New RS38's, what main jet to start?

[Guest]

What size of main jet should I start with for my RS38's? I put in 140's, they had 152.5's when I got them, I dont know what kind of bike they were used on.

[7981GS]

In your 1300+ cc engine?
Mikuni jet size of 145-155 would be a good starting point I would think.
Hopped-up 1100's (1168's, etc.) typically use 142.5's and up.

Eric







Of course, after no one else answered your question and I did, now the rest of the crew will correct me.

[bellucci]

I have a 1327...track 160, street with baffle is 155...

[gearhead13]

I have a 1327...track 160, street with baffle is 155...

Ok, I guess I am putting the 152's back in.
What size pilot jets do you run?

[gearhead13]

Installed the carbs today, runs ok for not being synced yet, one float leaked and the A/P wasnt working so I have the bowls soaking in carb cleaner. Some blockage in the A/P bowl passages. Hopefully get them reinstalled and synced tomorrow.

[chef1366]

Installed the carbs today, runs ok for not being synced yet, one float leaked and the A/P wasnt working so I have the bowls soaking in carb cleaner. Some blockage in the A/P bowl passages. Hopefully get them reinstalled and synced tomorrow.

Your bike is going to be a madman

[gearhead13]

Your bike is going to be a madman

Me, or the bike? LOL
Some yoyo PO mixed up the #2 and #3 bowls. The #2 has the passages for the A/P.

[chef1366]

Me, or the bike? LOL
Some yoyo PO mixed up the #2 and #3 bowls. The #2 has the passages for the A/P.

You have to be one to ride it.

[gearhead13]

Got it together tonight and went for a ride, carbs are so out of sync, sounds like its cammed to the moon
Lots of jump, seeing about 12-13 A/F at cruise but 14-15 when I give it throttle so tomorrow I'm going to raise the needles 2 notches and sync it.
I didn't want to wind it out because of the lean a/f.
And YAY, looks like all my oil leaks are fixed, although I won't know for sure until tomorrow.

[gearhead13]

Started with 150's went to 140's and now 135's and it still splutters under full throttle. a/p almost completely disabled. Seeing below 10 a/f under full throttle. I set the floats to 17mm, maybe a touch under 17. I guess I will try some 130's

[chef1366]

Started with 150's went to 140's and now 135's and it still splutters under full throttle. a/p almost completely disabled. Seeing below 10 a/f under full throttle. I set the floats to 17mm, maybe a touch under 17. I guess I will try some 130's

Could the pump be too rich?

[gearhead13]

Could the pump be too rich?

The pump is disabled
I put the 130's in it tonight and I am going for a ride tomorrow. They better work, cause those are the smallest mains I have I might take them apart and recheck my float level, set it at 18 mm maybe.

[Spot1000Kat]

Silly question , but do you have a dual outlet fuel tap?

My 1166 was starving at full throttle on my kat, so I tapped and threaded in a 3/16" hose tail opposite the existing one which is easy on the katana taps and whallah!, a dual flow tap , no more fuel starving, and fixed the lean breakdown at full throttle. If you look at the front of the tap opposite the existing outlet you'll see a perfect location which lines up on prime and shuts off when the tap is off. I'll post some pics hopefully this weekend if I get a chance.

Or fit a Pingel dual flow tap.

[gearhead13]

Silly question , but do you have a dual outlet fuel tap?

My 1166 was starving at full throttle on my kat, so I tapped and threaded in a 3/16" hose tail opposite the existing one which is easy on the katana taps and whallah!, a dual flow tap , no more fuel starving, and fixed the lean breakdown at full throttle. If you look at the front of the tap opposite the existing outlet you'll see a perfect location which lines up on prime and shuts off when the tap is off. I'll post some pics hopefully this weekend if I get a chance.

Or fit a Pingel dual flow tap.

Well, that could be. I am at a loss as to whats going on. I just have a T fitting on the stock petcock. When I turn it on prime all the fuel goes into one inlet, the T has to be exactly level for it to flow evenly. Maybe if I put the T up close to the petcock instead of down near the carbs. So, I would imagine that cylinders 3&4 would run out of fuel first. But doesnt explain the under 10-1 a/f ratio I am seeing. And it not like it runs wide open ok for a bit then stumbles, as soon as I open it up it, it splutters.

[Billy Ricks]

130 or 135 mains is what Mikuni calls for. They call for 140s in a full race prepped bike.