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Stripped threads on OS 46AX Engine Head - 12/1/2012 7:03 PM   
CrashedTrainer


 

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From: Islamabad, PAKISTAN
Status: offline 		Dear All!

Hi!


Today i finally did it... I stripped the threads on my OS 46AX engine head.... I am pretty sure that it happened due to me over-tightening the glow plug...

Anyways now coming to the point:
Q- Do I repair or replace the head? What is the recommended action when it comes to this type of failure?

I have taken the head off and given it to my local hobby shop guy who says he can get it repaired for something like 6 or 7 bucks...
Q- while the head is removed and engine is open i was thinking if there is anything such as signs of wear or damage that i should look for to determine if the engine is fine otherwise... the engine ran fine even today but i did hear some very slight coughing on the last flight...i think it was because of the leakage through the damaged threads of the glow plug... what do you guys think? the engine on some days starts just on first or second flip but on other days it won't start without the starter motor...

Lastly but most importantly.. I tighten the glow plug on my engine using the cross shaped wrench key set... I always used to wonder if i was tightening it enough or not..so i always used to tighten it until i couldn't tighten the glow plug any more without applying too much force... now i know that is a very vague description... The Result -> stripped threads... also a couple of de-shaped glow plug washers which were changed before this finally happened...
Q- is there something like a rule of thumb that could tell me that the glow plug has been tightened enough? Is there some torque value that i can use so this doesn't happen again...

Waiting for your response in anticipation...



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RE: Stripped threads on OS 46AX Engine Head - 12/1/2012 7:18 PM   
Mr Cox



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Status: online 		Get a new head and use a new, annealed, gasket each time. It really shouldn't require much force to seal.

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RE: Stripped threads on OS 46AX Engine Head - 12/1/2012 7:45 PM   
vpresley



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Status: offline 		Hmmm 6 or 7 dollars sounds awful cheap for the repair. I just sent mine out to Clarence Lee, and he charges $20.00 to put a heli-coil in. Gotta go with the new head, just easier.


Vince

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RE: Stripped threads on OS 46AX Engine Head - 12/2/2012 1:16 AM   
aspeed


 

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Status: offline 		For 7 bucks, maybe he knows a buddy kind of thing.  It is worth a try?  An insert could be pressed in and tapped by a machinist that just wants to help.  I just tighten the plug with two fingers on the Fox type wrench.

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RE: Stripped threads on OS 46AX Engine Head - 12/2/2012 1:24 AM   
flyinwalenda


 

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Status: online 		Unless it can be chased with a tap and cleaned up ,a coil needs to be pressed in and 7 bucks is cheap if that's what they are doing.


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RE: Stripped threads on OS 46AX Engine Head - 12/2/2012 1:44 AM   
aspeed


 

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From: Ruthven, ON, CANADA
Status: offline 		A helicoil needs to be drilled, tapped, and the insert screwed in with a tool and the tab snapped off.  It would likely cost about $5 for the insert,  I am guessing.  I put thousands in at work, but never paid for them.

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RE: Stripped threads on OS 46AX Engine Head - 12/2/2012 2:06 AM   
flyinwalenda


 

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Status: online 		Here's the kit to put them in
www.ebay.com/itm/290691422108


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RE: Stripped threads on OS 46AX Engine Head - 12/2/2012 8:59 AM   
CrashedTrainer


 

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From: Islamabad, PAKISTAN
Status: offline 		well to be honest i think he is ripping me off... actually the cost of such workmanship is way lower than what he is asking from me... but hopefully he will do the job fine since he knows the stuff...hence me paying more for now... btw thanks for the link to the kit on ebay flyinwalenda...
there are advantages of living in a developing country you see! cheap labor/workmanship costs ... plus i told you guys the amount converted from PKR so that might be a factor too... anyways!!

so... can anyone please shed some light on my other two questions?


Q- while the head is removed and engine is open i was thinking if there is anything such as signs of wear or damage that i should look for to determine if the engine is fine otherwise... the engine ran fine even today but i did hear some very slight coughing on the last flight...i think it was because of the leakage through the damaged threads of the glow plug... what do you guys think? the engine on some days starts just on first or second flip but on other days it won't start without the starter motor...

Lastly but most importantly.. I tighten the glow plug on my engine using the cross shaped wrench key set... I always used to wonder if i was tightening it enough or not..so i always used to tighten it until i couldn't tighten the glow plug any more without applying too much force... now i know that is a very vague description... The Result -> stripped threads... also a couple of de-shaped glow plug washers which were changed before this finally happened...
Q- is there something like a rule of thumb that could tell me that the glow plug has been tightened enough? Is there some torque value that i can use so this doesn't happen again...

