TRX250EX Carb interchange - Honda TRX Forum
 
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post #1 of 8 Old 06-10-2019, 03:11 AM Thread Starter
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TRX250EX Carb interchange

Hi all I'm a Newb to this forum, but I've been riding a long time. I have a question about the stock 250 EX carbs. I have a 2005 that seems to have a casting flaw somewhere in the carb body. It runs fine when cold but eventually once its warm fuel will start pouring out the overflow and it starts loading up etc.



Ive replaced the float, needle, and seat, resealed overflow tube etc., same result.


I've decided to just replace the carb, the Chicom replacements don't seem to be a good option.


So the questions is this: the 01-05 carbs from Honda sell for nearly double that of the 06 and later carbs (16100-HN6-A31). Are they essentially the same except for jetting/slide/needle? I have already rejetted my old carb so I figured I'd just buy the newer one (if it fits) and swap my jets over.


Any experience out there with this swap?
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post #2 of 8 Old 06-10-2019, 03:30 PM Thread Starter
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Crickets............So I spent some time online comparing component part numbers on the Honda diagrams. Looks like they are similar, many parts are same, jets definitely different, Pilot is way leaner, needle different. So I ordered an 06 carb,I’ll post what I figure out
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post #3 of 8 Old 06-10-2019, 04:33 PM
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Pretty impatient aren't you?

I just got online - the carbs are essentially the same - the 06 is in greater supply than the 05 and the differences are subtle, but important.

They use the same float needle, but different floats - the 05 and 06 had the same main jet (#95) but different pilot jets (05 #38 and 06 #42) this was done to complement internal dimensional changes in the cross drilled passages (the air passage for the idle circuit is larger to comply with EPA demands for leaner mixtures at low speed) and the profile of the fuel idle mixture screw was modified.

The slide profile was changed, the main jet holder was changed and the slide needle and needle jet were changed again to comply with EPA emission requirements.

The 06 carb will bolt right onto the 05 and function exactly the same - only difference is you will need to remember it is an 06 carb if you need parts for it and the info should be passed along to the next owner so he will be able to get the correct tuning info if needed.

It's cheaper because it has less materials (thinner), is a poorer quality of aluminum and had a longer production run (PDC1D-A 01 to 05 [5 years] - PDC1G-A 06-12 [7 years])
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post #4 of 8 Old 08-09-2019, 05:31 PM Thread Starter
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Update - Success!

LoL No I'm not patient.


So here's what I figured out. Yes they are pretty much the same but there are some key differences:


- The newer one (16100-HN6-A31) is not thinner, visually they look to be the same thickness, the stripped down late carb body actually weighs 12 grams more than earlier version.


- The earlier carb has "Keihin" cast into side, the later carb is cast "KYB" (Kayaba)


- Later carb has tamper proof idle screw that is covered by a brass plug. You'll need a motion pro 08-0242 socket to fit the d-shaped head on the idle screw. They are about $7 shipped on ebay. The early idle screw will work fine in the later carb, you'll need tne socket to remove the tamper proof idle screw.


- The late model fuel inlet has a small screen in it and fits 8mm (5/16) tubing vs the 6mm (1/4) on the earlier carb. I replaced the petcock with an aftermarket one that had the larger size since it appears that Stabil fuel stabilizer dissolved the screens in my stocker. Link here:


https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1


Slide is different design, but cutout is same. old and new interchange. Needles are different, use your old one.

Jetting of the carbs is completely different, like way leaner to keep the eco-nazis happy. Use your old jets, jet holder, pilot, needle, idle screw etc. Make sure your jets are clean before installing in new carb. Count idle screw turns in your old carb and set it the same in the new one. Fine tune once your quad is warmed up. If you forget this step, set to 1.5 turns out.

So overall, the swap was a success, my 05 runs absolutely perfect with the late carb and it was about $100 cheaper. Hope this helps anyone who needs an 01-05 carb, wants a factory "bolt-on" setup, and doesn't want to pay $230+ for the 01-05 carb. PM me if you have any questions about the swap. Good luck.

Last edited by Dan-o; 08-09-2019 at 07:52 PM. Reason: cleanup
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post #5 of 8 Old 08-09-2019, 06:17 PM
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The fuel inlet filter is not dissolved by StaBil, but from the alcohol in the fuel - the newer carb is slightly heavier in weight while being thinner in casting due to a higher content of zinc and less aluminum - the thinner casting dimensions are not visible, but are there and zinc is cheaper and heavier than aluminum.

