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Discussion Starter · #1 · (Edited)
So I got this last fall off facebook marketplace as a non runner. Replaced the carb and ran fine. The deck on it was in poor shape so I got a 2018 TB30R parts machine that had a blown motor. Got the deck swapped over and now can't get the engine to crank. The battery is good, if I short the 2 large terminals on the solenoid it cranks, but will not start due to no spark. According to the manual the safeties on the deck and the seat wouldn't be the issue as if the machine is in park it should start. I even swapped the safety switches out of the parts machine with no luck. I then jumped 12v to the proper contact on the solenoid and it turned over so the solenoid is good, has to be a safety switch but damned if I can figure it out.

EDIT: Well I made some progress, found another safety switch I wasn't aware of on the frame above the mower deck, not sure what that one is for but the connector was loose. Was able to turn it over and get it running but it's surging and stalls if I engage the mower blade, and only runs smoothly on choke. I don't imagine it's the carb as I just replaced it, and it has fresh zero ethanol fuel in it, thoughts?
 

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The safety switch on the deck is to make sure one of the blade covers are installed.

The safety switch above the deck on the frame is for the PTO, blade engagement lever.
 

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Discussion Starter · #3 ·
The safety switch on the deck is to make sure one of the blade covers are installed.

The safety switch above the deck on the frame is for the PTO, blade engagement lever.
Those were the two I was aware of, the PTO switch is visible outside of the frame, there is a 3rd above the deck between the frame rails, possibly for the brake pedal? Didn't have time to work linkages to figure it out, will have to wait until next weekend.
 

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The surging may be caused by either the carb or a leak in the intake connections. I have had problems with Chinese carbs causing the surge right out of the box. Check the seal between the carb and the intake and to the head by spraying choke cleaner on them while the engine is running. If it changes, you have found a leak. If z cheap carb. Send it back and try another. 50\50 chance.
 

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Discussion Starter · #5 ·
Yeah, I've heard that chinese carbs are a crapshoot, but the lure of 1/5th the price of an OEM carb ($105) was too great, even if I got a bad one and had to buy 2 replacements I'd still come out ahead. I'll try the spray cleaner trick this weekend and see what I find.
 

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Discussion Starter · #7 ·
Ok, so I tried spraying carb cleaner at the gasket locations and heard no difference. I had a 2nd carb on hand so I installed that with new gaskets and still no change. It runs a slight bit smoother but still stumbling at full throttle with no load. I can engage the mower OR drive it and it'll stay running but if I try to do both it dies. Also even when the engine is warm I have to choke it to get it to start sometimes.
 

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I had a 2nd carb on hand so I installed that with new gaskets and still no change.
Did you verify that the main jets in the new carbs were the same size as the original carb's jet? If adding choke smooths it out, then it's running too lean and needs a bigger main jet.
 
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It's possible those Chiense carbs all have the same size jets. I had one that ran ran away if above idle. Had to shorten the throttle linkage. If ur gonna use those carbs swap the main jet. I will start doing that.
 

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Discussion Starter · #10 ·
Did you verify that the main jets in the new carbs were the same size as the original carb's jet? If adding choke smooths it out, then it's running too lean and needs a bigger main jet.
I'll dig up the original carb and see, it's in the shed somewhere, I think, ty for the input
 
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