Anyone have tips on checking float level???

Brandon H.

Member
Mar 26, 2009
199
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I have a 2000 CR125, and this things needs jetted bad. There is almost no bottom end. It has a fresh topend, (less the 3 hours), always a clean filter, and fresh gas. It has Vforce reeds, ProX piston, and Pro circuit works pipe, and silencer.

There is no power down low. I know 125's dont have much, but this thing has none. My friends 96' Rm125 has decent lowend power, but not mine. Sometimes its really hard to get out of small holes or ruts when stopped. I need to give it quite a pit of gas and slowly work the clutch or it will just bog out. Whenever I ride up and down my neighborhood, whenever I get going and finaly have the clutch all the way out and start giving it some gas it sorta does a bog and chug feeling untill mid rpm where it cleans out and pulls hard from upper mid to high rpr range.

I was to start jetting it, as I think thats the cause. It has a 340 main, and #50 slow jet (stock slow jet, stock main would be a 360). I dont notice any RPM change turning the air screw out 2 turns, 3 turns, 4 turns, even 5 turns out.

I need to start with the float level, but I cant find much info on how to measure it correcty. My manual says it needs to be 15mm. Any guide or info on checking the float level??

Also my friend has a Go-Pro helmet cam, I am going to see if I can use it tomorrow to make a couple videos of what its doing.
 

julien_d

Member
Oct 28, 2008
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I wouldn't expect the RPM to continue rising after you reach the spot where it hits the highest idle on the airscrew. Hopefully this is around 1.5 turns. As you continue to go out the idle may not really change, but going in from there should cause it to get lower and lower and eventually die.

Anyhoo, my buddy has a yz125 we just finished rebuilding. It behaves exactly the same as you describe your CR running. We haven't gotten much chance to look into it yet, but my gut feeling after riding it a bit is that it's wicked rich low through mid. Needle position changes didn't help much. We've got jets for it now but have been too busy working on the other bikes to mess with it.

Get you a range of jets, and check the carb out really well. I'd guess that float measurement is from the top of the float to the mating surface when the float valve is just closed. The service manual should tell you how? You can always attach a clear rubber hose to the carb drain and run it up beside the carb. When you turn the fuel on the level in the tube will show the level of fuel in the carb. A few MM below the mating surfaces should be fine.
 

Brandon H.

Member
Mar 26, 2009
199
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julien_d said:
I wouldn't expect the RPM to continue rising after you reach the spot where it hits the highest idle on the airscrew. Hopefully this is around 1.5 turns. As you continue to go out the idle may not really change, but going in from there should cause it to get lower and lower and eventually die.

Anyhoo, my buddy has a yz125 we just finished rebuilding. It behaves exactly the same as you describe your CR running. We haven't gotten much chance to look into it yet, but my gut feeling after riding it a bit is that it's wicked rich low through mid. Needle position changes didn't help much. We've got jets for it now but have been too busy working on the other bikes to mess with it.

Get you a range of jets, and check the carb out really well. I'd guess that float measurement is from the top of the float to the mating surface when the float valve is just closed. The service manual should tell you how? You can always attach a clear rubber hose to the carb drain and run it up beside the carb. When you turn the fuel on the level in the tube will show the level of fuel in the carb. A few MM below the mating surfaces should be fine.

According to the manual, it looks like 15mm from the top of the float, to the mating surface of the carb. I guess being carefully to not compress the small plunger on the needle. I like the clear hose idea. I think I may try it. But where should the fuel be? your saying a few MM below mating surfaces is good, but what if its a tad bit higher or lower. Is this a accurate enough test?

I too think its running really rich on the bottom end. Pilot jet is a #50, what size would this be when ordering a couple smaller jets? I noticed they go like 12.5, 15....and so on.
 

helio lucas

~SPONSOR~
Jun 20, 2007
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http://www.procircuit.com/jettingspecs.htm#2000
some jetting specs from pro circuit may help...
to setup the float level on most of the comon carbs just get the marks on the float or the float arm parallel to the gasket surface of the fuel bowl :cool:

the manual should say how to measure the 15mm. may be in another chapter. if not, usually, is 16mm not 15, with upside down carb, from the top of the float to the gasket surface with the needle just closed.

before any atempt on jetting be sure that the exhaust packing is new and the engine don´t have any air leak. and the carb should be clean.
 
Last edited:

Brandon H.

