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Discussion Starter #1 (Edited)
I bought an X520 last Winter that had been hocked at a pawn shop for over a year. The guy never came back or made any payments on it so I bought it. It was surging when I got it out to test it today so I cleaned the carb and the surging went away. But when I went to put the float back in the bowl I realized it can go in either way and there is a difference in the offset of the tube where the pivot pin goes through. It will now run but stops at idle. I do not think a float issue would cause that but do any of you have a picture of the float? What is so aggravating about the float is that it has a dimple on one side of the float but thanks to Japanese engineering, they put one on the other side of the same float! So it can look correct either way. Talk about Murphy's law! One thing I got used to in aviation was that a new part could only fit one way. In the old days, mechanics would actually bend a preformed piece to make it fit the wrong way! So then the airplane builders put different fittings on each end so that it could not be done. This engine is a FD731V and a new carb is $425! Here is the blow-up of the carb. You can see the dimple in the float but if you flip it over there is also one on the bottom of the same float. It would move to the other side so I guess I will need to take the carb off and see if the dimple is on the side in this picture.
FD731V carb.JPG
 

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Check the tab where the float hits the needle valve. You should be able to tell from that, what way it was in before from a wear mark. As far as it shutting of at idle, maybe your idle speed is too low.
 

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Discussion Starter #3
I am going to check the tab and compare the picture of the float to the one in the picture above. The manual says that when the engine is at idle, there is not enough air through the throat to draw the gas into it so it uses a low-speed passageway and I think that is where the problem is. If that is blocked the engine will not run at idle. My problem is to figure out how to get to that passageway.
 

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Sounds like it is the Pilot system. Me and carbs do not get along very well, so my suggestion is a real basic one. Tried any compressed air to back flush the Pilot passages? Or remove what appears to be the adjustment screw to see if something is lodged in the seat or passageway?

I won't recommend my usual carb solution, but it is always successful. Throw it against the wall, and order a complete new replacement,....... works every time. :giggle:
 

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Discussion Starter #5
I hear you about buying a new carb but at over $400 that is not an option. This 520 only has 197 hours on it but it sat for a year. It's definitely clogged up with that wonderful crap called ethanol! This is the most complex carb for a Kawa I have seen and it will take a while to tear it apart. I'll let you know what I find. It was surging and I got that cured but I didn't go into the pilot circuit. That will be next. This is the downfall of buying an older mower/tractor with very low hours. It means that it sat with a carb full of this planet-saving garbage and will definitely need cleaning.
 

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Sounds like it is the Pilot system. Me and carbs do not get along very well, so my suggestion is a real basic one. Tried any compressed air to back flush the Pilot passages? Or remove what appears to be the adjustment screw to see if something is lodged in the seat or passageway?

I won't recommend my usual carb solution, but it is always successful. Throw it against the wall, and order a complete new replacement,....... works every time. :giggle:
Now that there is funny! LMBO! :ROFLMAO:
 

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I would have the carb ultrasonic cleaned while you have it apart! nothing worse than going through all the re/re time/cost process and the end result isn't succcessful!
 

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[QUOTE="Alien5044, post: 12412116, member: 371122"

I won't recommend my usual carb solution, but it is always successful. Throw it against the wall, and order a complete new replacement,....... works every time. :giggle:
[/QUOTE]

I've had good luck with that procedure....did that to 2) JDs with Kaw engines. They run pretty good after that.
The LX188 carb was apart and assemble at least 10 times; soaked in carb cleaner about 4 of those times..... must've been a clogged passage that didn't dissolve out.
The latest on the GX345 was because some numbskull broke off the high-idle limit cap and stripped the threads in the carb body.
gatz
 

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Discussion Starter #9
When I have a carb problem I look for prior "Work" done on it and if it looks like a one-armed gorilla did the work I just order a new one. But this carb was $425 and that was with a discount so I had no choice but to fix it.
 

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Send it here, the guy does really nice work.

 

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Discussion Starter #11
I have an update for my problem with the carb on the 520. It idles nicely and goes up to about 3200 rpm at WOT. The issue I am having is that I get black smoke at idle and when I move the throttle up. I have played with the two idle mixture screws and all the way in or all the way out on either or both have no effect on the engine nor does setting them at the factory recommended setting. What is happening? There are no other mixture setting screws on the carb so what is going on? It's as if they are being bypassed completely.
 

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Discussion Starter #12
I'm resorting back to my old "Can't clean it-so replace it" Mikuni carb mantra. I found one on eBay that had 10 hours on it for $195 so I bought it. I have the Kawa manual and unfortunately, like most manuals that cover several models and years, none of the numbers they offer for my carb are anywhere to be found on it. All of the valves have different numbers on them from the manual. It is very frustrating to not have something that can be relied on as the bible of that engine. I got a good deal on the X520 but it had been sitting for two years. Next time I will walk away from one like this.
 

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Discussion Starter #13
I got the used, 10 hour, carb today and mounted it on the X520. Cranked and cranked but no luck. Then I poured a little gas in the intake and it fired right up but then stopped immediately. I took the solenoid off of my carb and put it on the new one and it started right up and ran smoke-free! I wish I knew what it is about the Mikuni carbs that makes them so hard to clean. Since this carb looked brand new but was being sold used, I have a feeling that the solenoid failed but whoever was working on it must not have known about the shutoff solenoid. Anyway, my old solenoid and the new carb is just what I needed. Here is the 520 with the electric 3ph. It has a carry-all on it now and I lifted myself up, 230 lbs, with no effort. The 54-inch deck looks like new.
 

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I got the used, 10 hour, carb today and mounted it on the X520. Cranked and cranked but no luck. Then I poured a little gas in the intake and it fired right up but then stopped immediately. I took the solenoid off of my carb and put it on the new one and it started right up and ran smoke-free! I wish I knew what it is about the Mikuni carbs that makes them so hard to clean. Since this carb looked brand new but was being sold used, I have a feeling that the solenoid failed but whoever was working on it must not have known about the shutoff solenoid. Anyway, my old solenoid and the new carb is just what I needed. Here is the 520 with the electric 3ph. It has a carry-all on it now and I lifted myself up, 230 lbs, with no effort. The 54-inch deck looks like new.
Yeah, but 231 would've popped those front wheel like a dragster!! :)
 
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