Float adjustment = leaking fuel....?

mike-evans

Member
Sep 16, 2009
142
0
Thought I would do a bit of maintenance and check float level as per manual. Manual says 5.5-7.5mm, mine was reading 4.2mm, I adjusted it and got 6.1mm, put back together, and now leaks fuel out of overflow pipes? Floats were moving freely when I check before re-fitting bowl...any ideas what it could be? When I was adjusting the float tab to correct the float height, the tab seemed to be quite high and didnt look right, the tab was resting on the needle valve and not compressing it, as the manual says it should.....
 

scottiedawg66

Member
Sep 26, 2006
75
0
floats can be a pain. my experience on my kx65 was that I had to bend up the tab to keep the float from allowing fuel in too early so my bike would not leak when on the side stand. If you pull the bowl off you will see the straw that the overflow fuel flows out of....make sure your fuel level does not go above that level by adjusting the float
 

Matt90GT

Member
May 3, 2002
1,517
1
dont go by measuring it. Do it by sight. YOu want the tab to contact the needle point when the floats are level to the bottom of the carb. That should give you at the most 3/4 of the bowl full.

Doing it by measuring is never going to be a great way to do it.
 

laramik

Member
May 20, 2010
12
0
I have this exact same problem on a 1984 RM80. I will try your suggestion and see if that works. Would this also be causes me problems with idleing?? Bike starts well but does not like to idle. It has a brand new piston in it and when its running its fine. It just kinda seems like it starves for fuel after whats in the bowl burns off??
 

laramik

Member
May 20, 2010
12
0
Matt90GT said:
your idle problem is more than likely due to a plugged pilot jet. still be sure to inspect the needle/seat and float height.


I thought it might be the pilot jet!! Problem is, the jackass who put it in must have used an impact wrench to screw it in. Ill retry pulling it out again. Anyone know what clip my needle should be at?
 

whenfoxforks-ruled

Old MX Racer
~SPONSOR~
Oct 19, 2006
8,129
2
Merrillville,Indiana
Leaky carb after putting it back together, rap the bowl with the handle of a screw driver. The float valve hangs up sometimes. Unmaintained carbs get some really destructive corrosion between the different metals, and moisture does not help. The gallon cans of carb cleaner will get the scum off, do not leave it too long though. It will pickle/dis-color the aluminum. Jet from the pilot, and if you can not get the air screw to adjust with in range, after 3 pilot jet sizes, it is likely a problem some where else. The float valve itself is a likely culprit for rich jetting. They do not always leak on the ground, sometimes it fills the crank cases! Vintage Bob
 

laramik

Member
May 20, 2010
12
0
Well my float definately needed adjusting. In order to push the float pin in my bowl would have needed to be more than full. Pilot jet aint comin' out for sure though. And the brass pieces inside the carb all are covered in in a white like corrosion. Can I just replace the carb with another mikuni 26mm carb? Like the ones for pit bikes? I've seen them for like 30 bucks on the bay but don't wanna spend 150 getting one from the dealer.
 

mike-evans

Member
Sep 16, 2009
142
0
I removed the card, and carb bowl and re-adjusted the floats. I tilted the carb slightly, and adjusted the tab on the floats until the floats were parallel with the bowl mating surface, which gave me about 5.6mm, i could see the needle valve just seating in its position, so floats must now be in correct position? Re-fitted it all, and no fuel leaking. Stil a pig to start, think it might be down to my/wrong technique, as i got a spark and got fuel (wet plug), topend has approx 6 hours on it, noticed 1 of the reeds was slightly lifted on one edge, i turned the reeds over, and are now flat, not sure if you can do that though? Jetting is standard to the manual, so rich from factory, so might drop pilot down 1......
 

laramik

Member
May 20, 2010
12
0
mike-evans said:
I removed the card, and carb bowl and re-adjusted the floats. I tilted the carb slightly, and adjusted the tab on the floats until the floats were parallel with the bowl mating surface, which gave me about 5.6mm, i could see the needle valve just seating in its position, so floats must now be in correct position? Re-fitted it all, and no fuel leaking. Stil a pig to start, think it might be down to my/wrong technique, as i got a spark and got fuel (wet plug), topend has approx 6 hours on it, noticed 1 of the reeds was slightly lifted on one edge, i turned the reeds over, and are now flat, not sure if you can do that though? Jetting is standard to the manual, so rich from factory, so might drop pilot down 1......

