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High top caps / slides with low top carbs

Started by Economy Cycle John, May 20, 2021, 03:19:05 PM

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Economy Cycle John

Had a bike come in with RD350 high top caps and slides on low top carbs. Says it's not running well. Anyone have any experience running that set up? would it even work? I don't want to waste time trying to tune it and my plan is to just replace the caps/slides and cable with all lowtop stuff. Just wondering if anyone's running it or knows anything about it or is it just cobbled together mismatched parts. I don't recall seeing it before.
John
EC
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m in sc

the meat and potato parts are interchangeable functionally. both should be 2.5 slides. cables (obviously) are different. of course it needs low top slides and caps, or high top carbs and caps.

id check to make sure the needles are correct and slides aren't in backwards, the typical stuff. but yes you can change from high top to low top and vice versa. by swapping tops, cables, and slides. been there. done it.


soonerbillz

So humor me.
What is the difference between the 2?
Pics would be best as I'm more of a visual dude.

rodneya

this

Economy Cycle John

That's what I figured, she'll get a proper fix. He took a ride on my bone stock 400 came back smiling and said "make mine run like that!"







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m in sc

yup. ive done that as well.   :clap: frankencarbs

teazer

Hi tops were popular for a time and I always figured the reason was that OEM slides were longer, so in power restricted markets they fitted low tops to prevent full throttle and in other markets hi tops and long slides allow full throttle.

Long slides can be carefully shortened or replaced to work with low tops.

So hi top slides and hi tops should be the same as low tops with short slides functionally.  The rest is basic tuning.

m in sc

NAH. HAD TO DO WITH 'WATER INTRUSION.  or something. however i find it interesting the 400's went back to short tops. I think (in reality) it had more to do with the short top cables on 250/350s getting stuck in the cyl fins with the cable routing. .02

rodneya

Whatever it was, it makes buying a new throttle cable a bit of a pain n the ass. Most places to not specify which carbs they fit.

2t Fan

Indian Rajdoot Yamaha RD350 came with high top carbs. So these cables are cheap and easily available there

Economy Cycle John

so it had that going on and a 175P8 needle jet. Stock bike
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