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Logan410

400 ex Throttle won’t engage at all

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My mechanic had to replace the valve cover gasket because of an oil leak. Got the bike running and then realized now the throttle wasn’t engaging at all. It was moving on the carb but was revving. Dropping it back off to him today. Any ideas what it could be?

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Welcome aboard.  I'm not familiar with the sport bikes, but someone who is will be along shortly.  If the cable is hooked into the carb properly and opening the butterfly when you actuate the throttle, and not revving, sounds like the slide isn't in properly, but that's assuming that 400EX carb is similar to the utility wheelers.

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Yep sounds like the screws rattled out of the actuator arm. It has 2 small phillips screws going down into the slide that attatch the arm to the slide. Accessed from the top 3 screw cover on the carb. They are hard to get tight. I usually put blue loctite on them. Dont use red! They will strip off next time you have to remove them.

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Got it back. Throttle is engaging now. One thing though is the idle is high and it was like that before and when I shut it off it backfires. What could cause this? 2002 Honda 400 ex

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Is the cable too tight? Have you tried to adjust the idle down. I have a 2003 XR400. For most part the same engine. Is your mechanic any good? Sounds like 2 strikes to me.

 

Sounds like it might be running lean. Air leak around the carb??

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Where is the idle screw located? I’m far from a mechanic lol. My mechanics awesome And been going to him for years but think he’s been rushing through this cause he’s got so many other projects. How do I see if the wire is to tight and also if there’s a leak around the carb?

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I would try adjusting the idle. Its a flat blade screw with knurled edges so you can turn it with your fingers also. Access from the left side of quad near the choke lever. If you turn it counter clockwise the idle should drop down. If it doesnt change at all then your mechanic put the carb back on and didnt adjust the throttle cable propely. In which case i would suggest finding a new mechanic. If they cant adjust a throttle cable i would be very weary of them doing anything. Its as easy as changing the oil. The back fire is probably because your not idling on the pilot jet but on the fuel from the needle so it will be super rich and that rich mixture is going into your exhaust and combusting. It should go away when idle is settled down. If it doesnt i would think vacuum leak at carb to engine side. Or leak at header gaskets.

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Hey I really appreciate you guys getting back so quick on my questions. Will adjust the idle today. Have another question, when it was in neutral and I was revving the engine when I would push the throttle all the way in it would bog down here and there? What would cause that? 

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Well that second picture is the idle screw(black handle). That is not the correct carb for that quad though. Think its a 04-05 trx450r carb by the looks of it. Which is an upgrade so thats good news. Turn that black knob counter clock wise while the engine is running. It should lower the idle.

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I figured out the black screw was the idle adjustment. Lowered it down but it still is backfiring. 

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1 minute ago, Logan410 said:

I figured out the black screw was the idle adjustment. Lowered it down but it still is backfiring. 

Is it only when you shut the engine off? Or when you rev it?

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It’s when I Rev it and it happened a few times when I shut it off. Every time I push the throttle it has a small back fire

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Well digging alittle deeper that is actually a carb for a trx450fm utility quad it appears. But that sound is almost surely from sucking in air somewhere. Either header gaskets. Could be the exhaust gasket between the muffler and header. Or it could be a bad seal where the carb goes into the rubber boot on the engine side.

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Just ordered the exhaust gaskets, exactly what would the seal be from

the carb to the rubber boot? Trying to order that also. Thank you so much for the help 

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A mechanic that lives across the street said this is where the leak is happening. There’s a gap where these two meet. Is there any gaskets to buy for this area to stop the leak?

298B3DD0-8B57-44D9-8C56-0A62B5A60FB2.jpeg

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On 5/8/2022 at 11:06 AM, Logan410 said:

Or is it this screw?

7702AB7A-7214-4EE3-A75E-79272CD849B7.jpeg

I find this picture interesting.   How is the throttle cable outer sheath held from sliding?

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7 hours ago, 56Sierra said:

I find this picture interesting.   How is the throttle cable outer sheath held from sliding?

Its the wrong carb completely. They used a stock 400ex cable it appears. It should have a metal tube bent into a 90° angle with 2 nuts on it to lock it in place. The carb on it is for a foreman 450? I think? The pictures online look like the end of the cable sits down in a cradle and normally gets held in with the side cover so it doesnt rattle out. This picture they are 100% missing that cover. So it could rattle out at any point.

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51 minutes ago, SlammedRanger said:

Its the wrong carb completely. They used a stock 400ex cable it appears. It should have a metal tube bent into a 90° angle with 2 nuts on it to lock it in place. The carb on it is for a foreman 450? I think? The pictures online look like the end of the cable sits down in a cradle and normally gets held in with the side cover so it doesnt rattle out. This picture they are 100% missing that cover. So it could rattle out at any point.

Looks pretty hokey to me.

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49 minutes ago, 56Sierra said:

Looks pretty hokey to me.

Oh for sure! At first i thought it was a 450r carb which would be an upgrade. But who ever did this missed a very key aspect. The R. So this is a 450 utility quad carb which in term of bore size and specs is actually a downgrade. But its far from the worst i have seen on a 400ex or 450r that was "built" lol.

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Hey fellas yea I bought it like this. So the carb isn’t an upgrade? What type of carb should I buy? Want to get this super fast. It rolls good now but think the carb needs cleaned and just going to replace it

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In all honesty compared to what you have a stock 400ex carb would be an upgrade. All other options require some custom modifications to work. On my quad i run a 39mm fcr from an 07 yfz450r. But i have alot of time and effort into making this carb fit. It required alot of custom mods to do it. And i would bet i have near 500 dollars into it that mod alone. But thats a drop in the bucket to what i have in my quad.

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