I'm feeling you on the pig to start thing too. What's your compression when cold? I just got this bike and someone had just put in a new piston but skipped out on spending the extra 13 bucks for a gasket set and figured rtv silicone woulkd work just as well. Lemmie tell you, it didn't. So after cleaning all of it out of my cylinder head and original gasket I noticed that there was some serious gapping between the top of the cylinder and the head like someone must have used a screwdriver to seperate them. The new gasket on mine is not really filling that gap so filled it just on the outer lip with high taemp caulk but that only is over about 1cm of the actual outer surface. Its holds compression once ran for a minute at like 95 but once cold its at like 65. I basically got this thing for free because I got it along with a 97cr125r for 450. The cr needs a piston which is on order but after that I shouldn't have a problem dumping for at least a grand, but if I'm just on a losing battle with this thing ill just sell it for parts or to someone local for 200 bucks and use that towards a little 4 stroker for the kids.
 

whenfoxforks-ruled

Old MX Racer
~SPONSOR~
Oct 19, 2006
8,129
2
Merrillville,Indiana
Did I mention the float valve is SUPPOSED to be replaced every year? I know, they are expensive, and do I know! And they are NOT a visual inspection part, a strong magnifier or microscope, or, just replace the stupid thing! A chinese carb would be better than no carb, but, getting jets and needles, and they are junk. A new or used mikuni the correct size is the ticket. Use a bike similar in motor and application sizes jetting specs for a baseline. Lean for a minute will not likely kill the motor, and too rich will just eat plugs. And the float valve specs, the tang on the float is just touching, not depressing the valve? Honda is the only oem that generally does not use mikunis', but they are usually easier to jet. The carbs with a drain on the bowl are priceless. Hook up a clear hose and hold it up, you can see the level inside the carb, better than xray vision. Vintage Bob
 

mike-evans

Member
Sep 16, 2009
142
0
laramik said:
I'm feeling you on the pig to start thing too. What's your compression when cold? I just got this bike and someone had just put in a new piston but skipped out on spending the extra 13 bucks for a gasket set and figured rtv silicone woulkd work just as well. Lemmie tell you, it didn't. So after cleaning all of it out of my cylinder head and original gasket I noticed that there was some serious gapping between the top of the cylinder and the head like someone must have used a screwdriver to seperate them. The new gasket on mine is not really filling that gap so filled it just on the outer lip with high taemp caulk but that only is over about 1cm of the actual outer surface. Its holds compression once ran for a minute at like 95 but once cold its at like 65. I basically got this thing for free because I got it along with a 97cr125r for 450. The cr needs a piston which is on order but after that I shouldn't have a problem dumping for at least a grand, but if I'm just on a losing battle with this thing ill just sell it for parts or to someone local for 200 bucks and use that towards a little 4 stroker for the kids.
I am not sure of a compression, as I havnt put a gauge on there yet, but to kick it over, there is ALOT.....which makes me think it could be my technique? "whenfoxforks-ruled" yes the tang is resting on the plunger ontop of the needle valve without compressing it. I know that the needle valve is there to close off fuel flow in relation to the floats, but what is the plunger ontop of the needle valve for?
 

whenfoxforks-ruled

Old MX Racer
~SPONSOR~
Oct 19, 2006
8,129
2
Merrillville,Indiana
My best guess would be its pressure related. I have seen a lot of them that was solid, maybe old school? At 35 to 45 dollars is what they are! Yet, they both get set the same way. And I have read horror stories about non oem valves not working correctly. And change the seat when applicable. Jetting is easy, weeding through all the other variables is what makes it interesting/not easy. I did recently quit poking wires into pilot jets to get rid of gunk build ups, the last thing I want to do is scratch the orifice! Now I use a nylon brush bristle. Till the day comes to work on a 50 again, man the pilot jet is small! Vintage Bob
 

laramik

Member
May 20, 2010
12
0
Well good news, the RM idles just fine and runs like a mean little monster. Still is a son of a gun to start as my float seems to just want to let it flood regardless of what i do so I just shut it off at the petcock every time Im done with it. Now I'm on to bigger things. The piston came on my CR125 and I installed yesterday. Now its time to get it started. Boy, if there were a contest for how many bolts were missing on a bike, this thing would win.
 
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