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Post by timbomx5 on Jul 11, 2022 16:10:43 GMT 1
Hi guys,
Just joined forum seeking help! I have an Rd350lc 4lo 1981 with mikuni 31k 00 carbs fitted which I believe are ypvs carbs . Im having problems with correct jetting and set up to make these carbs work.
Needles currently lowest setting, main jet 210. It starts well and has good mid range and top end, however terrible pulling away bogging down badly to the point of almost stalling.If I raise the needles its fluffy mid range?
Anyone know correct sizes for idle jets, main jets and needle size. Been advised by local mechanic that possible wear on needles and emulsion tubes if anyone knows where to purchase? Any help would be great !! Cheers
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Post by midlifecrisisrd on Jul 11, 2022 18:19:47 GMT 1
You need to go up one size on the pilot jet
Steve
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Post by jon on Jul 11, 2022 18:28:42 GMT 1
I went up 2 sizes to 27.5 on my 31k carbs on an LC 350. 230 mains as well from memory. Standard apart from Allspeeds (which I don’t think need jetting changing?).
Jon
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Post by reedpete on Jul 11, 2022 19:42:44 GMT 1
Hi guys, Just joined forum seeking help! I have an Rd350lc 4lo 1981 with mikuni 31k 00 carbs fitted which I believe are ypvs carbs . Im having problems with correct jetting and set up to make these carbs work. Needles currently lowest setting, main jet 210. It starts well and has good mid range and top end, however terrible pulling away bogging down badly to the point of almost stalling.If I raise the needles its fluffy mid range? Anyone know correct sizes for idle jets, main jets and needle size. Been advised by local mechanic that possible wear on needles and emulsion tubes if anyone knows where to purchase? Any help would be great !! Cheers Make sure the pilot jet bleed hole is clear… no amount of trying different size jets will change things if that’s blocked , and pulling away would be exactly as you describe. |
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Post by timbomx5 on Jul 11, 2022 20:05:57 GMT 1
Thanks for advice guys, I'll let you know how I get on.
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Post by stusco on Jul 11, 2022 21:39:26 GMT 1
27.5 pilots on my 31k
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Post by chrisg on Jul 12, 2022 13:04:12 GMT 1
I went up 2 sizes to 27.5 on my 31k carbs on an LC 350. 230 mains as well from memory. Standard apart from Allspeeds (which I don’t think need jetting changing?). Jon Was that on the later 4L0 01 cylinders? |
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Post by jon on Jul 12, 2022 13:29:28 GMT 1
No mine has early cylinders, but I really don’t think jetting would change between the 2. Sure the main jet on early and late carbs is different but so are the carb bodies.
Jon
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Post by 4l04ever on Jul 12, 2022 18:27:29 GMT 1
I have 31W carbs on my 4L0, which are the same as the 31K ones. Running 25 pilots, 290 mains, clips raised one from middle slot to lean off slightly.
Modified airbox with TSA exhausts.
Are you running a standard air filter housing with the inlet trumpet fitted and the filter fitted? Which exhausts?
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Post by 4l04ever on Jul 12, 2022 18:29:32 GMT 1
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Post by timbomx5 on Jul 12, 2022 19:56:59 GMT 1
Yes standard airbox and exhausts.
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Post by 4l04ever on Jul 12, 2022 20:00:25 GMT 1
What airscrew setting?
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Post by jon on Jul 12, 2022 20:03:07 GMT 1
I had this same symptom once. The jetting was fine, it was just they needed balancing better.
I guess one cylinder wanted to pick up and the other was at that throttle opening not responding.
Jon
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Post by timbomx5 on Jul 16, 2022 17:16:14 GMT 1
Looks like it's wear on emulsion tubes and possibly needles. Anyone know where I can source genuine Yamaha parts as Im struggling to find?
Then I can change jetting to correct sizes.
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Post by midlifecrisisrd on Jul 16, 2022 17:55:03 GMT 1
Muttsnuts, Norbo or Allen's Performance
Steve
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