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Thread: 1985 250sx carburetor loading up

  1. #1
    Join Date
    Oct 2018
    Location
    Indiana
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    1985 250sx carburetor loading up

    So I’m rebuilding my new to me 1985 250sx. So far I’ve took the top end apart deglazed the bore put new rings in it ground the vaules then cleaned and put back in the frame. Next took out the carb took it apart and cleaned with whole can of brake cleaner. Bought the shindy rebuild kit and put it back together how I had found it hopfully. Threw that thing back in thinking it be running in no time started up after second turn over sounded great. Revved it a little, idle started to change and it started to load up sounding like the cam was as big as a bucket, I’ve now taken it out 4 times trying to mess with it only to get to were now the fuel is leaking out of the bottom of the bowl. I don’t know what else to do if ya could give some tips or pics on why it’s loading, how to fix it, and what I did wrong it would be much appreciated.

    More info: has a new k&n air filter and a little fuel filter on the hose going to the carb from the tank

  2. #2
    Join Date
    Jul 2009
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    Sounds like the float valve seat is either dirty or possibly scratched, pull it back apart and look real good .
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  3. #3
    Join Date
    Oct 2018
    Location
    Indiana
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    Well after 19 days of wanting to look at the response above I checked and there was nothing on the float valve seat. Took to the Honda dealer shipp to see if they would give me some tips they said to move the needle down to make it not get as much fuel. Tried it and now it ruins ok but not great kinda studiers, thinking to get a new carb any opinions or more things to look for.

  4. #4
    Join Date
    Apr 2014
    Location
    Edmond, KS
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    The new, cheap, Chinese carbs are a crap shoot at best. The best bet is OEM. If you can't figure this out. Give FlyingW a PM. He can work wonders with these carbs.

  5. #5
    Join Date
    Apr 2012
    Location
    USA
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    4,114
    Assuming the carb body is in good shape for the float valve, if you can't get it adjusted where it works correctly, maybe the float valve isn't sealing (worn?). You can get that part directly from Honda, not cheap though.

    https://www.partzilla.com/product/ho...2c730017b11d7a

    Also if you want to take the guess work out, you can get a new float as well to get the stock setting, or if it's damaged in any way. The service manual should explain how to set the float level, let me know if you can't find it and I'll try to dig it up.

    https://www.partzilla.com/product/ho...2c730017b11d7a

    Of course the easiest way is to send it off to FlyingW, he does do amazing work from what I've seen on here. He also rebuilds the 250es/sx rear diffs.

  6. #6
    Join Date
    Jul 2018
    Location
    TN
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    1,065
    Is the float level correct? Measure carefully and adjust it until it's within spec. I'm slowly finding out on all my trikes, Honda's are very picky about it. Mine absolutely hate it if there's a little too much fuel in the bowl and they act all kinda stupid when there is.

    I wish I knew the 250's enough to be of more help. I stick with 200's meself. Simpler machine for a simpler mind.
    I was born and raised on Venus & I may be here a while.....

  7. #7
    Join Date
    Apr 2012
    Location
    USA
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    4,114
    Nice to know the float level is pretty critical on Honda's, I've had a couple carbs in the past that acted super strange but ended up just swapping another carb on since I had spares, interestingly it was on the 200cc style engines for both cases (200es and 200x).

    Just wondering, what exactly is more complex about the 250 models vs the 200? The 200's have the mechanical spark advancement under the CDI cover, while the 250's do it electronically in the CDI, besides that I can't think of much more that's majorly different (really the mechanical advancement is more complex than the CDI in the end user sense). I guess the 250s are a higher package, so generally have more features electronically like 12v aux plug and such, but the 200es does too. I guess all the 250cc models have rear suspension, but that seems like a perk to me.

    Kinda off topic but I'm just curious

  8. #8
    Join Date
    Jul 2018
    Location
    TN
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    1,065
    Quote Originally Posted by ps2fixer View Post
    Nice to know the float level is pretty critical on Honda's, I've had a couple carbs in the past that acted super strange but ended up just swapping another carb on since I had spares, interestingly it was on the 200cc style engines for both cases (200es and 200x).

