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Discussion Starter · #1 ·
Im new to four wheelers and im looking to buy a 400ex soon. I see a common problem with these used quads that they need the carburetor jetted. Instead of jetting the carburetor, could I just buy a whole new carb. from the looks of the pictures and description there is no engine or exhaust mods. Thanks!
 

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There is no common problem with jetting - most problems with used quads it the previous owner screwed up the carb rejetting it 'FOR MORE POWER' with the misconception that 'more fuel is more power'.

I got a 2005 TRX400EX that was totally effed - the air box had been changed to an aluminum box with no top and huge K&N air filter - the exhaust was a slip on HMF that was gutted and the end cap missing. About all it would was start and idle and it didn't idle well either. The engine was untouched - stock head, stock cam and stock bore.

I got a used stock muffler, a new airbox and filter with lid and all - rejetted the carb to stock configuration and it ran excellent.

Where did you "SEE" that the carbs NEED jetted? There is a lot of misinformation on YouTube and Facebook - about 2/3 of all the "expert" suggestions are garbage. YouTube needs to 'fact check' the videos they allow to be uploaded as many contain obvious errors and some are outright lies about something.

If you test ride it and it runs fine, buy it if not, walk away - tell the owner to get it fixed and then you will buy it even if he wants to charge a bit more - many DA's are selling their problem so they can get something that runs right and start effing it up looking for more power.
 

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Discussion Starter · #3 ·
There is no common problem with jetting - most problems with used quads it the previous owner screwed up the carb rejetting it 'FOR MORE POWER' with the misconception that 'more fuel is more power'.

I got a 2005 TRX400EX that was totally effed - the air box had been changed to an aluminum box with no top and huge K&N air filter - the exhaust was a slip on HMF that was gutted and the end cap missing. About all it would was start and idle and it didn't idle well either. The engine was untouched - stock head, stock cam and stock bore.

I got a used stock muffler, a new airbox and filter with lid and all - rejetted the carb to stock configuration and it ran excellent.

Where did you "SEE" that the carbs NEED jetted? There is a lot of misinformation on YouTube and Facebook - about 2/3 of all the "expert" suggestions are garbage. YouTube needs to 'fact check' the videos they allow to be uploaded as many contain obvious errors and some are outright lies about something.

If you test ride it and it runs fine, buy it if not, walk away - tell the owner to get it fixed and then you will buy it even if he wants to charge a bit more - many DA's are selling their problem so they can get something that runs right and start effing it up looking for more power.
So would this mean that I can just buy a brand new carb and not have to worry about retuning the jets? Thanks, I appreciate your patience!
 

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Discussion Starter · #4 ·
So would this mean that I can just buy a brand new carb and not have to worry about retuning the jets? Thanks, I appreciate your patience!
The owner claims it will idle and run decent at low rpms but cuts out at higher rpms
 

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So would this mean that I can just buy a brand new carb and not have to worry about retuning the jets? Thanks, I appreciate your patience!
No - you cannot buy a new carb from Honda - they are discontinued - if you buy a new POS Amazon carb, it will have to be tuned to the application - Amazon sells carbs that 'fit' - it may fit, but the jetting is up to the end user.

Again, if it doesn't run right walk away - spend a bit more and get one that does not have the problem.
 

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+1000

Listen to "Here to Help", it really is the best advice.

The only possible exception is if you really want to be an ATV mechanic, study all the fundamentals, and use a project bike to work on. Learn to cut plugs and read the burn pattern, get a compression tester, get good electronic testers (with a peak voltage adapter!), GOOD torque wrenches... and finally a shop manual. Then hit up the old youtube for videos on repairing various systems. I find the Partzilla videos very well done.

I've rebuilt a few Chevy 350s over the years with good success. I took a stab at rebuilding a 400ex a couple years ago, did a few minor upgrades and it really turned out well and I had alot of fun doing it. It runs incredibly good atm. Had enough fun doing it I bought a "project" 400ex that needed love (way too damn much love it turned out), but it was mostly complete for $800. I thought I could put $500 into it and get it going. NOPE. Ended up putting in over $1000 in parts alone, but... it runs like a champ now, fires up every time and all the rest of the bike works now too.

That said, the first 400ex I bought a few years ago was 100% stock, even original OEM tires. The Banana we call it. It always starts right up, runs great. A little tired power-wise due to its age, but it'll climb everything the other two machines do. I think about rebuilding that one every once in a while, but then again... "it just works". I'm reluctant to mess with such a reliable machine. I just clean the filter and change the oil.

If you dont want to spend alot of time wrenching, spend a bit more and get something in better shape. But... IDK how prices are in other spots in the country, but 400EX's have nearly doubled in price in the past year. They used to run 1800 to 2100 (paid $1800 for the banana, $1550 for one needing a top end, and $800 for the one in rough shape) but now they are all around $3400-3600.

-DallanC
 

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Discussion Starter · #7 ·
No - you cannot buy a new carb from Honda - they are discontinued - if you buy a new POS Amazon carb, it will have to be tuned to the application - Amazon sells carbs that 'fit' - it may fit, but the jetting is up to the end user.

Again, if it doesn't run right walk away - spend a bit more and get one that does not have the problem.
+1000

Listen to "Here to Help", it really is the best advice.

The only possible exception is if you really want to be an ATV mechanic, study all the fundamentals, and use a project bike to work on. Learn to cut plugs and read the burn pattern, get a compression tester, get good electronic testers (with a peak voltage adapter!), GOOD torque wrenches... and finally a shop manual. Then hit up the old youtube for videos on repairing various systems. I find the Partzilla videos very well done.

I've rebuilt a few Chevy 350s over the years with good success. I took a stab at rebuilding a 400ex a couple years ago, did a few minor upgrades and it really turned out well and I had alot of fun doing it. It runs incredibly good atm. Had enough fun doing it I bought a "project" 400ex that needed love (way too damn much love it turned out), but it was mostly complete for $800. I thought I could put $500 into it and get it going. NOPE. Ended up being in it over $1000 in parts alone, but... it runs like a champ now, fires up every time and all the rest of the bike works now too.

That said, the first 400ex I bought a few years ago was 100% stock, even original OEM tires. The Banana we call it. It always starts right up, runs great. A little tired power-wise due to its age, but it'll climb everything the other two machines do. I think about rebuilding that one every once in a while, but then again... "it just works". I'm reluctant to mess with such a reliable machine. I just clean the filter and change the oil.

If you dont want to spend alot of time wrenching, spend a bit more and get something in better shape. But... IDK how prices are in other spots in the country, but 400EX's have nearly doubled in price in the past year. They used to run 1800 to 2100 (paid $1800 for the banana, $1550 for one needing a top end, and $800 for the one in rough shape) but now they are all around $3400-3600.

-DallanC
Thanks for the response, and I appreciate the information.
 
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