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Old 04-14-2013, 07:25 AM   #16
Airhead Wrangler
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Maybe try checking oil pressure when it's fully warmed up. If something has a loose enough fit to knock, then I bet it'll be bleeding a fair amount of oil pressure by the time the oil gets hot and runny.
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Old 04-14-2013, 08:05 AM   #17
Jay.T
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Same issue when I installed copper "compression" gaskets. When I would pin the throttle it would ping. It was more noticeable if rpms were low and at least one other condition- bike was loaded with gear, or headed up this hill by my house. If I kept the rpms up, the is wasn't a problem, or I couldn't hear it.
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Old 04-14-2013, 08:17 AM   #18
Plaka
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Originally Posted by Rucksta View Post
Can the big ends be accessed by dropping the sump?
No. You got the cam and the bores for the cam followers in the way. And then the rod bolts face sideways, not down. You wanna get at the conrod big ends you have to go in through the cylinder bore cutouts in the block.
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Old 04-14-2013, 08:22 AM   #19
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Originally Posted by Stan_R80/7 View Post
I have never had a rod knock under acceleration. If the knock happens under light load (i.e. constant speed), or it knocks after the engine warms up when stationary and letting the clutch out with the rear brake engaged - I would pull the cylinders and inspect the rod crank journals. The most daunting part of pulling the cylinders is removing the exhaust if it has not been off in a good while. Inspecting the journals is the only way to know for sure. Good luck!
You do not need to pull the exhaust to pull the heads.

It's worth trying the exhaust nuts with the heads on the bike, and use heat. But if cutting the nuts is in order it's easier to pull the head and do the operation on the bench. Cut the nuts in several places, don't go all the way through so you never touch the threads in the heads and then fracture them.
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Old 04-14-2013, 08:48 AM   #20
Rob Farmer
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I had the same symptoms with this one. Ran really sweet, chattered when changing gear and knocked at low rpm.



Crank was still good though

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Old 04-14-2013, 10:42 AM   #21
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Is this a new rebuild? If so, you'll get a knock if the rods were installed with the pins towards the rear instead of the front.

If old, no you can't get the heads off without taking the exhaust nuts off and at least pulling the headers out of heads.

No you can't get to the rods from the pan..maybe on a pre-69 engine where the cam was still on top but I don't think so.

If the oil pressure stays constant at around 80psi above idle, you've got pressure..if low, suspect the oil pump gears or a clogged oil gallery.

Might as well pull the heads and get to the rods. Bet you can feel some give when you pull on the rod...only takes a little to knock. Pull the rods, measure, balance, assemble.

Chris, if you're in a hurry, I have 3 rebuilt short blocks on the shelf (new chain, gear, seals, clutch pack, etc, sitting on the shelf for exactly this situation. Just swap out the short block.
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Old 04-14-2013, 11:43 AM   #22
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Is this a new rebuild? If so, you'll get a knock if the rods were installed with the pins towards the rear instead of the front.

If old, no you can't get the heads off without taking the exhaust nuts off and at least pulling the headers out of heads.

No you can't get to the rods from the pan..maybe on a pre-69 engine where the cam was still on top but I don't think so.

If the oil pressure stays constant at around 80psi above idle, you've got pressure..if low, suspect the oil pump gears or a clogged oil gallery.

Might as well pull the heads and get to the rods. Bet you can feel some give when you pull on the rod...only takes a little to knock. Pull the rods, measure, balance, assemble.

Chris, if you're in a hurry, I have 3 rebuilt short blocks on the shelf (new chain, gear, seals, clutch pack, etc, sitting on the shelf for exactly this situation. Just swap out the short block.
You should try pulling the heads with out disturbing the header pipes (except the crossover of course, loosen it). Then you won't have to say it can't be done anymore.
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Old 04-14-2013, 01:28 PM   #23
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Tried 2 weeks ago on an R100RT..couldn't pull the heads away from the block while the headers held them in. Had to pull the headers out of the exhaust ports so the heads could be pulled away. Pipes just barely stayed in the collector so easy to reassemble.

The only way I can maybe see this working is to take the mufflers and collector off so the headers just hang from the head.
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Old 04-14-2013, 02:57 PM   #24
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Originally Posted by Beemerguru View Post
Tried 2 weeks ago on an R100RT..couldn't pull the heads away from the block while the headers held them in. Had to pull the headers out of the exhaust ports so the heads could be pulled away. Pipes just barely stayed in the collector so easy to reassemble.

The only way I can maybe see this working is to take the mufflers and collector off so the headers just hang from the head.
What is this "collector" you speak of?

Yeah, the mufflers seem like a good idea, makes a long package to handle otherwise. I don't have things like "collectors" (???) or crossovers. Makes all sorts of things a lot easier. But I've pulled /5 heads with the pipes on. Screwing with the crossover was the only issue.

If the pipes come off easily then of course it's the way to play. But you are pulling the mufflers anyhow unless the headers fall off.
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Old 04-14-2013, 04:01 PM   #25
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Old 04-14-2013, 04:34 PM   #26
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Quote:
Originally Posted by Plaka View Post
What is this "collector" you speak of?

Yeah, the mufflers seem like a good idea, makes a long package to handle otherwise. I don't have things like "collectors" (???) or crossovers. Makes all sorts of things a lot easier. But I've pulled /5 heads with the pipes on. Screwing with the crossover was the only issue.

If the pipes come off easily then of course it's the way to play. But you are pulling the mufflers anyhow unless the headers fall off.
No one said what year/model bike we're dealing with..Around 1981 with the R80G/S and later airheads, the headers went back to a collector under the tranny before heading to the muffler(s). The headers curved under the tranny which made pulling the head off with the header on about impossible. Some early models had straight back header/mufflers with a single or dual cross over which may be what you meant.
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Old 04-14-2013, 04:43 PM   #27
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Originally Posted by Beemerguru View Post
No one said what year/model bike we're dealing with..Around 1981 with the R80G/S and later airheads, the headers went back to a collector under the tranny before heading to the muffler(s). The headers curved under the tranny which made pulling the head off with the header on about impossible. Some early models had straight back header/mufflers with a single or dual cross over which may be what you meant.
My '83 had dual crossovers. Nothing a sawzall couldn't fix.

Methinks the "collector" came in with the monos. Still nothjing a sawsall can't fix. I notice making that thing go away is a popular GS mod.
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Old 04-14-2013, 11:29 PM   #28
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I notice making that thing go away is a popular GS mod.
G/S collectors are extinct.and they self destructed.
This could be part of why its a popular mod.
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Rucksta screwed with this post 04-15-2013 at 04:58 AM
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Old 04-15-2013, 12:10 PM   #29
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Next week I will pull the heads off and check both rods and while I am in there I will go ahead and replace the bearings. The exhaust will come right off as I just installed them. Thanks for all of the suggestions.
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Old 04-15-2013, 01:02 PM   #30
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Next week I will pull the heads off and check both rods and while I am in there I will go ahead and replace the bearings. The exhaust will come right off as I just installed them. Thanks for all of the suggestions.
I just replaced my big end bearings. I must have screwed up with the plastigauge because when I got my new bearings they were exactly the same thickness as the old ones. I mean dead on with a digital mic. And there was only the most trivial scoring in the old bearing too. I could have run them without issue. Grrr...I put the new ones in 'cause I had bought them and labeled the old ones and put 'em on the shelf.

Need a smokin' deal on some R100 big end bearings? Half price of new, precisely the same thickness.
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