Exhaust pipe to power chamber gasket for '78 CB400TII

1250 Views 4 Replies 3 Participants Last post by longdistancerider, May 14, 2016

case_anomaly

Discussion Starter · Apr 24, 2016

Hi all, I’m looking for some help. I'm trying to find the right part for a 1978 CB400TII. I hope this is the appropriate form section for exhaust questions.

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When I purchased the bike, the PO talked me through the work that he had done already, and the things he hadn't gotten to. He mentioned that there was no gasket between the exhaust pipes and the power chamber. Following a diagram, I ordered [14](#18392-MG7-750 muffler gasket). Well, it arrived and it doesn’t fit. The gasket does not fit inside the power chamber or over the exhaust pipe, and the two are so close together there wouldn't be room for the gasket, anyway.

All I can think is that either the bike deviates from the diagram and I need a different part, the exhaust pipes are not stock, or I just ordered the wrong part all together.

I’ve since searched around and seen a few instances where copper rings have been mentioned as the gasket. I’m wondering what part I really need!

Any advice? Thanks!

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dtsmjr8dan

· #2 · Apr 24, 2016

Welcome to the forum. Great to see another 400 series here. Here's some good reading for you...http://www.hondatwins.net/forums/67...n/16105-basic-checklist-new-you-old-bike.html
Not original mufflers. Those mufflers were made to fit OVER a pipe, not inside one. Either get original mufflers, or you could salvage the situation by getting a short piece of pipe to fit inside of both with two clamps. The mufflers you now have on there would have to be swedged out to fit said piece of pipe. You have the correct gaskets if you had the oem mufflers.

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case_anomaly

Discussion Starter · #3 · Apr 24, 2016

Shoot, that's what I was afraid of! I suppose whichever PO changed the pipes just crammed them in and clamped them down :/

Time to channel my inner MacGyver. Thank you for your help!

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case_anomaly

Discussion Starter · #4 · May 14, 2016 (Edited)

So update, I came up with a sort of solution. The photo I posted further up had the pipe pulled partially out, the two actually fit pretty well, but the sides are not close enough to prevent exhaust from leaking out. First, I used some Permatex High-Temp Copper RTV silicone and ran a bead in the perpendicular spaces of the pipe and power chamber.

Some beads turned out nicer than others....

Then, I wrapped the end of the pipe in two layers of high-temp exhaust tape to build up a seal and keep the silicone from shredding when I put the pipe back in.

When I pushed the pipe back to the stop-ridge inside power chamber, it did make a tight seal, and the pipe sits all the way so that there's no tape showing. I haven't tested it yet, so hopefully nothing melts or burst into flames.

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longdistancerider

· #5 · May 14, 2016

Creativity

Hope it works

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