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Old 06-22-2013, 05:30 PM   #1
Kspit OP
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Location: Oakland, CA
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R100 knock on acceleration

I have been doing ages of reading, trying to figure out where to start. There are so many experts here, I would love someone to weigh in on my story!

So I got this /7(first airhead, I am a K75 guy I guess... :P) And it had been sitting for 3 years or so. New battery, adjusted the valves, cleaned the carbs, new gas(and a gas tank clean) and she fired right up! I rode it around maybe 150 miles and drained the oil and did an oil filter change. I used a new spacer and o ring, I installed it all the way I took it out, The white o ring had even compression on either side, and was reinstalled with the same filter plate gasket! Rode it around for a few weeks with no problems at all, clicked around like a happy little airhead should!

So now to my knock story... I was on a ride with some friends. Entered a tunnel, did a nice pull in 2nd into 3rd, reved it out pretty nice, probably the highest I have had it revved out before, but shifted well before 7000 RPM. On the run down in 3rd gear I heard a loudish knocking that wasn't normal from the right side(seemed louder at that side). The knock only happened on acceleration in low RPM's, Nothing at idle, or off of idle, only really under load and moving. If i kept the throttle in an even position, holding speed for example, no noise at all, but if I rolled into it to speed up a tad, i would get that loud tappet noise. If I kept the RPM's high I wouldn't get any clunky noise either. Finished my ride, I figured if it was going to die, it would, but it didn't. Maybe rode it 75 miles that way, keeping off the noise as much as I could.

The next day I went to ride it to check on the noise, and it wasn't there at all, until the oil got warm. I didn't ride it around long enough to get it very viscous, but I did get it to clunk a bit after warming it up a bit.

Everybody here says rod knocks are most apparent at idle, and once you are off, they are quiet. But even when I was on my ride, and the oil hot, it was still quiet at idle, only under load and acceleration. I tried getting in there with a screw driver to listen in, but couldn't hear anything out of the ordinary while it was idling or revving in neutral, so I need to dive into the motor and find whatever is wrong. The noise for sure was coming from at least the same plane as the bores, maybe it could be a slack timing chain? I have maintenance records for a LONG time from this bike, and don't see any mention of the timing chain being replaced. The bike has 67,000 miles on it.

I would love some input, but my idea right now is to remove the valve covers, make sure something didn't back off? maybe the high revs knocked a rocker lose? if not that, get an oil pressure gauge and check my pressure. after that drain and strain the oil, and inspect the filter; then maybe check the timing chain before I remove the jugs?

Thank you for reading and I appreciate all input!
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Old 06-22-2013, 05:41 PM   #2
Kt-88
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I'd love for you to find a loose rocker. Here's hoping.
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Old 06-22-2013, 05:50 PM   #3
dmftoy1
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Join the airheads mailing list a micapeak.com and post there, a lot smarter guys than me on there.

Good luck,
Dave
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Old 06-22-2013, 05:50 PM   #4
Stan_R80/7
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Tearing into the engine is one option, but trying some simple tests are where I would start:

1. Check the timing, make sure it shows full advance 'F' at ~2600-3000 rpm.
2. Run some higher octane fuel - add some octane booster to the fuel.
3. Examine the plugs and see how they look.

Ride the bike some and see when the knocking can be make to recur repeatably. Take note of the conditions when the knocking starts and stops and then ask about what could be causing the problem. Good luck!
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Old 06-22-2013, 05:51 PM   #5
disston
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Check the rockers certainly. Good chance there I think.

Now back to your story. You changed the oil. I hope you put Dinosaur 20W-50 oil in it, And for that matter it should be one of the oils that we are pretty sure have ZDDP in it. If you have not read up on the oil story in older machines get busy and Google it. We have done the whole nine yards here at AdvRider numerous times and it gets boring.

What kind of oil did you use?
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Old 06-22-2013, 06:01 PM   #6
disston
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Quote:
Originally Posted by dmftoy1 View Post
Join the airheads mailing list a micapeak.com and post there, a lot smarter guys than me on there.

Good luck,
Dave


But Dave, you have given up before we even started.
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Old 06-22-2013, 06:10 PM   #7
Kspit OP
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Howdy! Thanks for the replies!

I did change the spark plugs out, they were NGK 5534's. Oil was Castrol 20w50 dinosaur juice, did not add any ZDDP additive, I went in originally for some Diesel oil, but they did not have the weight I needed at the local parts house. California 91 octane is all I have run in it since I bought it.

