1985 honda 250sx carb replacement

[Speedgoat]

I need some expert advice from you all.
I bought a 1985 250sx about 6 months ago, it was a mess when i got it.
I removed carb, and cleaned it following Flyingw's masterfully done guide. i replaced petcock and straw filter, added inline fuel filter, added a uni air filter and oiled it, new gas, new honda oil, new fuel line, new spark plug, clipped end of spark plug wire and reassembled...

it ran ok once at speed but bogged when stab throttle.So i orded a shindy carb rebuild kit and installed that and it still bogged badly when i punch throttle from a stand still or if i am barely moving but runs great once its moving.
Any amount of choke kills it.
sounds like it is a common problem

really sick of trying to make this carb work. such a pain in butt to get in and out

has anyone had luck using a 300ex carb swap?
anyone had luck with an aftermarkert chinese carb?
should a search for a 1986 or 87 250 sx carb?

thanks

[Maico]

I put this exact carb on my '85. Pretty much plug and play. I set the idle speed and that was it. Takes a minute or 2 longer to warm up when cold at 20* but after a minute or so...will idle all day long.

http://www.ebay.com/itm/Carburetor-Honda-ATC-250SX-ATC250SX-Carb-85-1985-NEW-/192132917971?fits=Make%3AHonda&hash=item2cbc03aad3:g:0ZEAAOSwpDdVIUvi&vxp=mtr

[Speedgoat]

That's nice to know. Is the throttle responsive now throughout entire range ?

[atc007]

It sounds like yours needs sync'd.? You did that correct? Jim covers that in the tt. Other than that. It probably needs dipped in Carb dip,which is a total disassembly again.

[Speedgoat]

It sounds like yours needs sync'd.? You did that correct? Jim covers that in the tt. Other than that. It probably needs dipped in Carb dip,which is a total disassembly again.

i have it synced as far as I know. needle slide and throttle assembly move as one unit in unison. i followed flyingw and manuals instructions

[UPNATM]

If your having issues with it after all that work you may want to just contact Jim, and send it to him. He can make any turd carb run like a champ. Did two of mine for me, and couldn't be happier. :D

[Speedgoat]

yep, really defeated with this thing right now. just spent another 2 hours trying to figure it out. I have about 15 hours into the dang thing.
everything about it is perfect (starts instantly, idles perfect, air screw and idle screw work as they should, choke works as it should, purrs through gears with no sputtering or backfire) except it bogs and almost dies when i punch throttle from a standstill in 1st and when slowly moving in 2nd.

just rechecked sync and it was right on . i even took it out of sync to see if it made a difference, then synced it again. Tried needle on every setting and adjusted air screw on every needle setting. Cut spark plug cable and reattached end. tried a new plug cable and coil. ran with and without air filter. sprayed everythihg to check for air leaks. ran with and without inline gas filter. ran with gas cap off. ran a larger fuel line.

next step is either buy a different carb or go through the horribly painful process of pulling this carb and checking everything over a third time and putting back in .

Could my low compression of 154 make a difference?
i think it is suppose to be 170

[UPNATM]

Hey, quick question. Does it do it only when hot, cold, or all the time?

[Speedgoat]

Hey, quick question. Does it do it only when hot, cold, or all the time?

hot, cold and everything in between

[UPNATM]

hot, cold and everything in between

I know it may sound crazy, but do you have an extra CDI laying around?

I had the same sorta issue, thought it was the carb, like you, spent a ton of time on it, and all along it was a bad CDI. Replaced it and, was good to go.

[Speedgoat]

I know it may sound crazy, but do you have an extra CDI laying around?

I had the same sorta issue, thought it was the carb, like you, spent a ton of time on it, and all along it was a bad CDI. Replaced it and, was good to go.

someone else on atc animals said something about that. where the heck is the cdi on this thing?

[Speedgoat]

someone else on atc animals said something about that. where the heck is the cdi on this thing?

It must be the little black box under the front left side of battery case

[UPNATM]

It must be the little black box under the front left side of battery case


Yup, that's it.....

