Exhaust pressure fitting OS 15LA

[Tim Donald]

Today I ran up my OS15La (brand new but quite old) and noticed that the pressure nipple on the 871 silencer was loose.  It looks like somebody has over tightened it or cross threaded it.  It screws in but just keeps turning and never tightens (and leaks when the engine is running).  I'm not sure if it's the nipple or the thread on the Silencer but I expect it's the silencer.  Is there any way to fix this without buying a new silencer?  JB weld maybe?  

[Andy Stephenson]

Tim, drill it and tap it out a size bigger see...

https://www.modelfixings.co.uk/rc_fittings.htm#Pressure Nipple

https://www.modelfixings.co.uk/metric_taps.htm

[Don Fry]

JB weld would probably be good on a two stroke as the exhaust is cooler than a 4 stroke. And probably will stay good. But it’s still only a glue.

Andy’s solution is the engineers solution, done.

 

[Tim Donald]

Thanks Andy / Don.  That is a handy website that I've not seen before.  

[Paul De Tourtoulon]

Why not a bolt on one ?.

[Tim Donald]

Thanks,  that could also work.  

[Tim Donald]

OK I have just established that somebody has put a M3 nipple in but it's not the correct one for the thread on the silencer.  I tried one from a Thunder Tiger pro .46 and it fit's perfectly proving that the thread is ok.  Does anybody know what thread size it is?  It's between M3 and M4 but that's all I know.  I can't see M3.5 pressure nipples for sale so maybe not metric.  I think OS call it a No.7 but don't say the thread size.

[David Ovenden]

I just checked the pressure nipple on my OS15LA exhaust. It's a 3.5mm thread. 

[Denis Watkins]

Checked mine at 3.5mm too

And

The fabric washer fitted prevents the nipple going so far in th at it spins and leaks.

Check for the reddish/ Brown soft washer

[Tim Donald]

Thanks very much David and Denis.  Mine has clearly been pinched and replaced with the wrong one (and there is no washer).  

[Denis Watkins]

Don't want to " muddy the waters " Tim,

But a poll round my club has come back 50/50 on washer fitted or not.

But the washer does seem to solve some of the problem.

[Tim Donald]

Thanks Denis.  Mine is definitely the wrong thread so I will just order a new OS one which will hopefully come with the washer.  

[Paul De Tourtoulon]

If it doesn't come with a washer you can always buy a lathe and make one.

 

 

just being silly, now where did I put that glow plug washer ?.

[Richard Wills 2]

2 hours ago, Tim Donald said:

Thanks Denis.  Mine is definitely the wrong thread so I will just order a new OS one which will hopefully come with the washer.  

I have just had 2 of the no.7 nipples delivered from RCJapan, they do not come with washers.

[Engine Doctor]

Older models had a fibre washer but would often come loose until washer compressed fully. A small drop of threadlock will hold it and should also seal the thread from oil leaks . Personally I'd used a little Aradite Original as this wil make a permanent seal for the nipple. This can also be used to seal the exhaust to engine fitting. Just make sure that the screw threads are lubricated before tightening them. Makes a really good seal and unlike a gasket will only come loose when you want it to.