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RE: Stripped threads on OS 46AX Engine Head - 12/2/2012 10:22 AM   
Mr Cox



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Status: online 		With the head off, take a look at the inside and inspect the cylinder wall, there should be an even layer of nickel. If you see brass anywhere in the bore, then it needs a new cylinder too.

With a fresh gasket for the glow plug there is very little force needed, you just use your fingertips on the cross bar.

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RE: Stripped threads on OS 46AX Engine Head - 12/3/2012 3:08 AM   
captinjohn


 

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Status: offline 		Do the Heli coil.  You end up with strong metal for threads that does not wear like soft aluminum.  I have installed thousands of them...they are used in military parts.  Capt,n

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RE: Stripped threads on OS 46AX Engine Head - 12/3/2012 4:07 AM   
aspeed


 

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From: Ruthven, ON, CANADA
Status: offline 		I think the Timesert may seal a bit better than a Helicoil.  A Nelson plug hole could be prepared, and a new head wouldn't cost too much either, compared to say a 4 stroke.  A brass plug could be pressed in and drilled and tapped too.

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RE: Stripped threads on OS 46AX Engine Head - 12/3/2012 8:55 AM   
tiffitech


 

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Status: offline 		The threads in the head doesn't have much to do with the sealing (that's the purpose of the copper gasket) so helicoil will work,
but I personally would prefer the solid inserts. I saw some pulled out helicoils in the past already (not on model engines).

Remember: OS is "El cheapo" here, high quality Manufacturers like Enya have an threaded brass bush in the head that will last
longer even when the thread gets abused (changing the plug when the engine is hot).
OS is selling poor & simple stuff for high prices in my eyes, not that much premium... and the good support..? Forget about it,
there is no better support that anyone can do as Ken Enya's for example..

Regards,

Holm

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RE: Stripped threads on OS 46AX Engine Head - 12/3/2012 1:40 PM   
MetallicaJunkie



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Status: offline 		i might have a head for a 46 ax....the motor ingested something and got ruined, im pretty sure i still have it... lemme know if yur interested.

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RE: Stripped threads on OS 46AX Engine Head - 12/3/2012 2:18 PM   
Propworn


 

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quote:

ORIGINAL: tiffitech

Remember: OS is ''El cheapo'' here, high quality Manufacturers like Enya have an threaded brass bush in the head that will last
longer even when the thread gets abused (changing the plug when the engine is hot).
Regards,

Holm


Maybe they need any extra strength for the glo plug since they canted it forward towards the prop so when the igniter makes contact with the prop it doesn't take the plug with it when flung to the weeds. Used to be fun watching the guy with the EEEEEENNNNNYYYAAAA s replace broken props, bandage cut fingers and look for their glo igniter HE HE HE. Used to have a pool to see how long it took for one particular guy to do the whacked finger dance. He was a die hard Eny fan. You could tell by the scars on his hands. Just funnin with ya though I never could figure out the reasoning for having that glo plug tilted towards the prop.

Dennis

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RE: Stripped threads on OS 46AX Engine Head - 12/3/2012 2:45 PM   
1QwkSport2.5r



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Status: offline 		Smart Enya 4-stroke guys use a remote glow driver. Rear pushrods are a plus to me, cheaper repair in the event of a crash. Seems counterintuitive with the forward glow plug though. Just need to use common sense.

If it were me, I'd replace the head instead of repairing it. That's just me though.

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RE: Stripped threads on OS 46AX Engine Head - 12/3/2012 3:43 PM   
wcmorrison



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Status: offline 		You more likely cross threaded the plug on installation.  You could try using a 1/4 by 32 tap to chase the threads.  As an aside, I use a short piece of fuel tubing to start the plug in the threaded head.  That way I do not cross thread the plug at the onset and thus prevent a head job. 

BTW, I would use Mr Clarence Lee, he is truly the best of the best in those kinds of repairs.  He has been doing it for years and years.  And he is a nice fellow to boot.  Worth a try.  And very fast service.

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RE: Stripped threads on OS 46AX Engine Head - 12/3/2012 4:25 PM   
Propworn


 

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Status: offline 		Repairing a stripped out plug thread with a helicoil is no big deal. No need to drill just run the helicoil tap down the hole, count the number of threads and trim the helicoil to the right length and insert then break off the drive end. Both ends of the helicoil need to be below the original surface. The whole kit including 10 helicoils is about 30 bucks here is one source. http://www.blindrivetsupply.com/Recoil-14-32-UNEF-Thread-Repair-Kit-10-Inserts-In-Kit-34040-32_p_3626.html

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RE: Stripped threads on OS 46AX Engine Head - 12/3/2012 4:29 PM   
earlwb


 

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Status: offline 		A new head is $19.00 from Tower Hobbies, plus shipping. They have them in stock at this time too.

