KX Riders

Maintenance & Technical => KX250 / KX125 => Topic started by: jabba.rides on July 13, 2017, 06:12:42 AM

Title: Weird engine banging sound
Post by: jabba.rides on July 13, 2017, 06:12:42 AM

I have a 86 kx125 that I got at the beginning of the summer and have not had much time to work on it yet, but am excited to ride it soon. I have done a few thing like clean the carb replace the clutch discs and replace the spark plug. However I recently noticed that the engine makes this weird banging sound. I have a few other issues like the fact that the top end leaks coolant that I recently noticed. However I want to know if this sound is normal and if not what it could be. Any help would be appreciated as I am rather new to this bike and bike maintenance in general.
https://drive.google.com/file/d/0B1Y7U4BU9d14V19FT1ZHaWVGeWs/view?usp=drivesdk (https://drive.google.com/file/d/0B1Y7U4BU9d14V19FT1ZHaWVGeWs/view?usp=drivesdk)

Thanks, Jabba

Title: Re: Weird engine banging sound
Post by: KXDINO on July 13, 2017, 06:02:33 PM

DO NOT start engine , pull top end off and inspect , coolant in the combustion chamber is a major disaster waiting to happen.and needs to be fixed.

Title: Re: Weird engine banging sound
Post by: Rocco H. on August 01, 2017, 10:38:37 AM

Hello. I had the same problem with coolant leaking into the cylinder, took the cylinder head off and put a very thin coat of gasket maker on the cylinder and cylinder head. That stopped the problem.

Title: Re: Weird engine banging sound
Post by: umberto on August 01, 2017, 01:53:58 PM

Coolant leaking indicates a warped head. If you put it on a flat surface, such as a pane of glass, you should be able to see the warpage. I think there may be a guide on here on how to lap your head, I'll try to find it. As for the knock, that sounds bad. I would pull my cylinder off and check your rod clearances. You've most likely got some wear issues and may need to rebuild the bottom end.

Title: Re: Weird engine banging sound
Post by: umberto on August 01, 2017, 01:55:15 PM

Here is a handy guide on how to check rod tolerances if you've never done it before.

http://www.kxriders.com/forums/index.php/board,56.0.html (http://www.kxriders.com/forums/index.php/board,56.0.html)

Title: Re: Weird engine banging sound
Post by: jabba.rides on August 02, 2017, 04:15:02 AM

I took off the cylinder head and put it on a mill at my work and checked the flatness with a dial indicator it seemed to be fine. I've replaced the gasket and it is no longer leaking. I did not see any coolant in the cylinder when I first took it apart. It is still making that weird noise. I wonder if there is something wrong with the kips?

Title: Re: Weird engine banging sound
Post by: Rocco H. on August 02, 2017, 05:20:24 AM

Did you check clearance's on rod bearing's and that stuff?

Title: Re: Weird engine banging sound
Post by: Foxx4Beaver on August 02, 2017, 07:51:42 AM

doesn't sound like this does it? :|

https://www.youtube.com/watch?v=2XjmsMtcbL8