The ATC250SX/ES Cold Start Kit

[mad_max]

Well after a dozen or so phone calls I found a Honda dealer that had part # 06161-HA0-305 in stock. This kit has been discontinued by Honda, so the only way to get one is to find a dealer that still has on the shelf. I found this at Vernes Honda in Antigo, WI. The kit comes with no instructions but Scott at the dealership was cool and made a copy of the bulletin for me. For those that arent familiar with this kit it was the subject of a service bulletin dated November 1985 and updated in February 1986. It addresses a hard start when cold condition on the 1985 ATC250SX and ES (Big Red). It consists of a new starter jet and a number of vacuum hoses, tees, clamps and a bracket. The trickiest part of the upgrade is trying to pull the old starter jet out of the carb without damaging the carb body. This is done by screwing a sheetmetal screw into the old jet and slowly working it out of the carb. The new jet is tapped in, the hoses and tees are added and voila you have (or should have) a good cold starting carburetor. The difference in jet hole size is obvious. I saw a post once where sombody mentioned drilling out the jet. The hole is still small enough that drilling the old one out to a larger size would be a crapshoot. Also, there would be debris from the drilling that would get in the carb. I installed it last night and it works great, starting is almost instantaneous now. Anyway, enough of me, here a pic of the kit.

[250SX_rider]

That's cool...you got lucky to find a kit like that...

[Seabass]

Took me two weeks to find one in Canada, Still haven't installed it yet. Maybe this week-end? Looks a little tricky....

[rob0781]

you should take mesurments on those parts and make some diagrams it looks like it wouldn't be to hard to throw one of those setups together from scratch..Just a thought someone might be able to build those and sell them since you guys say they are discontinued i'm sure there would be buyers,heck tell me the measurments i'll try to build that same setup can't be hat with a torch and some metal and a drill ,dremel and a grinder,than just buy rolls of vacuume lines in bulk same for those c-clips..even those plastics fitting are easy to get they have identical ones at hydroponic supply stores.

[bbechtel16]

Or you could just swap out for a 350X carb. :twisted: Or an '86 stock carb.

[broook]

I had a brand new 85 with the cold start problem using the electric start but it always started easily with the kickstart.

The dealer at the time told me it was an "airlock problem" and when I kickstarted it the the trike would rock a bit and the air bubble in the carb moved and let it start.

I still don`t know if I should believe that or not. I still think it is the starter jet being too small.

:oops: Sorry I posted this to the wrong article before. :oops:

[250SX_rider]

Or you could just swap out for a 350X carb. :twisted: Or an '86 stock carb.

What did Honda change on the carb on the '86 models??

[mad_max]

250sx_rider: I believe the 86 carb is different as far as how the choke/start valve is mounted, I've heard that the 86 carb wont totally bolt on to the 85 because of it.

[eh_tee_see]

the 85 250sx shop manual says they wont fit and it shows 2 diagrams of the 85 carb and 86 carb, the 86 is slightly different i cant remember how.

[jeswinehart]

i too had the cold start problem with a es ( 1985 ) and bought a 86 modle carb and it fit right on w/o any noticable troubles. works alot better also.

broook,,, i don't think that sounds right either,,, air-lock thing.




john

[BigRedRunner]

I just bought an '86 carb the other day because of this! So far I've blown money on that, seat cover, innertube, fenders, and had the rear rack painted. Gotta sell this pig and get my 650R home from the dealer.

[Dirtcrasher]

Or you could just swap out for a 350X carb. :twisted: Or an '86 stock carb.

What did Honda change on the carb on the '86 models??

The 85 is a Keihin model 03 carburetor. In stock form the starter jet hole is too small and creates a hard cold starting problem. The vent hose kit is nice but does nothing more than " T " the hoses together.

The 86 and 87 250SX carb is 100% interchangeable with the 85 model. It is a Keihin model 08 with the exact same carb housing. Honda changed the diameter of the choke plunger (on the end of your cable). And also removed the pressed in starter jet (the one Max yanked out with a sheet metal screw) and put a rubber plug there. Then they drilled a hole on the side of that same passage and inserted a threaded starter jet.

If you buy an 86 or 87 carb you better ask that the plunger is included but they bolt right on to an 85.

The 350X carbs I have seen models Keihin 05 and 10 - the 10 has the same modified starter jet passage as the 86/87 250SX model 08. In other words I believe there must have been some problems with the 85 350X in the same respect.

A 350X carb - again - is a direct bolt on for a 85,86 or 87 250SX. The 350X carb has a larger throttle valve (the slide itself) and will allow more air to pass through the carb body. It also has a 138 main jet and I forget what size the other jets are but they are not designed for a stock 250SX motor. You can however simply unscre the 350X main jet (138) and install the SX 130main and it will work just fine. Or take the air box lid off, get a better breathing exhaust and with the 350X carb and the 138main jet I promise you some very nice power gains everywhere.

The 350X carb also has a fuel bowl with a large plug which allows you to change your main jet on the ATC rather than removing the whole carb and fuel bowl. This 350X fuel bowl bolts right on to an SX 03 or 08 carb.

The 350X carb also uses a lever mounted choke. Which can be used on the SX - but on full choke the lever will hit the SX round frame portion where the tube from the airbox to the frame is mounted. You can merely grind just a bit of the lever off and it works fine.

With this setup you can get rid of your sticking handlebar mounted choke lever setup and use a typical carb mounted lever.

With a piece of brass and a lathe the starter jet could easily be made. I'm willing to bet Keihin can provide the larger starter jet needed if you bugged them enough.


When buying used carbs....


If you buy an SX carb get an 08 MAKE SURE TO GET PLUNGER!!!!!! And make sure it has the rubber plug with it or you have will buy a 15$ gasket kit.

