got the R90 out in the sun

[8ninety8]

Nothing else to do this winter, knew I had to get new guides sooner or later, if anyone wants to look at an old set of seats and valves from a 900.

I was expecting recession. Looks like a valve job with new guides should get by for now. Don't think this needs new valve seats? Maybe new exhaust valves depending on what the tec says? Awhile back, somewhere, somebody said the older valve seats presented no problem as to the use of unleaded gas? Definitely oily.

[jgr451]

Imaginative build up to a very nice bike.

[mymindsok]

Nothing else to do this winter, knew I had to get new guides sooner or later, if anyone wants to look at an old set of seats and valves from a 900.

I was not expecting no recession. Looks like a valve job with new guides should get by for now. Don't think this needs new valve seats? Maybe new exhaust valves depending on what the tec says? Awhile back, somewhere, somebody said the older valve seats presented no problem as to the use of unleaded gas? Definitely oily.

So whats up with that valve and seat?

Maybe its a poor photo but that valve appears to be recessed and the seat looks narrow. OTOH, I ran a set of R90 heads for huge miles and 10+ years and still had good seats.

I'm also curious about why you installed a second lower triple clamp. I've never seem that before!

[8ninety8]

But it looked to me, as compared to other recessed valves, that this head has virtually no recession in the exhaust valve. After they're cleaned up and measured I'll probably get the bad news. The guides are shot. Time to find a good shop after Xmas and spend some cash.

The only thing about a second lower clamp is it reduces the leverage on the spindly forks tubes. First saw it in Dec. '83 on the B & S Pridmore superbike Daytona winner, restored by Armstrong, and wondered WTH it was. And I had an extra laying around.

Saw it again on a tricked out 750 by some guy, in the News, can't remember which issue. May lose a little fork travel, but with stiff springs and bottoming springs, last summer, didn't bother me at all.

[8ninety8]

Just another shot of cylinderheads, except these didn't need valve seats at 46K, or, I can't believe it, valves and guides. That's what the expert said. He said if I wanted to spend 700 bucks I could, but it would be wasted. Needed the cylinders honed with rings and a new valve job. Polished the pistons up yesterday. Winter is flying by. On a roll, guess I'll go buy a lotto ticket.

[toooldtocare]

Nice, look like they just came out of a machine shop.

[8ninety8]

Didn't realize it, but the technician decked the heads, flattened'em out, which with stock base .5mm shim/gaskets removed should give a little bit more CR. Can't wait for warmer climes so I can break in rings. Goin dry this time, with maybe a squirt of LPS-1 before start up. Can't git that red 90S out of my mind.

[8ninety8]

Here's a look at aluminum venturied inlet manifolds, 38 to 35.25mm, as I radiused the inner edge.

[toooldtocare]

Can't git that red 90S out of my mind.

Guess you saw the 77RS on Ebay today? http://cgi.ebay.com/ebaymotors/BMW-R...t_12568wt_1296 I can't get that one out of my head either.

Your heads look nice. Hope for an early spring to break in those rings.

[8ninety8]

I find the '77 R series the pinacle of development of the 247. If I had room, and the 48 hour rule was applicable, that is what I'd buy. The feds started fooling around with emissions after that, and I'd rather have a toilet between the tank and the intake, a good flush periodically clears the cobwebs. Have never grown to the envelope of the RS fairing, always love the wind on the helmet, elemental reminder of what's going on as speed increases. The red S is one saweet bike.

[8ninety8]

Got the light wrist pins, a mm shorter than stock, go figger, 39.1 grams lighter per side than stock, tapered inside diameter, guess I'll give it try, seem a lot lighter, if it blows up I'll be looking for another old engine. 78.2 grams is a lot of reciprocal weight. Pistons are now with everything included only 1.8 grams difference. Still not warm enough to get out the permatex.

[8ninety8]

Got the rings, are bit tight for the bore, I'm wondering, when filing the gap to spec, what about the length of the spring in the oil trio? It seals nothing, so its gap can be greater than the spec. of .25mm - .40mm? All the spring does is push the two scrapers out to the cylinder?

[toooldtocare]

I never worried about the spring gap as long as there is some. I always thought its purpose was it to keep the two scrappers separate, that is tight in the grove in the piston, not push it towards the cylinder. Anyway, I have had lightened wrist pins in my bike since 85, still has not blown up.

[8ninety8]

Think you're right about the spring, it keeps the two wiper rings positioned, just haven't used three piece oil rings before and it looks sort scary what with it flying up and down at 3500 ft.per minute. Just going to be very careful when it goes back together. Nothing else to do today, 2 degrees outside, thought I'd polish up the exhaust nuts, these things are large compared to the later ones.

[8ninety8]

Ice and snow last night, nuthin else to do, decided to try using 1X42 edge sander with new 120 grit Aluminum oxide belt, instead of buying a specialized ring grinder. And it works like a dream.