4 is is riveted. Obviously the end cap is easily removable but is this where I would repack the pipe also?

2. Which end cap actually comes with the T-4? I've seen the T-4 advertised with two different end caps (see below). I realize that the 2nd end cap style actually comes in different sizes for low end, mid, top end, etc, but how about the round FIM style?

3. Finally, any problems with the slip on fitting the stock header?




I have a complete T-4 system on my 02 and love it....BUT it's loud! When you repack it you have to remove the rivets and either go back with rivets or you can use screws (screws just require constant attention.

As for your other questions I would contact Pro Circuit

Thanks Satch. I guess it wouldn't be too much trouble to drill out the rivets. I wonder how often I'd have to repack it. I ride two to three times a month. The local shops don't seem to know anything about the different end caps. I've tried calling Pro Circuit but getting someone on the phone who can help is a pain. They're only 15 min away from me so I guess I'll stop by there and see what's up. Thanks again.

Just buy a $10 rivet gun from Home Depot and redo the rivets. After you do it once you will wonder what all the fuss was about.

True. It seems kind of a pain at first but it shouldn't be a big deal considering its only a few rivets.

Also, if anyone cares, I got through to Pro Circuit and apparently the round FIM approved end cap is what is standard on the new pipes and the end cap with the downturn is what it replaced. Just an FYI.

I can't believe it, somebody else has a t-4 on their bike. Mine came w/the bike I bought used. Here are some of my thoughts and advice for what it is worth. Can't find many people using the t-4 at least on a yzf. The pipe is LOUD! Mine has never been repacked so maybe that would help. Mine has the s/a in it. P.C. makes a "quiet core" insert for the pipe so I ordered one. Well all it is, is a big washer (tack welded in three spots) over the end of the screen cone to reduce the size of the opening. Only a small amount of difference in sound level and it ruins the "sound" of the thumper. Small drop in power too. All for $30.00 :thumbsup:

It's almost a given now that everyone who has a T-4 says its loud :thumbsup:. How would you rate it's performance compared to stock? Where does it shine? I don't want to lose any bottom end.

I've got one on my 99 400, OMG its so much louder than my fathers KLX 300 with a WB e series.. like 20 dbl it seems.

In my expierence (a short stint with the stocker) the PC seems to have a little more late-mid and top end at a cost to the low end. I'd say its a good "desert pipe" shrug. thats my 2 cents.


I have a full system on mines. The system is loud! It sounds really gnarly! The pipe makes great power and will rev with the best of them, despite being a moderately priced pipe. I notice even people with thumpers and big 450's hear my bike and turn around (I have a massaged over yzf420). The bike runs great and the local rangers haven't sweated me or anything but when you crack the throttle it sounds like "uuuhh, we better get out of dude's way!" I have the s/a in it and tried the quiet core but my bike wouldn't start with it, I'd need to jet down in order to restrict the exhaust a little. I'm leaving it as is because it runs so well! Hope this helps.

I had the t-4 complete system, loved it, broke it... The weld around the pipe where it attaches to the frame broke. I now have a complete yosh system. I would say they are all equally loud (aftermarket systems). The pro circuit system is more controllable and revs just as far. I personally like the t4 system better. The yosh system revs way too fast. make the bike way too fast for me. All aftermarket systems are good, they make the bike rev further and more controllable.

Good luck,



I have the T-4 slip-on mounted on my trail pig and its way loud (even on a freakin TT-R). The FIM endcap helps with the bottom end IMO. Before the bike was all choked up (basically a putt around bike) and now with the pipe, airbox work, and the re-jet it actually is an enjoyable hillclimb and tight trail mount!!! I wish Cali didn't have the 96db law, I doubt my bike would pass!

I have had a full T-4 system on my 02 YZ426 for about a year now and I love it! I had the chance to ride my bike with the Dr.D and P.C. T-4 before I had to buy either one and after trying both on the same track, the same day, I purchased the T-4. I'm sure the Dr.D is also a very good product but, my bike would just "bark" coming out of the corners with the T-4.

Good luck :)

For any body thinking about one of these pipes keep in mind HOW loud it really is!!nolongergreen came by to do a little work on his bike and when he started it the house shook!!!I have 3 of the yamaha thumpers one with a yosh,one with a fmf and even one with a race big gun and by far the t-4 pipe was the loudest pipe there!!I mean thats OK if thats what you want but just don't even think about going to a sound ck with less than a 110 limit!!!!!lol

To me it sounded good and seemed to help with the power but with it being that loud there will be no t-4's at this house!

I've got the t-4 on my '05 yz450f. I didn't really notice any difference with the stock can as far as how loud it is. I think my stocker was louder than the t-4. Got a little bottom end boost, bike is solid through the middle and has decent power on the top. I like the pipe.

My T-4 ran 110 dbA at 5600 rpm on a 04 yz250f. And it still doesnt sound as loud as the Ti-4 does on my 05 yz450f, now that puppy is loud :)

I just put a silent sport cartridge in the T-4 but havent retested it yet. Either way it's never going to be a 98 dbA pipe.

I went to the T-4 in 2003 from the stock system on my '02 426. While it is not a quiet pipe by any stretch of the imagination it is not any louder than the Jardine, F.M.F. and Yoshimura systems being used around here on the tracks. The response is great and with a JD Jetting kit and Boyessen Quickshot along with the 450 Decomp cam mod my 426 runs strong and clean across the band.

My single problem was a lost spring where the muffler cannister joins the mid-pipe. I am satisfied with the T-4 system.


as long as your considering a replacement. I looked at them all and ended up putting the "white bros" E-series S bend muffler on my sons 426, I had a couple of criteria, 1. had to be USAF approved

2. Versatile as far as tunning..(no. of disc's)

And the fact the previous owner had already installed the WB head pipe on after smashing his made it a no brainer. I haven't had any experience with the T-4 but the WB pipe isn't seams quieter than the stocker, and it opened it up quite a bit in the power dept. :D:)

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