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Old 07-11-2009, 09:30 AM
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zixxer
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Originally Posted by dead1dave
I have a Ninja JX.21 in a MBX6 ........this engine has been absolutley awsome and running flawless since day one with no leaking or flameouts what so ever .......I am 1/2 way through my 5th gallon of fuel and I have really tuned the motor 1 hr rich or lean since I've bought it for the first 4 gallons with no issues .....recently is has slowly started to become somewhat of a pain ......doesn't idle near as well ,flames out after a fuel stop " which it has never done once in 4 gallons " .....and overall just seem weird and fincky to tune on the bottom end .

So here is what I am getting at ....with the glow plug out ..cold .. there is no mechanical pinch what so ever but with the plug in it has a ton of compression .......the motor runs and has good power but it's ease of tuning manners have far deteriorated ..........I would not be unhappy if it were worn out at 4 1/2 gal. but I just don't want to struggle with a motor on a race day . Is this just how they start to act when they get worn out ???????

My friend has a 21-4 Nova in his car with 1/2 the compression mine does and no pinch at all that will run 45 minutes straight with no issues ..........I know all motors are different but I just need a little advice here on what to do because I don't trust this motor to finish a race anymore . Thanks guys !!!!
just my opinion ...the jx is o.s. based so it would probably be in the worn out category ....are you noticing any leakage around the front bearing ? that can be a possibility ...but other than that you may need a new piston sleeve and rod ....o.s. motors allthough easy to tune on race day ...dont have the longevity of say a nova rossi ....just my .02
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