Carb issues on 250SX

[Big Sal]

Hey guys looking for some opinions...
I can't get full throttle on my 250SX...it bogs badly, if I ease it it does ok....and on low end it stubles at light throttle just off idle and sometimes dies...I moved the clip all the way to the lean end...the air screw is out 2.25 turns...everything is tight...the rebuild kit I bought was from Moose...reading thru the posts they aren't real popular..lol.
My questions are...who's carb kit is recommended? What jet size is stock? (the bike is bone stock except for the Moose air filter) and where is the stock clip setting for the needle (I'm assuming it's in the middle) but figured I'd ask.

The owners manual also said something about syncing the carb, but it doesn't say wether you should set it with the throttle all the way closed (idle screw backed all the way out) or after the idle is set.

I think somebody has had the carb off and apart before I got it (hence the questions)...the little plastic baffle plate is missing also...but I don't ride that hard to worry about it...maybe it's time for a manual....lol

[Thorpe]

MOOSE kit... There is your problem... I had on my ES, a moose kit, that the jets were number correctly, but the hole size of the jets was massively different....

Here is the downloadable manual for your SX... http://www.3wheelerworld.com/showthread.php?56218-Get-your-trike-service-manuals-here!-Updated-9-13-07

[Big Sal]

So the Moose kit is junk....does Honda make a kit?

[Big Sal]

I found out something interesting looking for carb info for my 85 250SX...the Honda service manual says the main jet is a #130, I've read on here that some people dropped to a #92....big difference...it's still not getting to top end, runs badly just off idle and kinda misses thru the mid range, I've cleaned the carb several times, and checked all the adjustments, 2 turns out on the air screw, 2nd notch down from the top of the needle, zero space in the linkage to "sync" the butterfly and slide valves and still running a 130 jet (I assume, it's the one that came with the Moose rebuild kit).....it starts up fine and idles ok but it dies if I stab the throttle to WOT, still runs like crap, and turns the plug black...should I drop down the main jet? I have a #108 jet I can put in it....could it possibly be a electronics problem like a bad coil? Any and all opinions are welcome! :)

[tri again]

Does it have a stock exhaust and non modified airbox?

I heard that shindy was the oem honda jet supplier and even called their headquarters
trying to find the elusive cold start jet for the 85 250.

Found a shindy kit locally at a triumph dealer fpr 18$ and it worked great.

Just because the jets are new or clean doesn't mean the internal passages are.
I got so aggravated I just started boiling them in a pot of water with vinegar and blowing the internal passages underwater so I could SEE where the bubbles were going.


There is also an emulsion tube UNDER one of the screw in jets that I missed 2x on mine.
It's about eh size of a pencil lead and an inch or so long...full o' holes and plugged with rustdust.

Not sure why I like this chart, but it may help.

yupp, been thru at least 20 of those carbs.
Worst part is getting them off and on.

My latest sx has an aftermarket keihin with an accelerator pump
and a regular flip lever choke instead of that
enrichment circuit piston fiasco.

Of course, when they run right, we forget about the headaches.

Keeping the tanks full, NON ethanol gas and drain the float bowls if they sit for over a month.

Is there s number on that carb?
like keihin QA01?

and yes, electrical breakdown could be it too, as in bad frame ground?
so? it idles but nothing more than that?
will it rev with the choke on?
No difference? choke on or off?

nip the last tiny bit off the coil wire where the plug cap screws into.
I've had THAT screw me up for days after a major overhaul, worrying about everything except THAT!

I even shoved a guitar string into the coil wire and ran it direct to the plug, bypassing the sparkplug cap.
Didn't know whether to be aggravated or happy when I found that to be the problem.

STILL *&^$%me off when I think about it.

Had been thru that carb about 3x before I looked elsewhere.

When you finally get it going.
you'll forget about the pain.

ps - never personally had this prob but there's supposedly a weak electrical link near the battery on the sx's
apparently something moves with the suspension.

so again, it idles, but dies with any more throttle?
Can you rev it with the choke on?
Is the gas tank cap vent working?

I had one I KNEW the tank was full so I never checked it.
A friend happened to pop the gas cap and it wooooshed like it was holding a vacuum, not letting enough gas into the carb.

Can you get it to rev if you judiciously spray staring fluid into the carb while trying to rev it?

Has it ever run good that you know of?
did it just get bad over time or is this all new to you?
As far as electrical, some folks have changed entire wire harnesses only to admit that they
work only because they had to go thru every electrical connection to change harnesses and that
the old ones were probably ok.

After you get it running, make sure to change the gear oil in the differential.
it's only like 3 ounces and needs every drop..and they easily allow water in.

Can't think of any other obvious issues at the moment, but please keep us posted.

[Big Sal]

Hey drjoe...thanks for the reply...it starts fine, it's all stock air box to exhaust, the only thing it has it a Moose air filter (foam) which doesn't affect it any. I read several posts where the main jet being used is in the 90's, the honda service manual says it's a 130, I've even tried backing the needle all the way to the lean side. I found the tube under the jet...it just kinda sits in there and pokes into the venturi, that was pulled out and cleaned also. It starts and is rideable but it doesn't run "perfect" (like the breaking up just off idle and the bogging at the upper end of the throttle) so I'm trying to get it worked out so it's smooth across the entire RPM range. I will check the coil wire...didn't think of that. I know electronic problems are few and far between but I'm starting to think that it may be my problem. I change the oil in the diff every 3-4 runs or anytime I'm in deep water...cheap insurance...lol

[tri again]

I wrote down the jet placements but I have to look back thru 3 or 4
notebooks to find it.

Shoulda wrote it on the barn door.

So now it's just an annoying stumble?
ya know?
they say plugs can't be cleaned once fouled.
They'll track spark down the outside of the insulator instead of jumping the gap.

I DO clean them with a 10$ sandblaster plug cleaner from harbor freight
and that works about 4 or 5 times.

Is the gas nice and fresh?
I hate to suggest a new plug but I've seen that make a huge diff
but it sucks to foul a new plug for no reason too.

How's the valve adjustment?
compression good?

Hard to tell who's done what to these things over 1/4 century.

I'm gonna go ride right now and look for the jet notes I wrote down.

I just got another sx for 200$ less because it just wouldn't / refused to run right.

Next day, changed the gas and plug and that sucker almost flipped me over backwards accelerating Downhill.

did that jet chart help at all?
It idles like a dream?

How about if you throttle up super slowly?

Does your choke enrichment piston move nice and freely?
Does the choke on or off make any diff when acceleerating?

[Big Sal]

New plug, valve adjustment good, compression @170, slider doesn't bind, cut the end off the spark plug wire to get a fresh contact and nice fresh gas...I took care of the low end stumble (adjusted the "sync" to open the slider a bit sooner and it took it away) but it still dies when I push the throttle to full open ( sitting and idling)...under load it hesitates/bogs but if I back off the throttle a bit it picks up and goes. When it does start running badly wide open, it bogs/hesitates badly and sometimes it backfires a little bit (not a huge bang). Choking it while riding it makes it run really bad...lol. The plastic cap for the choke cable that screws into the carb has a chunk out of the very top where the cable goes into it (not at the base where it screws in)...should I get a new one? I'm running regular gas in it too, should I be running premium? I'm thinking of getting a new choke needle assembly too...the O ring looks pretty beat on it.

[Tippmann98]

I rebuilt my 250sx carb with a Moose rebuild kit. She ran great after that. . . . every situation is different.

[Headsup]

Big Sal, I also have a 85 250sx, Same problem, When at idle and i punch the throttle. She just dies..
Also my choke piece is broke also liek yours, Allowing many things to flow down there, I never got it fixed, But i am assuming now that it would have to be the choke cable.. i tired to seal it up but no help. Still same, Trust me, Its not your Jets, Or carb,
It simply cannot be,, I been threw this carb 10+ times with the same thing, Dies when stabbed throttle..
Pick yourself up a new choke cable, See if that helps. If not i will on mine and reply my results,

[Big Sal]

Maybe it's just the nature of the beast...I'll get one too and post up my findings...think I'm going to get a choke needle assembly too...can't be that expensive and it will eliminate the choke circut all together...

[Headsup]

Ok, Thanks, Also if u find a fix Please post, I been looking for maybe 2 months now, Messing with it everyday, Without the choke cable, i dont think it can be fixed, Must be it,.
As for Non grounded or Badly ground ground wires.. Idk, Never had any problems of such.,
Just dont waste another 2 hours tryin gto get your carb off and back on,, Stripping screws and whatnot, Just try for the choke cable. I am sure that air shouldnt flow into the plunger hole into the carb, Pretty much would make a Fuel air screw Useless.\
idk first timer also on a trike, Had it for 6 months or so, Always done it, I also bought a brand new Jets size for main was standard 130, No help, Just dont waste your money on carb, or rebuild for your carb without trying the choke cable first.

[tri again]

ok
the first one is the float
then 130 main
next is 38
next is the press in cold start jet
next is 45
and next is the pilot screw

[tri again]

I've got some sort of keihin aftermarket carb on a new sx
but I'll have to get the numbers off it.

has a regular flip choke and an accelerator pump which makes it
freakin' skreeeeeeeeeeeem

I also just hit the throttle a couple times before I start it and it squirts a little gas
from the pump so no choke needed.

I'm a pretty hard core stock kinda guy but this carb is super impressive.

[Big Sal]

Digging around a bit more I found that the plastc piece that screws into the carb is a separate part all together than the cable itself. The part is a "valve set, starter" (Honda part number #16046HA0013), it comes with the rubber sealing boot, cap (screws into the carb that the cable runs thru), spring and plunger, the parts fiche I have does not show the rubber O ring seal (at the base of the plunger) as being separate from the plunger itself, so I'm assuming it's one piece. The good news is Honda still stocks it, the bad news is that little bitty part is $49.07...lol. Not a bad price if it eleminates the problem, kinda expensive is it doesn't, seeing the fact that a relacement "chinese" carb isn't much more than that...

[Big Sal]

Thanks drjoe, they are what I have installed, it's either the choke assembly not sealing up correctly or I have electrical issues, the spark seems kinda weak to me, I had a spare coil so I swapped it out with no change, I guess I'll check all the connections from the CDI box and see if anything is corroded. Swapping for a new CDI is next...do they make anything after market? Maybe even a performance one?

[tri again]

you can try the classifieds on here for a cdi.
For cheap entertainment, there's a scary site called
sunLpartsonline that has cdi units from 69CENTS! but they don't really say what they fit.

dratv aka beatrice cycle seems to have a bunch and crossover info.

I found sx carbs on ebay..some place in Florida that I called directly
instead of bidding but wanted to stay stock.
They had 'one that would fit' with a flip lever choke.

and now my new sx has one that is just cool, simple and works
with the accel pump. and black plastic flip lever choke.
It's says keihin and I'm gonna get up, go outside and get the godbless'ed number off that thing.

After going blind reading wire diagrams, there is a ground that the cdi needs TO run that is laced thru the kill switch, which also grounds to Kill it. so I'd make sure that's all nice and clean.

Now is this trike new 2 you? has it ever run good?

Back in a minute.OK
it's a Keihin QB 01B A FO and then a square with a missing left side like a backwards 'c' and that A has a rectangle around it.

regular flip lever choke and accel pump that squirts gas.
seems to make this 2x faster than any of my other (7 or 8) 250's

[d_dudeck]

hey just wondering with the choke cable idea....one of you guys buy one and try it? i have the same problem with punch from idle and dies. i also have same issue with the choke cable. wondering if that fixed it?

[tri again]

hey just wondering with the choke cable idea....one of you guys buy one and try it? i have the same problem with punch from idle and dies. i also have same issue with the choke cable. wondering if that fixed it?

This chart may help.
The slow jet is so tiny, like the smallest electric guitar string (.008"-.010"),
it plugs easily, and usually with some very hard crystalline crud that may beg for a drill bit.

Free manuals can be found in the world class help section.

Welcome, btw.

Keep us posted.