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Oil Leaking from the manifold or Muffler connection - DT1

  • LuckyLuke
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Quick question for someone who might be able to help with this.   I have an oil leak and splattering of oil coming from where the muffler joins to the engine.  I put a new gasket for the manifold but this looks like it is coming from where the muffler inserts in the manifold.   Do I just need to clean this out a bit and get a tighter fit?  Is this normal and should I be thinking of other things that might be going on?

Thanks
05 Mar 2021 09:48 #1

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In my experience, this is rather ordinary.  This can result from running with the choke on a bit too long.

The muffler is sealed to the manifold using a thin, twine-like gasket material.  I make them myself using string and infusing it with permatex high heat orange gasket sealer.   Also, if your springs get old and weak, they can provide less holding power, leading to the leak.  All in all, it is not a serious situation.
You can just call me Dude.
Syracuse, New York
Current bikes: 1973 DT3, 1974 TY250, 1969 Triumph Bonneville, 1975 XS650, 1976 XS650, 1982 XS650, 1983 XS650, 2006 FJR1300
05 Mar 2021 11:22 #2

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There are a few threads on this, and I can't remember if I posted an answer one of your earlier ones or not! 

Anyway, as Dude says, there is a string type gasket in there - this is still available from Yamaha and you get one long piece that you cut to your preferred length, depending upon whether you want one or two diameters worth.

I'm pretty sure that the manifold is actually two pieces that will prise apart with a gentle tap with a wooden or rubber hammer. I would split them apart, clean them, reassemble then fit a new gasket. Photos are attached to illustrate what I mean.

    
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Last edit: 05 Mar 2021 11:38 by Gr8uncleal.
05 Mar 2021 11:37 #3

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  • LuckyLuke
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Thanks for the advice guys.   When I rescued the bike the front fender was full of oil and I thought it was maybe oil shooting out from the head, but now that I changed the gaskets on the head I notice the oil is coming from the manifold.  I did put a new seal between the manifold and the engine although I did not put anything between the muffler and the manifold.   If I am understanding you correctly all I need to do is put some string between the manifold and the muffler with some high temp sealant.   I did have the choke running for a bit and so there for sure was a rich mixture happening as I could tell from the smoke show happening.

Any thing that describes how to wrap the string around the muffler might be helpful otherwise I can do some trial and error....

Thanks again.
05 Mar 2021 13:51 #4

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Luke,This is the twine I used.  I rubbed the permatex into it thoroughly.  I used nylon gloves, very messy.  Then I hung it up overnight to dry. 

Cut just enough for the circumfrence of the manifold, like that picture above. Stuff it down into the manifold sleeve and pack it in there.

   
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Syracuse, New York
Current bikes: 1973 DT3, 1974 TY250, 1969 Triumph Bonneville, 1975 XS650, 1976 XS650, 1982 XS650, 1983 XS650, 2006 FJR1300
05 Mar 2021 14:34 #5

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Main thing is it's going to need the pipe burnt out to dry it right out as gets oil soaked right through as has packing along the walls of the main chamber. 100 mile ride at speed would do it--but, burn out is best. Check the pump setting but is probably just the result of non ideal riding for 50 years. Could premix it on modern oil for a cleaner burn & unhook the pump. Or of course if the pump is set good just an up to date good oil & carry on into the sunset.
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05 Mar 2021 16:09 #6

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  • LuckyLuke
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Hey this is great advice and definitely gives me some stuff to work with.  This site is great with lots of good heads.  

thanks a bunch!  
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05 Mar 2021 21:06 #7

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You should get enough length of gasket to have one attempt at fitting with the exhaust in situ. If still blowing, remove, split and clean manifold and you'll have enough gasket left for another fitment or two.

I only mention this because another member only got a good seal once he had split and cleaned the manifold. Others, though, have got a seal without having to do this. 
06 Mar 2021 00:34 #8

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Yep, also i guess you've found it but there's a compressible gasket that is recessed into the front of the cylinder. That tends to leak as well if re-used. I welded my pipe into the fitting & that fixed the leaking at the string for ever.
06 Mar 2021 00:41 #9

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here's a link to the gasket No11 but interestingly they don't show the string. String was always there in all models so maybe shows up in later year parts pics.
www.partzilla.com/catalog/yamaha/motorcycle/1968/dt1/muffler
06 Mar 2021 00:59 #10

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