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how to perform a leak down test

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So i have a crf450 sitting in my garage that wont run. The last time i worked on it was about 3 monthes ago and since then I have been real busy with work and school so it has been sitting ona stand. The problem is shortyly after i bought the bike i checked the valve clearances and they were tight so i shimmed them according to the manual. After i shimmed them the bike would not run. At the time i tried to check the timing and valve clearances but nothing worked. I also completly disassembled the carb , cleaned everythign and then reassembled. I have a complete week off this week and would like to make some progress on the bike( try to gte it running).

I did some searching and read that a leak down test can be very usefull when trying to find out what could be the problem with the bike.

My question is..How do you perform a leak down test for this bike? I did some searching but could not find and decent stuff..

Here is the original thread from 3 monthes ago if anyone cares to help me out..

http://www.thumpertalk.com/forum/showthread.php?t=720727&highlight=leak+down

Thanks

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It requires a leak down tester. I live just minutes from summit racing. Got one from there pretty cheap. The test is pretty simple. Install the tester in place of the plug, hold the crank at TDC and pressureize the cylinder chamber. The amout of leakdown will tell you where your problem is. Either by hearing air pass thru the intake, exhaust or past the rings. I have been told to pressureize it to 100 psi which is a nice round number to go by. And gives you a real good seal on the rings and shows a true percentage of leak. So 2 pound dif would mean a 2% leak. And a 4% leak is about as much as i have been told you should get before replacing the rings.

Hope this helps

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It requires a leak down tester. I live just minutes from summit racing. Got one from there pretty cheap. The test is pretty simple. Install the tester in place of the plug, hold the crank at TDC and pressureize the cylinder chamber. The amout of leakdown will tell you where your problem is. Either by hearing air pass thru the intake, exhaust or past the rings. I have been told to pressureize it to 100 psi which is a nice round number to go by. And gives you a real good seal on the rings and shows a true percentage of leak. So 2 pound dif would mean a 2% leak. And a 4% leak is about as much as i have been told you should get before replacing the rings.

Hope this helps

You can also rock the piston to see if the reading changes. Make sure you have a good grip on the breaker bar anytime there is pressure in the cyl. !

:)

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It requires a leak down tester. I live just minutes from summit racing. Got one from there pretty cheap. The test is pretty simple. Install the tester in place of the plug, hold the crank at TDC and pressureize the cylinder chamber. The amout of leakdown will tell you where your problem is. Either by hearing air pass thru the intake, exhaust or past the rings. I have been told to pressureize it to 100 psi which is a nice round number to go by. And gives you a real good seal on the rings and shows a true percentage of leak. So 2 pound dif would mean a 2% leak. And a 4% leak is about as much as i have been told you should get before replacing the rings.

Hope this helps

what method do you use to pressurize the cylinder?? And you simplt locate the problem by listening to where the air is escaping from?? Are the leak down tester kits universal for all different size plug holes? Thanks for the info.

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what method do you use to pressurize the cylinder?? And you simplt locate the problem by listening to where the air is escaping from?? Are the leak down tester kits universal for all different size plug holes? Thanks for the info.

The leak down tester will have an air chuck on it, just plug an air line into it. Better kits come with different size adapters for the plug hole. You can listen to the intake by opening the throttle and listening through the air filter boot and to the exhaust through the exhaust pipe. To the bottom end by pulling the crank case oil fill cap. Like I mentioned earlier make sure you have a good hold on the breaker bar that you are holding the crank with. A little off tdc and the piston will go down :)

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The leak down tester will have an air chuck on it, just plug an air line into it. Better kits come with different size adapters for the plug hole. You can listen to the intake by opening the throttle and listening through the air filter boot and to the exhaust through the exhaust pipe. To the bottom end by pulling the crank case oil fill cap. Like I mentioned earlier make sure you have a good hold on the breaker bar that you are holding the crank with. A little off tdc and the piston will go down :)

alright, thanks for the info. So if i check the valve clearances and the timing is good as well and i still cant get it to start. Would doing a leak down test be the next step in trying to figure it out?

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Double check your cam timing. If the valve clearence went to zero it is time for new valves.

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