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Also make sure to check keeper to valve seal clearance with the valve fully opened.

I had that problem a couple years ago. Thans had to come out to replace the gears for first.

He passed away several years ago. And he was into low revs when cruising along with low compression etc. as I recall.

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.

Thanks. So they are a little different, I wonder how that affects performance.

Do you have the specs on the shell #1 cam? Attached are the specs for my cam.

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...

Smaller in diameter for sure. I think these are the ones I just put in...

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.

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.

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

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...

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?

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?