Member
Mar 26, 2009
199
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helio lucas said:
http://www.procircuit.com/jettingspecs.htm#2000
some jetting specs from pro circuit may help...
to setup the float level on most of the comon carbs just get the marks on the float or the float arm parallel to the gasket surface of the fuel bowl :cool:

the manual should say how to measure the 15mm. may be in another chapter. if not, usually, is 16mm not 15, with upside down carb, from the top of the float to the gasket surface with the needle just closed.

before any atempt on jetting be sure that the exhaust packing is new and the engine don´t have any air leak. and the carb should be clean.
Carb is spotless and reeds look great. I would like to run a leakdown test to check for airleaks, I need to find some threads on how to make one. I will pick up some exhaust packing this week.

Hopefully Pro Circuits jetting should get me close to what it should be, I noticed the main is good, but they used a 40 pilot, and I am running a 50. Since I think I am running rich on the bottom, this should help. What kind of needle is a 20-69??

Also, where do I order these pilots? I noticed on ATVMC, they range in sizes from 12.5, 15.... not 40, and 50. Is there a conversion?
 

helio lucas

~SPONSOR~
Jun 20, 2007
1,020
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sizes that small should not be for your carb but for mikuni. kehin uses around 50.
usually you can get the jets directly from honda dealer itself but they are more expensive. i do not live in america and i cannot help you very much on places to get jets but it seems sudco is a trusty source. also jd jetting kit seems to work very good from the reviews on the forum.

http://www.sudco.com/Carburetor01.html
http://www.jdjetting.com/xcart/home.php?cat=6


edit: is the power valve on the bike working?
 

Brandon H.

Member
Mar 26, 2009
199
0
helio lucas said:
sizes that small should not be for your carb but for mikuni. kehin uses around 50.
usually you can get the jets directly from honda dealer itself but they are more expensive. i do not live in america and i cannot help you very much on places to get jets but it seems sudco is a trusty source. also jd jetting kit seems to work very good from the reviews on the forum.

http://www.sudco.com/Carburetor01.html
http://www.jdjetting.com/xcart/home.php?cat=6


edit: is the power valve on the bike working?

Hmm I dont know how I can verify that the power valve is working, I do know I put it together correctly when I had the top end off. I cleaned it very well, and the power valve was very very smooth,.

I am not sure what kind of carb is on it, but I though it was a Mikuni. I can verify that soon, at my girlfriends house right now.
 

KX_OUTLAW

Member
Feb 7, 2010
19
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Why do you think it's too rich? Do you need the choke much on start up?
Usually a bog means it's lean.
I don't think 50 is big on a 125, I had to move up to a 48 in my 100 because of a bog exactly like you describe.

But nevermind all that, it sounds to me like something in the carb is dirty or clogged.
 

Patman

Pantless Wonder
LIFETIME SPONSOR
Dec 26, 1999
19,774
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I find that most of the time when a carb is cleaned it really isn't done properly. I've been guilty myself of missing a dirt clod in one of the passages and have found the best solution is a good soak followed by some compressed air through all the passages and jets.
 

Brandon H.

Member
Mar 26, 2009
199
0
KX_OUTLAW said:
Why do you think it's too rich? Do you need the choke much on start up?
Usually a bog means it's lean.
I don't think 50 is big on a 125, I had to move up to a 48 in my 100 because of a bog exactly like you describe.

But nevermind all that, it sounds to me like something in the carb is dirty or clogged.

I don't need the choke to start the bike at all. Whenever I ride the bike (when warm), if I pull the choke up, it runs even worse, almost unridable. Its weird too because if I put the choke on and start the bike (when cold) it idles pretty high. But it starts and runs perfect without the choke.

I am very good at cleaning carbs, its like a weird fetish of mine. I have jug of Chemtool parts dip that will melt anything. I soak the jets in that, and the carb gets a very very good cleaning with carb cleaner. Squirting passages in both normal and opposite directions to make sure they are clear, then using a can of "duster gas" for pc's to spray air through them, and make sure I am getting plenty of air out the other side. Plus I am very gentle with the carb, so I am sure I didn't bend the float...ect.
 

jsantapau

Member
Nov 10, 2008
340
0
I have been lucky in that most of the bike carbs I have touched ..that if there is a seam on the floats or even the tangs of the float arm are set parralel to the carb body you will be close,.....one thing to watch is that the seat needle is spring loaded and the the weight of the floats while holding it upside down will compress the spring throwing off the measurement. You have hold the floats up,slowly lower them down until the needle just stops in the seat while looking for your measurement..

a worn top end or reeds can also mimic a running rich problem especially at a lower rpm
 

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