Carb problems? (Nitro 10)

[ColH]

I have acquired a Nitro 10 Mk3. I'm new to nitro cars, though I did have some diesel boat engines when I was a kid.
Incredible_serious kindly sent me manuals etc, which has helped a lot in understanding what I'm looking at, and points to the engine being the Leo 12.
First problem is that when I prime it, the fuel doesn't stay in the carb for more than a few seconds then runs back down into the tank. I'll be checking the pipe today, though it seems snug at first glance.
So perhaps a leak in the carb? I see it has 3 - edit: 4 - O-rings - I'd rather not remove the needle ones, for fear of losing the current settings. But perhaps it's leaking where it fits into the block. I'll try to get it out today, but compared with the manual it looks like whoever built it put the retaining/cotter pin in from the wrong side so the bolt is hard to get at...
I looked at possibility of taking engine plate out, but it seems the transmission is on top so I'd have to remove that too? Any tips on this gratefully received, as it would be a lot easier to look everything over by taking the engine out.
When I look at videos online, it always seems that people's cars are reasonably clean-looking. Whereas mine seems to have quite a sheen of [fuel] oil everywhere inside, especially around block and flywheel. Again, does this point to a leak?
If I'm quick with the priming/starting, then I can get it running. But it dies as soon as I remove the igniter. I have put a new hot plug in, and it looks to be glowing bright whilst on the igniter. Maybe this is related to a leak too, so I'll tackle that first, and see how the running goes then.

[ColH]

I noticed that after having it running (igniter attached....) for about a minute, the idle stop screw & spring are pretty wet with fuel, and some fuel sprayed up onto underside of air-filter body (on the linkage side of the carb). I wiped them dry, had another couple of quick goes at starting (un-successfully), wet again afterwards.
I don't know if this is normal..?

This, after wiping the flywheel dry, priming and half a dozen or so pulls on the starter.

[RC10th]

Will it stay running and run normal with the igniter attached? If so the carb isn't blocked as the engine is getting sufficient fuel to run. If the fuel mixture is too rich it can also cause the engine to stall when the igniter is removed. The igniter keeps the plug glowing hot enough to burn the rich mixture but as soon as you remove it the plug can't ignite the excess fuel.

[RS Chris]

Sounds too rich, excessive fuel everywhere. I had the same issue with a motor, leaning out the mixture screws helped for me. You can turn the needle screws all the way in to check. Just count the rotations in half turns and make note of where each end up, that way you can set them back to this setting.

[ColH]

Will it stay running and run normal with the igniter attached? If so the carb isn't blocked as the engine is getting sufficient fuel to run. If the fuel mixture is too rich it can also cause the engine to stall when the igniter is removed. The igniter keeps the plug glowing hot enough to burn the rich mixture but as soon as you remove it the plug can't ignite the excess fuel.

More or less, yes - I've had it going for 30secs+ with igniter still attached.
The plug is new, a hot N3 (on 16% fuel), but a bit of a random [sc]amazon make, as I was in a hurry lol. Maybe I should get something more definitely reputable. How should the plug look when on the igniter - I'm getting a lovely rosy glow, but orange like the embers of a log fire. Should it be more white-hot? [tried to take pic but camera is compensating and making it look brighter]. I spose that, even so, that doesn't necessarily indicate how much self-heat its going to keep with igniter removed.
I get a feeling that it 'holds the prime' better after I've left in an hour or so - after a few starter pulls the fuel is then always draining back to tank and is harder to get to stay in the fuel line.
Also getting quite a bit of fuel collecting in the silencer, but I guess that's inevitable if I'm re-priming, turning it over, and not starting. I've put a clear tail pipe tube on it now, so at least I can see when it's building up!
I'll try an 1/8th or so leaner on the LSN though, and see if I can get more life.

Thanks for the tips and advice folks, sorry if there's a lot of dumb/newbie questions.
(If only my lawnmower had such problems, I'd have an excuse not to cut the lawn this weekend.... )

[RS Chris]

The orange glow sounds about right, but the brighter the better. If the plug was bad it would barely glow, if at all. As for priming, you can put your finger over the exhaust tip and pull the pull-string a few times. This will help pressurize the tank and push fuel through the line to the carb. Might need to push on the tank lid to keep it from popping up.

If you're having trouble with fuel building in the pipe you could try putting a loop in the pressure line. I have to do this with some of my nitro stuff. Does the line go straight into the pipe? Or does it have a nipple it attaches to?

