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The TTR250 FAQ web pages -> TTR250 -> Repairs and maintenance -> Extremely low compression but bike runs just fine
Post Info TOPIC: Extremely low compression but bike runs just fine
Rydasc6102


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Extremely low compression but bike runs just fine
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hi everyone,  A couple months ago I was changing the spark plug on the bike and decided to do a compression test only to find that The gauge read only 60 PSI. I'm pretty sure it should be way higher than that. The bike still runs extremely strong and it doesn't feel like there's any power loss could this just be a faulty gauge or is there a pressure release I don't know about?



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katana


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There is the auto decompression to take into consideration, not sure what the procedure is with the TTR.

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JOHNYBOY


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does the engine start ok cold & hot how is the performance of it

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Rydasc6102


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JOHNYBOY, is seems to start fine cold and hot. sometimes there is a little bit of light blue smoke on cold startups though. But the blue smoke goes away about 5 to 10 seconds after the choke is pushed in.

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TTRfan


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If the compression was enough to pop your thumb off the plug hole with some force then assume it's a faulty tester wink

TBH, it doesn't sound as though you have anything to worry about if the engine isn't using oil smile

Brian



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JOHNYBOY


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as brian our ttr god says i also do not think you have a problem i would just run it & enjoy just keep an eye on the engine oil level just in case it gets any worse it could last for thousands of miles before it starts to use oil john

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Rydasc6102


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Thanks for the help I'll keep an eye on the oil level and just have fun. Thanks

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JOHNYBOY


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just had another thought about this one if you are only getting 60psi are you fully opening the throttle when turning over the engine because i would have said it will really run rough at 60psi

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Rydasc6102


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No throttle is closed.

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JOHNYBOY


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try it full throttle you may get a good reading

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Rydasc6102


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I'll try that next time. Can you explain why the throttle would do anything?

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ttboof


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Rydasc6102 wrote:

I'll try that next time. Can you explain why the throttle would do anything?

 Opening the throttle ensures full filling of the cylinder and correct compression reading 

with a closed throttle a vacuum is created in the inlet reducing the amount of air able to enter the cylinder 



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Rydasc6102


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I didn't know that. I gues you learn something new everyday. Thanks


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