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Diagnostic time (again) :(

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Thanks! I'll keep an eye out for some good fuel!! :) Unfortunately it was barely 50* today, so I didnt get the truck out.. Hopefully tomorrow!
 
The fuel, man ditch that stuff. Put a MC-59 plug in it and run a low oil 30% fuel.
I swear it will idle and and run much better and tune predictably, without being leaned to death.
You are experiencing classic false tune symptoms from poor fuel quality and too high an oil content. MC-59 plugs work great in all SH BB engines from my experience. The medium SH plug is good too, but works better after breakin. It will never work with Traxxas fuel though.
 
At the moment I have one HSP "medium" and one Odonell SS "purple sport med 25-30%" for spare plugs.. Are either of those worth a darn? Who makes the MC-59? Or do I just ask for a MC-59 and they'll know what I mean? Sorry, not very familiar with the Nitro stuff yet.. I'm gonna switch up fuel asap, but unfortunately I've only used about 1/4 of the gallon of the traxxas fuel.. (And I can't afford to pitch it) :(
 
OK thanks RCA! Ran the car again today.. Started to go ahead and "tune it" to run.. I had it running pretty sweet, still with the high idle.. Temps were around 210.. I richened the LSN a damn hair and it died as soon as I let off the throttle, on the first pass.. (Almost acted like a "flame out"? Might have the HSN too lean, tryin to compensate for the other crap?) Anyway, then it wouldnt re-start, and I noticed there was no fuel in the line up near the carb, so I tried to reprime it by blowing into the exhaust line, and it wouldnt let me? Fuel would go up into the carb but as soon as I stopped blowing it would push back down the line? (I'm wondering if it was sooo lean that the carb got hot and was not letting it draw fuel? Does that make any sence??) That's what it seemed like anyway.. The temp at the head was only 200-210, but I never got to try it at the carb.. (I didnt think about the carb being hot until later) And it was time to eat when this happened so I didnt get a chance to check it later.. Anyway, before I put it up, I richened the HSN a couple "hours" and put the LSN back where it was.. I'm gonna get this thing to run dang it, if it's the last thing I do!! :D hehe.. Who recommened I try nitro anyway??? Oh yea, it was my own bright idea.. DOH!!
 
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Yea, that's what it does.. That's been the story of this motor.. If nothing positive happens tomorrow, I think I'm gonna pull the carb off and break it down (soak it in something) and make sure there's not some junk in it somewhere.. There's either junk in the carb, or there's an air leak.. What's safe to soak carb parts in? Denatured alcohol or acetone or ??
 
I've always used clean fuel to clean engines. Make sure both of the needles and their seals are not damaged. Frustrating problem! Keep at it, you'll get 'er.
 
I've sealed the engine and carb before, so I'm wanting something that'll break down any roague RTV, if that's possible? I know that stuffs pretty tough, but was hoping DA or Acetone would eat at it? (And hopefully NOT eat up the seals?) I aint askin for much am I?? :) But by saoking it in Fuel would be a good way to get rid of some of this Traxxas crap fuel.. Hmm..
 
have you tried washing the inside through with WD40 to get rid of the trx fuel ??

Always works for me when i switch fuels, but you will need to use ARO to relube the back bearing.

Just an idea............shoot me down if you like
 
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Nah, I'm not tryin to waist the fuel, (too expensive) I just want to switch when it's gone. But I've got 3/4 of a gallon still.. :( But washing/soakin a carb would be a constructive way to use up some of it. :)
 
Tell me if this makes sence.. Well, first off I can once again get it to run like a raped ape, all execpt the idle is still way too high.. Then if I richen the LSN to where it should be it'll run for a second, but as soon as I let off the throttle it'll idle down (like it should) but then die.. So, I got to thinkin.. (I know, that's a problem in itself) :D But, what if I had the HSN set WAY too rich.. So rich that I had to lean the LSN out the arse to get it to run? The temps would still stay down cause it's getting flooded with fuel from the HSN, but it'd act "lean" due to the LSN?? Anyway, after messing with it for over an hour today, I finally decided to ditch the "Pull air filter, check idle gap, replace filter, etc." dance, and just adjusted the idle with the trim, then I set the HSN SOOOOO lean that it barely got fuel.. Well, this let me start richening the LSN, and the high idle setting off the trim let it stay running off throttle.. It was also the "VERY" first time I heard the RPM rise, when doing the "pinch" test on the fuel inlet line.. I was burnt out by this time, and everything was good and hot, so I washed my hands for the day and will try again tomorrow.. But what I'm thinkin is, hopefully the old manual I found, with the stock settings, had the HSN way too rich for my engine (Like over a full turn rich) and thats been throwing all the other settings off? I'll find out more tomorrow.. But what do ya think as far as the theory? Thanks as usual for listening! :)
 
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Make sense... keep at it. When you get it right, you'll know. Nothing like figuring it out for yourself....Tuning the LSN first is not always necessary, and it is a more advanced tuning process. Anyways like I said, sounds like you are on the right track. Totally sound explanation of what could be and prob. is happening.
 
Well, the LSN isnt "that" tight (lean), but it's WAY over leaned from where I started at "Stock".. I believe (hope) the manual I used to get the stock settings is a manual for an older model SH.28. It calls for both the high and low to be 3 full turns out.. I really wish I'd of noted the stock settings before I started turning screws, but that milks bent spilt.. :) Someone, maybe you RCA, mentioned turning up the idle to see if it'd let me richen the low needle, but I just now got around to trying it.. If this works out, it might go back to the threads I read that said some of these SH engines need a larger idle gap? I know the purists say it's a false tune, but that may turn out to be the only way to get the thing to act right.. It's not a stout enough motor to race with anyway, so if I can just get it to A) idle, and B) run at all throttle inputs w/o bogging or stuttering, I'll be a happy camper.. It'll be enough to let me learn the ins and outs of the truck.. If I get good enough to try and race it, I'll get a Picco or something for it, and let ExtremeRC put some magic on it.. ;) Thanks again for the all the help fellas!! And wish me luck, that I'm closing in on this mutha trucka!! :D
 
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Well, tried her again today.. lol.. I picked up where I'd left off yesterday, and she fired right up, and believe it or not she idled right and ran good for about 5 minutes.. Was running a "tad" fat, but running and idling like it should.. Then my rx batteries crapped out, so I had to stop and recharge.. When I started again I richened the low needle a gnats hair, and it started up with the spittin and sputtering and died immediately.. I had to lean the LSN 1/4 turn before I'd run again.. I never did get it back to the way it was earlier.. Afterwards I tore it all down again and did the soapy water/leak test.. I can hear a little air gettin out of the front of the motor, (I'm assuming the front bearing) but it's all covered up with clutch bell and what not.. None of the needles or carb or backplate areas had any leaks.. I'm wondering if it's just not completely broken in yet? That or maybe the carb is junk from the factory? Maybe they machined the LSN wrong or something during the manufacturing? I wish I had another carb to try on it, just to see.. But unfortunately I dont.. I've got a rotary carb off a SH .18, but dont even know if the neck is the same dia or not.. I've decided I'll live with the high idle if I can get it (and keep it) running, w/o getting too hot.. I checked the temp just before the battery died and it was running 200*+/- and dropping a degree or so every couple seconds, even with the exaggerated idle.. If it's not raining I'll be operatin.. err running it again tomorrow! :D
 
FUEL .....get rid if the Traxxas poo!!!!Some leakage at the front bearing is normal during breakin. No big deal, keep working with the tune.
 

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