HT131 help before I crush it for good

[DELETED (Struggle)]

I've left the kill wire disconnected no change. Good idea though.


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[lwn9186]

I had one that acted the same way. Finally found the exhaust seat had a crack.

 

[DELETED (Struggle)]

Looking into this now. You were able to visually see this?


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[lwn9186]

Cleaned it with Scotchbrite and still really had to look close it sucks.

 

[DELETED (Struggle)]

A crack at this point would be the most logical explanation. I wouldn't think it would pass a leakdown though


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[lwn9186]

Mine did pass a leak down test also. It had me on the verge of going nuts! Took a very bright light to see the crack. I know what you are going through.

 

[lwn9186]

I remember also taking valve lapping compound and polishing the seat and that may be what helped me see the crank.

 

[SawDoc441]

Replace the cam gear. If you've been running it with the top cover off (like in your pic), it probably melted. I learned this the hard way on a newer FS130. Lasted about 3 minutes of tuning before the lobe melted on the cam. It would still idle, but reduced lift would not flow enough volume of air to run at high speed. A brand new 4180 will melt the cam in less than 5 minutes under load without the shroud. That shroud IS a critical part that directs the cooling air over the cylinder.

 

[hseII]

Replace the cam gear. If you've been running it with the top cover off (like in your pic), it probably melted. I learned this the hard way on a newer FS130. Lasted about 3 minutes of tuning before the lobe melted on the cam. It would still idle, but reduced lift would not flow enough volume of air to run at high speed. A brand new 4180 will melt the cam in less than 5 minutes under load without the shroud. That shroud IS a critical part that directs the cooling air over the cylinder.

Thank You Tim.

 

[DELETED (Struggle)]

Came gear isn't melted only let it run long enough to see it not rev then shut down.

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[Onan18]

Pulse line tight?

 

[Lone Wolf]

Came gear isn't melted only let it run long enough to see it not rev then shut down.

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You sure the spark aint arcing out anywhere run it in the dark.

 

[SawDoc441]

If you've had enough, I'll sort it out for ya. I have a dealership full of parts to work with and every factory tool. Send me the complete power head and throttle handle. PM for address. Results will be posted for all to learn.

 

[DELETED (Struggle)]

Thanks for the offer and it might come to that but in the mean time I'll have to buy a new one grrrh as I needed it for jobs two days ago. I have lapped the valves and see no indication of cracks. I cleaned up the exhaust area to a shine and see nothing. Will reassemble now and run in dark and see i guess. About the only thing not done.

Impulse tighter than a boars ass at fly time


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[SawDoc441]

Any chance the spring fell out of the impulse pump on the carb? The HT133 is a better machine in every possible respect anyway. I'd grab one if my HT75 wasn't so much lighter.

 

[DELETED (Struggle)]

Put a brand new carb on it and went through the original one on the machine. No missing parts


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[SawDoc441]

Brand-new OEM carb?

 

[DELETED (Struggle)]

Yes all OEM Stihl parts. I completely took it apart and lapped the exhaust valve and took a dentist grinder tool and ground the entire exhaust port shiny leaving no carbon behind. Cleaned up some casting flaws as well. Cleaned reassembled using motoseal. Didn't pressure or vac test. Primed some fuel down spark plug hole and started it. It appears to run like a raped ape now. Excellent throttle response.

I have no bar on it t now and of course 9pm so no trying it out.

My concern is that grinding out the exhaust area maybe filled in a crack or couldn't see and it will return to running bad? No parts have changed this round. I also made sure I n disassembly that timing was correct and it was.

Makes no sense really but I'll be extremely happy to not have to shell out $700 tomorrow for a new one.

I appreciate everyone's suggestions. It really shouldn't be this difficult.

In cleaning the exhaust port there was carbon that could be chipped out but in no way would I have considered it restricted beyond maybe 10% or so. Are these engines that sensitive to that?.

I've seen trimmers run with exhaust ports more than 50% restricted and still run although lacking power


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[DELETED (Struggle)]

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[lwn9186]

It clearly doesn't appear to be cracked, nice job cleaning it up!