Keister's 400X build - VIDEO - Page 8

[keister]

Never loaded / linked a video before, hopefully you can see it.

Here's where we are now:

52 pilot / 152 main
No airbox lid
Starts nicely, idles perfectly
Runs great if I short shift

If I hold gears a little long, it does break up at the very top
When I let off from WOT, it backfires like crazy
Plug is white - no trace of creamy butterscotch color at all.

I tried one size larger on the main (#155) and it ran worse.
I hate to touch the pilot when it starts and idles so nicely.

Looking for ideas on how to work out the kinks when I get near redline?

[Louis Mielke]

How does it run at WOT? Does it actually run well wide open and then when you let off WOT it coughs? To me it sounds like your needle is way lean and your main is way fat. If you literally hold the throttle at half throttle in neutral how does it run?

Lower the clip on the needle a position to raise the needle to fatten it up at half throttle position. If your needle is too far out, even with no main jet in at all it would still look lean on the plug. Your main sounds way too fat, play with the needle till you get some color change. Also what plug are you running? Stock? You may want to go a heat range cooler.

How does it behave it you put the airbox lid back on?

[Louis Mielke]

The main jet really is only metering fuel when the needle is all the way up as in the throttle has raised the needle to the end of its travel. It sounds like at wide open throttle, the needle is out of the way and the way too big of a main is drowning the engine. When the needle is in the jet tube the taper of the needle is limiting the fuel regardless of how big the main is, you could go to a 200 main and the needle will only let so much fuel in until it moves out of the way.

I'd focus on making it run off idle and at mid throttle so it will put some color on the plug then worry about your main.

Most people only ever really utilize from 1/4-3/4 throttle for 80% of thier riding. (in our typical trail riding locations, west coast is going to be different obviously)

[Dirtcrasher]

If the airscrew doesn't help the decel pop, you are lean on the pilot.

You are shifting as soon as you hear it break up. It doesn't seem to be blubbering, but breaking up.

Easy test, throw the A/B lid on and test the main. Better or worse?? Your now restricting the air which tells you where you sit with the same fuel delivered.

That will help you figure out where the main jet is at because now you have less air in the mix but the same jetting.....

[fallguy666]

On mine(not sure of the bore size,only know its a 12:1 with cam) I'm running a 180ish main(drilled 150) and a 52 pilot,needle second groove from the bottom.no air box lid and a DG pipe.mine is god awful now.it will pull fifth and sixth gear wheelies like there's no tomorrow. the little shot of nos I have on it is a real kick in the britches too!!!

[keister]

How does it run at WOT? Does it actually run well wide open and then when you let off WOT it coughs? To me it sounds like your needle is way lean and your main is way fat. If you literally hold the throttle at half throttle in neutral how does it run?

Lower the clip on the needle a position to raise the needle to fatten it up at half throttle position. If your needle is too far out, even with no main jet in at all it would still look lean on the plug. Your main sounds way too fat, play with the needle till you get some color change. Also what plug are you running? Stock? You may want to go a heat range cooler.

How does it behave it you put the airbox lid back on?

The main jet really is only metering fuel when the needle is all the way up as in the throttle has raised the needle to the end of its travel. It sounds like at wide open throttle, the needle is out of the way and the way too big of a main is drowning the engine. When the needle is in the jet tube the taper of the needle is limiting the fuel regardless of how big the main is, you could go to a 200 main and the needle will only let so much fuel in until it moves out of the way.

I'd focus on making it run off idle and at mid throttle so it will put some color on the plug then worry about your main.

Most people only ever really utilize from 1/4-3/4 throttle for 80% of thier riding. (in our typical trail riding locations, west coast is going to be different obviously)

This helps a lot. I was actually hoping / thinking it was a needle clip position issue, but wanted to get some confirmation before I started messing with it.
It basically runs perfectly everywhere except WOT, at which point it breaks up. I will try the half throttle in neutral test.
Never considered a plug change. It is, of course, DR8ES-L. What options do I have for a cooler plug?

I'd focus on making it run off idle and at mid throttle so it will put some color on the plug then worry about your main.

It already runs perfectly off idle and at mid throttle. The issue is WOT and crazy backfiring going from WOT to throttle closed position. Keep in mind this engine still has under an hour on it.

[keister]

If the airscrew doesn't help the decel pop, you are lean on the pilot.

You are shifting as soon as you hear it break up. It doesn't seem to be blubbering, but breaking up.

Easy test, throw the A/B lid on and test the main. Better or worse?? Your now restricting the air which tells you where you sit with the same fuel delivered.

That will help you figure out where the main jet is at because now you have less air in the mix but the same jetting.....

I haven't touched the air screw at all. Didn't realize that might help my decel issue.
I did throw on the airbox lid. It ran slightly worse, barely noticeable actually. I also went up one pilot jet size (#55) with airbox lid on and off. It ran noticeably worse, so I went back to the 52.

I just want to get it dialed in nice and tight before my Hatfield McCoy ride in May. Of course, the temp and elevation will be different there.
Thanks a bunch for the help, guys. I will try these things out.

[Louis Mielke]

The number of the plug depicts heat range, smaller number is hotter, larger is cooler, looks for a DR9ES-L but before you worry about that just focus on what you have.


