Exhaust (and intake) thoughts for CRF50 (and 70 for that matter)

I have more of a theoretical question about exhaust and intakes for the crf50 (2004, 2006) and xr70s (2002).  Right now they are all stock and will remain that way for some time, but as my boys grow, I plan on potentially mod'ing them a bit.  One thing I noticed about the 50's in particular is the somewhat lack of exhaust options - I know there are several mfgs out there, but I was surprised to see not too many mufflers only - just full exhausts.  It appears the same can be said for the 70.  I've done some reading and it appears an exhaust and intake on otherwise stock bike doesn't get you much gain - I'd need to look at engine work and bigger carbs - this true?  I was also surprised to see that really the only exhaust mod's out there are removal of the arrestor and/or the end cap.  I did see some mufflers on amazon, but I'm guess they are just cheap chinese mufflers that may look cool but thats about it?  I was maybe hoping to see a name brand muffler only - or is all the HP gains with these in the head pipes?

The reason there aren’t any mufflers out there is because the stock exhaust is a single unit, so you would have to cut up your current pipe to be able to fit an after market ‘muffler’ on there. So it’s much easier to just sell/buy a full unit

Guess that makes sense. Wouldn’t keep my from cutting it off though. Lol.

So the no namers on amazon cosmetic only and likely a downgrade in performance from stock?

For the most part yeah. Some to this day even argue that stock is better than the good aftermarket stuff because of jetting and valve problems lol. But yeah I’d keep it stock (keep the baffle in) until you can get something decent. I got an eBay special exhaust for like $30 Chinese crap for my crf 70 just to try it and it was genuinely aweful lmao. Fit was terrible, came scratched to shit, didn’t sound very good either. Just save your money and time for not having to cut up your stock pipe lmao. The stock exhausts go for quite a bit online actually.

A 18mm Keihin carburetor on a stock engine makes far more difference than a pipe alone. If you add a manual clutch it'll also gain some snap. The meat of the power is off idle, the auto clutch dulls it.


I did a 88cc, race head build in my daughter's CRF70. My advice is leave it stock and sell it for a more powerful bike when the time comes. If you are looking for an excuse to build a hot rod then the best value is to buy a Piranha 140 motor from TBolt.









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