[ColH]

The orange glow sounds about right, but the brighter the better. If the plug was bad it would barely glow, if at all. As for priming, you can put your finger over the exhaust tip and pull the pull-string a few times. This will help pressurize the tank and push fuel through the line to the carb. Might need to push on the tank lid to keep it from popping up.

If you're having trouble with fuel building in the pipe you could try putting a loop in the pressure line. I have to do this with some of my nitro stuff. Does the line go straight into the pipe? Or does it have a nipple it attaches to?

Yes, that's how I'm priming it, and initially the fuel line stays full. But once I've turned it over a few times times the fuel is draining back into tank and then on priming again the fuel doesn't want to stay in the pipe. If I'm quick I can get it to fire before it drains back.

EDIT: it looks like the loss of prime might be due to the fuel line. I get it primed stably, then just lightly flick the line with the tip of my finger and the fuel shoot back into the tank. It feels tight on the carb inlet, but apparently not. Better try a new piece, I guess.

Makes sense I suppose that if I keep priming, keep failing to start, then the fuel has to go through to the tail pipe. As I say, with a clear pipe I can now spot when it's getting full (i.e. blocked).
This is the arrangement of pipes

[RC10th]

If you blow in the exhaust pressure line with the throttle fully open does the fuel flow freely without much effort?

Does the engine ever hydrolock by way of too much fuel in the engine?

When it does run does it sound like it's running out of fuel or choking on too much fuel?

Fuel shouldn't go from the tank to the tail pipe, the pressure port in the tank should be above the fuel level.


If I were you I would try to reset the needle settings back to factory, as a "guess" I would say the low speed needle is far too rich and the high speed needle too lean (or blocked, but blowing in the pressure line would tell you this). I don't know the needle settings for that engine (Incredible_Serious where are you ) but judging by the first picture it looks too far out, most engines factory settings have the low speed needle flush with the end of the carb.


Try priming it this way.... With the radio off manually open the carb to full throttle, pull the pressure line off the exhaust pipe and blow into it. Watch the fuel in the line as it just enters the carb (normally you can hear it) and continue blowing for 1 - 2 more seconds then stop, put the pressure line back on the pipe, turn on the radio and then try to start it. It works every time and only takes about 3 seconds.

[ColH]

If you blow in the exhaust pressure line with the throttle fully open does the fuel flow freely without much effort?

Does the engine ever hydrolock by way of too much fuel in the engine?

When it does run does it sound like it's running out of fuel or choking on too much fuel?

Fuel shouldn't go from the tank to the tail pipe, the pressure port in the tank should be above the fuel level.


If I were you I would try to reset the needle settings back to factory, as a "guess" I would say the low speed needle is far too rich and the high speed needle too lean (or blocked, but blowing in the pressure line would tell you this). I don't know the needle settings for that engine (Incredible_Serious where are you ) but judging by the first picture it looks too far out, most engines factory settings have the low speed needle flush with the end of the carb.


Try priming it this way.... With the radio off manually open the carb to full throttle, pull the pressure line off the exhaust pipe and blow into it. Watch the fuel in the line as it just enters the carb (normally you can hear it) and continue blowing for 1 - 2 more seconds then stop, put the pressure line back on the pipe, turn on the radio and then try to start it. It works every time and only takes about 3 seconds.

Thanks for the comments, they're appreciated. I'll work through the suggestions, but some initial clarifications:
1 - I'll try that
2 - Not a full-on hydraulic lock, no (I remember the feel of this when playing with model diesels decades ago). It gets firmer when I'm re-priming again and again to explore the apparent leak - perhaps flooded at that point. Once I get to be able to start it more repeatably then I'll begin to get a feel for it lol
3 - Not had it running long enough to get a feel for it. Again - I need more time n experience
4 - Sorry if not clear, fuel is going to tail pipe via the engine and silencer. As I say, probably inevitable when I keep re-trying without anything catching light much. I keep an eye on it and drain it so as to not cause back pressure problems on top of everything else.
5 - I did find online some 'factory settings' tips - has some 'half confirmed' numbers for the Leo 15 as opposed to my Leo 12, but might be a good comparison. Certainly worth checking that number of turns [same make, similar size, maybe even same carb] given your thought of the LSN typically being flush.
6 - Sorry if I'm misunderstanding your point, but I can get fuel down to the carb. And if I've left it an hour then the fuel line stays full. But as soon as I begin trying to start it, it 'loses the prime', and when I try to re-prime the fuel instantly drains back to the tank. I might need to shove GoPro in my mouth and video it - just don't expect a commentary

I've ordered new fuel line, but I can't believe its not tight on the nipple. I've even trimmed 1/4" off so as to have on unstretched piece on the nipple. It feels snug - needs a firm pull to get it off. I'll keep re-testing my theory that flicking the tube is letting air in - tried it half a dozen times, but I know from work that a sound technical theory can still have a loophole!!
So frustrating. It is giving a bark, and has run for 30secs, so I don't think I'm too far off.
It's the 'loss of prime' which seems to be stopping me readily moving onto the next phase. Am trying to suss out any root problem - without going random and changing everything all at once, trying to keep some method and traceability to what I'm doing... :S

Thanks again for the input.

