Mikuni jetting help needed

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monument7
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Main scooter: Li auto conversion 180
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Hi,
I bought a good condition Mikuni TM28 carb off a lammy that apparently was running but can't get it to run properly with my set up and jetting information i've found on the net is confusing to say the least.
Here's what I have.
Li 125 with a 185 kit, GP crank, JL3 exhaust, 12v electronic conversion, fast flow rear exit tap that is working fine,timing set at 19 degrees. The main jet when I got it was 190, tick over was perfect but it was bogging down badly after 1/4 throttle. Changed the main jet gradually down to the smallest i currently have which is now 110 while is is marginally better it still wont rev up without bogging ( tickover still perfect ). Moving the needle up or down makes no difference Changed the coil for a known working one and still the same. Plug is brand new as are the lead and cap.
I was going to go even smaller on the main jet but looking on the Mikuni sites most carbs seem to be set at or way above the 190 it had in originally.
peter357bikes
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what pilot is in it? mine (TMX30) on a 185 imola came with a 40 which drowned it ..got down to a 27.5 which allows you to set the main better...as for less than 190...? look on the carb setups on this site..excellent to show how off the mark you can be...see corrados set up with a TM27
vespanic
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Being hopeless at carb set up have you thought about the needle size as it may not be the jets. Check yours against other peoples set ups.
monument7
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Thanks for the input,
The main problem I have in doing it myself is ( apart from not having a scooby doo :cry: ) not having a selection of needles and jets to play with as per set up charts etc. Going in the right direction at the start saves time and money but might have to bite the bullet and go back to the 190 main jet then mess with the pilots.
A donor bank of carb jets and needles would be a solution where you could "borrow " bits to try for the cost of what you use plus postage or just give it to someone who knows what they're doing :roll:
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corrado
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The TM is a flat slide and the TMX are D slides so it may not have much relevance what's fitted to a TMX. Most TM24 carbs [flat slide] on 186 Mugellos were running between 175 and 200 main jets. Needle is critical but finding any info on different ones is near impossible.

Here's a couple of vastly different set ups from Lloydies site.

Lambretta 200 stage 4 (Indian) with Mikuni TM28mm JL KRP-4 race exhaust
main = 170
needle = 5EJ11
needle jet = 169-N6 (trimmed to 2.8mm)
slide cutaway = 2.5
pilot jet = 30

Imola 185 with Mikuni 28mm flatslide & ScootRS exhaust
main = 300-340
pilot = 25 - 30

Though the second one doesn't look like it's much help.
monument7
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Joined: Fri Dec 28, 2012 6:38 pm
Main scooter: Li auto conversion 180
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Cheers Corrado,
Now the first one looks interesting as the main jet is nearer to what was originally in my TM so think it may be the way to go to put it back in and work around the pilot to see if that makes any sort of difference as the main jets didn't seem to be doing anything.
Like I said previously there are some vast differences in jets on similar engine set ups its worse than hopeless to try to guess.
monument7
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Joined: Fri Dec 28, 2012 6:38 pm
Main scooter: Li auto conversion 180
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Just took the pilot out and it's either a 51 with a square within a square or vice versa and it's 15. If it's 51 then looks massive oversize compared to Peter357
peter357bikes
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Either way 15 or 51...would seem too small or too big..20 to 35 seems the norm..............the more tune or cc the larger pilot to an extent
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