So for the cost it is flip a coin as to whether to have it repaired or get a new one. I would likely just order a new one though.


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RE: Stripped threads on OS 46AX Engine Head - 12/3/2012 4:37 PM   
aspeed


 

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Status: offline 		I think $20 will buy a head though, or get the one from Metallica Junkie and be careful with the wrench next time. I don't think it was cross threaded, if the washer was squashed it was likely torqued too much.  A hard lesson that everyone does and learns from.  I never really thought much of OS either (or Enya's for that matter) But after comparing a bunch of .15's, the LA is really pretty good, the LA .25 that we are forced to use instead of the Fox .35 works better than an old .35, and I just bought a Twist from a swap meet for $80 that came with an OS .46, and it really impresses me.  It runs fast, and idles great.  I have heard stories of peeling liners and bad bearings, and hope mine isn't a victim, but they really are fairly good.  Way overpriced compared to some other garden variety stuff that is similar though. Lucky for me there are swap meets.  Hey Earl snuck in there before me. Hey so did Dennis.  I have to type faster.

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RE: Stripped threads on OS 46AX Engine Head - 12/3/2012 4:46 PM   
earlwb


 

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Status: offline 		One other thought, is in some cases one may be able to have the head carefully drilled out for a Turbo Plug too. These plugs are racing plugs and larger in size versus a regular glot plug.  But by careful is that you have to not drill all the way through and you have to use a bottoming tap as the step or shoulder on the inside is used to seal the plug instead of the washer. So one needs to be more careful doing one of these, but it would not need to have a insert put in for it.


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RE: Stripped threads on OS 46AX Engine Head - 12/3/2012 4:49 PM   
aspeed


 

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Thanks Propworn.  A set of 10 inserts is only $6 after the initial price of the installation kit.  That is quite reasonable. Until the shipping is added of course.  I don't feel so bad for wrecking all the helicoils at work now.  Probably hundreds over the years.  Maybe 5% of them buggered up on installation.



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RE: Stripped threads on OS 46AX Engine Head - 12/3/2012 5:39 PM   
CrashedTrainer


 

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Status: offline 		@wcmorrison: No... i know i didn't cross thread it... it was over torqued for sure, excessively... as aspeed said.. i have learned my lesson too, the hard way... i think the poor engine head tried to cope up as much as it could but gave up in the end... anyways

@metallicajunkie: thanks... i would most definitely want to get it from you but it would cost me a fortune, i think, to get it shipped here to Pakistan all the way from the US? :/

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RE: Stripped threads on OS 46AX Engine Head - 12/3/2012 6:36 PM   
Four Stroker


 

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Status: offline 		Not necessarily anything that you did. The last thread in the head tappers down to paper thin. When you tighten the plug it can break off a piece which works it's way down into the threads. When you screw a plug in over this piece it's all over but the crying. I always insert a plug with a piece of fuel tubing over the stem and tighten down. Then put the wrench on it.

As Clarence Lee said 40 years ago. Get a 1/4-32 die and clean up the threads of each new glow plug before using.

Some plugs are not threaded all the way and if the washer is too thin, the last thread in the head will snap off.

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RE: Stripped threads on OS 46AX Engine Head - 12/3/2012 7:15 PM   
CrashedTrainer


 

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ORIGINAL: Four Stroker

As Clarence Lee said 40 years ago. Get a 1/4-32 die and clean up the threads of each new glow plug before using.




hmmm... i actually did some research on stripped threads on the internet and found the same advice as above mentioned somewhere else too... noted it down already since it made quite some sense ... thanks for the advice!

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RE: Stripped threads on OS 46AX Engine Head - 12/3/2012 11:08 PM   
Propworn


 

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ORIGINAL: tiffitech

@Popworn: Besides of that, we are talking of an OS AX here, an El cheapo 2 cycle engine,
so why you come up with an Enya 4C now? There are no Enya 2 Cycles with an angeled plug at all.

SCNR,

Holm


HMMM last 2 stroke Enya I remember seeing was something like a 40 but the size of a 60 would have made a good sinker no where near the power or rpm of a GOOD modern 2 stroke. I have a Norvel AX40 that will eat any comparable size Enya fer breakfast. There is a reason you don't see many EEEEENNNNYYYYAAAAs around. Is there even a dealer left in the US. A factory authorized dealer and repair depot not some guy working out of his garage or basement claiming to be a dealer. I know people who have stopped looking for parts nothing seems to be available so they have turned them into paper weights. Better luck finding parts for a old K&B. Better engine of the two anyhoo. Oh by the way Mecoa has some leads on parts but isnt it a site for discontinued and antique engines. Nuff said have a good day Homey.

Dennis


< Message edited by Propworn -- 12/6/2012 2:43 AM >

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