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URGENT KDX200 carb issue

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Post Fri Jul 01, 2016 9:37 am

Posts: 581
Trying to get buddies 84 KDX200 sorted out for Saturday's vintage race. Bottom end was filled with gas. Discovered petcock was leaking, fixed that. While we were at it, replaced the float valve assembly. With bike not running, and petcock on, gas is pouring out of carb overflow hose. Was late did not have time to pull carb again. The only thing I can think of is float height issue? But being a new float valve assembly, wouldnt it still shut off fuel flow even with a high fuel level? Only have a short window sat morn to fix before race, so looking for opinions. Mikuni VM32 with the black plastic independent floats.
"It just needs a carb cleaning"

Post Fri Jul 01, 2016 10:14 am

Posts: 937
Definitely double check float height. Every needle valve is going to be ever so slightly different and you might be right on the edge of spec. Also verify the floats actually float and that they move freely on the rods and the float arm moves freely. Also verify if the float arm is installed correctly or upside down.

Good luck and hope to see you tomorrow!
Tom A.
SRCR President
Vintage Series Racer
1974 MT250, 1977 MX3, 1977 RM/TS 175, 1980 CR250R, 1981 YZ465, 87/88 RM125,

Post Mon Jul 11, 2016 12:47 pm

Posts: 581
So I adjusted the floats and that stopped the carb overflow problem. Buddy ran it at Flatrock, ran fine, but we checked the pipe after the race and it was again filled with gas. So there is still an issue. Before I try to source a replacement carb, what would you check? Running stock slide, jets and needle. new float valve and seat. Move the needle down? More float so is shuts off fuel quicker?
"It just needs a carb cleaning"

Post Mon Jul 11, 2016 4:33 pm

Posts: 937
Did you adjust it to spec? How is the color of the plug?
Tom A.
SRCR President
Vintage Series Racer
1974 MT250, 1977 MX3, 1977 RM/TS 175, 1980 CR250R, 1981 YZ465, 87/88 RM125,

Post Tue Jul 12, 2016 10:16 am

Posts: 581
Went in again and adjusted it some more. This carb has those independent floats and the first time I tied to measure by estimating off the bottom of float, but Im thinking in those carbs you measure from the carb body to the point on the float arm where the float pins would touch the arm. So I set the arm at 23mm this time. As usual it was too late to fire her up...we shall see. Im not completely confident in this measure because I had to bend the tang so far (usually those tangs only need to be bent a bit).

If it is not floats could it be a leaky choke? Plug did not look too wet, but did not do a true plug chop test. Willing to buy a new replacement carb but they are not available until end of August.
"It just needs a carb cleaning"

Post Tue Jul 12, 2016 11:45 am

Posts: 937
The measurement should be form the float arm to the carb body at the surface the bowl seals against. Don't measure the compressed needle either, the tab should be touching the needle lightly.

You can check the choke seal by blowing air through the feed tube as long as you plug the inlet to the choke circuit at inlet to the carb body near the airbox boot. I found my choke hold down tab was put on incorrectly and allowed my choke to randomly richen at any time. :(
Tom A.
SRCR President
Vintage Series Racer
1974 MT250, 1977 MX3, 1977 RM/TS 175, 1980 CR250R, 1981 YZ465, 87/88 RM125,


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