Cafe Racer Forum banner

1 - 6 of 6 Posts

·
Registered
Joined
·
222 Posts
Discussion Starter #1
Gents:

A bit of a noob question, I know. I'm following some online suggestions for needle position on my RD400's carbs. They suggest moving the needle to position 4. Is that position four from the top or four from the bottom?

Right now, I have the needle on four from the top, meaning the needle if further away from the slide. Any help is appreciated.

--Thanks, Chris
 

·
Registered
Joined
·
2,740 Posts
I'm not sure what the online suggestions are trying to cure - but the further down the needle you move the clip, the fatter your going to make your low to mid range on the bike. The further up the needle you move the clip, the less gas will get to the cylinders at a low throttle position. Usually the mid position is the proper setting for the clip on most bikes.
 

·
Registered
Joined
·
222 Posts
Discussion Starter #3
Thanks for the response. Bear with me because I'm still learning 2-stroke tuning.

The bike is an RD400, and the suggestion is taken from the MotoCarrera website:

RD400; stock carbs, pods, DG expansion chamber pipes: 220-240 mains, 27.5 pilots, needle position in #4.

I'm currently running 220 mains, the 27.5 pilots. I counted down 4 positions from the TOP of the needle and reinstalled. I understand that this is a suggested starting point, but in bike tuning lingo, I'm curious if the "#4" position is from the top of the needle or the bottom.

--Thanks, Chris
 

·
Registered
Joined
·
2,740 Posts
In the carb tuning world - you must first get the proper main jets and then the remaining carb tuning process is determined from that point. 220-240 is a major main jet size range and is the difference between molten metal and gas pouring out of the exhaust ports.
If your not sure about what your doing, I strongly recommend you do a web search on carb tuning or better yet go to an online book store and educated yourself. Getting information off a web site may help - but don't take everything as reliable information. Those guys will not be around when your replacing pistons. Done right, carb tuning is not that difficult but you better know what your doing before you start.

Good luck
 

·
Registered
Joined
·
93 Posts
Chris,
You are correct. Position 4 would be forth from the top.


I'm running 210 mains, 27.5 pilots, with the needle in the 4th position on my rd right now and it's running great.

My set-up: 1975 rd350 w/ stock carbs, single K&N filter with y-boot, Toomey chambers, boysen reeds, high output coils.
 

·
Registered
Joined
·
5,778 Posts
On RD's, I always tend to jet safe, which is rich and then slowly lean it out from there. Plugs are way cheaper than pistons.

Ken
 
1 - 6 of 6 Posts
Top