cutting out

[1187shooter]

Newbie here. I'm having trouble with my 400EX. I'll give a little Info for starters. I bought the quad with no info from the previous owner. Didn't run. I started off with top end rebuild. Had it bored 85.5mm OEM style piston, has a WB cam, not sure what stage, new crf450r tminig chain, valves seated, removed the WB CDI and put a new stock CDI,has aftermarket HP coil, K&N air filter no lid, carb rebuilt, Big Gun full exhaust. My problem is, the quad starts good, has rough idle and cuts out above half throttle. I've tried 38-45 pilot jets, 148-160 main jets, no change in performance.

[sprayedgt]

Welcome to the site. First off were these Keihin jets? If they were I would then check to see where the fuel screw is set at. Turn it all the way in counting how many turns it goes. Normally it's set somewhere around 2 to 2 1/2 turns out depending on what it wants to make it run right. I ask about the jet brand because not all jets are rated the same way by jet size. A Dynojet 160 is not the same as a Keihin 160.

[1187shooter]

They were, directly from the local Honda dealership. I started with mixture srew 2 1/4 turns out and tried both directions. I wish I knew a little more info from the previous owner, mabey it was an issue before. Do you think its possible that it could be electrical? I tried a factory coil off my brothers quad but no change. I also checked the carb for air leaks. I'm no certified mechanic, I've worked on all my motorcycles and quads for years but cant seem to find the problem.

[sprayedgt]

Does the jet have a little star on it? If it does it's a Keihin. If not it's some other brand. I would try a 162 Keihin jet and see how that works. How about the needle? What notch is it on?

[1187shooter]

They are keihin jets. Its the only brand the local Dealership carries. I dont mind buying more jets you guys still think its a jetting issue.I just thought for my setup 160 would be large enough. Needle is in 3rd slot.

[sprayedgt]

For your application a 160 may not be enough. Some people are using a 158 with a stock motor, a full exhaust and filter. Not every bike responds the the same mods the same way. Try moving the needle one notch down and see what that does.

[1187shooter]

Thanks man, Ill give it a shot first thing in the morning. Mabey Ill pick up a couple even larger. Right now Im at 45 pilot and 160 main.

[sprayedgt]

I would drop the pilot to a 42. I just now saw the 45. A 42 should be plenty for that combo.

[MtnEX]

Ahhh....

Open the top of the carb, and work the throttle while you watch the slide...

I bet the screws rattled out that fasten the slide lift arm to the slide.

[1187shooter]

everything mechanical in the carb working correctly, I guess its just running way too lean ????

[MtnEX]

Originally posted by 1187shooter
everything mechanical in the carb working correctly, I guess its just running way too lean ????

Well, the only time I saw this, I had issues with the slide and also once slide & butterfly timing. But I did not have a rough idle.

How's the spark plug look?



Aside from that...
Good premium gas?
Clean tank?
How's the fuel line look?

[1187shooter]

OK. I made my trip to the Honda shop to get some more jets this morning. I down sized pilot to a 42, put in a 165 main no change tried a 170 no change. Checked the gap between the link arm shaft and throttle link arm per Honda service manual just to make sure the slide was working properly. everything is good. Is there any way this could be mabey the CDI. I have a new one on the quad. because iI took the WB CDI out. I read somewhere that the 01 and 02 are different, something about changing pins??? But I dont think it would run if the pins were crossed??? I'm not sure of the year model because the frame has been PC red, so no labels on frame. I'm lost!!!

[78ta]

double check timing, pull the plug after as hard of a run as you can and post up a pic.

does it run rough the entire time, or just idle ruff and run ok then cut out half throttle?

[1187shooter]

Idle is not real smooth, but it will idle. response is good when you give it gas up to about mabey half throttle, then it cuts out from there to WOT. is there a chanch it could be one tooth off on the cam and still run?

[n811]

This may be a long shot but I had a problem with the switch in the clutch lever. have you tried to rev it up with the clutch pulled in? It opens the switch. i had to cut and splice the wires on mine.
Hard to blame the CDI when you took one off of another running quad. Maybe a air leak at the intake? Get it running and then spray some carb cleaner around the intake and on the cylinder if it changes rpm or how it runs you have a leak.

