Carb problems? (Nitro 10)

[ColH]

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.

Well the head of your LSN is standing proud like mine is - so that helps. It appears to be same carb, though I have the HSN as in the 96 catalogue. Block is different too.
If NIB then I guess it should have [correct] factory settings. Would you be able to see how many turns-from-closed you have on the LSN?

[ColH]

I'm suspecting the carb isn't seated properly. Gonna be a pain to get it out/in though... might get to the bolt if I remove the silencer and have a good spanner, otherwise going to have to remove engine plate

[RC10th]

Well that's definitely not right, fix it first and see how you go.

[ColH]

Well that's definitely not right, fix it first and see how you go.

Yeah, looks like more of a scarf than an O-ring!

Edit: Might try to get it at least starting & idling reliably on the bench whilst it's out.

[ColH]

Now then - where's the jet washer
And the blue paint.... or red paint....

[ColH]

Carb re-seated this morning, and it's now holding the prime.
After re-reading (properly...!) the various guides on tuning, it turns out I need to start with the HSN, not the LSN as I'd been fiddling with. ("Setting it up at idle, that'll be the LSN" I thought. Intuitively I thought, but wrongly!! )
A click or two on the HSN has made all the difference to getting it started, and it also keeps going without the igniter. And it revs up and down with the throttle rather than just lumping along regardless. Major result.
So, to get it right... A lot of guides talk about 'too little/much smoke' - not easy to judge with no experience. The 'pinch test' seems another recommended practice - e.g. does it keep going for a few seconds before cutting out, as opposed to cutting out immediately. But what if it keeps going say 5-10 secs? Still too rich?
I'm running it on the bench at the moment, btw, so there's no load on it when I open throttle. Just wanted to be able to get to it all easily while I suss it out.
(I get a bit freaked by the amount of revs these little things do - even more than my RX7 used to do - get nervous when the thing gets really screaming!)

[RC10th]

Good job on getting it running. Yes the tuning sequence is

1. High speed needle
2. Low speed needle
3. Idle speed screw

Just be careful with free revving the engine with no load, it's not good for them. You could find that it runs great with no load but as soon as you put it in the car its a bit sluggish under load from being too rich.

So..... put it in the car and take it for a drive. I wouldn't worry too much about the amount of smoke as long as your getting some smoke, the performance is good and it's not getting too hot. Always tune from rich to lean. 220°f - 230°f is about as hot as you want to get it. Even if it spikes to 250° you should be ok, just shut it off and let it cool, however, over 300°f is where you start to do damage to the chrome liner.

Soooo...... you can use an infrared thermometer to get an idea if you have one, use a drop of water down around the glow plug hole. It should bubble off in 3-5 seconds. Or if you can hold the head for a few seconds...

Once you get the high speed needle set (good top end power and smoke) you can move on to the low end needle which only controls roughly the bottom 25% of throttle..

After that set the idle speed for the lowest maintainable idle (clutch not engaging)


Start to tune on a full tank as they tend to lean out slightly as the fuel level drops. Most of all have fun and report your progess back here.