Author Topic: Troy Bilt 4 cycle trimmer  (Read 158 times)

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Troy Bilt 4 cycle trimmer
« on: August 05, 2015, 07:23:06 pm »
I received a Troy Bilt 4 cycle trimmer for free.   
The problem was hard starting and once it started it would die when trying to rev the engine.   
So I replaced the carb which is a Walbro WYLA series.   
The trimmer is still hard to start but it will rev alittle better but it does not seem to go to a high enouph RPM to lock the clutch in real well.
I checked the valve lash which is at .007.
I dumped the old fuel and put in known good fuel.
The compression is at 85 psi which seems low to me.
I made new gaskets for the intake and carb and made sure the impulse is lined up correctly.
I checked the spark arrestor and no carbon build up at all.
It will also sometimes die for no reason and then hard to start again.
I took the metering lever in the carb and raised it just alittle to richen it up a bit.
I have tried also to adjust the carb needle and it does not help.

Now the only thing that I can think of that is not right is the compression. 
So is 85 psi to low for a 4 cycle string trimmer putting it right at the edge making it difficult to run but yet just enouph to get it started.
PP 505, 475, 445.

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Offline 660magnum

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Re: Troy Bilt 4 cycle trimmer
« Reply #1 on: August 05, 2015, 08:20:24 pm »
I have something like one of those that the Dolmar dealer gave me several years ago. I haven't bothered with it. He mentioned some problem they seem to have with the cam?
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Re: Troy Bilt 4 cycle trimmer
« Reply #2 on: August 05, 2015, 08:30:50 pm »
Is it the intake lobe on the cam that worn down and not taking in enouph fuel and also not creating enouph vacuum to work the impulse.   
I am trying to understand this so I can recognize this if I come across it again.   

What about the 85 psi, that seems low to me.
PP 505, 475, 445.

Offline 660magnum

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Re: Troy Bilt 4 cycle trimmer
« Reply #3 on: August 05, 2015, 08:49:50 pm »
It's been a few years and hard to remember now?  But the problem was somehow related to the cam? Apparently the problem was more involved than what the dealer wanted to mess with as he was a Echo dealer. He had opted out with the customer.

85 psi does not sound good to me either?
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Re: Troy Bilt 4 cycle trimmer
« Reply #4 on: August 05, 2015, 09:02:06 pm »
I tore a different make 4 cycle trimmer apart last year and I think the psi was more like 120.
PP 505, 475, 445.

Offline 660magnum

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Re: Troy Bilt 4 cycle trimmer
« Reply #5 on: August 05, 2015, 09:19:44 pm »
120# is more like it.
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Re: Troy Bilt 4 cycle trimmer
« Reply #6 on: August 05, 2015, 11:17:31 pm »
I was on google and it popped up with a guy doing a compression test on you tube for a Troy Bilt 4 cycle string trimmer.
He was able to hit 150 psi.    Yep I think 85 is low.
PP 505, 475, 445.

 

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