Seven Fifty cafe-racer. Exhaust downpipes.

Looks like I am knocked out by flu or cold at least for a few days… But show must go on, so here is this post about exhaust system of my Honda CB750 café-racer project.

As original exhaust of my Seven Fifty was too damaged the first real version of exhaust downpipes was in fact a set of pipes from Honda CBX750.  I bought it with lot of other parts from CBX750 in the Spring’ 2016, but about this I’ll write later, when it’ll be a time to talk about engine works.

img_5479So I got a set of CBX downpipes but I wasn’t satisfied. The point of dissatisfaction was an asymmetry of first and fourth cylinder pipes. Firstly I noticed this asymmetry on Seven Fifty pipes but thought that was a result of first cylinder pipe damage.  Turned out, this is a feature of CB750, CBX750,  CB700 original downpipes so roots of this question  originated in 198*… And I see no reasonable explanation for it.

Here is a picture which better than any words explains the matter:

img_8003Upper pipe is 4th cylinder pipe and lower is the 1st. The difference in length is quite obvious.

As this downpipes are two-layer pipes (pipe in pipe) there was nothing I can do to fix this asymmetry.  This two-layer pipe design which decreases real diameter and thereafter pipe throughput was also an additional reason to look for other downpipes.

img_7991In the beginning of the Autumn I   found what I wanted.  That was complete 4in1 exhaust for Seven Fifty, it was made for internal Japanese market by local Japanese manufacturer, but came to Ukraine with imported motorcycle. One of the bike owners replaced it by stock exhaust system years ago and in such way this exhaust popped into sale exactly when I needed it so badly.

I was a bit excited after I bought it, so I cut off header pipes right after I brought exhaust in my garage and there is no photo of that exhaust before cutting or in process.

The downpipes I got were made of steel, so there was no problem with their modification. The advantages were in their lengths which allowed me to move mufflers further backward and in one layer design, which has better throughput.

The only question I had after modification was the downpipes coating. I read a lot about exhaust painting and coating and finally decided to coat my Honda CB750 pipes in ceramic.  There is only one company in Ukraine  providing such services and when I called them they told me that they are out of stock due to lack of materials so I had to wait  for around a month. I decided to wait.

You might have seen   the pictures of exhaust after modification, but before coating in one of my earlier posts, but as for now I have no ability to reshoot photos of motorcycle with coated pipes, let them  also be here:

img_6979 img_6836_1A week or so ago my waiting ended and downpipes were coated. They look great I suppose:

img_7794 img_7824 img_7828Looks like original coating of these pipes was also ceramic, so I do hope  new coating shall be as good as the old one, and that was many years ago when it was coated first.

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