RD350 carbs on LC

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evan_calgary
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RD350 carbs on LC

#1 Post by evan_calgary » Sat Jan 16, 2016 2:53 am

Can I use AC carbs on the LC? Heard its difficult to jet but has anyone sorted?

solo 2
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Re: RD350 carbs on LC

#2 Post by solo 2 » Sat Jan 16, 2016 11:27 am

They should work fine Evan, you may need to play with the main and needle but not much more. The big problem I've read about is using the Y-boot although I was going to give that a go and see for myself.

evan_calgary
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Re: RD350 carbs on LC

#3 Post by evan_calgary » Sat Jan 16, 2016 11:43 am

Ah, got it. I couldn't remember from our conversation what the problem was other than that there was one. I may just run individual pods. I have a big flat spot on my 200 motor just before the powerband and I am curious if this is partially due to the pods I was running. May have to find some Uni's without the big flat spot at the end of the like the current ones I have.

75RD350rider
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Re: RD350 carbs on LC

#4 Post by 75RD350rider » Sat Jan 16, 2016 12:14 pm

I have had bad experiences with flat backed K&Ns on piston port and to a lesser degree with reed valve motors. Uni foam pod filters and proper tuning should take care of that.
I love the smell of Blue Marble in the morning!
Tim Steele in Front Royal, VA

evan_calgary
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Re: RD350 carbs on LC

#5 Post by evan_calgary » Sat Jan 16, 2016 12:24 pm

Thanks Rider, I suspected it may be at least part of the issue but we did basically no tuning since the bike was finished just before racing. What is the best source for cheap unis?

Any idea where to start jetting these carbs? At 3000ft ish elevation.

Bare
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Re: RD350 carbs on LC

#6 Post by Bare » Fri Jan 22, 2016 12:03 am

IMO :-).. Lose the pod filters.. in whatever form you have.
Stock simple stoopid Airbox delivers the most power and throttle response on anything other than a purpose designed/developed Race engine.
But Hey! Free will.. says you can happily dick around incesantly... until you too realise what others before you have.

evan_calgary
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Re: RD350 carbs on LC

#7 Post by evan_calgary » Fri Jan 22, 2016 3:38 am

Not sure who sh*t it your cornflakes Bare but not really an option nor possible on the bike I was talking about...wasn't even the question either :)

Hooligan
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Re: RD350 carbs on LC

#8 Post by Hooligan » Sat Jan 23, 2016 1:39 am

Evan, a set of 6mm reed spacers can help to minimize or even eliminate that midrange stumble. They worked miracles on my LC.
'82 RD350LC in '81 colours, OEM pipes, UNI filters
'85 FZ750

evan_calgary
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Re: RD350 carbs on LC

#9 Post by evan_calgary » Sat Jan 23, 2016 3:12 am

Thanks Peter. I believe this helped on my 200 as well although it was the only way I could get LC reeds in the small barrels as well.

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OldTZracer
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Re: RD350 carbs on LC

#10 Post by OldTZracer » Sat Jan 23, 2016 3:57 am

The air cooler 28mm carbs work pretty good with minor jetting changes. You can also hone them out to 29.5 if you want to fiddle with more jetting. Check your oil pump adjustment is still in spec with the larger carbs.

I'm not a fan of pod filters either but use the biggest ones you can find.
Some Two strokes will create a "fog" of fuel behind the carbs that coats the pod & messes with jetting.
"...its a 2-stroke ya twit - Its supposed to smoke..."

hondaror
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Re: RD350 carbs on LC

#11 Post by hondaror » Sat Jan 23, 2016 1:39 pm

...also, only use K&N all others will fail.
Rory
2 1984 RZ350s
1985 RZ350
9 1986-1990 RZ350s
2000 ST2
2005 749
2005 749 with 999 engine

Hooligan
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Re: RD350 carbs on LC

#12 Post by Hooligan » Sat Jan 23, 2016 1:51 pm

hondaror wrote:...also, only use K&N all others will fail.
My Uni filters scoff at your girly K&Ns. ;)
'82 RD350LC in '81 colours, OEM pipes, UNI filters
'85 FZ750

hondaror
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Re: RD350 carbs on LC

#13 Post by hondaror » Sat Jan 23, 2016 2:42 pm

Lol. Everyone seems to like them Peter. I was referring to pods.
Rory
2 1984 RZ350s
1985 RZ350
9 1986-1990 RZ350s
2000 ST2
2005 749
2005 749 with 999 engine

evan_calgary
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Re: RD350 carbs on LC

#14 Post by evan_calgary » Sun Jan 24, 2016 4:30 am

so....jetting? Ideas?

Thanks for the thoughts on oil pump, don't want to mess up the fresh motor.

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OldTZracer
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Re: RD350 carbs on LC

#15 Post by OldTZracer » Sun Jan 24, 2016 3:47 pm

Sorry Evan - I looked but couldn't find my old notes...

Which AC carbs? Some aftermarket carbs come jetted for 4-strokes & will be way wrong. Early RD350s were jetted leaner than later bikes partly due to a more restrictive airbox design, so check the needle jet size can flow more than enough fuel to accommodate the range of main jets you are working with.

If your 26mm carbs are jetted close, I'd use them as a baseline, go up about 4 on the mains & carefully work your way back down. With the pods, you might even end up leaner. As I recall there isn't a big difference jetting-wise between the 26 & 28s - but jets & plugs are cheaper than pistons...
"...its a 2-stroke ya twit - Its supposed to smoke..."

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