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450X Bogs when choke is off and held at little to 3/4 throttle

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47 minutes ago, YZF_R said:

Lets start at the beginning. When you purchased the bike was it running right?

 

 

Owner of a 2005 450X since 2007.

When I bought it the bike had been sitting for six months because owner got injured. It ran like it had bad gas and needed a carb clean. It definitely ran lean still now that I think about it, but at the time I figured after the carb clean it would be fine. Supposedly it ran fine for the owner but he said it was always cold blooded, needed lengthy warmups, and would bog on really hard WOT accelerations (all lean conditions). 

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Also for those curious, I did confirm that the sizes in the all balls kit were as listed on the picture I sent a few days ago. My leak jet is a 70 so when I do the o ring mod I’ll switch to a 55. 

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First of all the 450x comes out of the box lean due to EPA standards. Very cold starter stock, after she warms up she's fine.

When the mods where made to the top of the air box you induced more air into the box creating a leaner mix.

There's no need to make the mod to the top of the air box, it runs like a beast already.  Removing the screen in the air box, well helps maybe a little.

There's no need to buy aftermarket kits for the carb, the stock carb will run just fine with a few adjustments. Again the bike is fast as hell so what more do you want.

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21 minutes ago, YZF_R said:

First of all the 450x comes out of the box lean due to EPA standards. Very cold starter stock, after she warms up she's fine.

When the mods where made to the top of the air box you induced more air into the box creating a leaner mix.

There's no need to make the mod to the top of the air box, it runs like a beast already.  Removing the screen in the air box, well helps maybe a little.

There's no need to buy aftermarket kits for the carb, the stock carb will run just fine with a few adjustments. Again the bike is fast as hell so what more do you want.

I have not made any mods to it. The bike came with all of those air mods and I’m trying to fix the issues I believe those mods have caused with the fuel/air mixture. If it were my preference I would have an all stock bike set to run a little richer than stock and maybe a slip on. My friend had an all stock one and I loved the way it rode. 

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1 hour ago, YZF_R said:

First of all the 450x comes out of the box lean due to EPA standards. Very cold starter stock, after she warms up she's fine.

When the mods where made to the top of the air box you induced more air into the box creating a leaner mix.

There's no need to make the mod to the top of the air box, it runs like a beast already.  Removing the screen in the air box, well helps maybe a little.

There's no need to buy aftermarket kits for the carb, the stock carb will run just fine with a few adjustments. Again the bike is fast as hell so what more do you want.

I don't totally agree with this.   Yes, it does come lean from the factory and even when jetted properly, it's cold blooded.

But I would not say that it "runs fine" when warmed up.  In my particular case, it was always a 50/50 chance if it would stall off idle right from day 1 and I got it brand new.  It popped considerably on decel (even with smog blocked off), had a bit of a hanging idle, and ran very hot because of being lean.   In short, it ran pretty poorly.  

 In regards to not needing to buy after market kits, certainly you can buy jets and needles yourself and get off far cheaper, but in the case of the JD Kit, you get a pair of multi-taper needles that cannot be purchased else where.   With that said, I am sure you can get it to run well with regularly available parts, but you may not be running as well as you could.

The other thing you get with after market kits is a proven setup.  In the case of JD, all their setups are dyno tested and when you install according to their instructions, it is pretty spot on and there is no guesswork.   That is worth something.

Personally even with a stock bike, I would open the air box a bit and re-jet just for the fact that it runs better, cooler, and produces slightly more power.   I don't think there is many that would disagree that this is a good thing to do.  It's not about more power, but just a matter of getting to to run right, which if it wasn't for emission standards, would be the way it would have been delivered.

Jim.

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On 12/11/2017 at 7:15 AM, Dirtbug26 said:

On 4T's, the fuel/air screw controls the amount of air that goes into to carb, by turning clockwise (closing it) you reduce the air in, and thus richen the mix (more fuel than air).

No.

 

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Unless I missed it, no one has mentioned the hot start cable.  If the plunger on the hot start is not sealing/closing all the way inside the carb, or there is NO slack (needs 1/8th inch) then it will be lean as all get out and bog like crazy.   With the air box taped off the air flow was limited making for a richer mixture and overcoming the extra air being ported through the hot start channel in the carb body. 

