Drilling out stock muffler tip?

14 replies to this topic
  • slowxr

Posted November 25, 2003 - 03:04 PM


I just bought and 03 XR650(California Model) Has anyone drilled out the stock muffler tip? I ordered the HRC tip($140) which is supposed to open the hole up a bit. I was curious if this drilling accomplishes the same thing as the HRC tip and/or does drilling out this tip void the spark arrestor or make the bike excessively loud? I'm in CA. so noise is a concern. Any thought?

  • JR650

Posted November 25, 2003 - 03:24 PM


i drilled mine cuz im a cheap bugger. Doesnt touch the spark arrestor and its pretty quiet but not sputtery (sounds nice). Also cut the little baffle off the end that is held by the four metal straps, not much noise increase but it makes more power and is still quieter than the hrc tip. i just take my tip out completely when i really want power and up the main about 5 sizes. As for drilling, i have heard some people cut through it in like 2 min, mine took an hour, 2 bi-metal holesaws and 4 beer. Maybe its just the 2003 tip that are like that?? (my old tip went missing so i got a new one with the bike, long story) Go slow, oil lots, and if it wont go, hold er wide open and burn the $%^&* through. Its probably exactly what you are after if the hrc tip is too loud, JR

  • BWB63

Posted November 25, 2003 - 04:13 PM


The stock tip is sorter then the HRC tip.

  • jaybert600

Posted November 25, 2003 - 04:49 PM


I believe that there is a big difference in the two tips. The drilled stocker has decent low-end, but falls short on the mid-top end. Plus the HRC tip sounds better!

  • Roll_it_on

Posted November 25, 2003 - 06:18 PM


When you get your HRC tip that you ordered you will see that there is a significant difference in the two configurations. You may want to drill out your stocker and keep it handy if you want your bike to be a little quieter without being strangled. The HRC will provide the maximum output from the stock pipe with an increase in sound :)

  • BWB63

Posted November 25, 2003 - 06:29 PM


There are two baffles just inside your stock muffler. (walls that the tip slie threw) The stock tip has a small baffle at the end (that most cut off) and a baffle inside that most drill out)You can drill out the inside baffle out of the stock tip with a 2" bi-metal hole saw or use a 1/4" drill and drill lots of hole next to each other around the baffle then bend it back and forth till it brakes out. The HRC tip is longer (a little longer then the stock with the baffle at the end) so that it goes past the muffler baffles. You can get the stock tip to work close to the HRC tip if you drill the inside baffle out and by bending down those two baffle walls inside the muffler housing. :)

  • BWB63

Posted November 25, 2003 - 06:34 PM


The HRC tip just makes under the 96db sound limit. You have to rejet! 68s pilot, 175 main. If you go with a UNI air filter you'll need a 178 main. Holes in the air filter cover 178 or 180 main depending on elevation. I live in So. Cal. and run way over 105db :D :) :D :D :D :D :D

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  • smashinz2002

Posted November 25, 2003 - 09:13 PM


Drilling out the stock tip makes some improvement, but not as much as the HRC tip. You can drill the stock tip to 34mm or 36mm, which is either inside the ring or outside the ring. Both mods are a pain in the A**! But I'm glad I did it because I use the drilled out stock tip in Colorado to keep the noise down.
The HRC tip provides a lot more power all over the place. If you don't need the spark arrestor part and the baffle cap, then you can cut off those parts from the HRC tip leaving only the bell reducer exit part. This provides the best power output, increasing mid and top end power.
But since you're interested in low noise, I'd say to drill out the stock tip, and use the HRC tip you ordered also to see what you think about it. I bet you will like the HRC tip a lot better!
To answer your main question, NO, drilling out the stock tip does not accomplish the same thing as using the HRC tip.

  • BWB63

Posted November 25, 2003 - 10:11 PM


Look here http://www.xr650r.net/ and go to the left side and click on making the XR650R run right (uncorking it) and look at #3 and you'll see a stock tip drilled out to 51mm. We are drilling out the stock tips to 50mm with 1/4" drill bit, 51mm with a 2" hole saw. The biggest difference in flow is acheaved when you beated down the two baffle walls in the Muffler housing itself. When you look down the muffler without the tip it looks like it just goes straight threw but, if you look up frount just inside there are two walls that the tip slide threw. The exhuast(and noise) hit the first wall bounce' back and forth on that little plate on the back of the stock tip through the small gap, hit the next wall and threw the screen then tord the back plate at the end of the screen down the 20mm hole in the inside tip muffler and out. It's amazing that anything can get out. I don't know how you only get a 36mm hole when you drill it out but, it must be a pain. With a 1/4 drill it takes less the 15 minutes on a drill press and another 15 to grind it smooth inside. What realy lets it flow threw the stock tip is getting those baffle walls out of the way to stop the devertion. The only difference between the stock drilled out tip and the HRC is the HRC makes it past the secound wall so more Exhuast can flow threw the screen. (longer with more screen area) with the baffle bent down you are acsompeshing real close to the same thing. You don't have to bend them all the way down. If I could find a way to bend them forward that would be way better. I use a huge bar that has a point on the end and hit the plates or walls on the top and the bottom of them bending them back. Some effort and you get a good size hole on the top and bottom of them. Be carefull not to miss and put a hole in the muffler it self. I do this with the muffler on the bike. You'll see all this when you get the HRC tip and study it all. Even with out messing with the inside baffle walls drilled out to 50mm it's close to the HRC. Lots of XR650R's to mess with and this has been the verdict once jetted right.

  • slowxr

Posted November 26, 2003 - 09:24 AM


Great info. If the HRC is actually 96db or below, that sounds like the ticket.
Also, I read the uncorking recommendations. Is a UNI filter recommended? I'd replace it if it is. And if so, I'll need to up the main to a 178. True?

  • BWB63

Posted November 26, 2003 - 12:24 PM


Yes, make sure you get the UNI with the frame in it not just the UNI filter. and you don't need that back fire screen :)

  • slowxr

Posted November 28, 2003 - 05:55 PM


I ended up drilling out the stock tip and returning the HRC to the dealer. Anyone know if this will actually pass the 96db sound test? It seemed loud to me. Anyone?

  • slowxr

Posted November 30, 2003 - 02:06 PM


Took my first ride today. Did some fireroads above Rowler. The drilled out tip seems as loud as the E-Series I had on my 600. The E Series didn't pass the new sound limits(tested at 98db) so I'm concerned about this drilled out stock muffler. If anyone tests their's, I'd be interested in the results.

  • BWB63

Posted November 30, 2003 - 07:54 PM


I have seen three pass. I run a R4 series White Brothers and it's nowhere near 96 db. I live in So. Cal. Two where with the lowder HRC tip and one with the stock tip drilled out with the small four prong baffle thing removed. If you go to Gorman or Ocotillo Well and go to the rander station they will test it or send you to where they are testing. They test at 2000 rpm. The BRP is just starting to get loud there.

  • slowxr

Posted December 01, 2003 - 09:12 AM


That's goooooood news. Thanks.

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