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Discussion Starter · #1 ·
Thank you to all who take time to read -

I recently purchased a TRX400FA7 and ever since I've had it, it will not run unless the choke is completely engaged (pulled up). Even when it's hot, if I try to push down on the choke, the engine starts to stumble and will eventually cut off.
I can turn the idle screw in and the ATV will idle up but I still can't push the choke in without killing the engine.
Before I get too tied up with adjust the carb in such a way that will make my problem worse, I'd like to get expert guidance on what should be my next move.
Filter is clean, gas is good - not sure about the plug as I haven't changed it yet.
It's only got 900 miles on it and it's very clean.

Any help would be greatly appreciated.
 

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well you need to have a good plug or it will never run right
have you actually removed the carb and cleaned it?
if nOT I would start there
that sounds like it needs a good complete cleaning
look on here for post's on how to clean a carb, shoudl; be a ton, if you don't know how, its not that hard, most average backyard tool turners can do it just fine
and your sure the fuel lines are not blocked or patrially blocked??
that can also be a problem
as you didn't list what yr the atv was?
but they haven't made a 400 foreman in a few yrs so, I know its at least a few yrs old, and fuel lines do go bad!
same as vents on the carb
make sure all things are good, and clean the carb
and that should slove the issue I'd say!
 

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pilot jet has some trash into it. This is the circuit that controls your fuel mixture at idle. Download the manual from this site to help you with identifying parts. Also read the sticky on carb cleaning. Check your float valve also as it may have trash in that also restricting fuel flow, as well as the fuel valve on the tank, or a kinked fuel line. Shouldn't be hard to get it right again. Start with the carb clean and go from there.
 

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Discussion Starter · #5 ·
All great ideas but I must admit, I'm not that familiar with the forum setup. How do I search for sticky's?

Also, and this may admittedly be a stupid question, but should I rebuild it (new needles, float, etc..) or should I take the jets and needles out, clean it and put it back together?

Thank you!
 

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carb rebuild kits are cheap
so I'd say why not rebuild it
as for sticky's
look in the how to section
or go to the search option(third from the right up top/ish)
and then enter what you want to find, it will help lead you to like subjetcs/posts/treads!
good luck!
 

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Discussion Starter · #7 ·
Thank you MrBB!
Found it!
I will order the rebuild kit as well. Looks like I've a good weekend night project!
 

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You can attempt to rebuild it without a kit if you are gentle with the gaskets and the brass jets. Use some Brake Kleen, compressed air and soft copper wire to clean out all holes and ports. Use eye protection because the solvent can burn your eyes.

Rick
 

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Discussion Starter · #9 ·
So, I'm full of stupid questions tonight - is brake cleaner the same as carb cleaner?
(I happen to have both but would be great for future knowledge).

My dad wasn't exactly around all the time to teach me the finer things in life, like, carb vs brake cleaner :)
 

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Discussion Starter · #10 ·
Want to make sure I get the correct item -
My sticker says my ATV is a trx400fa7.
I found this on amazon:

CARB REBUILD KIT 1003-0095

Is this the correct one?
 

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Discussion Starter · #12 ·
So,
I'd like to provide an update - this may be a little long.
First, replaced main jet, and idle jet and I believe secondary jet. Also, replaced the main throttle needle. Did not use all the parts in the kit (o-rings, a couple of washers). ATV started right up and idled nicely once I turned the idle down. One problem - now, at full throttle, it bogs down a bit - almost like it's not reaching it's top RPM's. Sputters slightly, again, at full throttle.
The only problem I had was with the throttle needle - it's encased in a large black plastic sleeve. There's a white cap in that sleeve (plastic) and the main needle is under it. I was obviously able to get it out but when I put everything else back together, and when seating this white plastic cap over the main needle, I twisted the spring between the plastic cap and the new needle. So, my rebuild kit had a spring that was similar, but not the same, so I used it. The new spring a little shorter and stiffer so that may be my problem.
Any ideas?
I'm super proud of myself to just getting to this point but I wish the top end RPM's ran better. BTW, I was sure to seat the clip around the new needle in the same place as the old needle.
Thank you for reading!
 

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Thank you to all who take time to read -

I recently purchased a TRX400FA7 and ever since I've had it, it will not run unless the choke is completely engaged (pulled up). Even when it's hot, if I try to push down on the choke, the engine starts to stumble and will eventually cut off.
I can turn the idle screw in and the ATV will idle up but I still can't push the choke in without killing the engine.
Before I get too tied up with adjust the carb in such a way that will make my problem worse, I'd like to get expert guidance on what should be my next move.
Filter is clean, gas is good - not sure about the plug as I haven't changed it yet.
It's only got 900 miles on it and it's very clean.

Any help would be greatly appreciated.
Always start from the source follow it down and you will always find the problem. Always best to change the lines and filters first. Gas tank is a big factor when it comes to rust and must be addressed with a good cleaning, a liner or other remedy to fix it. Soak the carb in brake cleaner or use a tank and cleaner system at most hardware stores these days. use pins, wires or anything to clean each and every hole flush it out with cleaner so you can see that the opening is clear. Then use a new kit that you can trust. Make sure of all the settings as you take it apart or you will have problems. There are videos online on YouTube that will show how to do it. You should be good after that. Remember any dirt in the system will cause a needle and seat to stick open and cause the over flow to shoot gas out of the bowl. It will happen every time.
 
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