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air hissing with plug removed and high compression?

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I removed the plug from my 440 yesterday and noticed a sound like air leaking through something. It went on for a minute before all pressure was evidently removed. Is this normal, I never noticed it before???

After replacing the plug, the bike was hard to start (which is very unusual.) It did finally start, so I ran it a couple minutes and then tried to start it again. This time, it felt like the engine was locked up. I would push on the kickstarter and it would actually come back up at me. I always use the manual decomp lever, but it didn't really help. Finally, I got it to turn over and it started normally. I'm a bit worried that I dropped some junk into the spark plug hole. Any ideas on possible damage or other explaination for what happened? Any connection with the air escaping before the plug was replaced?

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It is possible that some accumulated crud fell into the cylinder. It is a good idea to used compressed air to blow the debris away from the plug before removal. I carry a length of 5/16 rubber tubing to blow crap away from the plug in case I need to remove it on the trail. The tubing can also be used as a siphon hose or to transfer gas from one bike to another.

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What would you guys do next? Start and ride it (will the debris likely go out the exhaust, or do I need to take the head off?)

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You make it sound like air was escaping from around the plug as you removed it. Is that right? If so, then either the piston was on a compression stroke or maybe the crankcase vent line is plugged up/kinked.

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TR, air was leaking somewhere with the plug completely out. I couldn't understand why, and I thought may or may not be related to the engine not wanting to turn over

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Go ahead and make sure the crankcase vent line is clear.

The only other thing that can become pressurized is the fuel tank. If the vent in the fuel cap is plugged up, the tank can't breathe, nor can it deliver fuel to the carb if there's a vacuum drawn on it.

Make sure none of your tires is leaking. LOL

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Make sure none of your tires is leaking. LOL

That's funny!

Well, you were right...hose was definitely crimped. That would explain both issues, right??? I didn't realize that much air passed out of the breather (enough to cause hard starting???) I assume all the air is going OUT and not in? The bike had a filter on the end of the breather hose (should that stay on, or is it not needed?) Thanks.

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Leave the filter on it, just give it a cleaning. The cranckcase vent line moves air both ways as pressure in the case fluctuates between positive and negative. Not much negative, but enough that it can suck dirt into the case, hence the filter.

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