Help me diagnose this engine sound, please. - Wrist Twisters
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post #1 of 18 Old 03-19-2020, 06:56 AM Thread Starter
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Help me diagnose this engine sound, please.

Last year my chain broke while I was riding, which shattered the guard part of the case, but didn’t cause an oil leak. The chain did bind up a bit around the front sprocket, but as far as I could tell it was spinning fine after I removed the chain.

There was a bit of a sound when I ran it with no chain to check for damage, but I as hoping it was just rattle caused by lack of tension. I slapped a new chain and sprockets on hoping for the best, and now I’m experiencing a significant engine rattle. I can’t tell if it’s just cam chain slap or if it’s something worse like rod knock.

Oddly enough, when I shift it into 1st, the noise stops completely, until I let off the clutch, then it comes back and increases with RPMs.

Here’s the link: https://youtu.be/ZVANQxRPOsg

Any suggestions would be appreciated.

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post #2 of 18 Old 03-19-2020, 09:27 AM
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Holy snotbag! I think you may have busted some teeth off on your transmission gears.
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post #3 of 18 Old 03-19-2020, 09:56 AM
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Using logic, if the noise stops when the clutch is disengaged the cause is downstream of the clutch, so no camchain or crankshaft problem. Determining the etiology of the noise is going to take some doing, but is limited to the transmission / oil pump / water pump which at least narrows the focus.

Sound is a good way to narrow the focus further. At idle the crankshaft is turning ~1200 RPM, or 200 RPS (Second). This rotates the clutch at ~800 RPM, or 13.333... RPS (1.52:1 reduction). Counting the cyclic noise in the video against the counter yields a period of 0.5 second. Given that information the task now is to find a transmission component that makes a full revolution at that RPS. Here is a good source of information that can shed some light on the problem : https://www.gearingcommander.com/ It has listings for thousands of motorcycles' drive lines. And there it was: the second gear on the countershaft is twenty six teeth, resulting in a period of 0.5 second. It's located next to the output bearing, which means that when the chain wrapped around the front sprocket the forces flexed the bearing, countershaft, and the engine case enough to damage the teeth then in contact with the matching mainshaft gear, damaging at least two teeth.

I may be off base here, but logic indicates it is a strong possibility. Frankly, I hope I am wrong due to the fact that the engine will have to be partially torn down to effect repair.

Good luck. You're going to need it.

Rob
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If it has already been done, it is safe to assume it is possible to do it.
On the other hand, if it has not been done never assume it is impossible to do it.
------- Rob --------
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post #4 of 18 Old 03-19-2020, 10:38 AM Thread Starter
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Quote:
Originally Posted by robtharalson View Post
Using logic, if the noise stops when the clutch is disengaged the cause is downstream of the clutch, so no camchain or crankshaft problem. Determining the etiology of the noise is going to take some doing, but is limited to the transmission / oil pump / water pump which at least narrows the focus.

Sound is a good way to narrow the focus further. At idle the crankshaft is turning ~1200 RPM, or 200 RPS (Second). This rotates the clutch at ~800 RPM, or 13.333... RPS (1.52:1 reduction). Counting the cyclic noise in the video against the counter yields a period of 0.5 second. Given that information the task now is to find a transmission component that makes a full revolution at that RPS. Here is a good source of information that can shed some light on the problem : https://www.gearingcommander.com/ It has listings for thousands of motorcycles' drive lines. And there it was: the second gear on the countershaft is twenty six teeth, resulting in a period of 0.5 second. It's located next to the output bearing, which means that when the chain wrapped around the front sprocket the forces flexed the bearing, countershaft, and the engine case enough to damage the teeth then in contact with the matching mainshaft gear, damaging at least two teeth.

I may be off base here, but logic indicates it is a strong possibility. Frankly, I hope I am wrong due to the fact that the engine will have to be partially torn down to effect repair.

Good luck. You're going to need it.

Rob


Thanks for the in-depth analysis. I’m fairly certain I was in 2nd gear when the chain R.I.P.’d, so that would make sense. I figured the transmission was fine because when I tested it after installing the new chain it went through the gears normally. Well, at least if I have to tear the engine down I’ll have an opportunity to learn something...
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post #5 of 18 Old 03-19-2020, 10:45 AM
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Bring a dentist along with you when you crack open the lower.
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的 said I never had much use for one.
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post #6 of 18 Old 03-19-2020, 11:34 AM Thread Starter
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Quote:
Originally Posted by Bigdaa View Post
Bring a dentist along with you when you crack open the lower.
Unfortunately my dentist isn’t accepting patients due to the corona virus outbreak. 😂
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post #7 of 18 Old 03-19-2020, 12:18 PM
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Hahahahahahaha! Never let anything take away your sense of humor, including that transmission!

