Originally Posted by SAPB
Looking at this, it seems the spark arrester (#7 on this) is $63. The lower part is just the spark arrester screen, which slips off (not sure which post showed this). So, I think Ed@Ford posted he modified the muffler on his XR400. It seems a cheap mod would be to get the SA out, and enlarge the holes (which you can't see in this schematic) to make it a bit more free flowing, and a little louder, way less $ than any aftermarket muffler, while still retaining the cat. Point being if you went a little at a time, enlarging the holes, and got too far, easy enough to put it back the way it was. Some of these DB ratings I'm reading about are just way to obnoxious, just my 2¢. Will the ECU "relearn" the mod?
Yes, compared to this CRF spark arrestor, the "windows" that are covered with screen in the XR400R spark arrestor are HUGE by comparison. BUT, there is also a snuffer in the end of the XR400 spark arrestor that keeps the noise down to 86dB..I think. If you take that snuffer out, it is VERY noisy...way over he 96dB allowed in offroad events now by AMA. I created a snuffer with much less restriction similar to the ones created way back then by XR's only. By comparison, the CRF has fairly small windows...but no snuffer. My thought is to take a stock CRF spark arrestor, or a reasonable copy, and hog out bigger windows, add screen, and get to a reasonable sound level, with a reasonable power increase. I am personally not interested in spending $700 to remove 7 pounds, and end up with a nasty loud muffler...and yes....anything over 90dB is LOUD in my book...but the stock CRF is 80dB....is similarly over kill in the opposite direction. I have a sound meter, and plan on taking some dimensions off the stock XR400 "windows" and the CFR "windows" over the next couple weeks.