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    277° rephase cost VS vibration reduction (2024)

    He passed away several years ago. And he was into low revs when cruising along with low compression etc. as I recall.
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    277° rephase cost VS vibration reduction (2024)

    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.
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    Rephasing, What is it?

    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.
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    700cc kit with a Shell #1 cam in a 78XS650E

    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.
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    700cc kit with a Shell #1 cam in a 78XS650E

    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.
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    700cc kit with a Shell #1 cam in a 78XS650E

    Thanks. So they are a little different, I wonder how that affects performance.
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    700cc kit with a Shell #1 cam in a 78XS650E

    Do you have the specs on the shell #1 cam? Attached are the specs for my cam.
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    700cc kit with a Shell #1 cam in a 78XS650E

    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.
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    700cc kit with a Shell #1 cam in a 78XS650E

    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...
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    Black and White Spark Plug

    Smaller in diameter for sure. I think these are the ones I just put in...
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    Black and White Spark Plug

    Zoom in and look at the lip of the seals. Seems like the ones I took out won't do a good job of scraping oil off the valve stem.
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    Black and White Spark Plug

    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...
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    engine teardown:

    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.
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    OEM Valve Guides

    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.
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    OEM Valve Guides

    What is the difference between part numbers 256-11134-11 and 341-11134-11?
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    OEM Valve Guides

    Going to be using OEM valves. One thing I need to do is if I use stock guides is to shorten them. Interestingly I was comparing dimensions of the Kibblewhites found here https://www.mikesxs.net/valve-guide-exhaust-bronze-xs650-0-001-oversize.html with an OEM guide I have on hand and I can...
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    OEM Valve Guides

    Thanks for that and I guess I'm a dummy for overlooking that information in the shop manual that I have. :rolleyes: So what are the pros and cons between stock iron guides and the bronze ones made by Kibblewhite? Wouldn't the bronze ones wear more quickly?
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    OEM Valve Guides

    Been trying to put together a set of 1st oversize valve guides for a winter project but there appears to be some confusion on part numbers and dimensions. Anybody know where I can find this information?
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    Valve Guide Question

    I thought so at first too. I swapped engines using the same carbs, ign, etc and had a little black on that plug but I cleared it up with fixing the carb bowl gasket and choke. Swapped engines back and the black is back. I had suspected it was oil and gas both so now I'm left with oil.
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    Valve Guide Question

    Pretty weird... I've had valve seals fail from a combination of not enough clearance and too many rpms and the plugs didn't look like that. And I've had excessive oil burning from worn bores and again plugs never looked like that. Only other thing I can think of is a head gasket problem.
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