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58-CD idling around 4000

Old 04-23-2009, 07:20 PM
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Default 58-CD idling around 4000

Good evening,

I'm looking for some advice on my 58-CD that I'm not able to achieve an idle less than around 4000 rpm. In reviewing other posts I see it's not an uncommon problem. Few of the other posts seem to include the solution, other than a suggestion of more break-in time.

S/N 2556
Byron 4-Cycle 10% Fuel w/16% Castor/Synth blend
11x6 APC

I went through normal break-in last summer per instructions. After around 4 tanks of fuel the engine was running very strong and smooth with no sag at acceleration. It seemed to be ready to take to the air, so up it went. And over the next few tanks of fuel it ran like a top. But I still wasn't able to get a reliable idle less than around 3800.

In my last session of the season I accidentally ran the low speed needle valve in so far that it disengaged from the threads. I didn't realize it at the time. I just knew the engine wouldn't start. But I was personally done for the year, so decided to leave it until this spring.

So this spring I discover what I'd done, fixed it, and the engine is running fine again except the 4000 rpm idle.

At this point the engine has run through just over half a gallon of fuel.


Old 04-24-2009, 03:49 AM
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Default RE: 58-CD idling around 4000

The 2 58CD's I have are quite happy to idle around 1800 rpm.
It does sound as though the idle mixture is way out.

I find this method is great for setting a starting point for idle mixtures.
Close the throttle till you can Just slide a pin in the gap.
Connect up some tubing to the carb and blow through it, adjusting the idle mixture till there is a faint bleed of air.
Reconnect fuel, start engine, adjust top end then bring to idle.
Adjust idle while engine is running the same way as you would the top end, ie: adjust to max rpm and then richen slightly.
Works for me on any brand of engine.
Old 04-27-2009, 05:14 AM
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Default RE: 58-CD idling around 4000


Think the previous contributors advice is v good, thats certainly one method of doing it. Essential you get the throttle close to closed, so the pin method is a good one. And you can hold the engine up to your ear to hear when the flow starts. Would probably recommend that you start with a setting of +1/2 turn from where you can just hear the air flow starting.

Another test you can try is to see if the situation is better with the glow battery connected. Get the engine completely warmed up then get it to the minimum idle you can manage without glow. Then reconnect the glow. If it speeds up the mixture is rich so try screwing the idle needle in. If it makes no difference the idle mixture is lean so try screwing the idle needle out.

Idle > 4000 is extreme. Could possibly a carb fault, so if the problem persists after the above suggest you return it to the company we have transferred our model engine business to:- Weston UK. 01795 521030.

Westons are now the main dealer for RCV and will handle all sales/spares/service issues. But for the US they utilise BJ's model engine service centre for servicing advice and spares:-

BJ's Model Engine Service*, 51 Hillside Dr., Beacon Falls, CT 06403
phone: 203-888-4819, email: [email protected]

Keith Lawes

Technical director RCV

Just had a thought. There should be a very tiny o ring around the idle needle to seal it. If that fails or is missing you get v similar symptoms to those you describe.
Old 04-29-2009, 01:16 PM
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Default RE: 58-CD idling around 4000

Thanks Keith and mboland for the excellent troubleshooting advice exactly what I was hoping for.

I'll pull the carb off and check for the washer. It looks pretty straightforward from the parts blowup. Otherwise I'm waiting for a non-rainy day to pull it out in the yard and work through your tuning steps.

Thanks again,

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