1992 Yamaha 175TXRQ Stumbling Throughout RPM Range: Fuel? Carburetors?

StrikerMac

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Hello, I'm running a 175TXRQ, previous owner removed oil injection, so I premix @ 50:1 and use Startron additive. Motor ran great last weekend, took it out today and right outside of harbor it feels "soft" or weak on acceleration, stumbles, misses regardless of throttle setting. All I've done so far is to remove and dump fuel from powerhead mounted fuel bowl, which did not help. There appeared to be no water in the bowl, and minimum debris. I added a 10 micron spin-on filter a couple of seasons ago, and swap the filter each year. I am looking for suggestions because the only thing I know to do is swap my spin-on filter again, which I will do tomorrow. What else should I check? My manual (Seloc) is less than helpful on this. Thanks!
 
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StrikerMac

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Re: 1992 Yamaha 175TXRQ Stumbling Throughout RPM Range: Fuel? Carburetors?

Re: 1992 Yamaha 175TXRQ Stumbling Throughout RPM Range: Fuel? Carburetors?

Well I changed my water separator filter, no change. Maybe I'm going "overboard" and maybe not, but I've ordered rebuild kits for the carbs, and I'm draining the fuel tank (pulling it through a water separator) into a drum for use in my POS car. I'll soon be cleaning the tank as best I can through the sender unit mounting hole, rebuilding the carbs, inspecting the fuel pump diaphrams for trash (fuel pumps were swapped 2 seasons ago as a maintenance item) and crossing my fingers.
There is an anti-siphon check valve internal to the built-in tank, and I suspect it is restricting flow. I can hear it rattle and the bulb refills slowly. I plan to use carburetor cleaner, sprayed into the output of the pickup tube to clean the check valve. Can anyone recommend a solvent I can use in a garden sprayer to clean the inside of the tank? It's made of 0.125" aluminum.

Thanks
 
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StrikerMac

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Re: 1992 Yamaha 175TXRQ Stumbling Throughout RPM Range: Fuel? Carburetors?

Drained tank, (It was spotless) rebuilt carbs, changed 10 micron filter, fuel bulb is firm throughout rpm range, tried running on main and aux tank (fuel from separate source) NO CHANGE......Hey Rodbolt, please give this a read and see if I missed something obvious. The problem sounds and feels like a fuel problem, but I've checked/cleaned/replaced everything up through carburetors. When I rebuilt the carbs I found nothing too far out of the ordinary. Float settings were off by no more than 2mm, that's about it. Ignition now???

Gotta get her running right within 2wks, or I'm gonna buy a new motor, I swear.


Thanks!!
 
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StrikerMac

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Jul 20, 2008
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Re: 1992 Yamaha 175TXRQ Stumbling Throughout RPM Range: Fuel? Carburetors?

I ran a compressions test, and all was well. Naturally I pulled the plugs for the test, and found one plug badly fouled (almost bridged) with a brown/white deposit. I cleaned the plugs and she runs again! In fact, better than ever with the reworked carbs. So here's a little lesson, a chance to learn from someone else's mistake instead of peeing on the electric fence for yourself: Always remember the fundamentals. Run that compression test and clean and gap those plugs!!

So now the question is, WHY did it foul the plug?
 
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