[honda400-4-ever]

i had the same problem on mine check the fuse because i was riding one day and it started to do the same thing i thought the battery was bad because there wouldnt get enough spark to ignite the fuel but it was just a fuse. so check it

[bigbad400]

sounds like an air leak to me too i had a blaster that did that it was intake after carb the 2 smokes have reeds but that was were it was. i also used the ether/starting fluid trick to find it. but just tighten all of the air intake stuff and you should fix the problem.

is air filter good and clean? what about lid on or off?

why did you take off the wb cdi? did it not run at all or just the same problem? if it the same with either cdi thats not it, cdi will either work or it wont, wont do anything if its bad, no spark.

intake on the motor has a gasket that could be cracked or just not tight too, make sure all of it is clean and no dirt or sand in the seals, clean the entire carb with ether, carb cleaner is only part ether and its alot more thorough to use pure. but be very careful of sparks or anything around any of that stuff. jetting more than likely was not the problem, unless something was changed (pipe, intake mods,such things) and immediately a problem developed.

[bigbad400]

when you got it would it fire? or nothing at all? why a new topend? no compression? you changed alot of variables, did you try it without the cdi befor the topend? have you tried to put the wb cdi back on? do anything different or same thing? why the timing chain, was it stretched? or just wanted hd? answering these accurately could greatly help us eliminate things this is needle and haystack stuff here. if you can remember put jets back to what they were when you got it or leave 42 pilot that should be fine. put cdi back on and see what happens, check the air intakes and all that for leaks like i said befor (i didnt realize just how much you changed all at once, always do one then test things out, all is good do the next. eliminates guessing games!!) at least she runs its alot easier to diagnose it.

[1187shooter]

First of all I would like to thank you guys for helping me with my problem. It is for sure a carb issue. After hours of trial and error, I now have in a K42 pilot jet, and a K155 main jet. I now have the needle set in the top notch, not the bottom, I guess it was too rich, which solved my cutting out in mid throttle. I still have a little cutting out on top end. the A/fF screw is about 3 1/4 turns out, is this OK or should I drop to a 152 main? This is the first time I have ever had to change the needle setting on anything I have ever owned. I guess you live and learn.

[MtnEX]

The 42 pilot is considered to be OK.

The fuel screw sounds too far turned out though.


The way you are describing it, yes I would drop main jet sizes, and adjust the needle back towards the middle. Just remember to check your slide/butterfly timing each time you mess with the needle.

As it is now, you are at maximum fuel restriction on the needle, indicating the main is large.

[1187shooter]

Can you explain the timing procedure so that I can make sure everyting is good. With the needle in the 3rd position, it cuts out so bad you can hardly ride it. Today is the only time i moved the needle. All other jet combinations were made with needle in the 3rd position.

[MtnEX]

Yeah... hang tight... I think I can get you a link... I think I posted it.


+++++++++++++++++++++++

Found it faster than I expected...

http://www.exriders.com/vbb/showthread.php?s=&threadid=367355&highlight=slide+butterfly+link+shaft

[MtnEX]

Originally posted by 1187shooter
Can you explain the timing procedure so that I can make sure everyting is good. With the needle in the 3rd position, it cuts out so bad you can hardly ride it. Today is the only time i moved the needle. All other jet combinations were made with needle in the 3rd position.

Also I was thinking it might be important to explain what this does and exactly how this becomes important...


Basically the function is that it syncs everything up....

It controls the timing of the opening of the butterfly and the lift of the slide. But at the same time a third variable is involved... the physical spray of the accelerator pump.

So see, if this minor thing is out of spec, the whole operation is off and you can't even dream of dialing in jetting.

If the slide is ahead of the butterfly, the needle is lifting out of the holder, allowing the flow from the main to pour on too soon.

If the slide is behind the butterfly, the opposite, is true. The needle is late on the lift and restricting the flow from the main.... and what's worse is that the slide may be physically still in the way of the nice boost squirt from the accelerator pump when you roll on the throttle hard.