New to BMW

Discuss all things 1970 & later Airheads right here
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Zombie Master
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Re: New to BMW

Post by Zombie Master » Fri May 05, 2017 11:23 pm

Rob wrote:
Fri May 05, 2017 3:06 pm
And while you shouldn't expect to be doing a complete tear-down at this point, you will probably want to drop the oil pan to clean it out, as well.
Don't forget to clean the oil pick up screen while you there. :)
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Ken in Oklahoma
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Re: New to BMW

Post by Ken in Oklahoma » Sat May 06, 2017 11:30 am

jskafff wrote:
Fri May 05, 2017 6:07 am
Thanks for all the extra tech links. I'm only 26 so online is usually the norm for me. I got then Clymer manual for now and I'm actually kind of excited to go 'old school' and just flip through the manual for the info I need.

Update 1: Engine wasn't turning over from rust and it looks like it's probably just the right cylinder which is a bit frustrating since the left looks pretty good. I started spraying each cylinder down with penetrating oil so I'm hoping I can get it to break free if I spray it every so often over the next week or two while I work on some other stuff. For whatever reason the right side of the bike has way more oxidation. I removed the gas tank and a fair amount of very terribly varnished gas. There's tons of rust so I'm going to clean it and see if I can get it to be usable without having to send it out. Doesn't look like it rusted through at least it just looks like surface rust. The fuel lines basically disintegrated when I took them off (as expected). The left carb came off no problem and looks like it'll be fine with a good cleaning but the right one is completely cemented with white powdery oxidation so I couldn't even get the throttle cable out. Are there any tips to breaking that free other than some penetrating oil and prayers or with it being so bad should I just cut the cable and expect to replace the carb/cable for that side?
I'm not a fan of soaking carbs in carb cleaner. One of my bought-for-parts airheads had evidently been soaked in some kind of cleaner for a long period of time. The plastic plate on the carbs had actually melted! But aside from that I see carb cleaner being ineffective. If you examine the carbs you will see some teeny tiny orifices on both sides of the throttle butterfly. There are other 'drillings' on the carbs. If you examine the outside of the carb bodies you will see casting runners which have been drilled and capped off. By looking at the drillings you can pretty much determine what fuel and what air goes where.

Realistically, carb cleaner and any other solvents has a hard time getting to where the crud is to dissolve it. My approach is to clean the passageways and verify that they are open using a shot of air. You shoot a little spray carb cleaner into an orifice, hold the tip of the air gun to an orifice, squeeze the trigger, and see where the air blows the cleaner out. I try it a few times to give the method a chance of working. But if that doesn't work and the passage ways don't flow air/cleaner I then resort to mechanical means of cleaning the passage ways. My tool of choice is a small length of a thin steel guitar string (little e string). But before I do any probing with that 'scary' tool I take the length of string, cut off the length I want, and then lightly touch the end of the string to a grinder wheel. You're not trying to sharpen the length of guitar string. You're trying to round off the end so the string won't scratch the orifices.

Ultimately I'm able to determine that the passage ways are going to deliver the fuel (or air) as intended.

This approach is much more satisfying to our 'mechanic' frame of mind that dunking the carb parts into an ultrasonic cleaner or bucket of carb cleaner, and waiting and wondering.

Plus you end up with a better understanding as to what goes on within the carb body as the carb does it's 'thing'.

There's no such thing as too many airheads

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Zombie Master
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Re: New to BMW

Post by Zombie Master » Sat May 06, 2017 1:15 pm

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Re: New to BMW

Post by Rob » Sat May 06, 2017 2:16 pm

Does anyone have a favorite non-metal probe for these passageways?
I thought I had heard this discussed once.

I wonder if lawn trimmer cord would work? I believe it comes in different diameters.

Or was it solid copper wire? Any metal that is softer than the casting.
Rob V

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Re: New to BMW

Post by SteveD » Mon May 08, 2017 10:33 am

Fishing line, spray some cleaner thru the orifices to soften the crud first. Run the line up and down a number of times, then spray again. Watch for junk coming out, then clearer fluid.
Cheers, Steve
Victoria, S.E.Oz.

1982 R100RSR100RS supergallery.
2006 K1200R.

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Re: New to BMW

Post by jskafff » Sat May 13, 2017 9:21 pm

Update: Got the seized piston free from the cylinder with a lot of patience, PB blaster and Maeve mystery oil haha. And the piston actually cleaned up really well. Almost all of the corrosion was just surface crap so I got like 99% of it off. Same for the cylinder. The valve seats definitely need to be cleaned up though I had a harder time cleaning the gunk off. Going to have my machinist inspect everything but so far me and a few car tech friends of mine think I should be able to get away with just honing it. Crossing my fingers that's it because then I'll just need get the cylinders honed, the right side head cleaned up, and new rings rather than worrying about boring it and finding new pistons/rings. I've been keeping my expectations low and so far I've been surprised every time I look at another part of the bike haha

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