400ex Problem

[Nate105]

Hey guys,
I'm new to this forum but here is what my problem is. I did all my mods that are in my signature. the problem is when its on an idol for a couple seconds and I just tap the gas it dies or cuts out but now if I turn up the idol alittle bit it goes away. the other problem is it backfires on decel and when I pull in the clutch. I put new exhaust gaskets in last weekend none of the new gaskets are leaking and my jetting is 160 main and 55 pilot anybody have some advise please help

[hocman123]

sounds like u are a little rich in the pilot jet i would put a 52 in it and that should fix ur problems

[JOHNDOE83]

I say your 160 main is to small but thats not were your having your issue.

If your backfiring on decel it generally means that your pilot is to lean or your air fuel screw isnt turned out enough.

Are you 100% positve you have a 55 pilot jet?

I would recheck it just to be sure and if it is a 55 pilot jet the you either have a air leak or something else isnt working properly.

If your haveing a problem at idle and it seems to help by turning up the idle but now seems to idle to high, your pilot jet is to lean.

[JOHNDOE83]

and how did you seal your hotstart?

[Nate105]

I sealed the hotstart with rtv and with the jetting I started with a 180 main and that was way to rich and the pilot I was up to 58 and the idle problem was real bad went to 55 and it might of gotten a little better but i'm pretty sure its a 55 in there now

[JOHNDOE83]

how many turns out on your air screw?

[Nate105]

I think i'm at 21/2 or 2 3/4

[Nate105]

and if I take the air box cover off and the air filter and put my hand over the tube it will bog down and die so i don't think its lean on the pilot

[JOHNDOE83]

does it get worse or better when you take the lid off and go for a ride?

[Nate105]

I haven't tried taking it for a ride with the air box top off I will try it tomorrow and let you guys know

[Nate105]

I turned the fuel/air screw out 1/2 turn and the idle thing seem to stop. but it still back fires and I have one other problem that i forgot to post the motor is ticking pretty loud. I don't know if its the valve lash or if i'm running to low of octane or what? what do you guys run for octane in the 440's?

[hocman123]

will the bore dosen't matter its the compression if u has 11:1 or less then u should be good with 93 octain pump gas if it is bigger then u need rce gas

but most likely it is the valves they all tick some louder then others but if u have a hotcam it makes it do it louder

[Nate105]

if its cold it don't seem so bad but when it gets good and warm it gets louder do you think i need to readjust the valve lash I have only done it once since I put the motor together it has about 5 tanks ran threw it now

[hocman123]

u could re check them it might help a little but trust me they can tick really loud and there isn't anything u can do sometimes

[JOHNDOE83]

If it seemed to help by turning out the screw you are safe going to 3 1/2 turns out and the ticking is usually one or multiple things.

It could be the top motor mount, the jetting or a valve adjustment, might as well check the easy stuff before trying to reset the valves.

I have a 440 with a cam, bigger valves and 450r carb, with custom intake and crankcase mods and it ticked for awhile then I did a frame rebuild and changed some jetting and the ticking is almost 100% gone.

[Nate105]

ok what do you mean by changing the jets will help the ticking? what can I do to the upper motor mount?

[Nate105]

?

[JOHNDOE83]

Well Im not sure which one fixed it but I noticed when I was unbolting my motor that the bolts were actually tweeking the motor slightly crooked like and it was hard to get the bolts out.
I also learned a new better way to jet so when I re did the frame I used bigger jets and re did the bolts and it fixed all these issues and I noticed that the tick was gone, then I actually read some threads on here that said the same reasons fixed their ticking.

If you cant undo your motor mount bolt and slide it out then the motors tweeked in the frame, the thread I read here said he went to take his head off to see what was ticking and saw the bolts were tweeked so he fixed only that and said it didnt tick as bad.

I also know that ticking can come from being to lean in some cases and I was told about a different jetting method then saw the same thing on www.jetsrus.com so I tried it and my quad has ran like a dream ever since.

I would re-do the bolts if they seem pressed against the mounts and check valve clearences and if they are right or adjusting them along with the mount doesnt work then Id try jetting differently.

[Nate105]

ok thanks so its just the top mount? I still don't get the back firing I can't get it to go away.

[CJM]

Start it up, stick your hand over the exhaust and make sure its sealed. You will hear air hiss out if its an exhaust leak. An exhaust leak would cause a lean condition on decel possibly.

