Author Topic: Engine knock  (Read 2111 times)

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Offline connie_rider

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Re: Engine knock
« Reply #50 on: September 14, 2019, 08:14:56 pm »
I don't think you ever determined if the sound is at the top or bottom of the engine?
Should be EZ to hear. Just move around the engine and listen.
If not, {you can use a piece of water hose as a stethoscope and} listen to various places on the engine to find the loudest .
The recording does sound bad, but you might get lucky and all that is bad is a valve adjuster that has backed off. {as m in sc suggested}
If it's that, it's a relatively EZ fix.

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Offline Holliday

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Re: Engine knock
« Reply #51 on: May 11, 2020, 05:39:42 am »
So a update on this thread I threw a rod on piston 1 I ordered a replacement engine that is being installed my only worry is the compression is 125 on1 and 3 and 150 on 2 and 4 when I found it my mechanic said to get it but when it arrived he said that the compensation was to low any thoughts

Offline Bud

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Re: Engine knock
« Reply #52 on: May 11, 2020, 09:52:07 am »
Unless you bought the replacement engine to start working on, I'd send it back and make sure that the next one was tested for proper compression before purchasing.  Would be interested in hearing where the replacement engine came from as well as
 age, miles and price.  Did you and the mechanic know these compression numbers before you bought it?
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Offline Daytona_Mike

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Re: Engine knock
« Reply #53 on: May 11, 2020, 01:09:00 pm »
So a update on this thread I threw a rod on piston 1 I ordered a replacement engine that is being installed my only worry is the compression is 125 on1 and 3 and 150 on 2 and 4 when I found it my mechanic said to get it but when it arrived he said that the compensation was to low any thoughts

Even more important than a compression test  is a Bent Rod test. These engines have the propensity to bend a connecting rod due to a hydrolock event. The connecting rod can be slightly bent  and cause a small loss of compression. Most owners are not aware they have a slightly bent rod and the engine runs fine but the engine  is a ticking time bomb..  Make sure you have a Bent Rod Test done. It is just as important and/or more important than a compression test. Your replacement engine might have a bent rod. If it passes the Bent Rod test then usually all that is wrong with the engine is the valves maybe too tight or there is carbon buildup on the valves  both of which will cause a loss of compression.


« Last Edit: May 11, 2020, 01:15:06 pm by Daytona_Mike »
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Offline Bud

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Re: Engine knock
« Reply #54 on: May 11, 2020, 05:48:50 pm »
So a update on this thread I threw a rod on piston 1 I ordered a replacement engine that is being installed my only worry is the compression is 125 on1 and 3 and 150 on 2 and 4 when I found it my mechanic said to get it but when it arrived he said that the compensation was to low any thoughts

Even more important than a compression test  is a Bent Rod test. These engines have the propensity to bend a connecting rod due to a hydrolock event. The connecting rod can be slightly bent  and cause a small loss of compression. Most owners are not aware they have a slightly bent rod and the engine runs fine but the engine  is a ticking time bomb..  Make sure you have a Bent Rod Test done. It is just as important and/or more important than a compression test. Your replacement engine might have a bent rod. If it passes the Bent Rod test then usually all that is wrong with the engine is the valves maybe too tight or there is carbon buildup on the valves  both of which will cause a loss of compression.
I had the same thoughts, but the compression was the same in pairs.  My memory sucks, but will hydrolock bend 2 rods ie 1 and 3 or 2 and 4 equally?
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Offline Victor Salisbury

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Re: Engine knock
« Reply #55 on: May 12, 2020, 10:13:53 am »
A bent rod is not the only causal item for low compression. 
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Offline Bud

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Re: Engine knock
« Reply #56 on: May 12, 2020, 11:28:28 am »
I understand you can have crusty valves or ring issues.  Is it just coincidence that 1 and 3 have the same compression of 125 and 2 and 4 have 150?  Did someone adjust the valves improperly and end up like that?  Trying to understand those matched pairs of numbers.
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Offline connie_rider

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Re: Engine knock
« Reply #57 on: May 12, 2020, 05:30:29 pm »
Before doing anything, check for bent rods.
ie; If bent, not worth pursuing further.

Yes; It is possible to bend 2 rods.

If not bent; I would first suspect; valves are not sealing properly.
Either valve adjustment or carbon build up on valve seats.
Being paired, I would look closely at valve adjustment.

Ride safe, Ted
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