I could post pictures and video's as per your above request as I have few cabinets full of trophies but I dont really think that is required to prove any credibility as most that own and tune a clockwork racing engines modified motor know that the proof is in the pudding, huge smiles all round, I have assisted many racers through out Australian events that have had tuning issues weather they have been stock motors, modified motors, CRE motors and even HES motors.

I myself ran novarossi carbies on my werks engines as I felt that it was easier to tune a nice clean crisp bottom end with a single stage idle, the werks carby is just a little more sensitive and the nova carby opened the perfect window a little making it easier on race days where the weather changed a fair bit from the the last tuning point.

Lots of editing going on in this thread too, maybe time to get back to topic on this thread

I have learned a lot from this thread and have had a lot of success tuning my 121VR engine. My focus is racing so I am now tuning to get the best balance of performance vs. fuel economy. What facts effect fuel economy?

I have installed a 7.0mm venturi and am able to run consistantly about 9:30 minutes. I plan to try a 6.5mm venturi but would also like to consider another pipe. I am using the Reedy 2035 pipe which is supposed to be a good balanced pipe. I selected this pipe since I am running a Reedy engine and the cost was decent to get started. Now I want to understand what other pipes can do for the performance vs. Fuel economy trade-off.

How do you choose a pipe?

Pipes can be hard bro

There is much advice to be had in the forums about pipes but there will definitely be some deep searching involved and alot of reading

Supposedly reedy engines are similar to old os vspec so find what pipes people are choosing for the arrow which i know is identical to old vspec

My guess is 2090 pipe

Ok I have been trying to tune my idle using the methods in this forum. I broke in my engine. Got it tuned pretty good. Runs good it idles. it will idle about 15 to 20 seconds befor dropping to a lower idle. But the idle seems very unstable. It never consistent I can make a lap come in may drop sooner or take longer. Some times it will idle back up some times it won't. I sealed up the engine. With rtv, carb back plate pinch bolts. The engine I am trying to tuneis a dynamite .21 platinum xp. I also have a Orion jtb addition that is acting similar to this one. My sons losi 350 was a snap got it diled in the first round. any ideas? 20% nitro also on all engines

I've found the most common mistake is too big idle gap and compensating with a rich lsn, with a big idle gap you will be chasing a tune all day and cause a two stage idle, if your idle gap looks about right and you think your tune is close more than likely could be a possible air leak if the two stage is still there.
I still learning myself but couldn't count how may times the rich bottom, lean top, too big idle gap has caught me out, best to set idle gap reset needles and start again with the tune.

What should the idle gap be set at with the restricter installed .07? Or should it be set with it out?

With my fusion motors I set the idle gap to about 0.6mm checking it with the restrictor out.
Someone with experience with your dynamite motor could give you a more accurate answer as what your idle gap should be, from what I know most engines 0.6mm is a good starting point.

... or too little nitro percent in the fuel. Some engines just can't run on 20%. Try 25% if it isn't a tuning issue.

so everything i have found on tuning so far is for tuning two needle carbs, anyone know where i can get a guide on tuning a three needle carb? or maybe just some tips you can give me?

Your "crossover" screw should be "flush" to 1-turn in (clockwise).

The top end/Main should be: 4.5 turns out from fully "closed"

The low end/idle should start (and be rich) at 1-turn in from flush (if the engine is broken in). You may end up going down *up to* almost 1.5-2 turns in on the bottom (from flush). If the engine is new/not broken end start with the bottom needle flush.

Idle air gap should be .6mm to start with.

dont touch the needle seat adjust (third needle or "mid" needle)

cool thanks guys, i will give this a shot come summer, started snowing today so now its time to put em up for a couple months.

what a great post. it reminds me of how i learned to drive a stick shift. my dad explained while drawing diagrams on paper of how it mechanically works. by understanding what is physically happening it makes the learning process much easier and faster. the way the author describes exactly how the carb works in detail has been by far the most helpful guide to proper tuning that i have ever read. i wish i found this post a year ago when i got my first nitro! It still runs strong but i'm sure it could be better. big thanks to ron paris and houston!

Ive written many posts regarding the subject of a faux idle. As another member posted, too much idle gap with a rich lsn compensating.

the indicators for a faux idle are a overunning idle after wide open throttle. and a dropping idle at rest.

the key is to understand that the IDLE screw and LSN must be tuned in unison. increasing the idle gap will richen the mixture as well. when you increase the gap, in effect the lsn is opening as well, the needle moves out from the seat.

best practice I find is to ensure all leaks, hoses and gaskets are good. then use a spring or rubber band between the hsn and carbt to hold the idle back to prevent chattering idle gap.

then richen the top needle 1 or two turns, it doesnt matter how many turns, the objective is to allow maximum fuel pressure.

then I set the idle gap at 1mm as a starting point and when I do, I ensure my bottom needle lsn is not pushing hard against the seat and ensure it's not too lean. I open the lsn to begin with.

Without using the throttle, its a matter of attempting a start, removing the plug and seeing if the mixture is too rich (spray of fuel versus mist) clear the crank and keep repeating the process of clearing the crank, attempting a start until the engine fires first time. If the engine iss too rich I lean the LSN incrementally. If too lean I richen it.

from there I know my bottom mixture is somewhere in the ballpark. I then give it 1/8th throttle to see if I am in a state of faux idle. the engine usually over runs if I am too rich with too much idle gap. So I then reduce the idle, this by default leans the low speed mixture. if I stall, I lean the bottom.

All the time flushing the crank by removing the glow plug to be sure.
So I begin to lean the lsn until I reach a happy idle. In race tuned I wont get a continuous idle either, it will be slightly rich.

Once Ive setup my LSN with a very rich HSN, I roughly tune the HSN on the rich side and put the car on track and complete the tuning under load and once engine is up to temps.

hope this helps.

low speed tuning