Two Stroke Motocross
Two Stroke Motocross Forum => Technical => Topic started by: od111 on March 01, 2011, 02:18:19 AM
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Hi Guys. I raced my CR for the first time on Sunday and found that right off the bottom there is an almighty bog (probably renowned for this). Its all standard apart from a HGS pipe. Is there an easy solution to eliminate or reduce it? Gearing or something? All help greatly appreciated.
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What year? Most 125's have little low end but CR's especially were known for it-you have to keep them singing.That doesn't mean you don't have a problem either.More info please.
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2006 (in title :) )
Coming out of slow, tight turns when the throttle is opened it just doesnt have the revs until I feather the clutch then eventually it does come then its brilliant.
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That was dumb wasn't it :( :D Oh well.It sounds about like a CR125 to me :) You can certainly gear it down for the track you run if you're too high a speed to down shift to the next one.Try two teeth more on the rear and see how you like it.One tooth likely isn't enough for what you describe.Is yours a 5 speed?
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go leaner on the pilot jet, you have a rich condition, try to work it out with the Air screw first though,1/8 to 1/4 turn
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Yeah, that's what I was thinking and also what other people have said but I thought I'd try the 'specialists' on here too. I have a one tooth bigger sprocket so I will throw than on first then try two if that isnt enough.
Thanks for your help :-)
Myck...
Good thinking!!!.......that will be my first option!!! Less work!!!!!!! ;)
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I just googled it and found it's a 5 spd.Yamaha tried that for a couple years too.Way too much spread between gears for a 125.You need to gear down.
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changing the gearing won't do anything for the bog, it will, however, let your motor pull longer into the meat of the power.
Warm up the motor real good, adjust your idle screw so the bike will idle, then slowly turn the air screw in (clockwise) until the idle starts to slow, it should only be about about 1/2 a turn. Then turn it the other way until the idle goes up. Some where in between those two points is where you need to be. then give the throttle a blip and adjust the screw until there is no hesitation, if you still can't get the bog out drop a size on the pilot, it's better to be lean on the bottom and rich on top than rich on the bottom and lean on the top.
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That's true but I took it from the wording of his question that he wasn't an experienced 125 guy-maybe moving off a 250 or 4t.
Every 125 "bogs" off the bottom if you ride them that way.Properly done,as you pull in the clutch and downshift for a corner,you keep the throttle about 1/3-1/2 open(depending on the bike) then ease the clutch out as you open the throttle more-slipping the clutch just a bit to control traction-not pumping it like a squirt gun trigger like you see some doing.
I considered my 02 SX to have the bottom end of doom compared to my other 125's but more accurately,it had a better lower-mid.
Any of my 250 2t or 4t riding buddies that rode it complained it bogged off the bottom.Of course,they were letting the revs drop too much then trying to power out like they could do on theirs.If you do that do a 125,it goes waaaaaaaaaaaaaaaaaaaaaaa until it gets to the mid then takes off like a scared cat.
Conversely,the first time I rode my bro in laws YZ250(I knew better but habit is hard to break) I came in to a 180 corner preceding a jump about 20 ft farther on,downshifted,kept the revs up,slipped the clutch and nailed the throttle about 3/4 the way through the corner-and went flying up over the berm off into the woods.Once he was done laughing and gagging he said-I've never seen anyone try to ride a 250 like a 125-can you do it again?Bah :(
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I know this is not an easy fix or cheap but a boyesen rad valve will give you more bottom end & throttle response. And a step up from that would be a phathead flat top head up grade with a wiesco flat top piston. Check your timing !!!!!!!!
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The stock reeds are 3 separate very thin carbon fiber reeds,connected at the base. The reeds are not sealing anymore, get a RAD VALVE, take the reeds out and polish the inside smooth, install rad valve problem fixed. My 06 cr125 is stock with rad valve,pc silencer,and icat. The cylinder is stock,along with the gearing,and pipe. I,m 175 lbs. in b.suit, it comes off of corners a gear higher than other 125,s and pulls much better than stock, from low to mid.
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CR125 usually benefit quite a bit from these so called ''power blades''.
(http://www.motocrossdirect.co.uk/ProductImages/1842/BIG/BIG/BIG/1842.jpg)