HH250 muffler gut job

Posts: 627

I just wanted to show some pics of what I did to my HH250 stock muffler. They say this is already somewhat of a performance muffler, but I wanted to open it up a bit more. Below are some photos of this thing taken apart. The nuts on the end that kept it together were welded onto the rod, so I ground the welded part down enough that I could get the nut off. Then it comes apart pretty easy. Then, all I did was drill some more holes in the center baffle area to make it more free-flowing (third pic). Lastly, I took out all of the honeycomb-looking stuff at the inlet pipe (fourth pic) so it was completely opened up. It really didn't get much louder after the mod. To put it back together, I had to unscrew the rods a little bit and drill another hole for the cotter pin to go through. Then I put a lock washer and two nuts on the end to keep it from coming loose (last pic). Hope this helps anybody that was curious about opening one of these up.

Posts: 923

Ah, nice job Ron, do you notice a big differance.

Posts: 23

Thanks for the pictures would it be okay to not drill holes but just remove the plate.

Posts: 627

I'm not sure, but I think the plate holds the packing material in place. If you completely removed the plate, I think the packing material would rattle loose and you'd have problems. You can gut that plate much more that what I did,though, if you really want to open it up. I heard a little back pressure is a good thing which is why I didn't go too crazy.

Posts: 164

Great write-up and pics. I've looked at my HH250 muffler several times and noticed the welds. Glad to hear it doesn't take too much to take them apart and put back together again.

One major question - hows the performance now?

Posts: 627

I'd like to tell you that it made a big difference, but I really don't know. I did that, the UNI, and rejet at the same time and I did gain a couple mph top speed. I was mostly curious about what was in there and just decided to punch a few more holes while I had it open. It didn't cost me anything and I certainly didn't lose any performance. Hope that helps.

Posts: 57

I drilled 8 3/8" holes in mine but did not remove the comb stuff... I finally found the right jet I think (140). I did not gain any top end, may have even lost 2 or so... I'm not sure I gained any low end performance either... Wonder if taking that comb out would make the difference... Rolling Eyes

I took a little different approach for taking mine apart... I just unscrewed the back and let it break off the carter pins in the front... The bought new all thread rods and drilled holes out the back of the muffler... then just put nuts on both ends :p

And you speak of packing material being held in place by the center plate... What are you talking about? I don't have anything in the muffler... Unless you mean the comb stuff....

Now I'm still on the hunt for top end speed mods... I can hit 39-41mph (by myself or with my wife, it doesn't matter) and I'd really like to get 46 or so (for those 45mph roads Very Happy

)

Andrew

Posts: 23

I removed the center piece baffle it was just hanging there anyway cut off honey comb.One of the rods broke where the cotter pin goes ,so I used all thread,just drill two holes install all thread and I double nuted the ends.improvement in speed and power still working on finding the right jet size.

Posts: 627

Inside the muffler, I think it's fiberglass packing that lines the inside. It's what muffles the sound.

Posts: 57

Oh, so you think the metal plate holds the metal mesh on the sides of the muffler that holds in the fill.. gotcha.

Today I removed the comb stuff in the pipe... And noticed zero difference in noise level or performance.