Congratulations on the swap and thanks for the info. It is the sharing of info that makes the forum valuable to all the members.
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post #6 of 8 Old 08-09-2019, 07:12 PM Thread Starter
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TRX Carb screen melt

Quote:
Originally Posted by Here 2 help View Post
The fuel inlet filter is not dissolved by StaBil, but from the alcohol in the fuel
This bike has been running pretty high alcohol content in the fuel (California blend) without any problems since new. There's literally been oxygenated fuel in the tank for 14 years straight. I had no issues until it was stored for 2 years with Stabil in the fuel. Then the screens and the plastic standoff mysteriously turned to green goo. So I don't think its the alcohol.
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post #7 of 8 Old 08-09-2019, 08:02 PM
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Quote:
Originally Posted by Dan-o View Post
This bike has been running pretty high alcohol content in the fuel (California blend) without any problems since new. There's literally been oxygenated fuel in the tank for 14 years straight. I had no issues until it was stored for 2 years with Stabil in the fuel. Then the screens and the plastic standoff mysteriously turned to green goo. So I don't think its the alcohol.
Well, you are wrong - alcohol starts doing damage when blended fuel is left undisturbed for over 21 days. The alcohol will separate from the gasoline when the alcohol has absorbed .4% water from the atmosphere. As the alcohol separates from the gasoline, it continues to absorb water. The green goo is usually algae growing in the water. Alcohol will not kill algae, but it will make the algae go dormant and growth is retarded, but it still grows. After the gasoline evaporates, the alcohol/water which is in a layer under the gas begins to evaporate - the alcohol evaporates faster than the water, but eventually it evaporates too.

I was not aware that the vehicle sat unused for that period of time. Now I understand why you needed to replace the carb. Alcohol and water will destroy a carburetor and the alcohol will deteriorate fuel lines, petcock seals and plastic fuel tanks. I use non-ethanol fuel in all my seasonal engines (snow blower, lawn mower, off road motorcycle, street bike, stand-by generators, my Dodge Dakota RT which is only driven in the summer and my pressure washer) - I will use alcohol blended fuel in my Mercury Grand Marquis and my Ford F150, but only for local driving - when I take a trip, I use non-ethanol fuel - the Merc gets 4 miles more per gallon (over 80 miles) with non-ethanol fuel than it did with ethanol fuel. Also, using ethanol blended fuel demands use of fuel 2 octane points higher than the minimum octane required by the engine manufacturer. Your 250 is designed for 86 or higher octane non-ethanol fuel, so you should run 88 or higher octane and it is not approved for use of alcohol concentrations above 10%.

Anyway, glad to hear you are happy with it.
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Quote:
Originally Posted by Here 2 help View Post
Quote:
Originally Posted by Dan-o View Post
This bike has been running pretty high alcohol content in the fuel (California blend) without any problems since new. There's literally been oxygenated fuel in the tank for 14 years straight. I had no issues until it was stored for 2 years with Stabil in the fuel. Then the screens and the plastic standoff mysteriously turned to green goo. So I don't think its the alcohol.
Well, you are wrong - alcohol starts doing damage when blended fuel is left undisturbed for over 21 days. The alcohol will separate from the gasoline when the alcohol has absorbed .4% water from the atmosphere. As the alcohol separates from the gasoline, it continues to absorb water. The green goo is usually algae growing in the water. Alcohol will not kill algae, but it will make the algae go dormant and growth is retarded, but it still grows. After the gasoline evaporates, the alcohol/water which is in a layer under the gas begins to evaporate - the alcohol evaporates faster than the water, but eventually it evaporates too.

I was not aware that the vehicle sat unused for that period of time. Now I understand why you needed to replace the carb. Alcohol and water will destroy a carburetor and the alcohol will deteriorate fuel lines, petcock seals and plastic fuel tanks. I use non-ethanol fuel in all my seasonal engines (snow blower, lawn mower, off road motorcycle, street bike, stand-by generators, my Dodge Dakota RT which is only driven in the summer and my pressure washer) - I will use alcohol blended fuel in my Mercury Grand Marquis and my Ford F150, but only for local driving - when I take a trip, I use non-ethanol fuel - the Merc gets 4 miles more per gallon (over 80 miles) with non-ethanol fuel than it did with ethanol fuel. Also, using ethanol blended fuel demands use of fuel 2 octane points higher than the minimum octane required by the engine manufacturer. Your 250 is designed for 86 or higher octane non-ethanol fuel, so you should run 88 or higher octane and it is not approved for use of alcohol concentrations above 10%.

Anyway, glad to hear you are happy with it.
If you theory were true then the screen would have dissolved years ago since this quad sat every winter for 12 years with ethanol laced fuel with zero problems. And if you actually read my original post you'd find that I replaced original carb due to an internal casting leak. It had nothing to do with"algae" in the fuel, corrosion, or fuel contamination. The green goo was the melted plastic on top of the petcock. You don't know what you are talking about.

-Dan
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