Problems with Nova 21-4C tune

Old 02-23-2011, 09:09 PM
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Default Problems with Nova 21-4C tune

Hi

I've got a bottom end tune problem with a Nova 21-4C. Motor has new plug, approx. 6 litres on it.

When I'm off throttle on track the idle sounds high. Bring the car into the pits and it will sit there on high idle then step to a lower idler and then die. This takes all of 5 secs. If I have a decent stack on track then the motor will often die. When I refuel it will often die even when giving it a good rev once the tank lid is shut.

I've read a few other posts and I'm thinking I've got the idle too high and a too rich low speed needle to compensate.

Any other ideas?

Thanks
Hack
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Old 02-23-2011, 09:18 PM
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Sounds like your rich on the lsn, Keep leaning the lsn until the idle is consistent and does not drop and you can turn the idle down.
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Old 02-23-2011, 09:21 PM
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Yep, You will probably find you are a little lean on the HSN too.........
Good luck !
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Old 02-23-2011, 09:51 PM
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Originally Posted by hack_1979 View Post
Hi

I've got a bottom end tune problem with a Nova 21-4C. Motor has new plug, approx. 6 litres on it.

When I'm off throttle on track the idle sounds high. Bring the car into the pits and it will sit there on high idle then step to a lower idler and then die. This takes all of 5 secs. If I have a decent stack on track then the motor will often die. When I refuel it will often die even when giving it a good rev once the tank lid is shut.

I've read a few other posts and I'm thinking I've got the idle too high and a too rich low speed needle to compensate.

Any other ideas?

Thanks
Hack
Sounds to me like you are way to lean on the bottom end? When it steps to the lower idle does it clean out when you hit it? Go 2 hours rich on the bottom and see what happends you can never go wrong when richening it.
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Old 02-23-2011, 09:59 PM
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Originally Posted by tomdex View Post
Yep, You will probably find you are a little lean on the HSN too.........
Good luck !
Good addition to above post...
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Old 02-24-2011, 11:02 PM
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LSN should be flush or +/- 2 hours from flush on a newer engine. If the engine is healthy, the LSN should be in that range.

Most engines that are broken in and "ready" run right at (or at) flush.

HSN should be flush; or fractionally in from flush, but that's a good starting point as well. Typically you'll be able to lean it from there until the temp comes up properly (210-260F).

Engine should run and idle there. If not, set the idle speed accordingly.

Make sure your linkage pull-barrels are not holding the carb open.

Novarossi C6TGC; C5TGC (if it's cold out); OD77T/OD97T... it should run on any of these plugs with no problem. If it's below 70deg. F ambient temp, the OD77T would be preferred. The Nova C6 will run down to about 65; then I prefer the 5.

As far as having a full tank of fuel and the engine quitting, usually thats where fuel gets sucked into the pressure line momentarily. If the engine is tuned incorrectly, it can cause issues. Put the HSN/LSN at flush, set idle speed and reevaluate. If that doesn't work (with a fresh glowplug), you may have to lengthen your pressure line slightly.

Good luck.
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Old 02-25-2011, 10:19 AM
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From what iv learned these engine r very altitude finicky, for example at 4500 feet my needles r 1.5 turns in from flush on top, and 1 turn out from flush on bottom, in Elsinore at 0 elevation my top needle is 1 turn in from flush and 3 1/2 hours in from flush on bottom needle, so if your around 2500ft go between those setting or use those as a guide because the nova plus 4 carb I don't even tune, I take altitude reading at the 4 tracks I drive at n I have specific settings for each track, I literally don't touch anything but the idle these days because I no the nova carbs so well, to me it sounds like ur low speed needle is wrong, see if it's around flush to begin with and set it to ur altitude, if ur at higher altitude u need a richer setting on bottom n leaner on top and vise versa.
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Old 02-26-2011, 05:49 AM
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double check everything your tank no leaks then check carb boot has no holes or cracks, just to be safe seal your carb throat and back plate with lucky 7 so theres no leaks make sure your head bolts are nice and tight, and if you feel you are really unsure just go back to factory settings hsn all the way in 3.5 turns out and lsn all way in then 5 turns out. tune it from there.
cheers
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