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Author Topic: 2003 rm125 jetting and float height  (Read 3296 times)

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Offline MetalMike1982

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2003 rm125 jetting and float height
« on: March 27, 2012, 07:51:52 PM »
 Just pulled my carb apart to fix a long overdue problem of the float being set to high . How do I lower the float height ?just bend the metal tab? Also I've read that pc states that the main should be 460 and the pilot should be a 40 . The bike has a pc works pipe and 304 silencer and has a 460 main but a 27.5 pilot and still seems to run rich . Whats the deal ?

I am a  middle of the pack b rider I run 32:1 prohonda hp2 with 93 octane fuel . Ive heard these bikes dont like anything but race fuel so should I mix 50/50? The bike flat hauls ass and revs to the moon but when putting around it loads up fast .
« Last Edit: December 31, 1969, 04:00:00 PM by ' »

Offline Travis616

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2003 rm125 jetting and float height
« Reply #1 on: March 27, 2012, 09:44:23 PM »
Get your float height set properly and then see how the jetting is, usually float height doesn't have a dramatic effect but that's the place to start. What is your airscrew set at?
« Last Edit: December 31, 1969, 04:00:00 PM by ' »

Offline MetalMike1982

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2003 rm125 jetting and float height
« Reply #2 on: March 27, 2012, 11:12:14 PM »
 I adjusted the float a little and changed the 460 main for a 440 the airscrew is 2 turns out . everythings back together for the most part but I had my shock seals replaced so I have to wait on that to finsh putting it back together completely . then I will see whats up . Also repacked my silencer and threw in a new air filter . Hopefully it will be closer to what its supposed to be with the changes Ive made so far.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »

Offline MetalMike1982

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2003 rm125 jetting and float height
« Reply #3 on: March 29, 2012, 01:22:52 PM »
Alright I got it all back together and now it bogs on top . Pulls really clean and strong from the bottom to midrange then starts smoking and bogging once you go farther . I did get the float set at a better height but the change to the main made it even richer it seems . Im stumped , gonna put the 460 main back in and start over i geuss
« Last Edit: December 31, 1969, 04:00:00 PM by ' »

Offline cnrcpla

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2003 rm125 jetting and float height
« Reply #4 on: March 29, 2012, 02:12:23 PM »
If its bogging in the top, I would think that it isn't getting enough fuel. The only thing I can think of for a restriction of fuel would be clogged main, which shouldn't be the case seeing as you changed it, or a clogged gas intake valve that is controlled by the float. Check and make sure that isn't clogged or stuck. The smoky exhaust makes me think you are running really rich or fouled a plug though.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »

Offline MetalMike1982

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2003 rm125 jetting and float height
« Reply #5 on: March 29, 2012, 05:23:17 PM »
 Yeah its running rich alright . I took 3 laps around the yard last night after installing the 440 main and it fouled the plug . The carb is spotless from top to bottom , the jets brand new . The only thing that makes wonder what the heck is going on is that pc recomends a 40 pilot and this things got a 27.5 pilot , wouldnt changing it to the 40 make it run even richer ? Im confused . I'm about to say the heck with it just carry a spare plug with me from now on . I'm being told my particular bike is a pita to jet , also being told that i need to run race gas in it to straighten it out . Might start mixing 93 with 110 50/50 and see what happens.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »

Offline cnrcpla

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2003 rm125 jetting and float height
« Reply #6 on: March 29, 2012, 05:51:13 PM »
The pilot doesn't have anything to do with the high RPMs though. The pilot jet takes care of the idle and the low range RPMs. The high RPMs are all from the main jet. So if its bogging in the top, then it has to be the main or a fuel delivery problem.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »

Offline MetalMike1982

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2003 rm125 jetting and float height
« Reply #7 on: March 29, 2012, 07:06:22 PM »
The pilot doesn't have anything to do with the high RPMs though. The pilot jet takes care of the idle and the low range RPMs. The high RPMs are all from the main jet. So if its bogging in the top, then it has to be the main or a fuel delivery problem.

Alright then yeah It must be something other than the pilot . Whats funny is that with the 460 main back in it its still turns the plug black but it dosent bog anywhere in the rpm range just straight rips . Im gonna 50/50 the fuel and see what happens .
« Last Edit: December 31, 1969, 04:00:00 PM by ' »

Offline cnrcpla

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2003 rm125 jetting and float height
« Reply #8 on: March 29, 2012, 08:26:34 PM »
My 250 always turns the plug black. But I purposely mix rich. You can try the 50/50 mix of fuel, but like you said, if your bike is hard to jet, then its hard to jet. You should be happy you got rid of the bogging because I would rather mix rich and deal with plugs than mix lean and deal with pistons...
« Last Edit: December 31, 1969, 04:00:00 PM by ' »

Offline MetalMike1982

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2003 rm125 jetting and float height
« Reply #9 on: March 29, 2012, 10:44:40 PM »
My 250 always turns the plug black. But I purposely mix rich. You can try the 50/50 mix of fuel, but like you said, if your bike is hard to jet, then its hard to jet. You should be happy you got rid of the bogging because I would rather mix rich and deal with plugs than mix lean and deal with pistons...

 eff it I'm just gonna leave it the way it was and try some 50/50 racegas and see if that helps any .  Yeah I wont mix gas and oil at any other ratio than 32:1 no matter what anybody says . I'm gonna try and hollow my crossbar pad out enough to stick a spare plug in :D :D
« Last Edit: December 31, 1969, 04:00:00 PM by ' »

Offline cnrcpla

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2003 rm125 jetting and float height
« Reply #10 on: March 30, 2012, 01:41:21 AM »
Yeah, 32:1 no matter what for me too. You could always zip tie the spare plug to the inside of the frame  ;D
« Last Edit: December 31, 1969, 04:00:00 PM by ' »

Offline MetalMike1982

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2003 rm125 jetting and float height
« Reply #11 on: April 01, 2012, 03:08:42 PM »
 I decided to adjust the needle clip to see if it would help and its all the way at the top and the bike friggin rips now even more than before . How do you know if a bike is running to lean other than plug color ? or is that the only way ? I always asume when I hear bikes surgeing that they are running lean like if it were running out of gas
« Last Edit: December 31, 1969, 04:00:00 PM by ' »

Offline tweetakt

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2003 rm125 jetting and float height
« Reply #12 on: April 01, 2012, 04:48:04 PM »
If it's lean it will surge like you wrote.  

I bog is from the bike taking a big gulp of air... not enough fuel


Try a JD jet kit.  It cured my 03 CR250 which was doing the same thing as your ride.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »