85 250sx carb issues

[fordsohc46]

hard to start when cold when warmed up runs good sometimes. spits sputters, backfires and dies other times and revs up high at idle in nuetral. leaks out of overflow on bottom of carb sometime sometimes its ok. should i get a kit and rebuild this thing needing suggestion i am an auto mechanic dont know much about atc's. any help would be appreciated. saw on forum some people were getting new carbs.


1985 250sx

[tri again]

Since no one's replied, I'll give it a shot.

The hardest thing about those is getting them on and off wrestling the hoses.
The rest is very straight forward.

Take it apart and clean it, take the jets out and make sure the internal passages are clear too.
There is one jet that has an emulsion tube underneath it and very easy to miss.
It pulls out easily with a bent paperclip and is usually full of mud.

Make sure the choke enrichment piston moves freely but whatever you do, do NOT
yank the cable out of it. They can become terminally stuck so take your time on that.

There was a cold start recall on some of the 1985 models but general consensus is to drill out the
cold start jet to .080" but I would check on that.

Make sure the float needle spring tip moves freely and i think that's about all the surprises I can remember.

Also might be easier to start with a couple well placed kicks on compression stroke,
slosh the trike side to side to splash gas internally...maybe.

Let us know what you find.

Most of the time you don't even need a rebuild kit.

Just uninterrupted time, good light and vision and no chance of losing tiny parts in the dirt.

I have a brand new garbage can lid just for carb parts to fly around in.

I also blow into the fuel line and turn the carbs over to make sure the float opens and closes.
You can hear them hiss and then stop when you turn them over before you put it back on.

To answer your last Q, I hear that 85-87 carbs for the 250cc hondas are hard to find.

The 185-200 folks are very lucky getting 20$ carbs from ebay NEW that usually work great.

ps - the cold start bulletin is for an es but the carbs may be the same.
keihin QA 01?

[beets442]

Take the carb off, take it apart and clean it.

[ailll1]

A new carb is way too expensive for the SX/BR. Clean it first and make sure everything works as it should. If nothing changes, just buy a carb kit on ebay. They're about 20-30 bucks. Bought one last summer, runs great since then. Sometimes jets or needle wear out and no matter how many times you clean it, it wont run right.

Pissing gas through the overflow usually means a stuck float or float valve.

P.S: Ebay carb kits wont solve your cold start problem.

[Dirtcrasher]

It's all in the starter jet, I am 100% that is your issue............

An 86 or 87 Keihin08 model carb will fix it also.