Also, if you have any other air leaks it can cause a backfire sometimes as well.

[4WheelinDemon]

Ok heres my 2 cents on everything here... Go ahead and do a 165 or 168 main with a 52 pilot, 3Rd clip slot on needle, 3 1/4- 3 1/2 turns out. Do what he said about putting your hand over the exhaust tip on the muffler and make sure its sealed good. As for the ticking...make sure you cam chain tensioner is good, check clearance on the valves. intake clearance is .005 and exhaust is .006 i believe? That stage 3 cam you have is DEF going to give you a louder tick than a stage 1 or 2 cam would since the stage 3 cam is a more aggressive cam ( I know how it is since i had one in mine), but yeah. Thats what i have to say. Oh!!! just read your list of mods and im sorry but you really should get that namura outta there bro. I had a buddy who put one in his 400 and the piston literally melted at the top. Ive read reviews about those pistons and alot of them melted on people. Sorry but if your going to get a piston, i'd go with JE or Weisco. Hope this all helps!!! And make sure that hotstart has zero leakage.

[Nate105]

thanks for the advise but if I put a 165 or 168 main in. its to rich it just sputters when I grab full throttle and when I had those jets in when I would take the air box lid of it would get better thats why i'm at 160 main. I will try the exhaust test let you guys know

[Nate105]

I tried the exhaust test and I don't think the exhaust is leaking I didn't hear any air coming out

[tri5ron]

Originally posted by Nate105
I sealed the hotstart with rtv.....

I have painstakingly read through this complete thread.
The main issue, (mistake) that you made with the 450r carb, is using the rtv. (And yet, no one here, has addressed this for you)
It is a common misnomer.
You don't need to feel like the Lone Ranger.

Although you may be dealing with additional issues, (i.e.- jetting),
you are NEVER going to get it to run right by sealing (only the top), of the Hot Start Port, with RTV.
(go ahead,... ask me how I know this :cool: ).

If you are of average mechanical "prowess",
You Must , (let's repeat that,... MUST ! ), use the hot start plunger, on the 450r carb.

Now as a disclaimer,
Sure, there ARE possible exceptions to every rule.
And there are a couple of members here who CLAIM to have successfully run the 450r carb, by using RTV.

BUT,... to do so,...
You would have to have a thorough knowledge of the internal function of the plunger, AND you would have to meticulously apply the RTV to those ports/circuts within the carb.
Theoretically,
that would do the same thing as the plunger itself.

We have discussed this many times in the past.
It is not a matter of just sealing off the TOP of the hot start port.
The plunger closes a port/fuel circuit, AT THE BOTTOM OF THE HOLE.

SOooo,... unless you are of better awareness, and exceptional mechanical skill,
than the average 400EX rider/mechanic,...

It is just BETTER, and EASIER, (to avoid any Hot Start related problems),
by simply using the Hot Start Plunger.

or in other words,
Unless you REALLY know what you are doing,...

If you do not use the plunger in the carb,...
It won't run right.
Period.

Start there, then re-evaluate what your additional issues may be.

[Nate105]

thanks alot man is that what they call a valve set? you must just screw it in and thats it or is there something else I have to do to?

[Stickman400]

Yep, that's what it's called on a partsfische. You put the plunger and spring down in the carb., then the plastic holder over it and screw it in. But you want to fill the plastic holder with RTV just to ensure that it's fully plugged and sealed off.

[Nate105]

ok thanks I will have to get the plunger and the spring and the plastic holder when I got the carb it didn't have the hot shot start on it

[Stickman400]

Number 8 on this: http://www.motosport.com/atv/oem-parts/HONDA/2005/TRX450R-%28KICK-START%29/CARBURETOR-%28'04%2C'05%29 should include the holder, spring and plunger. I'm not sure if you can get the parts separate.

[Nate105]

so it comes with all 3 things all would be sweet. they don't say what it comes with

[Stickman400]

I'm assuming it would because you can't order it in separate pieces.

[Nate105]

ok I will get this coming and I will put it in and see how it goes. I will let you guys know what happens

[CJM]

Comes all together. You still need to put RTV in there but that little plunger piece is what ya need to seal everything right.

[Nate105]

ok thanks I should be getting it on weds and i will let you guys know what happens.