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Author Topic: Changfa 1115 knocking  (Read 2839 times)

Mike72

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Changfa 1115 knocking
« on: August 29, 2023, 10:43:55 PM »
Hi everyone, new to the forum and excited to learn about these very unique engines.  I just acquired a Changfa 1115 with an ST-12 head from an estate sale.  Brought it home and surprisingly it fired right up.  Being unsure of the grade and age of oil that was in it I drained it after running for about a minute.  Replaced with straight 30 weight.  Engine starts right up and seems to run fine aside from a terribly disconcerting knocking sound.  I know these engines tend to be a little noisy but this sounds downright terrible.  Loudest when operating at the “start” rpm but definitely still sounds terrible at the 1800 rpm operating speed.  Anything I can do to confirm
If this is normal or not?

38ac

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Re: Changfa 1115 knocking
« Reply #1 on: August 30, 2023, 12:20:34 AM »
Impossible to say without actually hearing it. The direct injection models are definitely noisy, my 1115 sounds like it is being hit with a 2 lb hammer when running at lower RPMs but less so at generating speed. 
If you leve the decomp on and spin it over does it knock while cranking? One easy check is to run it up wide open and quickly move the fuel lever to stop. If it keeps knocking as it slows you problems inside.
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Mike72

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Re: Changfa 1115 knocking
« Reply #2 on: August 30, 2023, 12:32:56 AM »
The knock is definitely at its worst when at “start” rpm.  Becomes quite loud as you increase the rpm and then quiets down a bit once the commanded rpm is reached.  Very little knocking as the rpm is reduced until it “catches” at the lower rpm. Also fairly quiet when shutting down and doesn’t seem to knock while cranking with the decompression valve held.
« Last Edit: August 30, 2023, 01:40:47 AM by Mike72 »

38ac

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Re: Changfa 1115 knocking
« Reply #3 on: August 30, 2023, 10:58:25 AM »
Sounds like everything is OK.
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Mike72

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Re: Changfa 1115 knocking
« Reply #4 on: August 30, 2023, 03:35:19 PM »
Here is a video of it running at low RPM

https://youtu.be/iECmIm1CxKE?si=6uWfUxgdxQex60vJ

sirpedrosa

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Re: Changfa 1115 knocking
« Reply #5 on: August 30, 2023, 06:06:42 PM »
Hi Gentles

Im with Butch. Direct injection. But you can take a look at injection point, it could be a bit earlier.

But with no load it sound ok at 1st glance.

Cheers
VP
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Mike72

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Re: Changfa 1115 knocking
« Reply #6 on: August 30, 2023, 06:27:53 PM »
Thanks for the feedback.  Here is a video of it running around 1800 RPM.  It should be noted that the fuel being used in these videos could potentially be quite old.  I will be draining it and replacing with new later today.

https://youtu.be/r8AHbwl7Vzc?si=-X6_1j3BD2MjGpXM
« Last Edit: August 30, 2023, 06:35:05 PM by Mike72 »

old seagull man

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Re: Changfa 1115 knocking
« Reply #7 on: August 31, 2023, 01:08:50 AM »
Sounds no worse then mine.

Mike72

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Re: Changfa 1115 knocking
« Reply #8 on: August 31, 2023, 02:48:27 AM »
Hi Gentles

Im with Butch. Direct injection. But you can take a look at injection point, it could be a bit earlier.

But with no load it sound ok at 1st glance.

Cheers
VP

How is the ignition timing adjusted and verified on these engines?  Don’t see any mention of it in the manual.

38ac

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Re: Changfa 1115 knocking
« Reply #9 on: August 31, 2023, 11:08:09 AM »
The pump is timed by the number of shims under it. More shims retards, less advances.
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Mike72

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Re: Changfa 1115 knocking
« Reply #10 on: August 31, 2023, 01:59:38 PM »
The pump is timed by the number of shims under it. More shims retards, less advances.

Am I correct in assuming that this timing is fixed through the entire operating range of the engine? Optimized for around 2000 rpm?

veggie

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Re: Changfa 1115 knocking
« Reply #11 on: September 02, 2023, 06:52:03 PM »
The pump is timed by the number of shims under it. More shims retards, less advances.

Am I correct in assuming that this timing is fixed through the entire operating range of the engine? Optimized for around 2000 rpm?

You are correct. There is no timing advance/retard for various RPM's.
Your engine is a "ZS" and is direct injected.
That engine sounds quite normal in the video.
Other things that can be construed as abnormal noises are the gear lash in these larger Chinese engines.
Due to having straight cut gears with lots of lash, the Cam, Counterbalance, and Start shafts, have a lot of gear clatter. And that too is normal.
« Last Edit: September 02, 2023, 06:53:37 PM by veggie »
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38ac

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Re: Changfa 1115 knocking
« Reply #12 on: September 02, 2023, 08:48:23 PM »
Yep Veggie, I forgot about the gear noise. My PowerMart branded  1115 had considerable gear noise when new. Now with about 400 hours the gears have quieted considerably.

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keith71

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Re: Changfa 1115 knocking
« Reply #13 on: September 02, 2023, 10:01:03 PM »
Also maybe double check that the flywheel nut is properly tightened.. 

And also the nuts that hold the pulley on to the flywheel.
If either of these have loosened a bit, it will make some pretty loud knocking..

But as others have said these engines knock during startup to full speed..  Nature of the beast with these engines.
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Mike72

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Re: Changfa 1115 knocking
« Reply #14 on: September 03, 2023, 02:01:27 PM »
Thanks everyone for your feedback.  Much more enjoyable tinkering with this thing when I know the rod isn’t going to fly out of the block. Next thing on the to-do list is to better understand this hopper cooling system.  When using an infrared thermometer, what temps should I be seeing around the exterior of the cylinder head and cylinder?
« Last Edit: September 03, 2023, 02:12:42 PM by Mike72 »