LRP Z28 won't idle long...

[bull8042]

I am using a 250cc Ofna tank with an IRC mid-tank kit, an LRP Z28 and an Ofna 086 pipe. I am having a bit of trouble figuring out why the engine dies after idling for 30 - 45 seconds even after running for a while and being at operating temp.
I noticed that the temp would climb slowly at idle, so I richened the LSN between 1/8 and 1/4 turn so now it drops a degree or so every 3 - 5 seconds.
I have a decent smoke trail while running and it drops to a normal idle right after a WOT pass. That leads me to believe that I am fairly close on the HSN, but don't want to lean it out any more right now since I only have around a 1/2 gal on the engine.
I am just wondering if anyone can think of a potential reason the engine would die after idling a bit right-side-up.
I did plug the fuel line and submerge the entire assembly (tank, hoses, and filter. NOT the truck) and pressurized the system. No bubbles indicating any leaks.

 

[Purenitro]

The LSN is a fine balance between too lean, perfect and too rich. With a good tune (slightly rich) they do have a tendency to load up at idle, ever so slightly lean the LSN to the point that it is not gaining temp, but isn't loading up either. It sounds like you are very close if it will idle for 30+seconds already, it may only take one hour or less of adjustment, but I'm sure that's all it is, a tiny adjustment, 1/8-1/4 is way to much of a change.

 

[smileyman63]

Just a thought did you check the gap of the idle screw? I think it should have a Gap between 0.5mm and 1.0mm open. That is according to the sticky thread factory engine settings. Good Luck

 

[bull8042]

The LSN is a fine balance between too lean, perfect and too rich. With a good tune (slightly rich) they do have a tendency to load up at idle, ever so slightly lean the LSN to the point that it is not gaining temp, but isn't loading up either. It sounds like you are very close if it will idle for 30+seconds already, it may only take one hour or less of adjustment, but I'm sure that's all it is, a tiny adjustment, 1/8-1/4 is way to much of a change.

I will try that. Initially, the temp would climb a couple of degrees every 3 - 4 seconds when idling, and I had never touched the LSN. So that is the reason for the rather large adjustment. But I would much rather be rich than running too lean and damaging something. But I guess that goes without saying. Actually, I would rather just be rich, period. :Xfingers:

Just a thought did you check the gap of the idle screw? I think it should have a Gap between 0.5mm and 1.0mm open. That is according to the sticky thread factory engine settings. Good Luck

I have it adjusted just below the point it causes the clutches to start grabbing and moving the truck.

 

[Purenitro]

You should set the gap like mentioned and then tune for it. A large gap can mask other problems which you will then tune for and that will leave you with less then a perfect tune.

 

[bull8042]

You should set the gap like mentioned and then tune for it. A large gap can mask other problems which you will then tune for and that will leave you with less then a perfect tune.

I thought some jerk was playing off your username, then realized you changed your avatar when I saw your sig.
I will try to gauge that first before doing anything else. One question about that that I haven't seen addressed before.... When inserting a 1mm gauge rod into the throat of the carb, do you keep it parallel to the side wall of the throat, or at an angle splitting the difference between the slide and the carb wall?

 

[Purenitro]

LOL, I saw someone else was using it and this one fits the bill with all the stuff I've been working on lately. I would shoot for closer to .5mm but anywhere in the .5mm-1mm is fine. If you place the carb on a flat surface, with the gauge rod or stalk end of a drill bit, set the gap to the thickness with the rod pointing straight up. You are only setting the "open" gap, not including any angles present in the ventury.

 

[bull8042]

LOL, I saw someone else was using it and this one fits the bill with all the stuff I've been working on lately. I would shoot for closer to .5mm but anywhere in the .5mm-1mm is fine. If you place the carb on a flat surface, with the gauge rod or stalk end of a drill bit, set the gap to the thickness with the rod pointing straight up. You are only setting the "open" gap, not including any angles present in the ventury.

I should probably be using that avatar as well. hehehe
Thanks for the explanation, makes perfect sense. I will start mic'ing bits and shoot for 0.5mm +1 hair and start tuning again from there.
Thanks again Robin, much appreciated.

 

[Purenitro]

Any time bud, happy to help out.