You say the plug is white but putting the airbox lid on makes it worse? That's kinda of opposite of what we'd expect.

Not that you should hold the throttle wide open for any extended period of time but when I say WOT I mean just that, not specifically 6th gear tapped out, I mean the throttle completely open in any gear.

If you open the throttle wide open (in neutral sitting still), just an easy roll on of the throttle, not a stab, how does the engine sound/feel at its highest RPM? I don't mean hold it there for a long period but roll on the throttle till you reach highest rpm and then back out of it once you reach the top for a second.

Part of the problem here in trying to do this through forum posts is that how one person describes engine sounds and the way someone else might can be very different, and a lot of times you may never get an engine to behave a certain way so you don't know that the specific behavior is possible.

Buy a few plugs. Put a brand new one in and start it and let it idle, let it idle for 15 mins if you have to, if it puts color on the plug just idling (any color other than white/grey) then I would think the pilot should be close.

Dirtcrasher, lean on the needle can cause pop on decel too, not only too small a pilot, if it was poping between half throttle and idle I'd agree with you but as he described it it sounds like its poping on decel from WOT.

Keister is hat correct or are we both misunderstanding?

[keister]

If I am at WOT and I leave off the throttle completely, it pops and backfires. Pops happen between WOT and throttle closed position.

As for the airbox lid, that was exactly the opposite of what I was expecting too. But the difference was very minor, almost negligible. In real world riding, I probably would not even notice. It did seem to start easier with the lid off, but that could just be my perception.

All the rest of the stuff I will try tonight and get back to you. thanks again for helping me out.

[Dirtcrasher]

As Lou said, the A/B lid test seems completely opposite to your plug readings (as you said it was whiteish ) so, if you put the lid on and restricted the air intake, lean jetting would have better results. But you said it was worse?? Completely baffling.

I hear you short shifting it (in the video) and that's no fun for all the work to now have a fresh built motor. The guys I ride with have seen me stab my throttle fast and held it at WOT with no break up. They all shook their heads as if I were crazy. But I believe I am in some sort. In my case it is a 10.25:1 with no lid, ST exhaust (what exhaust do you have?) 52 pilot and I think a 152 main. And it runs thru all speeds great. I don't claim in the least to be a jetting expert, it is a PITA sometimes. It popped a little bit on decel and 1/4 turn on the airscrew eliminated that.

That white color plug screams lean but the A/B lid test didn't show you what it should have. Is it possible you have an air leak somewhere?

This can be well argued but the main jet plays a huge roll in all final jetting throughout the range.

The airscrew I believe should be somewhere about 1.5 turns out from bottoming it. Do so lightly and make sure the oring has silicone grease on it and is in the correct order.

Screw, spring, washer then o-ring. That way when you turn the air or fuel screw, there is no damage to the o-ring seal.

Your A/B lid test with a lean indication on the plug is completely opposite of what I would have anticipated; Louis said that as well.

I'm sure it bugs the heck out of you with a fresh 400 motor. It's not even able to race or be ridden hard.

Just wait until I put the FCR 39mm on mine and see how much difficulty I have jetting it!! A call to Mr. Hall may be necessary at that point

EDIT!! - ALWAYS do 1 jetting change at a time or you will be lost beyond words. As Louis suggested, get the 1st portion correct and work from there. I am certain that different needles can resolve issues. I honestly have never experimented with different needle tapers.....

[jays375]

Has the oring on the intake been changed?May look good but may leak also.What gives with these 350X's and jetting problems lately.Is the pilot port definately open?

[Louis Mielke]

If I am at WOT and I leave off the throttle completely, it pops and backfires. Pops happen between WOT and throttle closed position.

Pops happening between WOT and throttle closed... That's kinda a broad range man. lol. If you slowly easy the throttle off from WOT instead of just letting it snap closed how does it behave?

[CRAZY70MAN]

Taking a longshot and thinking you have an exhaust leak somewhere?? I know that has nothing to do with your plug color and your jetting may be off still. I have had my 350x do the same several times when it works a header nut loose.......or when you wheelie it at Elmira indoor and run ice studs through the header cause you have it too low . Just a thought since the build is new.....check the exhaust... Nice freakin build Peepers!! Real nice bro....

[keister]

If you open the throttle wide open (in neutral sitting still), just an easy roll on of the throttle, not a stab, how does the engine sound/feel at its highest RPM? I don't mean hold it there for a long period but roll on the throttle till you reach highest rpm and then back out of it once you reach the top for a second.

Did some more testing last night. It was 20-30 degrees colder than last weekend. I warmed it up and rode it around, and it ran A LOT better. There was still some minor breaking up at the top, but not nearly as bad.

I put it in neutral and revved it up the whole way and held it there for a few seconds. Sounded fine. Nothing odd at all. Did not seem to break up at all.

[keister]

Pops happening between WOT and throttle closed... That's kinda a broad range man. lol.

Ya, I guess so. Thing is, I never really listened for exactly WHEN it was happening.
Upon further review, the backfiring happens when the RPMs are almost all the way back down. Doesn't really happen as soon as I let off the gas. It happens when it is almost back down to idle. It still did this last night.