If you buy an X carb get a 10 and it will have a lever choke.

Hope this helps clear up the 85 versus 86/87 and the 350X carbs. :-D

[BigRedRunner]

The 86 and 87 250SX carb is 100% interchangeable with the 85 model. It is a Keihin model 08 with the exact same carb housing. Honda changed the diameter of the choke plunger (on the end of your cable). And also removed the pressed in starter jet (the one Max yanked out with a sheet metal screw) and put a rubber plug there. Then they drilled a hole on the side of that same passage and inserted a threaded starter jet.

If you buy an 86 or 87 carb you better ask that the plunger is included but they bolt right on to an 85.


You just about gave me a heart attack. I spent $32 on an ebay carb only to find out I might be SOL if I don't get the plunger. However, I checked the Honda part numbers for 1985, '86, '87, and they all use a 16046-HA0-013 plunger set, so I don't think this is an issue then. :)

[Dirtcrasher]

The 86 and 87 250SX carb is 100% interchangeable with the 85 model. It is a Keihin model 08 with the exact same carb housing. Honda changed the diameter of the choke plunger (on the end of your cable). And also removed the pressed in starter jet (the one Max yanked out with a sheet metal screw) and put a rubber plug there. Then they drilled a hole on the side of that same passage and inserted a threaded starter jet.

If you buy an 86 or 87 carb you better ask that the plunger is included but they bolt right on to an 85.


You just about gave me a heart attack. I spent $32 on an ebay carb only to find out I might be SOL if I don't get the plunger. However, I checked the Honda part numbers for 1985, '86, '87, and they all use a 16046-HA0-013 plunger set, so I don't think this is an issue then. :)

I have owned at least 20 or more of these X and SX different carbs and my 85 plungers are smaller in diameter than the 86 and 87.

Not sure about the part numbers but I hope it works out for you.

[bbechtel16]

Or you could just swap out for a 350X carb. :twisted: Or an '86 stock carb.

What did Honda change on the carb on the '86 models??

The 85 is a Keihin model 03 carburetor. In stock form the starter jet hole is too small and creates a hard cold starting problem. The vent hose kit is nice but does nothing more than " T " the hoses together.

The 86 and 87 250SX carb is 100% interchangeable with the 85 model. It is a Keihin model 08 with the exact same carb housing. Honda changed the diameter of the choke plunger (on the end of your cable). And also removed the pressed in starter jet (the one Max yanked out with a sheet metal screw) and put a rubber plug there. Then they drilled a hole on the side of that same passage and inserted a threaded starter jet.

If you buy an 86 or 87 carb you better ask that the plunger is included but they bolt right on to an 85.

The 350X carbs I have seen models Keihin 05 and 10 - the 10 has the same modified starter jet passage as the 86/87 250SX model 08. In other words I believe there must have been some problems with the 85 350X in the same respect.

A 350X carb - again - is a direct bolt on for a 85,86 or 87 250SX. The 350X carb has a larger throttle valve (the slide itself) and will allow more air to pass through the carb body. It also has a 138 main jet and I forget what size the other jets are but they are not designed for a stock 250SX motor. You can however simply unscre the 350X main jet (138) and install the SX 130main and it will work just fine. Or take the air box lid off, get a better breathing exhaust and with the 350X carb and the 138main jet I promise you some very nice power gains everywhere.

The 350X carb also has a fuel bowl with a large plug which allows you to change your main jet on the ATC rather than removing the whole carb and fuel bowl. This 350X fuel bowl bolts right on to an SX 03 or 08 carb.

The 350X carb also uses a lever mounted choke. Which can be used on the SX - but on full choke the lever will hit the SX round frame portion where the tube from the airbox to the frame is mounted. You can merely grind just a bit of the lever off and it works fine.

With this setup you can get rid of your sticking handlebar mounted choke lever setup and use a typical carb mounted lever.

With a piece of brass and a lathe the starter jet could easily be made. I'm willing to bet Keihin can provide the larger starter jet needed if you bugged them enough.


When buying used carbs....


If you buy an SX carb get an 08 MAKE SURE TO GET PLUNGER!!!!!! And make sure it has the rubber plug with it or you have will buy a 15$ gasket kit.

If you buy an X carb get a 10 and it will have a lever choke.

Hope this helps clear up the 85 versus 86/87 and the 350X carbs. :-D

Well done!!!! :clap: :clap: :clap:

[broook]

:-D Thanks for the information Dirtcrasher, after 19 years we finally find out the truth. I always suspected the starter jet being the problem but how do you argue with a "Certified Honda Dealer".

Thanks :-D

[Dirtcrasher]

This was my post 18 years ago, and it may help some newer members today. I had to dig up the corpse for someone who needed help.

The biggest issue, if your SX doesn't start in the cold, is the pressed in starter jet. You can use a .080 drill with some grease on it to catch the majority of brass chips, now you'll have the improved sized starter jet. Be aware that brass grabs drill bits easily and violently, less rake on your drill bit is better, or a drill press where you can control things a bit better.

Be sure to remove all other jets, the pilot screw, and blow out any chips when your done...

[keister]

How time flies. When this post was made the 1986 models were 18 years old and ATC parts were still kicking around shelves at Honda dealers.

I love the symmetry of this post being 18 years ago. I wasn't a member yet, but I was definitely lurking on this site.

Good info, DC. Thanks for bringing it back.

[Supraman0614]

One tip I've learned over the years as it relates to drilling and carburetors is to cover any holes with petroleum jelly (once you remove the jets). It will catch all of the chips, can be blown back out when you're done drilling, and any residue won't affect anything.