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mikuni tm28 vs tm28ss

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i have a mikuni tm28ss from a suzuki rm80 i would like to fit on a 1974 bultaco aplina 250. bultaco.com gave me an initial starting point for a tm28

main 220

pilot 30

slide 2,5

needle 5dp39-4 [slot]

needle jet 175 p-8

air jet 1.2

the tm28ss seems to have a fixed air jet, the slide is a 4.0 and the needle jet is a 182 p-2, the needle, pilot and main match. sudco shows a 182 p-8 needle jet so i should be able to match that, but i am not sure the tm28 2.5 slide can replace the 4.0 slide on the tm28ss. can i use the tm28ss 4.0 slide and use a richer needle?

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here is what i have learned from sudco.

I am not exactly 100% on the exact difference between the 2 carbs as I am Mikuni Aftermarket and the TM28SS is an OEM carburetor.

I do know the 182 series is primary style needle jet and the 175 is a bleed style. Primary style needle jets run about 4 size richer than the bleed style.

The throttle valve major effect is right about 1/8 throttle if you are having a lean bog right around there then the 4.0 slide is an issue.

the tm28ss came with a 182 p-2 needle jet, so it should = the 175 p-8. any thoughts on the throttle valve cut, like can i go one needle jet richer to feed the leaner slide? the only 2.5 slide i have found is $85 and a new tm28 can be had for $115. also i will be adding a mzb cdi ignition rather than the standard points, condenser set up.

Edited by dr1445

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