04 CRF50 high rpm bog?

Ok, first post, been a forum pirate for awhile now, jus sort of lurking as "anonymous", until NOW! Finally back into the dirt bike world. Picked up on a 2004 model honda crf50 for a christmas present for my boy, going to get it in tip top shape between now and dec.ImageUploadedByThumper Talk1379650059.057694.jpg

I havent had a chance to mess with it yet but the previous owner informed me of high rpm bog. Does this sound carb related? And what are some specifics as to would could potentially be causing my problem.

Also, this bike has 88 (which im really not positive of what it includes) kit and honestly thinking about it now, im not sure what exhaust, and a new carb. And should i assume the carb should probably be jetted differently?

Not very familiar with any of this stuff but realllly enjoy dealing with it. Knowledge is everything for me at this point.

Thanks for any reply, uin advance.


Whenever I get a used bike, I assume that no maintenance has been done.  Unfortunately, this assumption has turned out to be true more often than not, no matter what the seller says.  Even "bulletproof" engines need maintenance.  Proper maintenance is what keeps "bulletproof" engines from breaking.  Anyway, if the bike has any issues, I do all the maintenance before trying to troubleshoot.  This includes:

valve adjustment

clean the air filter

replace spark plug, or at least check the plug and set the gap

drain the tank completely (remove the tank to do this, it's easier) and fill it up with fresh gas

clean the spark arrestor screen

change oil

clean the carb thoroughly



Give that a shot and see where it gets you.


If you have the problem still, post back with more information such as throttle position when the bog occurs, what carb you have, jet sizes (make note of them when you have them out while cleaning the carb), needle clip position, any other mods, etc.


Good luck.

Edited by Punkinhead

All it took was a new air filter. Thanks alot!!

Thanks for letting us know how the story ended.  9 times out of 10, it's something simple.  A dirty air filter is an indication that the prior owner didn't put basic maintenance at the top of his list.  At a minimum, you should check/adjust the valves, change the oil and clean the spark arrestor screen.  It was running rich with the dirty filter.  This will contaminate the oil and plug up the screen.

How do i "check/adjust" the valves? Pull the fairings, tank, and cam cover? Never dug into a 4-stroke, ive only performed 2-stroke rebuilds.



its pretty simple, but you should get a book.  The 30 bucks for a manual will save you a lot of cash by doing it yourself.  Doing the work in your garage sure saves the cost of $90 an hour shop time for simple things.  Basically, you remove the stator cover and set the bike at TDC.  Then remove the valve cover caps and check the gap with a feeler gauge.  Then its a simple 10mm wrench and screw driver adjustment to set them.  Caps back on, stator cover back on, and she will run even better than before.  keep up on the basics and she will last forever.  As i have read from Pumpkinhead, they are bulletproof, but only if you take care of them properly.  A little love with these bikes will go a long ways for you.

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