[redsox]

take this for what it is. its not a slight in any way. every situation is different, and this is just my experience. I have two SX's. an 85 and an 86. I also have an 85 ES. I've sent all three carbs to Flying W, and i sent an additional SX carb to him for a friend. i've been very happy with the results. The 3rd carb, however (on the 86) has similar symptoms to what you're describing. If i just bury the throttle from idle, it coughs and will die if i don't give it a little cajole. I even contacted Flying W about the issue. He said that it was not uncommon, and occurs more so on engines during warm up. I have found that the slightest bit of throttle control will solve the issue. At least in my case it did. It is not even noticeable to me now. The tiniest bit of sensitivity is required to achieve smooth acceleration. It has had zero change on performance, as it is only required from idle, and not while accelerating during normal riding. I have the utmost respect and admiration for Jim's work, and would highly recommend it. He provides a quality service at a great price. He is timely and communicates great. Take a look at his feedback page. It sounds like you have taken your time and done things right. I think that it may just be how that particular carb performs. I would encourage some saddle time to see if you can get used to a throttle range. Its not just an on/off switch. Try an almost imperceptable amount of smoothness in your thumb. (also, make sure your cable is free, properly adjusted, lubed, and not stretched) See if the issue is something that can be overcome. I would recommend that over a Chinese carb all day. Hope this helps and please keep us posted.

[Speedgoat]

take this for what it is. its not a slight in any way. every situation is different, and this is just my experience. I have two SX's. an 85 and an 86. I also have an 85 ES. I've sent all three carbs to Flying W, and i sent an additional SX carb to him for a friend. i've been very happy with the results. The 3rd carb, however (on the 86) has similar symptoms to what you're describing. If i just bury the throttle from idle, it coughs and will die if i don't give it a little cajole. I even contacted Flying W about the issue. He said that it was not uncommon, and occurs more so on engines during warm up. I have found that the slightest bit of throttle control will solve the issue. At least in my case it did. It is not even noticeable to me now. The tiniest bit of sensitivity is required to achieve smooth acceleration. It has had zero change on performance, as it is only required from idle, and not while accelerating during normal riding. I have the utmost respect and admiration for Jim's work, and would highly recommend it. He provides a quality service at a great price. He is timely and communicates great. Take a look at his feedback page. It sounds like you have taken your time and done things right. I think that it may just be how that particular carb performs. I would encourage some saddle time to see if you can get used to a throttle range. Its not just an on/off switch. Try an almost imperceptable amount of smoothness in your thumb. (also, make sure your cable is free, properly adjusted, lubed, and not stretched) See if the issue is something that can be overcome. I would recommend that over a Chinese carb all day. Hope this helps and please keep us posted.

If I am easy on the throttle,like you mention above , it runs perfect. I simply have a hard time accepting that outcome. I ordered a new cdi tonight. I will se if that makes a difference. If no improvement with that I am either going to live with it or try a used 300ex carb. I appreciate your response.

[redsox]

not easy on the throttle,,, smoooooooth on the throttle. :cool:

like they say,,, slow is smooth and smooth is fast,, er something'... just don't direct pin it cold and you should be ok.

[Dirtcrasher]

You should be able to nail it.

Is the air filter box closed up or does it have any holes in it?

What exhaust are you running?

No air leak if you spray around the intake while it's running?

[Speedgoat]

You should be able to nail it.

Is the air filter box closed up or does it have any holes in it?

What exhaust are you running?

No air leak if you spray around the intake while it's running?

sprayed everywhere with no change in idle speed or sound. tried airbox closed, airbox open, filter and no filter. no change with any of the above.
stock exhaust

[Speedgoat]

I know it may sound crazy, but do you have an extra CDI laying around?

I had the same sorta issue, thought it was the carb, like you, spent a ton of time on it, and all along it was a bad CDI. Replaced it and, was good to go.
Just replaced cdi. Nothing changed. Exact same idle and throttle response.

[dragonslayr]

I'm gonna weigh in here too for sending to Jim and let him do his magic on it OR follow his advice like I did (cause I'm a cheap trailprotrailprotrailprotrailprotrailprotrailprotr ailpro) and drill out your starter jet and this will help a bunch in cold starts!! I am in Michigan and even when it's fifty degrees I need to use the "choke" and then a little throttle and feather it a bit. I can definitely relate to the lack of finesse with a throttle but am learning;;;;; I think. I should also add that even after I have run it till I KNOW that the engine is warm and then shut it off for an hour I (may) have to duplicate my cold weather starting procedure. I now have Two 250sx's and a third that belongs to a buddy and ALL THREE do EXACTLY the same thing you are saying; if I am following correctly. Once these are warm like Speedgoat says you should pretty much be able to nail the throttle and get instant acceleration!! Good luck, Walt~