    Just wondering, what exactly is more complex about the 250 models vs the 200? The 200's have the mechanical spark advancement under the CDI cover, while the 250's do it electronically in the CDI, besides that I can't think of much more that's majorly different (really the mechanical advancement is more complex than the CDI in the end user sense). I guess the 250s are a higher package, so generally have more features electronically like 12v aux plug and such, but the 200es does too. I guess all the 250cc models have rear suspension, but that seems like a perk to me.

    Kinda off topic but I'm just curious
    The carburetors are more complicated as is the wiring. I hate external oil lines. The overall size of the machine just feels TOO big to me. Parts are more expensive and harder to find and I would rather repair a pull rope any day than nurse a bruise in the arch of my foot. LOL!!!
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  9. #9
    Join Date
    Apr 2012
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    USA
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    I see, on the wiring you'd have to compare like a 200x/200s to like a 350x/250r, and the 200es vs 250es/sx. I can see the point of the external oil lines, but seen any issues with them in the 20+ machines I've owned or parted out. Defo can see the rest of the points though, personally never had an issue with the kick start layout except when the one way bearing goes bad on the 250sx/es, doesn't seem like the 350x had the same issue, but I have a 350x that doesn't compression release right so it is hard to kick (crazy compression to deal with). The valve cover is broken and the shaft misses the compression release internally. Haven't fixed it since my other 350x has been problem free and is more of a beater/rider. I know exactly what you mean by the too big feeling, I tried some wheel spacers on my 250sx and yea it was more stable, harder to slide for some reason in the back, and I started hitting a lot more roots and such in the trails. Took them off promptly after that trip and never used them since, probably should ebay them some day to get some money back out of them.

    Probably should mention I did start with a 200es for 5 or so years before moving to a 250es/sx and fell in love with those machines and soon later the 350x. The 200es was more fun than the 1999 Yamaha Warrior for some reason, the warrior clearly had more power/speed. I like power/speed, power slides, donuts etc and I ride hard and a bit on the edge, so they probably match my personality/ride style better. It's always good to see different opinions though =).

  10. #10
    Join Date
    Oct 2018
    Location
    Indiana
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    Thanks guys for all the post, I’m getting ahold of Flyingw as we speak to see what he says to do and possibly send it off for a look. Thanks again for all your help.

  11. #11
    Join Date
    Oct 2018
    Location
    Indiana
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    Ya ordered one from amazon just to see what it looked like it’s let’s just say it’s on it’s way back to China. Not impressed

  12. #12
    Join Date
    Oct 2018
    Location
    Indiana
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    When I took my carb apart there was no adjustment for the float all the farther I went was to take out the float and then the thing that seals the float valve and I replaced that with what was in the rebuild kit.

  13. #13
    Join Date
    Apr 2012
    Location
    USA
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    4,114
    Care to share any details on the China CDI kit from Amazon? Was the wiring just complete trash (like everything else china made I've seen), or was the CDI itself garbage looking too? I'm sure the connector is lower quality than the Japanese ones I use.

    Each model of carb is slightly different, but generally the metal tab the float valve hooks onto is bent to adjust the float level. Just happen to have the sx service manual open so lets see if I can find that section.

    Well, the SX is non-adjustable, but there is a spec for the float level. I'd say try to measure it and see if it's close to spec, if not you might need a new float like $27 + shipping if your kit didn't come with one, which I'd assume it doesn't. If it's out of spec, you could try to heat the plastic a little and bend it, but expect it to be junk afterwards. Don't forget that the gas will need to evap away or wash it before any open flames/sparks or you'll have a nice little fire lol.


  14. #14
    Join Date
    Apr 2014
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    Edmond, KS
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    I'm happy with the job that FlyingW did on my 85 250Sx carb. It looked better than new when I got it back. You'll be very happy too.

  15. #15
    Join Date
    Jun 2009
    Location
    Leander TX
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    FlyingW works with OCD level detail. Everything I've ever seen that he worked on was perfect.
    His carb article on this site is great: http://www.3wheelerworld.com/showthr...ebuild-Tutoral

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