Author Topic: left hand cylinder hotter than right hand  (Read 3169 times)

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Offline zorro

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left hand cylinder hotter than right hand
« on: 09 Apr 2015 at 15:39 »
Hi, after engine rebuild on my mk4 the left hand pot is running a lot hotter than the right. Has anyone come across this before? Checked the timing and tappets,seem as they should be by the book.Any suggestions please.

Offline Doug

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Re: left hand cylinder hotter than right hand
« Reply #1 on: 09 Apr 2015 at 19:02 »
Zorro,

It is not clear if you checked the valve or ignition timing (or both). Ignition timing and carburetion can have a dramatic effect on temperature.

Checking the ignition timing on one side only is not adequate. Too many have reported that vagaries in the Lucas magneto cause the timing to not be exactly 180 degrees between cylinders. If the other cylinder is running too retarded, it will run hotter.

With the carburetion, one side could be running too lean, and therefore hot.

Have you re-bored and fitted pistons and/or rings during the rebuild?

-Doug

Offline eddie

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Re: left hand cylinder hotter than right hand
« Reply #2 on: 09 Apr 2015 at 19:39 »
Zorro,
         When you rebuilt the motor, did you fit the camwheels on the correct side? They are marked up 'L' and 'R', but that is as viewed from the front of the motor, so the wheel marked 'L' is actually on the right hand side of the machine, and vise versa. Whilst the gears look identical, one has the keyway aligned with a tooth and the other aligns with the space between two teeth. If the wheels have been swapped over, the valve timing would be far enough out to cause one side to run hot.

  Regards,
               Eddie.

Offline zorro

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Re: left hand cylinder hotter than right hand
« Reply #3 on: 09 Apr 2015 at 20:29 »
Thanks for your replies, I've fitted new rings to the pistons gapped at 6 thou. Almost certain the cam wheels are the correct sides but will check again.I fitted new old stock carbs set both to basic settings.Starts ok and revs easy.But it does concern me the difference in temperature.

Offline zorro

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Re: left hand cylinder hotter than right hand
« Reply #4 on: 10 Apr 2015 at 18:26 »
checked valve and mag timing ok.Tried to richen the hot side carb fitting a90 main jet.Got worse.put back to 80
Would swapping the plug leads prove if one side is running retarded? grasping at straws.

Offline graeme

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Re: left hand cylinder hotter than right hand
« Reply #5 on: 10 Apr 2015 at 22:37 »
I'd be doing a thorough check for any air leaks on the hot side that could be causing lean running. Have you checked the colour of the plugs?

Offline zorro

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Re: left hand cylinder hotter than right hand
« Reply #6 on: 11 Apr 2015 at 21:04 »
The problem was the carbs.I went back to initial settings then adjusted left hand by altering the position of the needle to where it ran evenly and slight rich mixture. Then opposite carb.Seems ok.Thanks for the replies.

 

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