Engine won't Idle!
Just got an RC8.2 with the Reedy .21 (RTR), and it just won't crack. I can't get it to idle and that's preventing me from tuning the HSN and other stuff. I do believe that it has something to do with the LSN, either way too rich or way too lean. The buggy just won't start unless i give it some throttle, and then cut off if i let go of the throttle or if i took away the igniter. I leaned it out from there and the igniter problem went away, but it still cut off if i let go of the throttle. Basically, it won't stay running for more than 10 secs. I'm doing all of this with a new glow plug as well, i'm beginning to suspect an air leak somewhere. Also, is it normal for an LSN to become unmovable if leaned out for a couple of turns? Thanks.
Oh yeah, engine was also preheated before starting each time. :) Here's my idle gap. http://i1200.photobucket.com/albums/...pszlplyfl3.jpg |
The idle is actually controlled by the Low speed needle. Try leaning the low speed. You may just be blobering rich on the bottom.
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Assuming it is used check the compression. Using a finger or thumb while the engine is off and cold, and try and Spin the flywheel. If it doesn't give you a good bit or resistance to rolling over the engine is shot.
Since it is hard to quantify that, an easy test is to take the engine out of the chassis. Hold the engine sideways by the flywheel. If it flops over, it's done. Not enough compression. If it had compression, put another brand new glow plug in. (New ones can be duds). make sure the exhaust system seals completely. Any wetness around the gaskets or on the chassis / engine below / around means they need to be changed. reset the needles to flush with their housing or in up to about half a turn. (An engine should at least start and idle like this). Make sure there are no tight bends or kinks whatsoever on the fuel or pressure lines. Preheat and start. It's OK if you have to stay on the had a little until the engine comes up to temp, but then you have to tune it to idle and run right. It is normal for the lsn to bottom out after a couple of turns. Hsn too. Try this and see if it works. |
Alright, thanks. I'll check it out right now.
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It passed the compression test, and everything else seems to be dry. I'm going to move all needles to flush and see if it'll start tomorrow. It does have a pull start though, if that changes anything. Do you think it'll be fine if i cut that? Reedy doesn't sell a backplate for this motor, and i have no use for it so.
Oh and it did take a while to prime, maybe that should give someone an idea. |
Sounds like a pressure leak in the exhaust or fuel tank, possibly.
Holding your finger over the exhaust tip, how fast is fuel moving through the line to prime? I've seen the tuned mufflers come loose and cause annoying lack of pressure to drive fuel in at idle, but do ok with some RPM. It just sounds like a leak in pressure from the little info available here. |
By holding my finger over the exhaust during prime, i actually see little to no fuel (or maybe im just blind idk) going to the engine. You may be right about the leaks in the fuel tank or the exhaust, is there any way i can test them for leaks??
Edit : I did an underwater test for the fuel tank, and there seems to be a leak at the lid of the tank. Could this have caused all the tuning problems? |
Also check the clutch. Some binding due a weak or broken spring or even a bad bearing can cause a bad idle as well.
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If the line was already primed, you'd see nothing.
You can pull the fuel line at the carb and aim it at a rag you're throwing away to test priming/pumping action. Every pulse of the motor should pulse a bit of fuel out. What are you using to crank? You mentioned a pull start you wanted to cut. If it's a bump box or similar, then the fuel should fill from tank to line within two to three seconds. The unnoticeable prime (assuming line is empty at start of crank) has me further suspecting a leak between engine exhaust port to fuel line. The leak in the tank lid _could_ cause it, too. Often your LHS will have tank rebuild kits to seal them back up. One more thing, though, before you go buy parts... how long did this car sit before you got it? It could be that the fuel circuit in the carb is gummed up and will need a good cleaning out. I'm not sure what most folks around here do for that. For me, carbs are cheap enough to just buy a new one, so ive not messed with it. I just know that tye fuel sludge seems impervious to most of what I have that will eat metal (gold prospector, I have some serious chemicals for dissolving metals :) ) |
Originally Posted by Roelof
(Post 13372042)
Also check the clutch. Some binding due a weak or broken spring or even a bad bearing can cause a bad idle as well.
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My bearings still have a lot of play in them, and my clutch/springs look good as new with no sign of damage anywhere. But, i'll pick up a fresh set soon. So i tried starting it with both lsn and hsn flushed, and it started up with no problem but it still wouldnt idle. It would cut off as soon as the ignitor was off, i kept leaning the lsn but it felt like i wasnt getting anywhere close to that sweet purring engine sound. I even tried it with an alternate fuel tank(my truggys) and still kept the same symptoms.
Mikey, i actually dont know how long the buggys been sitting. The whole buggy shows very little wear, so probably a while. If i have to rebuild the whole engine to fix this, i will. |
Ok so i think i may have found the cause. My LSN is way too rich, but i cant lean it out because it bottoms out way too early preventing the shaft from moving. I think theres something binding the carb. How can i fix this?
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Maybe your LSN screw could be bent, which could be why it is bottoming out early. How many turns in are you leaning the LSN?
I also found that leaning the HSN will slightly affect the when you're on a rich setting all around (LSN, HSN, idle all rich), as the HSN dictates total fuel flow. Try leaning the HSN 1/2 turn and see if that helps, and if it's better, then try another 1/2 turn (of course making sure that you're not over-leaning your engine so that it will overheat). If that fails, try to crack open your carb and see if there are any signs of scuffing or scratching, and then try to diagnose if there was a stone caught in the slide or if a screw is bent, etc. From here on out it's just going to be a bit of trial and error I think. You may also want to consider replacing the carb. I'm only a newbie at this kind of thing, so take my suggestions with a grain of salt. It's very possible that my suggestions are highly misguided and could do further damage to your engine (although unlikely considering it seems to be the carbie). |
Thanks for the info though, ill try it once i fix my starter box .-.
The LSN begins to become unmovable at the flush position, so something is very wrong. And i would replace the carb if i can find out the part number for it, usually theres like no part support for rtr engines :mad: I did open up the carb, and its very dry. Its almost as if there was no fuel going through it. Is that normal? Edit : I took apart the carb, and gave it a cleaning. The lsn seems to be fine now, it still bottoms out though but now its at 4-5 turns from flushed so that should be normal right? As for the dry carb thing, i did an air leak test on it and noticed that the hsn nipple was blocked in a way since air was having a hard time getting passed it. So i loosened the hsn and its pretty good now. I hope this solves my tuning problems! |
Setting the needles to "flush" is not really a factory setting.
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