# Troy-Bilt TB490BC



## JayClue (Jun 4, 2009)

Heres the story on this one...

Got out my dads trimmer with no luck getting it to run. Primer bulb was leaking when dpressed, I replaced it and it worked fine.

Unit still wouldn't start and being as their was gas in it from 2 previous seasons ago, I drained refilled and tryed again to no avail. Replaced plug sprayed a little starting fluid in it got a sign of life so continued with carb removal and overhaul. Now it also has a new coil. But won't run.

Curious as to what you guy's thoughts might be and I appreciate your time for reading anyways...

Jason


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## wrenchhead (Oct 26, 2007)

if u have spark take the plug out and clean it up then put a little fuel in cyl put plug back in and try that sounds like not getting fuel or is flooded but even know u put a new plug in it might have gotten fuel soaked when starting hold the throtle open try that let us know how u make out


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## JayClue (Jun 4, 2009)

wrenchhead said:


> if u have spark take the plug out and clean it up then put a little fuel in cyl put plug back in and try that sounds like not getting fuel or is flooded but even know u put a new plug in it might have gotten fuel soaked when starting hold the throtle open try that let us know how u make out


Well before I messed with some starting fluid, sprayed it in the intake and got a little kick out of it. But I couldn't visually verify good spark. It ignited starting fluid so there was some spark... Now I can visually see blue spark, and cant even make it spit or sputter. I know the push rods aren't bent. and I can see both valves moving. It has compression. I don't understand why I can't even make it spit or sputter now.

Jason

*Edit - Tryed removing muffler/spark arrester made no difference.


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## 30yearTech (Sep 14, 2006)

May want to take a look at the flywheel, the flywheel key may be broken causing the ignition timing to be off. You will have spark, but it may never start and run if the spark is at the wrong time.


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## JayClue (Jun 4, 2009)

Wow. I didn't know how timing was controlled. I took the head off. Found the flywheel valves pushrods and I didn't understand how timing was set. That may be the right direction. I had the motor down to the crank and flywheel, but I didn't try to take it any further because i saw absolutley nothing that looked like it could be ailing it. Especially since both the exhaust and intake valves cyle.


Ill try that tomorrow.
Jason


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## 30yearTech (Sep 14, 2006)

JayClue said:


> Wow. I didn't know how timing was controlled. I took the head off. Found the flywheel valves pushrods and I didn't understand how timing was set. That may be the right direction. I had the motor down to the crank and flywheel, but I didn't try to take it any further because i saw absolutley nothing that looked like it could be ailing it. Especially since both the exhaust and intake valves cyle.
> 
> 
> Ill try that tomorrow.
> Jason


I am referring to "Ignition" timing and not valve timing. It's hard for the valve timing to get changed without tearing down the engine.


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## JayClue (Jun 4, 2009)

Flywheel is tapered to the crankshaft. There is a keyway style slot in the crank, and what trys to be a key on the flywheel, but it seems like it isn't real tight. How much play should the flywheel have in it while holding the crank? I'm sure once you tighten the nut and spacer and everything back down that it couln't move any, but making sure its centered when you have 5 or 6 degrees of movement would be kinda tough I would think.

Jason


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## 30yearTech (Sep 14, 2006)

The key molded into the flywheel should hold the flywheel fairly snug to the crankshaft when pushed into position by hand. The retaining nut needs to be tightened with flywheel in the proper position for ignition timing to be correct. DO NOT hold the flywheel when tightening the retaining nut as this can cause the key to be sheared. Use a piston stop or the "rope trick" to prevent the crankshaft from turning while tightening this nut. Once tightened ignition timing should be alright.


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