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Never said I didn't know how to use it."
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post #8 of 18 Old 05-31-2020, 03:33 PM Thread Starter
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Turns out the diagnosis on this thread was spot on. Finally got around to opening the transmission yesterday and found 1 broken tooth. Thanks, guys!

https://imgur.com/gallery/1UGg2Jq

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post #9 of 18 Old 06-01-2020, 11:01 AM
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Quote:
Originally Posted by Bigdaa View Post
Holy snotbag! I think you may have busted some teeth off on your transmission gears.
This was a really good call!
Cook yourself another one of those 2 inch thick steaks and have some beerS.

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post #10 of 18 Old 06-01-2020, 01:40 PM
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This was a really good call!
Cook yourself another one of those 2 inch thick steaks and have some beerS.

Mmmmmm mmmmmmm mmmmmmmm mmmmmmm mmmmmmmm mmmmmmm mmmmmmmm mmmmmmm mmmmmmmm mmmmmmm mmmmmmmm mmmmmmm mmmmmmmm mmmmmmm mmmmmmmm mmmmmmm mmmmmmmm mmmmmmm mmmmmmmm mmmmmmm mmmmmmmm mmmmmmm mmmmmmmm mmmmmmm mmmmmmmm mmmmmmm mmmmmmmm mmmmmmm mmmmmmmm mmmmmmm mmmmmmmm mmmmmmm mmmmmmmm mmmmmmm mmmmmmmm mmmmmmm mmmmmmmm mmmmmmm mmmmmmmm!

Come on by. Dinner and drinks are on me!
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post #11 of 18 Old 06-01-2020, 02:22 PM
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Originally Posted by Bigdaa View Post
Mmmmmm mmmmmmm mmmmmmmm mmmmmmm mmmmmmmm mmmmmmm mmmmmmmm mmmmmmm mmmmmmmm mmmmmmm mmmmmmmm mmmmmmm mmmmmmmm mmmmmmm mmmmmmmm mmmmmmm mmmmmmmm mmmmmmm mmmmmmmm mmmmmmm mmmmmmmm mmmmmmm mmmmmmmm mmmmmmm mmmmmmmm mmmmmmm mmmmmmmm mmmmmmm mmmmmmmm mmmmmmm mmmmmmmm mmmmmmm mmmmmmmm mmmmmmm mmmmmmmm mmmmmmm mmmmmmmm mmmmmmm mmmmmmmm!

Come on by. Dinner and drinks are on me!
If I could I would!

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post #12 of 18 Old 06-01-2020, 03:29 PM
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When you are near, come on over here!
Goleta California!!!!!!

的 said I never had much use for one.
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post #13 of 18 Old 06-03-2020, 04:14 PM
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If I could I would!
I'm getting ready to put one on the grill in a half hour.
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的 said I never had much use for one.
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post #14 of 18 Old 06-03-2020, 04:17 PM
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I'm getting ready to put one on the grill in a half hour.
Meanwhile, here in Calgary, the freshly cooked roast beef in our kitchen is near finishing its post oven cook and will soon be carved.
I'm thinking of cutting a slab 2 inches thick and pretending......................

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post #15 of 18 Old 06-03-2020, 09:16 PM
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Meanwhile, here in Calgary, the freshly cooked roast beef in our kitchen is near finishing its post oven cook and will soon be carved.
I'm thinking of cutting a slab 2 inches thick and pretending......................
Do you use a nice creamed horseradish by any chance?.

的 said I never had much use for one.
Never said I didn't know how to use it."
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post #16 of 18 Old 06-04-2020, 06:45 AM
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Do you use a nice creamed horseradish by any chance?.
No I don't.
Generally we season the roasts such that horseradish wouldn't be the best addition.
I do like horseradish though, preferring a good and hot simple ground one.
The creamed ones I've been exposed to can be eaten alone by the spoonful.
I like more edge, but not off scale.

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post #17 of 18 Old 09-18-2020, 03:20 PM
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I was thinking about prime rib and horse radish today and thought of your post.
I found some horse radish with an edge like you were talking about.
The name of it is simple: Atomic
That's it. That's all.
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post #18 of 18 Old 09-18-2020, 04:23 PM
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Quote:
Originally Posted by Bigdaa View Post
I was thinking about prime rib and horse radish today and thought of your post.
I found some horse radish with an edge like you were talking about.
The name of it is simple: Atomic
That's it. That's all.
I can just imagine what that must be like!
So far, the hottest I have ever had was home made stuff we used to get from Mennonites in the St. Jacobs area of Ontario, circa 60s into the 70s.
(Whenever we make a trip to Ontario, we still go to the same two farms for summer sausage and maple syrup.)
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