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At low revs the vibs in a rephase varies a lot with engine load. Cruising on level road at low revs its pretty smooth and the vibs increase when climbing a hill. With a gearing change cruising at 75 or 80 isn't bad at all. On mine with 40/75 gearing the best sweet spot is from 40 to 55.
So which design point has the potential for the least vibration? I have always thought it would be the 270 because it is better at canceling vibration caused by the reciprocating mass.
I think that makes sense. As compared to my stock motor the modified one has quite a bit more midrange torque. With the stock motor I consistantly found myself running it to higher rpms before shifting.
Did you need to shorten the valve guides with that cam? Even with low profile valve seals I had zero clearance on the intakes before cutting them down.
There is a very noticeable difference in power between a stock motor and my modified motor according to my seat of the pants dyno. BTW I have a stock special exhaust that I modified by cutting it open and enlarging the internal holes. Seems to work well and it's louder than stock but not too loud.
Was looking with great interest at your dyno curves. Except for a rephase mine is similar with 707 cc (was 700 with the same pistons you have) and a similar megacycle cam. With the stock air boxes and kn filtets I also find it runs best with 132.5 mains... I think the kn's don't flow the same as...
Problem apparently solved by replacing valve seals. Took it for a test ride after replacing them and cleaning the plugs and no signs of black deposits after the ride.
The valve seals that were in it were low profile seals from Hoos that I installed last winter. The ones I put in this week came...
If you are just doing the top end you don't have to remove the engine. It can be lifted and then tilted to the left enough to remove the top end. I just did that to replace valve seals.
I've been looking at pictures of these on the web and have noticed a couple differences. Some of them have a shoulder for the inner valve spring to keep them centered and others do not. The ones from Mikes have a groove for an O ring where it fits into the head and others do not.