How do you make them last?


How do you make them last?

Postby Mechanic » Fri Nov 26, 2004 4:23 pm

I have a set of very good original exhausts for my 1979 Honda. I’m loathe to put them on however as I know how quickly they rot out. Does anyone know of any tricks or tips for prolonging the life of these almost unobtainable items?

A friend poured thinned roofing tar into the second set of pipes for his ’73 CB 750 (the first ones started to break thru and were replaced within a year of the bike being new!!). These are largely still in tact after 30 years, however he was able to do this from new. My pipes already have exhaust deposits, and some rust inside them.
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Postby Mike Barone #123 » Mon Nov 29, 2004 11:16 am

The biggest issue with exhausts is rust through where the mufflers and headers meet.



I don't have an answer for this but often wondered if a small hole there might help out.



Mine rusted through and I had a friend braze them........they look great and since the stockers have that aluminum looking paint in this area ....simply repainting with high temp paint in this area makes the fix unnoticeable for the most part



As far as internal rust............no clue here.....sorry



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why exhausts rust

Postby Mike Nixon » Mon Nov 29, 2004 5:09 pm

The engine produces water, many engineers say at a rate equal to the fuel consumed (i.e. a gallon per gallon). I don't know about that, nor do I pretend to know much about chemistry, but it is clear the engine is a water factory. This moisture is created by combustion, because of the presence of oxygen and hydrogen, and normally is evaporated out of the inside of the exhaust through use. The problem is, OEM exhausts (particularly Honda's) use mechanical baffling as opposed to fabric baffling, making the units heavy and massive. It therefore takes a lot of use to heat up the exhaust enough to evaporate the moisture created by combustion each time the engine is started, and to continue to evaporate the water as the engine is used. Add in the fact that this moisture has acidic components due to the byproducts of combustion, and you have a ticking bomb as far as corrosion is concerned. (Note also that the thinner wall aftermarket exhausts, most of which also use less dense fabric baffling, rust out far slower than the stock system.) The answer? Use the bike as thoroughly as possible each time the engine is started. No short rides -- they're death on the exhaust (as well as other parts), and none of this starting the bike in the garage every so often. Forget that. If it's carb preservation you're after, the only way is to use fuel preservative. Forget also this nonsense about warming the bike up before riding. That also contributes to rusty exhausts because it warms the exhaust system too slowly. The best way to warm up the engine (and exhaust) is by riding the bike. Just postpone the wheelies and burnouts for a few miles. :-) Your exhaust will thank you. I have seen this principle proven among my customers who ride all different ways. The ones who fuss around waiting for the engine to warm up, or ride short trips, replace their exhausts often. The ones who don't, don't. :D
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Postby sixofsix » Mon Nov 29, 2004 11:48 pm

I have to agree with Mike here. I have a 79 CBX with 105,000 kms and an original exhaust. It is used for long trips exclusively. I have owned it for 23 years. Also, I believe a killer for the OEM exhaust, is getting water down inside by rain or car wash spray, and not riding a fair distance to thoroughly heat the exhaust. I have rusted out two other exhausts, by short trips and letting the bike sit outdoors or in an unheated garage. Thus; keep water out of the exhaust outlet by all means, and if it does get in, ride the CBX until it evaporates all water out, even if it is raining all the way to Wyoming! I once rode to Nevada cuz the rain would not quit! Ha!



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Postby Mechanic » Tue Nov 30, 2004 9:42 pm

Thanks for the info folks.

I have heard that longer runs are less harmful as the pipes stay "drier". Wouldn't it be nice if there was some proprietary "substance" you could pour into them to coat the insides. Oh well - just have to leave them under the bed for now. 8)
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