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Exhaust Joints


Phil_P
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It seems to be common practice to have a sort of ball and socket joint on exhausts, presumably to allow relative movement. These joints are periodically opened up and treated to a coat of graphite grease. I wondered if anyone had tried using silicon sealant on these joints, as it would seem to be ideal, still allowing movement but maintaining a really good gas-tight (and mucky two-stroke oil-tight) seal.

Before you all laugh hysterically and tell me it won't stand the temperature, I suggest you try it out. I've seen it used in garages on cars, and have been using it myself on my motorbike exhaust. The only joint where the silicon won't stand the heat, is the primary head to manifold joint.

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Graphite grease will blow out in one flight. Use Hondabond HT instead but allow it to dry before reassembling to get max life. Use the HT version as it stands for High Temperature. Also use this between the expansion pipe and the muffler. Available from most motocross suppliers. More details are available on a forum search under 'Hondabond'. Also, don't forget to add some protection for the exhaust springs to ensure that in a failure case they can't go through the prop.

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Is hondabond a silicon product? if so you are both saying the same thing.

If not then, re phils suggestion silicon: would that actually stick the halves together and the movement be in the flexibility of the silicon? in that case would you need to offer it together then wait til it sets before putting on the springs to allow a thickness of silicon in the bond?

re v32nb suggestion hondabomd: you say let it dry:- does this "set" or remain tacky for when you put the parts together? If it sets does it remain pliable so then squash together to form a seal when the springs are applied?

I have used silicon on exhaust maniforld to pipe joints in cars very effectively and you can get very high temperature silicon products.

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Sorry, I should have expanded on my reply. Yes Hondabond HT is a silicon based solution. A lot of experimentation has gone into this by the Black Devil group on Yahoo and we found that the best longevity was achieved by coating both sides and then allowing them both to dry (24 hours ideally) before reassembling. This would give 25-50 hours typical operation before needing to be repeated.

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very helpful, many thanks.

I just dold my parajet and I used copper grease on the joint but had to apply it regularly. If Geof is reading this you might want to Hondabond it!

Thank to Phil for bringing up this useful point.

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Up till now I've had success using 'el-cheapo' clear bathroom silicon in a bl**dy great tube from a builders merchant. It's bound to be a lower price than anything Honda Corp are flogging! My thoughts now are to apply a nice thick bead to the joint, then just bring it together and wait till it sets off. At this point, then fit the retaining springs. Hopefully this will leave a nice thick cushion, under compression, allowing plenty of movement and a good seal.

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