Author Topic: Cylinder temperature difference  (Read 4846 times)

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Offline Manley

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Cylinder temperature difference
« on: 23 May 2006 at 16:11 »
I have run the engine for the first time after the re-build  :D and after 8-10 minutes of running have noticed that the leading cylinder gets far hotter than the rear cycliner to such an extent that the rear is touchable but the front is not.  I suppose that the rear may get some oil cooling due to the rotation of the crank but it just seems a bit too different.  Confess it might be different when i get moving and some air-cooling takes place but until then..... :frown:
2004 Modified Triumph Thruxton
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Offline Chris

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Re: Cylinder temperature difference
« Reply #1 on: 23 May 2006 at 20:00 »
It is a common misconception that the rear barrel of an in line engine will overheat because it receives less cooling. You have proved the opposite. I do not know which model you have but to help to overcome the problem the early models relying on splash lubrication have an additional oilway in the front cylinder to increase oil supply to the piston and bore. Having said that, the temperature difference front to rear is not usually that striking. Are you sure that the piston in the front cylinder is not running tight or that it is not receiving a weaker mixture? (manifold joint leak perhaps). In any case, it is not a good idea to run an air cooled engine, designed to be cooled by its forward motion, for long periods while stationary. Engines designed by Douglas for stationary use were always supplied with cooling fans. Chris.

Offline trevorp

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Re: Cylinder temperature difference
« Reply #2 on: 23 May 2006 at 22:31 »
another thing to make sure of is that the rear cylinder is firing twins run reasonably running on one cylinder and if the rear isnt firing then the front cylinder is picking up the slack

Offline Doug

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Re: Cylinder temperature difference
« Reply #3 on: 24 May 2006 at 04:15 »
I've seen faulty magneto cam ring housings that caused quite a deviation from 180 degree spark timing. You could have the timing right for the rear cylinder and retarded for the front. A lean mixture for the front cylinder can make a even more marked rise in temperature. Uneven fuel distribution, or as mentioned, an air leak, could be the culprit. But the most like cause is as mentioned by Trevor, perhaps the rear is not doing anything at all but pumping air.  After a few minutes running, you should not be able to touch either cylinder if they are firing. 

-Doug