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crf250r bad bog when wrapping the throttle fast


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I have a 2008 CRF250R and when i wrap the throttle fast, it bogs down and dies unless i let go of the throttle right away. i have cleaned the carb twice now and put new feul in it and it still does it. I also replaced the AP pump diaphram, and no luck. Any advice?

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I were reading TT and wondered why all are complaining about crf250r bog. as well I have even stock '06

but then one day I got all bogs, corner exit bog, landing bog. and this starts suddenly. But actually it wasn't without reason I had changed stock air filter to aftermarket. made o-ring mod, leak jet 50, one size bigger slow jet and problem solved. as well now bike is even too sharp for me. but I have '06

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The leak jet is the small jet in the float bowl itself. You must remove the float bowl to get to it. The 40 leak jet seems to be the ticket almost every time. Also, if the jetting is stock, the main jet is a 188 which is too rich. You need to get a 172 and replace that stock pig. You'll feel the difference in the seat of your pants. No need for the AP mod with the O-ring as mentioned by shakapars. That was only on the 06 models. 07 and newer have a different linkage set up which remedied the issue the 06 had.

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yes, o-ring mod is for '06 and older

I really don't have a lot of experience with the 04/05 carbs, so I didn't want someone reading this post getting the wrong message! Thanks for the clarification! If I don't know the answer to a specific question on the 04/05, I always point them to Moto_x2005. He has a lot of experiece with the 04/05 and he's a real good dude! 06/09 is my strong point. Quickly learning the 2010, but I'm not buying one yet! Looks like a few issues that need to be resolved first! Have the 09 450 and have had 0 issues with it, knock on wood!

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my bike has a #70 leak jet, which is stock, wont a 50 be to small? i ride at about 3600 feet main jet is a #185, low jet is #42, needle clip is 2nd, feul screw is 1 5/8 turns

not to threadjack, but i always wonder this, myself... i'm curious if you guys with WOT bog problems run really low in the rpm's constantly (i.e. staying a gear high very often, run in very tight track conditions, or trail ride often)? the only time i experience bog is WOT from dead idle...

if not, and the problem is really a too-rich scenario... maybe i just have "dodged the bog bullet" by being at slightly higher elevation, having removed the air filter screen due to flame retarding filters, or simply staying closer to the rev limiter?

👍

of course... it's also entirely possible i'm a crappy rider and just don't notice it... lol! 🤣

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  • 10 months later...

I just want to amend my opinion, on the '08. I also feel the 40 leak is even better than the 50, crisper. With a 45 pilot at 1.5 turns and a 172 main summer, 175 winter, is the way to go with jetting. The 45 pilot starts on the first kick, even when cold. I have not felt the need to mess with the needle. This handles basically everything at around sea level form summer to winter in east central Illinois. Obviously a little in on the screw in the summer, nearer 1 turn. That is with the stock pipe, I will need to run a quiet pipe this summer, so will have to see what happens then.

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I'm glad I found this. I heard that either a Scary Fast carb thing and/or a accelerator pump would fix this. I'll go with the leak jet first.

Good idea. If that doesn't do it, there are pleanty of folks that know pleanty about these carbs and can get them right. Just have to be willing to do a little trial and error. There are some bastard carbs out there that can be a PITA!

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my bike has a #70 leak jet, which is stock, wont a 50 be to small? i ride at about 3600 feet main jet is a #185, low jet is #42, needle clip is 2nd, feul screw is 1 5/8 turns

A lower number on the leak will give your bike more fuel when twisting your throttle. Think I can say the leak works against the vaccum building up in the accellerator pump, so lower is more, make sense:bonk:

Think #45 pilot, needle stock and a #178 main, with a #40 leak and o-ring mod will cure the bog.

Mr P

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A lower number on the leak will give your bike more fuel when twisting your throttle. Think I can say the leak works against the vaccum building up in the accellerator pump, so lower is more, make sense:bonk:

Think #45 pilot, needle stock and a #178 main, with a #40 leak and o-ring mod will cure the bog.

Mr P

depending on the altitude and the temp. 45 pilot may be fine but the 178 is probably going to be too rich. If that's what you have, give it a shot. The 40 leak will be great. You can loosen the boot clamps at the front and back of the carb and twist it to get to the 17mm cap on the bottom of the bowl to access the jets if you have to play with the jetting.

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i had the same thing on my 07. i put a 50 leak in it and if you take off the black plastic side cover from the carb there is a pulley/spool system in there that controls the accelerator pump, there is an adjustable screw that stops the pulley, i tightened the adjustable screw until there was no slack/freeplay in the pulley movement and it eliminated my bog.

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