'79 r100rt that's new to me :D

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mawhin
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'79 r100rt that's new to me :D

Postby mawhin » Wed Aug 09, 2017 12:28 pm

So, I paid £2,700 for a '79 red smoke r100rt, and I need somehow to keep track of what I've noticed about it, and what I've done. I'm sorta tinkering with losing the fairing next summer, but perhaps that's not right. Dunno. Let's see if I hate the fairing. Loving it at the moment, apart from the rattling at low revs.

So.

I had a problem first day I tried to ride it, petrol pissing on my right foot, fixed by dropping the float bowl and jiggling the float. The fuel in the bowl looked clean, but had a few drops of water in it. Haven't had the left bowl off yet. Oh, I started without the petrol turned on just before this. Hasn't happened since.

Starts, easiest from cold (10C ambient), on ?full choke?, but that only on the left pot I think, the right one only seems to want to kick in as I ease the choke off.

I usually let her warm for a couple of minutes on a slightly open throttle (gotta love that little friction thing). I usually wait for the engine note to rise before loosening the friction thing and setting off.

Seems a little noisier on the right than the left, and I'm a bit worried that she's too quiet, and she's probably not got unleaded heads, so this weekend I'm planning to check valve clearances and rocker end play.

Choke (enrichener) lever seems to move the enrichener arm on the carbs at the same time and to the same angle, and there's a quiet click from both sides at the same spot.

Lastly, I've not run it hard at all, but on a couple of rides I've noticed some hesitancy pulling hard in fourth at 50. I think, can't be sure. I think I need to go clearances - timing - spark - carbs in that order?

None of this is by way of a question or request, but feel free...

Pics in the next coupla days - it's nothing special, except that it's a smoke red bmw r100rt from 1979. :D

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windmill john
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Re: '79 r100rt that's new to me :D

Postby windmill john » Wed Aug 09, 2017 5:23 pm

Might be worth sticking this in the Airhead tech section.
Hesitant starting on both pots, strip your carbs fully, that's fully inc. chokes and clean; new gaskets, seals etc.
Make sure all jetways are clear.
Then repeat :grin:
Hesitant pulling at speed, check your diaphragms; see above.

Try a winter with the fairing, you'll love it. The buggers do rattle and creak.
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Best roads: 623 Burgos to Santander. A back road to Metz; can't remember which!
Schorsch 1978-80 R65 - bit of a Shetland pony; frisky and naughty.
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CharlieVictor
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Re: '79 r100rt that's new to me :D

Postby CharlieVictor » Thu Aug 10, 2017 8:44 pm

In my experience, if your /7 does not run flawlessly, the basics (before going into dismantling anything) are valve clearance.
Then cable routing and operation, then idle mixture and speed, then carb synch (which will allow you to check if those vacuum ports are properly plugged by the adhoc screws... Don't ask me how I know...)

If that doesn't end up in a perfectly tuned engine, you will want to move further, and start checking your points, can, sparkplugs, coils, lead wires and caps, and possibly a full carb rebuild and ultrasound cleaning.
:smile:
1978 BMW R100S "Naked"
1999 W650 "Twin with a kick"

mawhin
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Re: '79 r100rt that's new to me :D

Postby mawhin » Sat Aug 12, 2017 3:15 pm

Well, that was exciting.

John, I know that eventually all roads lead to the Carb Rebuild Gyratory system, and that I'm going there one day. But I don't feel ready yet. A little more pottering around the estate first.

So me and the streak of uselessness that is my son check our vavle clearances today. Had much trouble working out which cylinder we were on compression for, but I reckoned that the side with no play or movement on the rockers is the other one. So the procedure was, in fifth with the handlebars strapped with a tie down to a site transformer and thus the back wheel off the ground, find OT in the window, and go pushing and pulling at the rockers, and adjust the side that moves at all.

I found I had little to no clearance anywhere. So went round both exhaust and inlets, made a gap, then cranked them down to just before they'd properly grip a feeler at 20 and 15 thou respectively.

Put everything back together, and she starts!! Perhaps better than before, still starts on left pot with choke on and both once the choke's off. Lots more tickety noise, coming evenly from both heads. Only ran her for about a minute. I think that's gone OK.

Had a look at the plugs as well, right looks right as rain, except for a tiny bit of flaking on the insulation beneath the central electrode, left pot has 'carbon deposits'.

Question - I know the gaps are supposed to be 20 and 10 thou, but (a) I think 15 was once recommended for intake, and (b) I don't have a 10 thou gauge on the set. Will I get away with setting the intake gap too wide? I think it should cause the bike to run a little leaner? Not sure.

Also, I suspect the rocker end clearance wants adjusting - I could move it around enough that I could feel it move, and I could easily see the oil film going in an out. Or is that just right? I've got the impression that if I can feel the play there's too much, I should *only* be able to see the oil film move. Have I got that right at all?

Happy days.

Mart

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CharlieVictor
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Re: '79 r100rt that's new to me :D

Postby CharlieVictor » Sat Aug 12, 2017 5:41 pm

You are welcome mawhin.
1978 BMW R100S "Naked"
1999 W650 "Twin with a kick"


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