Author Topic: Crankcase Sealant  (Read 274 times)

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Offline dieseldoc

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Crankcase Sealant
« on: May 10, 2019, 07:41:02 PM »
Why is it some people think RTV Silicone is a 'cure all' for all surfaces.
I have just opened up this American import RD400D for inspection. What a mess! Red silicone sealant everywhere.
Because the last person to do this on this engine, the two halves never clamped together correctly to create the correct clamping force for the bearings and seals. The R.H. crankshaft seal and outer bearing had been turning and there is some wear to the seal area.
The triangular bearing retainer was broken in two pieces. The clutch hub nut was only finger tight, as the locking washer tab had not been bent over on the nut to stop it turning!
I'll be burning the midnight oil on this one.
Yambond was created for a reason. Saying that, I have used Blue Hylomar on a lot of RD engines and that works fine as well.
« Last Edit: May 11, 2019, 09:38:21 AM by dieseldoc »
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Offline 5port

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Re: Crankcase Sealant
« Reply #1 on: May 12, 2019, 08:16:24 AM »
Thanks for posting those.  :)
Overall, liquid gasket is just as specific in its function as mechanical parts.  Unfortunately, the advice on the tubes does not really convey whether you are using the correct/best type for your job, unless you are very well informed.  In many circumstances, different goo's will do a sort-of job where it is non-optimal and, it is your individual choice.   Very generally, quality manufacturers like Yamaha will make the best choice for OE and it is wise to use the same goo or a similar version with the same properties.  ;)  Here is a recent reply I wrote on another thread:
"ThreeBond 1104 is the same as the Yamabond used for the original case sealing.  It really is the one to use for a standard rebuild because of the way it cures to a semi-hard rubber that bonds to the metal surface, has physical strength and is fuel and oil proof.  The RTV alternatives are not as good. Generally, they do not bond onto the metal surface and they are much softer, not really suitable for any pressure joint IMO, I am surprised that you see them so often.  The gooo's like Hylomar and Wellseal are just thick gooey stuff with some solvent that don't really set.  They are approved for some applications but, they are really just thick petrol resistant goo.
Of course, use what you like but, if you need to follow the Yamaha spec, use the ThreeBond 1104/1104NEO."

Like I say, "use what you like" but, the OE is usually the best guide.  Cheers

5port   
5port

Online Barnett

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Re: Crankcase Sealant
« Reply #2 on: May 14, 2019, 10:34:38 PM »
omg!  :o I feel sick. yuck. I am agree with both on this, did use hylomar years ago and never had problems but now am wiser and have deeper pockets I stick to threebond, its great to use as well, a little goes a long way.
Yamaha 1974 RD125 (AS3) fully restored 2018 on road
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Yamaha 1972/3 U.S. early RD350 ongoing project.

Offline ozmadman

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Re: Crankcase Sealant
« Reply #3 on: May 14, 2019, 11:28:24 PM »
Hylomar and Wellseal are a world apart!!  Blue hylomar is thick rubbery gunk that you can roll off with your fingers and which can form snot like blobs which can fall off and block oil ways.  Wellseal is thin sticky toffee like liquid which is put on very thinly with a small brush and which sticks like the proverbial S**t to a blanket and which was recommended by VW for the vertical non-gasket crankcase halves sealant on their air-cooled engines, which is where I first discovered it back in the late 70's.  I will never use anything other than Wellseal ever again as I have never had any leak using it with or without a gasket as for Blue hylomar, it is no better than the old red Hermetite  from he distant past ie: c**p in my opinion
"Tolerance and Apathy are the last virtues of a dying society" Aristotle

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 1960 Model 8 AJS 350cc.

Offline dieseldoc

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Re: Crankcase Sealant
« Reply #4 on: May 15, 2019, 09:02:31 AM »
Depends on which Blue Hylomar you use. Go for the Aerograde product and use a very thin bead. You won't get any spreading out the sides potentially blocking any oil ways.Works for me and does a great job.
There again, use what you are happy with. If you have had a bad experience with certain products, you will never go back to them.

