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Which crankcase sealant?

Hi. I’m just starting the post-blowup rebuild of my Dommie 99 engine. I’ve always used Permetex Motoseal to join crankcase halves together and I’ve never ever had any leaks. The only trouble is I can’t get it in the U.K. any more. There’s plenty in the States but postage is horrific. Motoseal isn’t a silicon-based sealant - it’s more like a thin paste that sets semi-hard. The only Permetex I can get now is an RTV silicon one called Ultra Grey - I’m not sure that RTV is a good solution for joining crankcase halves. I’ve got Wellseal but I’m not sure if the hot oil and vapours will dissolve that.

Does anyone have recommendations for what I can use?

Thanks

Regards

Tony

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Tony; I use Yamaha's Yamabond. I like it because I can thin it with MEK and paint it very thin with a stiff bristle brush. It also cleans up nicely with MEK. 

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Hi Tony,

Loctite 5660 is similar to 3-Bond/ Honda/ Yama/ Kawabond and is often easier to get. It is an aluminium grey silicon sealant that simply works. I use it on all my engines and they don't leak. 3 of them have wet sump lubrication too.

Hope the rebuild goes well. 

George 

 

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Always works for me. The cam cover on my alternative Honda 250 is notorious for oil leaks but wellseal has sealed it completely.

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Thanks everyone. I discovered a Threebond variant that is supposed to be the equivalent of Yamabond so I’ve decided to give that a try. It’s not cheap at £20 a tube but its formula seems very much like the Permetex that I used to use. George, I want to stay clear of anything silicon-based just in case small ‘strings’ get squeezed out into the crankcase and break off leading to them ending up in the oil and oil pump.

Ian, I’ve had mixed success with Wellseal on my timing cover so don’t want to risk it on the crankcase as I don’t fancy taking the engine apart again once I’ve put it together this time.

Regards

Tony

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A respected bike engine builder of my acquaintance uses basic clear silicone RTV. 

I have used this for my restoration on all my sealed engine joints (with or without gaskets) apart from the head gasket (blue hylomar) and it works well with no leaks.

Easy, cheap and simple to use. It may even have solved my kickstart shaft leaky X ring (fingers crossed).

 


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