[Incredible_Serious]

I don't know the needle settings for that engine (Incredible_Serious where are you )

You say that like you expect me to be some sort of nitro whisperer.... barking up the wrong tree there, mate! There's a number of reasons why I have so many non-running Nitro 10s.... well, laziness is the big one , but I'm just not that good with nitro engines... why do you think I want to get you involved with them?

Thanks for the comments, they're appreciated. I'll work through the suggestions, but some initial clarifications:
1 - I'll try that
2 - Not a full-on hydraulic lock, no (I remember the feel of this when playing with model diesels decades ago). It gets firmer when I'm re-priming again and again to explore the apparent leak - perhaps flooded at that point. Once I get to be able to start it more repeatably then I'll begin to get a feel for it lol
3 - Not had it running long enough to get a feel for it. Again - I need more time n experience
4 - Sorry if not clear, fuel is going to tail pipe via the engine and silencer. As I say, probably inevitable when I keep re-trying without anything catching light much. I keep an eye on it and drain it so as to not cause back pressure problems on top of everything else.
5 - I did find online some 'factory settings' tips - has some 'half confirmed' numbers for the Leo 15 as opposed to my Leo 12, but might be a good comparison. Certainly worth checking that number of turns [same make, similar size, maybe even same carb] given your thought of the LSN typically being flush.
6 - Sorry if I'm misunderstanding your point, but I can get fuel down to the carb. And if I've left it an hour then the fuel line stays full. But as soon as I begin trying to start it, it 'loses the prime', and when I try to re-prime the fuel instantly drains back to the tank. I might need to shove GoPro in my mouth and video it - just don't expect a commentary

I've ordered new fuel line, but I can't believe its not tight on the nipple. I've even trimmed 1/4" off so as to have on unstretched piece on the nipple. It feels snug - needs a firm pull to get it off. I'll keep re-testing my theory that flicking the tube is letting air in - tried it half a dozen times, but I know from work that a sound technical theory can still have a loophole!!
So frustrating. It is giving a bark, and has run for 30secs, so I don't think I'm too far off.
It's the 'loss of prime' which seems to be stopping me readily moving onto the next phase. Am trying to suss out any root problem - without going random and changing everything all at once, trying to keep some method and traceability to what I'm doing... :S

Thanks again for the input.

Having said that, I do have a NIB Leo 12.... although it appears slightly different to yours Colin - red head, tuned pipe, and no pullstart. These pictures may help, or may not.... let's see.

Watching all the posts here, and will chime in when I can add something useful

Alex

[RC10th]

I'll chime in after work.... Hard to type out a decent post on your phone with limited time


Alex, that looks like a GT manifold and gasket ?

[Incredible_Serious]

I'll chime in after work.... Hard to type out a decent post on your phone with limited time


Alex, that looks like a GT manifold and gasket ?

In that in this instance, GT means what, exactly? I assume it's a tuned pipe manifold, rather than the original cast unit, although I could probably sort one of those if necessary...

Just have to work out what looks better, red head or blue....

Alex

[RC10th]

I'll chime in after work.... Hard to type out a decent post on your phone with limited time


Alex, that looks like a GT manifold and gasket ?

In that in this instance, GT means what, exactly? I assume it's a tuned pipe manifold, rather than the original cast unit, although I could probably sort one of those if necessary...

Just have to work out what looks better, red head or blue....

Alex

GT as in Team Associated manifold for the RC10GT/NDS. Sorry, didn't want to sound dumb and ask if it was a factory Schumacher manifold

Cant help you with your decorating choices, it all comes down to personal preference

[Incredible_Serious]

GT as in Team Associated manifold for the RC10GT/NDS. Sorry, didn't want to sound dumb and ask if it was a factory Schumacher manifold

Cant help you with your decorating choices, it all comes down to personal preference

Sound as dumb as you like, mate.... all friends here

From memory, the manifold is the Schumacher factory upgrade part... think it's this one:

Alex

[RC10th]

Interesting, it's exactly the same..... who knew.... Thanks for sharing