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Old 04-05-2021, 05:29 PM
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85 inch Extra 300 Cowl cut with muffler

Newbie here again. Attached is a pic of the muffler and cowl. I cut the cowl for the head for the DA-50. No issues there. The problem I have now is I have a standard bison muffler and I don't see how it is going to fit. There is no way to fit the cowl over the two pipes, regardless of how big the holes are because the lip on the bottom will not clear. The pipes are not too long and would "jut out" an inch or so. Unsure of how to handle this.
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Old 04-05-2021, 05:55 PM
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Guided by JR Propo
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You will need to cut out a good size air exit, Else the engine will over heat.

i would cut out a D shape like this pic, Maybe even a little larger. This will give good cooling exit and solve the Exhaust exit issues as well.
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Old 04-05-2021, 07:45 PM
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That ^^^
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Old 04-05-2021, 08:59 PM
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wrongwayfeldman
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The angle of thoes pipes is enough they will never just drop thru a slot or hole anyway....
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Old 04-05-2021, 11:00 PM
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What Hodge and RC said... Just say that it would slip on with just the holes cut, how would all the hot air escape? You need more exit hole area than inlet hole area or the heat gets trapped.
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Old 04-06-2021, 05:51 AM
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On the 70, I cut the outlet pipes and made extensions from Teflon tubing from McMasterCarr. I put on the cowl and then install the tubes.
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Old 04-06-2021, 06:27 AM
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cowl cut response

While Keith's idea of cutting a large hole is good, there is a lip on the other side that seats into the wooden dowels so I will not be able to "slide" the cowl on since I don't want to cut the lip (structural integrity). I will leave a little fiberglass on the lip end. To be honest, I don't think that may work but I will mess with it today and see what goes.
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Old 04-06-2021, 10:31 AM
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Once the hole is cut you lean the cowl forward to allow the pipes to enter, then you go the other way and seat the cowl.
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Old 04-06-2021, 10:45 AM
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wrongwayfeldman
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I Believe his root problem is the particular pitts muffler he is using has much more of a rearward angle than is necessary for his particular model.
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Last edited by ponyboy082662; 04-06-2021 at 11:13 AM.
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Old 04-06-2021, 06:13 PM
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If you don’t want cut the bottom of the cowl the only way is to make it a split cowl. Plenty of articles on FG to help you do it.
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Old 04-07-2021, 09:35 AM
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Cut Cowl Done

I made it work (barely). I agree with Ponyboy. Cowl is really not made for this muffler. I bought a spare cowl that I have lying on the shelf and will go with this for now, however, will probably get a different muffler. Thanks for everyone's help.
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