In need of 85 250SX carburetor help

[AF79]

I started working on the new to me 85 250sx today, my first atv let alone atc :). The engine would kick over pop pop pop and die out, so I figured I would start by cleaning/rebuilding the carburetor. I ordered a moose racing carb kit as safe precaution. Everything was going great until I looked at the pilot screw or should I say what was left of the screw. It looks as though the previous owner snapped the head clean off at the carb. Have no fear, screw extractor to the rescue. Drilled a nice straight hole, inserted the extractor, slowly started backing it out and....SNAP. The extractor broke off dead center in the broken head of the screw. OK...grabbed a diamond bur for the dremel to grind the hardened steel extractor tip out of the bit. After a few minutes of slowly grinding, looked like we are back to square one. Repeat drill, insert, and what I did not want to hear again... SNAP. Second extractor broke off. At this point I am worried there is not enough material to even attempt to grind out and try another extraction. Beside I am thinking the previous owner must have either really cranked this screw down or even cross threaded it for it to not even move. Does anyone have any other tricks to getting a broken pilot screw out or have an old 250sx carb taking up space on their shelf they could part with? Thanks.

[Flyingw]

normally I have rebuilt SX carbs for sale but I'm out right now. I can't tell you how many carbs I've tossed because the brass pilot screw was fused in the hole. If there's not enough pilot screw meat left then you're better off buying a used carb off Ebay and transferring your carb kit in to it. The ES carbs are basically the same as the SX carbs so dont limit yourself to just SX carbs. I am more than happy to help you with your carb any way I can. I have had many guys send me their carbs so keep that as an option.

[AF79]

Thanks Flyingw. I thought the es carb was the same too. I will look into that as an option. Would the seals from the kit match up on the es carb? I am really excited to learn as much as I can about this bike. Thanks again.

[Flyingw]

The ES/SX/350X/TRX250 carbs are all QA series carbs. There is a QA number right below the fuel inlet nipple. The difference is the venture bore is larger on the X whereas the jet arrangement is slightly different on the TRX carb but the ES/SX will not run right with a TRX carb in it. With all that said, yes, the bowl and top cap seals are the same. Now, when you go to switch the carb kit from the bad carb to the replacement carb, you will find the bowl gasket is too large and wont fin in the groove. No worries, its supposed to swell when exposed to fuel. The fix, rinse the bowl gasket with rubbing alcohol. When your wife isn't around, set the oven to about 150-170F and with a piece of wire hang the bowl gasket in the oven for about 10-15 minutes. It will shrink back up. Like I said, if you want to do the rebuild yourself, I will give you a step by step with pics. Its pretty simple but there are a few areas that need attention in order to ensure the carb is clean and adjusted right.

QA01A = 85 ES
QA02A = 85 SX
QA04A = 85TRX250
QA05A = 85 350X
QA07A = 86/87 ES
QA08A = 86/87 SX
QA10A = 86 350X

I tell you this so you know which carbs are which so if you do buy one, you'll know exactly what carb you have.

[Flyingw]

This one might look bad but look at the butterfly, Its clean.

http://www.ebay.com/itm/OEM-1985-Honda-250sx-Carburetor-Keihin-QA-Carb-85-Atc250sx-86-87-250-sx-/181225439510?pt=Motors_ATV_Parts_Accessories&hash=item2a31e0c116&vxp=mtr

This one isn't bad either

http://www.ebay.com/itm/HONDA-ATC250-SX-CARBURATOR-/150679209501?pt=Motorcycles_Parts_Accessories&hash=item23152e461d&vxp=mtr

Stay away from the aftermarket carbs available on Ebay. Guys have reported nothing but problems with them.

20 hours left on this one

http://www.ebay.com/itm/Honda-ATC-Big-Red-250es-Carburator-NR-85-87-/331031094950?pt=Motors_ATV_Parts_Accessories&hash=item4d12fda6a6&vxp=mtr

[wonderboy]

I had this exact issue on my 85 SX carb. It wasn't that hard to drill out the pilot screw. Basically, it seizes near the end of the screw near the head. If you drill a bit, as close as you can get to the threads without touching them. You can drill out most of the brass of the threaded portion until only the narrow part of the needle is left in the hole. Stop at this point and use a needle nose and just pull out the needle. As for the siezed threads, just drill slighly bigger until you can see the threads of the housing through the brass. You should then be able to pick the coil of brass out of the carb body threads and you are back in business. I have an 85 carb for sale in the classifieds that I had to use this technique on. It works without too much trouble.

On a side note, when you get your replacement, use antisieze on the threads so that you won't have this happen again (or to the next guy 20 years from now).

[AF79]

This may be a dumb question but where do I find the classifieds?

