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cold lock up


legionnair
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just curious if any one has had a cold lock up.

Loaded the bike outside temp wasabout -3C drove about 20 min and unloaded the bike. Went to kick the bike over and it was frozen like a seized motor. Removed the spark plug thinking it might be full of coolant but nothing. My riding partner then mentioned he had a propane torch after I mentioned it might be a cold lock up. After slowly heating the cylinder on all sides I started rocking the bike and slowly the piston started to move and then was free up completely. Reinserted the spark plug and first kick she flashed to life, let it idle until fan kick on and rode it all day with no problems.

I thought I would just share my story

Dustin

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I had the same happen on my Gas Gas a couple of weeks ago when it was -7 and -8 two nights on the trot. Left it for a week weather "warmed" up tried again and all was good :icon_salut: Luckily i diint have a trial over that weekend.

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just curious if any one has had a cold lock up.

Loaded the bike outside temp wasabout -3C drove about 20 min and unloaded the bike. Went to kick the bike over and it was frozen like a seized motor. Removed the spark plug thinking it might be full of coolant but nothing. My riding partner then mentioned he had a propane torch after I mentioned it might be a cold lock up. After slowly heating the cylinder on all sides I started rocking the bike and slowly the piston started to move and then was free up completely. Reinserted the spark plug and first kick she flashed to life, let it idle until fan kick on and rode it all day with no problems.

I thought I would just share my story

Dustin

Not surprizing. Trials engines run really tight piston skirt/cylinder clearances, in the neighborhood of .0015"/.002". Another good reason why you, on "normal" weather days, should allow the cylinder to get warm before taking off and rev'ing the engine, it will reduce piston wear a huge amount over time.

Jon

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Not surprizing. Trials engines run really tight piston skirt/cylinder clearances, in the neighborhood of .0015"/.002". Another good reason why you, on "normal" weather days, should allow the cylinder to get warm before taking off and rev'ing the engine, it will reduce piston wear a huge amount over time.

Jon

Jon, are you saying that when the temps drop below freezing, the cylinder shrinks enough (relative to piston) to create an interference fit? I.e. the piston is physically seized in the cylinder?

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happened to me once a long time ago - someone reckoned any condensation in the engine can freeze particularly on the mains or where the rings touch the barrel and it doesn't take much to lock it up, a camping stove under the bash plate sorted it out eventually and it ran fine once freed

Edited by tonybroad
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Jon, are you saying that when the temps drop below freezing, the cylinder shrinks enough (relative to piston) to create an interference fit? I.e. the piston is physically seized in the cylinder?

Not an inteference fit, but possibly very "snug" all the same with any frozen condensation and thick oil entering into the process. Also bear in mind that a good deal of the contact surface in the cylinder/piston

area is ceramic, in addition to metal. Nikasil being Silicon Carbide particles in a Nickel matrix and piston composition being about 14-22% Silicon Carbide in most cases. This may be part of the equation, although I'm not sure as I've had no reason to experiment.

I'm sure it doesn't happen all the time, but a little warmth applied to the cylinder when starting at extreme low temps might be a good idea. I've run my bike at those temps without any problems (for the bike that is, not for my old body....).

Jon

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Well I am glad to here I am not the only one. I do let the bike warm up completely everytime. 0.0015 to 0.002" is very tight most of the diesels I rebuild run from the tightest 0.003" right out to 0.006". When I mic a cummins M11 crank we wash it first in a hot water cleaner and then I have to let it cool down over night cause it will grow 0.004" when it is hot.

Anyways thanks for the reply

Dustin

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... When I mic a cummins M11 crank we wash it first in a hot water cleaner and then I have to let it cool down over night cause it will grow 0.004" when it is hot....

4 Thou? What's it from? a ship? :rolleyes:

I knew of a 315 years ago that lived in a small shed and regularly cold locked...never harmed the bike at all,ran very well in fact.

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just curious if any one has had a cold lock up.

Loaded the bike outside temp wasabout -3C drove about 20 min and unloaded the bike. Went to kick the bike over and it was frozen like a seized motor. Removed the spark plug thinking it might be full of coolant but nothing. My riding partner then mentioned he had a propane torch after I mentioned it might be a cold lock up. After slowly heating the cylinder on all sides I started rocking the bike and slowly the piston started to move and then was free up completely. Reinserted the spark plug and first kick she flashed to life, let it idle until fan kick on and rode it all day with no problems.

I thought I would just share my story

Dustin

Hi there. When you let it idle until the fan came on, was the choke on or off? Thanks

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