Hylomar Aero Grade is a highly engineered, polyester-urethane based non-setting and non-hardening gasketing compound, for use in the aeronautical industry. Hylomar Aerograde was developed in conjunction with Rolls Royce - Aerospace Division for sealing joints in jet turbine engines. Hylomar Aero Grade can operate at temperatures from approximately –500C to 2500C (-580F to 4820F).
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Offline ozmadman

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Re: Crankcase Sealant
« Reply #5 on: May 15, 2019, 11:19:56 AM »
Thanks for the info, never heard of that one.  I was referring  to the normal off the shelf stuff. Could that be used on a copper head gasket (corret for the bike) as I can't quite seem to get a good seal on my old AJS even though using a pattern composite one seems to work
« Last Edit: May 15, 2019, 11:25:30 AM by ozmadman »
"Tolerance and Apathy are the last virtues of a dying society" Aristotle

Bikes..
 1974 Yamaha RD250B US import
 1960 Model 8 AJS 350cc.

Online Captain Scarlet

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Re: Crankcase Sealant
« Reply #6 on: May 15, 2019, 06:26:47 PM »
I have got some of the Aerograde blue hylomar if you want to try some Paul.You can probably guess where it came from :D

Offline dieseldoc

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Re: Crankcase Sealant
« Reply #7 on: May 15, 2019, 08:18:19 PM »
Have you tried lapping the cylinder head and barrel gasket areas? Also, anneal the copper gasket. It might help.
 
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Offline ozmadman

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Re: Crankcase Sealant
« Reply #8 on: May 16, 2019, 12:10:55 PM »
I have got some of the Aerograde blue hylomar if you want to try some Paul.You can probably guess where it came from :D
Thanks, got a good idea!! Will get back to you once I find the time to have a look at the AJS again.  The composite gasket seems to be holding up ok at the moment after ANOTHER re-torque

Cheers 


Paul
"Tolerance and Apathy are the last virtues of a dying society" Aristotle

Bikes..
 1974 Yamaha RD250B US import
 1960 Model 8 AJS 350cc.

Offline ozmadman

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Re: Crankcase Sealant
« Reply #9 on: May 16, 2019, 12:14:57 PM »
Have you tried lapping the cylinder head and barrel gasket areas? Also, anneal the copper gasket. It might help.
yes to both of those...  the issue is that there is a small oil feed through the gasket up to the head/rockers and a notorious candidate for a leak. it is only about 1/8th an inch away from the barrel spigot so not a lot of material there.  Typical bad Brit design, they tried to solve it with a composite one which works fine but they eventually leak as well but if you can get the copper ones to seal then its good for life!!
"Tolerance and Apathy are the last virtues of a dying society" Aristotle

Bikes..
 1974 Yamaha RD250B US import
 1960 Model 8 AJS 350cc.

Offline dieseldoc

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Re: Crankcase Sealant
« Reply #10 on: May 16, 2019, 03:02:53 PM »
I had quite a few British bikes back in the 1960's / 70's. Never had one that didn't leak oil somewhere!!

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Online Captain Scarlet

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Re: Crankcase Sealant
« Reply #11 on: May 16, 2019, 06:21:52 PM »
Where can you buy genuine Threebond 1104/1104NEO as searches bring mostly America and could it be good to use between the rubber inlet manifolds and barrels as I have dread of them letting in air as they get old,mixture going lean and bang goes the engine. :o

Offline Budgie

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Re: Crankcase Sealant
« Reply #12 on: May 16, 2019, 10:24:49 PM »
Just bought some off eBay... plenty of sellers on there... I always get mine from Rex Caunt Racing... he sells on eBay... always competitive on price and easy to deal with....
HTH.

Online Captain Scarlet

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Re: Crankcase Sealant
« Reply #13 on: May 17, 2019, 11:11:18 AM »
Thanks Budgie,i have just bought some from Rex Caunt Racing,if its the genuine stuff then it must be handy to have in the toolbox. ;)