[wonderboy]

I don't think you can see them yet... there is a time and post count restriction in order to see the classified ads. You need to put in a bit of time and posts before you get access...

[AF79]

The ES/SX/350X/TRX250 carbs are all QA series carbs. There is a QA number right below the fuel inlet nipple. The difference is the venture bore is larger on the X whereas the jet arrangement is slightly different on the TRX carb but the ES/SX will not run right with a TRX carb in it. With all that said, yes, the bowl and top cap seals are the same. Now, when you go to switch the carb kit from the bad carb to the replacement carb, you will find the bowl gasket is too large and wont fin in the groove. No worries, its supposed to swell when exposed to fuel. The fix, rinse the bowl gasket with rubbing alcohol. When your wife isn't around, set the oven to about 150-170F and with a piece of wire hang the bowl gasket in the oven for about 10-15 minutes. It will shrink back up. Like I said, if you want to do the rebuild yourself, I will give you a step by step with pics. Its pretty simple but there are a few areas that need attention in order to ensure the carb is clean and adjusted right.

QA01A = 85 ES
QA02A = 85 SX
QA04A = 85TRX250
QA05A = 85 350X
QA07A = 86/87 ES
QA08A = 86/87 SX
QA10A = 86 350X

I tell you this so you know which carbs are which so if you do buy one, you'll know exactly what carb you have.

Flyingw,
I could use all the help you can give. I really would like to do the work myself and have some mechanical knowledge, but have never rebuilt a carb.
Thanks for the help.

[Flyingw]

Ok, give me a day or so to put the instruction together. I'll post it here in segments. Don't be intimated by the carb. They really are pretty simple. Right now I don't have any SX carbs so I will be using a 350X for illustration purposes but the X and SX carbs are very similar. In the mean time, get yourself a rebuild kit coming your way. Be sure to order for the year carb you have.

[AF79]

Thanks flyingw.
I have the carb kit, but with the pilot screw snapped off in the carb body I am at a bit of a stand still. :(

[Flyingw]

Ya that's a problem. Well, until you get that pilot screw out or replace the carb, you're at a stand still. I would take Wonderboy's advise for getting the pilot screw out.

[AF79]

Looking at the package for the moose carb kit, it looks like this is for the 86-87. Will that work on a 85 carb or did the guy at the shop order up the wrong kit for me?

I am going to try to drill the pilot out ...what have I got to lose. :)

[Flyingw]

Wrong kit, you need an 85 kit. There is a primary jet in the 85 kit that is not in the 86 kit otherwise the rest works. Both kits should have a #130 main and #38 slow jet. What the 86 kit does have the 85 kits don't is the spring and bolt for the idle knob. I wish both kits had that but they don't. You might just keep the 86 kit and pickup an 85 kit that way you'll have a new idle knob spring/bolt and a set of spare jets and gaskets.

[Flyingw]

Ok, let me know how you make out. I am posting the rebuild tutorial here for all to read.

http://www.3wheelerworld.com/showthread.php/161746-ES-SX-350X-Carb-rebuild-Tutoral?p=1257154#post1257154

[AF79]

Wow that looks like the start of a great instructional write up, thank you.

Because of the poor cold starting of the 85 carb, would I be better off looking for a 86-87 carb?

[AF79]

Success! I was able to drill it out. Does anyone know what size tap to use to clean up the threads? Pretty excited I got that out, not gonna lie. :)

[Flyingw]

Wonderboy and I were having a conversation about that very thing. The pilot screw diameter is 5.95mm but the thread pitch is super fine, less than 0.5mm. My gage stops at 0.5 so its somewhere in the hood of 0.4 or 0.3mm. Good luck finding a cleanup tap that fine commercially available.

[Flyingw]

and yes, if you are going to do the rebuild yourself, an 86 carb is most desirable.

[Flyingw]

Wonderboy determined the tap size for the pilot screw hole is 6mm x 0.5 and they are available retail online.

http://www.amazon.com/6mm-High-Speed-Steel-Plug/dp/B0006FI7TU

[AF79]

Ok, let me know how you make out. I am posting the rebuild tutorial here for all to read.

http://www.3wheelerworld.com/showthread.php/161746-ES-SX-350X-Carb-rebuild-Tutoral?p=1257154#post1257154

Flyingw, this tutorial is turning out great. The photos are perfect.

[AF79]

I have the body soaking in carb cleaner. What is the best way to clean the outside of the carb body? Soda Blaster?

[Flyingw]

I use a #12 glass bead but soda is fine too. I will be covering the prep for media blasting as soon as I get a carb. If you don't want to wait for me then use your common sense when making the body.

[pat b]

How do you set the idle on 85 250sx carb. I see the knob with the spring on it. Looking to find out where adjustment is. Like for example all the way out then 2 turns in.. any info would be appreciated.