I will check my timing. I am fearful; and have already accepted I may have destroyed a bearing, but it is worth a check. I definately gave it a few good revs before this, maybe not this fast in 2nd gear, but Who knows. The bike was really well maintained until it sat for 3 or 4 years so I guess it could be a multitude of things due to sitting, but in my once over it all seemed fine!

Here is to hoping it is a valve rocker, but my luck never turns out that way :P I am a bit nervous to ride it anymore just because I do not want to do any more potential damage to the crank, but I may take it for a spin tomorrow and see if I cant get a recording/localise the noise with a screwdriver or whatnot.
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Old 06-22-2013, 06:15 PM   #8
disston
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Not riding is a good idea.

Oil sounds fine.

Don't know about those plugs but this is not a spark plug noise.

Timing at full advance is worth checking. Have to rev engine to 3K to reach full advance.

It a bearing and from the sound you describe most likely is a rod big end bearing and they are easy to replace.
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Old 06-22-2013, 07:01 PM   #9
Stan_R80/7
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Tearing open and unfolding the oil filter will show if bearing material has been removed. The airhead email list on micapeak.com has guys such as Robert Fleisher (i.e. Snowbum), Tom Cutter, Anton Largiader, and Joe Cuda (not so sure about Oak Oakensen) and many others that can be asked about the noise. I am sure they can give you some guidance. Generally, the lower end on airhead engines is fairly bulletproof. Good luck!
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Old 06-22-2013, 07:02 PM   #10
Kspit OP
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Advance was fine. I started it and checked it in under 30 seconds. I really just wanted someone to tell me it was a rod bearing. I'm going to drain my oil and check for metal, and do an oil filter analysis, and check the valve covers tonight, as soon as i can get my hands on an exhaust wrench I'll start removing the jugs. Maybe some pictures will come!

Wish me luck airhead gods!
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Old 06-22-2013, 08:42 PM   #11
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Well, Tried to get my oil pan off, man shes stuck on there, gonna have to bust out the heavy artillery tomorrow, but I did cut open my oil filter and I found this!

http://imgur.com/vG5jRks

http://imgur.com/Ry1x0KG


Some delicious bearing in my filter. Yummmm

If I can get to an exhaust nut wrench tomorrow maybe I'll be able to check my bearings out as well! Hopefully the crank isn't scarred up and this is a "relatively painless" boxer refurbishment.

edit, holy shit, giant resolution. I'll turn those into clickable links :X
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Old 06-22-2013, 08:55 PM   #12
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Heating the oil pan at the gasket area helps. Most say it is safer to use a heat gun. I use a propane torch. I use a large blade screwdriver and then a putty knife sometimes to pry with. But of course don't dent the oil pan.

You may want to work on one side at a time but I do think that both should be done. Of course getting to the side where the noise was loudest may tell the story.

These events often come out OK.

Good Luck.
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Old 06-24-2013, 09:43 AM   #13
Kspit OP
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Good morning all!

So Not much has gotten done, been searching for an exhaust nut wrench, and I found one I can borrow today, along with a connecting rod socket so I can inspect my crankshaft and see how big my bill is going to be for this project!

I did end up getting my deep sump pan off, was cool to see my oil pan for my German motorcycle was made in the USA! Did put a little knick in the mating surface, but will make it better, nothing to worry about! The propane torch did the trick, thanks disston!

Everything looked normal in there, no chunks of metal or anything. I was nervous at first but all of the dots were just casting marks. I may strain my oil I drained tonight but i feel like all of the bearing material made it into the oil filter, which is a good thing I guess. Oil pickup looked nice and shiny and firmly attached. I may be able to get a gasket from BMW SF or BMW of San Jose, but I don't think anything bad will happen with it just tacked up to the case for now. Good opportunity to clean it all up!

I do have a Haynes manual someone let me borrow, so with the power of this forum, the rest of the internet and that book I should be able to disassemble the top ends tonight depending on how lazy I feel.

Thanks again for the words of wisdon, hopefully more pics tonight
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Old 06-24-2013, 07:02 PM   #14
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Change the oil and filter and ride....
Report back in the morning.
Put some fresh gas in there.:
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Old 06-24-2013, 08:04 PM   #15
Kspit OP
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Well, I was rather motivated. Had my borrowed exhaust nut wrench. then this happened.



Shucks. I'll have to go get my friends, and this time not destroy it. She was on there nice and firm too, oh well. I wanna tear this sucker apart so bad! Gotta fix her up before all of my sunny summer is done with

And like every good airhead. She even marks her territory when her oil is drained. good girl.

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