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Tuning issues an older Reedy 121VS

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Tuning issues an older Reedy 121VS

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Old 04-06-2019, 07:23 AM
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Default Tuning issues an older Reedy 121VS

Having issues with getting this thing going got a new glow plug but it's an O.S. A5 which is a cold plug and have no idea why the LHS recommended it as this particular engine calls for a hot plug could this by my issue?

Here's the systems I have the carb at factory setting LSN and HSN all the way in then 3 turns out and idle set around .8mm:

-Draws fuel upon priming but spits fuel from carb

-When started will idle but eventually die and when I give it gas it will die or be sluggish then rev up and die

I am getting a hotter plug but could the factory setting be to rich?

Engine has descent compression, carb orings and needles look great and fuel tank seems to be sealing fine. Also exhaust coupler looks good as well.

This is on a RC8.2 buggy.

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Old 04-06-2019, 07:46 AM
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Have you looked at the manual:

https://www.google.com/url?sa=t&sour...lXBV5UmZD-PmrY
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Old 04-06-2019, 07:53 AM
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Low speed sounds too fat. With a cold plug, you must lean the mixture down a bit to advance the ignition and clean out the pooled fuel in the crankcase. If itís a long needle carb, you need to lean the low speed mixture so itíll idle and throttle reliably. A hotter plug will help some, but Iíd not run a hot plug. Rather a medium plug will give the best balance of power and fuel economy for many cases. Also make sure the idle gap isnít real wide.

Shouldnít this thread be moved to the engines forum?
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Old 04-12-2019, 07:05 AM
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I got it running just need to get it tuned in better LSN seems touching. At factory setting all the way in and 3 turns out on both LSN and HSN with about a .7mm idle gap the engine seems really rich but as I turn the LSN in one turn the after WOT the car won't come back down to idle so I am assuming it's way to lean. It draws fuel but hard to start still if I put a couple drop of fuel into the carb it starts right up then. Anyone know what that would be?

The engine also calls for a hot plug and I'm running a medium plug right now, so I am going to change plugs and re-tune. Any other input would be great.

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Old 04-12-2019, 12:08 PM
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I am about to give up on this thing and buy a new one. Just won't run I can get it to start and that's about it. Idles high and won't come back down and it won't sit and idle or wan I try WOT it dies as well. The only issue I see is that the front bearing is leaking very minimally.
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Old 04-12-2019, 01:23 PM
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LS-5 on amain is cheap as...like 159usd
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Old 04-12-2019, 06:45 PM
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Too lean most likely. Tuning must be done in SMALL increments. Like 1/16th turn each adjustment with a run at WOT a few times to then verify if that’s enough or not. Start rich and work lean a tiny bit at a time. If you go too lean down low, it can affect the top end and cause it to be too lean.

As you lean the low end, the rpm will rise as you get to the peak idle setting for that idle gap setting. Lower the idle gap slowly until the idle drops. Then keep working the idle mixture leaner and the idle gap lower until lowering the idle gap causes it to flat out quit. Then open it back up to the previous setting and then work the high speed - only at WOT. Run WOT and lean it down until you get no more gain in sound or speed. Then richen the high speed back up 1/8-3/16 turn. Re-verify the idle and transition with a 10-15 second idle. If it throttles up a little rich and burbly, you’re real close. If it flat out quits immediately, the bottom is too lean.
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Old 04-13-2019, 10:05 AM
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Originally Posted by SlowLST2 View Post
Too lean most likely. Tuning must be done in SMALL increments. Like 1/16th turn each adjustment with a run at WOT a few times to then verify if thatís enough or not. Start rich and work lean a tiny bit at a time. If you go too lean down low, it can affect the top end and cause it to be too lean.

As you lean the low end, the rpm will rise as you get to the peak idle setting for that idle gap setting. Lower the idle gap slowly until the idle drops. Then keep working the idle mixture leaner and the idle gap lower until lowering the idle gap causes it to flat out quit. Then open it back up to the previous setting and then work the high speed - only at WOT. Run WOT and lean it down until you get no more gain in sound or speed. Then richen the high speed back up 1/8-3/16 turn. Re-verify the idle and transition with a 10-15 second idle. If it throttles up a little rich and burbly, youíre real close. If it flat out quits immediately, the bottom is too lean.
Even at factory setting though I start it and it starts idling high and there's a lot of smoke and REALLY boggy when I give it gas, which it tells me it's rich. When I get warmed up and clean out after WOT idle stays way high. Could this be partially do to much idle gap yet? I have it around .8mm factory stays .5-.7mm which seems low to me.

Thanks for the advice!
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Old 04-13-2019, 11:27 AM
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Lowering the idle gap will lower the idle rpm. It will also change the idle mixture, so both must be balanced. 0.8mm is on the very big side to me. I always start at 0.5mm and go up from there as necessary. Every engine is different, so having a solid starting point and working from there is a good idea.
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Old 04-13-2019, 05:47 PM
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Start by reading the tuning bible thread. I think your LSN is way off from where it needs to be. I had the same issues you seem to be having with my old Hyper 8 port race. I was ready to just be done with it as I was never able to get it tuned right but I finally got it and it screams now! Its going to be a good practice motor because I have a protek LS-5 for race nights. First thing is to get it preheated with an engine warmer or a hair drier and start with the factory settings. I got the engine warmer off eBay from rcjuice and it works awesome. I think it was like $18.99 shipped. After the motor was preheated I started it and let it run for a minute with heater still on the head. I had to keep leaning the low speed until it had a consistent idle. After I revved it I listened to the idle. When it was rich it would idle high for a few seconds and then lower. If this is happening lean it and rev it again. Keep leaning until it stays consistent. You may need to lean the high speed a little as well if you feel you can't get it right. When it consistently idles high and doesn't drop lower your idle to where it is low enough the clutch doesn't engage. It takes time so don't give up.
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Old 04-17-2019, 12:44 PM
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Well I took the motor all apart and it still has good pinch as well. Put it back together and did a leak test covering the carb inlet and exhaust and had carb open to full throttle. used soapy water and I found a pretty substantial air leak coming out between the carb slide and carb housing. There's no way to fix this issue as there's no o-ring there, I find this a bit odd as the rest of the carb and o-rings look just fine. Unfortunately the carb isn't even available anymore.

Will other carbs work with this engine?

Thanks,
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Old 04-17-2019, 04:05 PM
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What seals the slide is the outer boot. Carb slides have a groove to allow air in and out of the seal (boot) so it doesn't form pressure or a vacuum inside the boot.
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Old 04-17-2019, 05:00 PM
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The boot is fine...... So i'm at a loss here!
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Old 04-17-2019, 05:08 PM
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They dont fit very tight, because they dont have to. Maybe youre blowing too hard during the leak test?
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