'74 RD350. Yeah... I know....

I just looked at my Seca service manual and found this...I guess I called and talked to John...:umm:

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Jim - do your VM28's have one choke, a choke tube and are the NJ's primary or bleed type? Also, are the carb tops regular or "high top"? I'm getting a suspicion that there were different VM28's around (don't know what's OEM and what's aftermarket genuine Mikuni)
Um... yeah. This is turning into quiet the mystery. This pallet of bits came with 2 complete (subjectively... :rolleyes: ) carbs and one oddball body painted black. Since there were 2 R5 motors on the pallet and no RD's, I just assumed the complete ones were R5's. Now I'm not so sure...
Anybody care to take a guess as to what's what? :umm:

Btw.... all 3 are VM28's



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Can't tell from pic. Does the black one have the choke plunger blocked and have a fitting for a choke tube? Maybe pics of the top for it?

IIRC there were OEM VM28's they referred to as "small body"
 
Can't tell from pic. Does the black one have the choke plunger blocked and have a fitting for a choke tube? Maybe pics of the top for it?

IIRC there were OEM VM28's they referred to as "small body"
Choke tower is undrilled and has the crossover barb.... makes it the right carb. Here's both right's... side by side.



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Jpdevol is right track some models had black carbs, some had high tops. I am not sure what went with what. I can post photos of the RD carbs if that is helpful.
 
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After Cerakote back to black - have high tops - choke tube fitting at right of left carb
View attachment 230907

So... assuming yours are RD carbs...
My "set" don't have the shoulder around the choke tower and don't have the little angle casting underneath the choke crossover barb. I'd say that indicates mine are R5's. Thoughts?

My single black body does have both of the above... so it's an RD carb... :umm:



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I'd venture a guess that the black carb is (was) an OEM "small body" VM28 and the polished one's an OEM "regular" spigot-mount. The issue then becomes the NJ; do the regular take a Series 175? I've tried 175's in my "small body" and they fit, but don't run worth shit below half throttle - the small body need Series 169. Maybe you need a bleed type 175 in those (maybe regular) polished VM28's:shrug:
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I'd venture a guess that the black carb is (was) an OEM "small body" VM28 and the polished one's an OEM "regular" spigot-mount. The issue then becomes the NJ; do the regular take a Series 175? I've tried 175's in my "small body" and they fit, but don't run worth shit below half throttle - the small body need Series 169. Maybe you need a bleed type 175 in those (maybe regular) polished VM28's:shrug:
View attachment 230914

Now we're gettin' somewhere. :geek:



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Like I said before, stock RD needle jets are the bleed type, with small holes on the side. And the main jet should be #140, or #105 if it came with a baffled air filter. Maybe only 75 had those.
Those mangled NJs indicate R5 carbs, or RD carbs with Dale A mod.
But the real identifyer is the Autolube nipple on the black carb. Only the RD har those. The R5 had a oil injection fitting on the cylinder IIRC.
 
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Bitsa Hi-jack: So, just as there were differences in US/Non-US XS carbs, there were apparently differences in DS/RS/RD carbs. If ya go to CMSNL and look-up NJ you get a bleed type (maybe 175), if ya go to Partzilla, you get a primary type. 🤯

Anyway, Series 169 it is......

FWIW, jetting for mods appears to stay consistent between NJ types (all jet sizes).
 
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