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gregjet

MT/FZ07 cyl timing and my comments re: phase. Apology

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gregjet
I have made a large number of comments re: problems with exhaust and inlet out of phase overlap problems. I have been seriously misinformed and much of what I have said on this subject is now rescinded.
I had believed the literature that had described the motor as being a 90deg offset firing order  motor. As hordboy ( thank you) pointed out, and I confirmed by checking the valve timing , the motor is way more unusual than that. The cranks ARE at 90deg, but the firing order is a pretty unique 270deg. This gets rid of the problems of intake overlap almost entirely and makes the exhaust phase problems less severe ( I still have to model it but I suspect it now only effect one of the two of the pulse returns).
After the official Yamaha literature describing the yzf125r motor, that I used to race ,as a oversquare motor ( it's undersqure) , I should have been more circumspect.
My thanks to hordboy for the correction.
So in a nutshell : Because of the 270deg offset, rather than 90deg, the 2 into one exhaust is a much more reasonable option.  There is still a phase problem but much less so overall. For the inlet there is no problem.
 
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gregjet
Went researching on the net and Triumph's new twin is 270deg also. Might be becoming more common.

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markstertt
Went researching on the net and Triumph's new twin is 270deg also. Might be becoming more common.
No problem, more than a few guys have put 270* billet cranks in their vintage Triumphs for the better balance characteristics than the 360*. 

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