So...how much play is in the hot start, and is it retracting all the way in the carb?  Is the rubber tip on the plunger sealing/damaged?

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CRF DOC is correct.  The mix screw controls amount of "trim" fuel that is fed during closed and low throttle %

 

It does not control any air...well unless the O ring is missing and sucking air past the screw threads lol.

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14 hours ago, CRF DOC said:

No.

 

Sorry, I was ...wr...wr...wr... wrong and confused the 2 T with 4T carb. On 2T the adjustment screw meters air, and on 4T the screw meters fuel. Now I will go to my room.

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There is no mystery to the jetting on a 450.

NEW 45 pilot. Number one cause of poor starting/idling/throttle response after a bike has been sitting.

Fuel screw at 1 7/8 out from seated.

Needle clip in stock position.

Main jet for 2200 feet is a 162.

 

If the bike isn't running fantastic with those jets, something else is the problem.

Edited by Leardriver

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Hey guys I got the JD kit and gonna install tomorrow. Due to all the air mods already on the bike I was hoping to skip the Additional air box mods on the JD instructions. Still gonna try and install the 170 main jet because of the multiple air mods. Also,  before I install the kit im gonna try to raise the needle I have now and see if that helps at all. If not the kit is going on. Let me know what you think and I’ll update you with the results. 

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I would recommend the air box mod. I was a little hesitant to do mine only with the fear it would pull too much mud, dust ext...

Didn't really see a notable difference with the air cleaner. I say go for it.

As for the needle you might as well go for while you have things apart. I did everything and it took me about an hour in the garage (3 cold beers) and never had to actually remove the carb. Just loosen up the boot clamps and you should be able to rotate the carb back and forth to access everything. 

Get it done, good spring time trail riding is just around the corner!! 

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11 hours ago, DanielX450 said:

Hey guys I got the JD kit and gonna install tomorrow. Due to all the air mods already on the bike I was hoping to skip the Additional air box mods on the JD instructions. Still gonna try and install the 170 main jet because of the multiple air mods. Also,  before I install the kit im gonna try to raise the needle I have now and see if that helps at all. If not the kit is going on. Let me know what you think and I’ll update you with the results. 

 As for the air box, you do not have to remove the whole top of the box and some of the side.  Some just remove the top.   But at a minimum, you should remove the snorkel and poke at least 6 1" holes in the top to open it up a bit (a pipe heated up with a torch works great).

As far as the needle and #170, WHY are you messing around with it....you bought the JD kit, just follow the setup and be done with it.  Your just making things more complicated.  As Leardriver said, the setups on these is not a mystery.  If your thinking of returning the kit because you might get it running right without the kit, then just check the Jetting FAQ and follow a setup there.

Also once again if you go the DIY route and are not going to follow one of the FAQ setups, keep in mind that tuning is done top down and you want to change one thing at a time.  For example, changing the main to a #170 might require a change in needle or raising the clip position as well because when you go bigger on the main, your enriching the entire mid-range on down.  And the only reason for changing the main in the first place is if your having an issue at WOT, not else where.

If you don't do it top down or change more than one thing at a time, you'll be chasing your tail on this and wasting a lot of time.

My .02.

Jim.

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4 minutes ago, Jim Dettman said:

 As for the air box, you do not have to remove the whole top of the box and some of the side.  Some just remove the top.   But at a minimum, you should remove the snorkel and poke at least 6 1" holes in the top to open it up a bit (a pipe heated up with a torch works great).

As far as the needle and #170, WHY are you messing around with it....you bought the JD kit, just follow the setup and be done with it.  Your just making things more complicated.  As Leardriver said, the setups on these is not a mystery.  If your thinking of returning the kit because you might get it running right without the kit, then just check the Jetting FAQ and follow a setup there.

Also once again if you go the DIY route and are not going to follow one of the FAQ setups, keep in mind that tuning is done top down and you want to change one thing at a time.  For example, changing the main to a #170 might require a change in needle or raising the clip position as well because when you go bigger on the main, your enriching the entire mid-range on down.  And the only reason for changing the main in the first place is if your having an issue at WOT, not else where.

If you don't do it top down or change more than one thing at a time, you'll be chasing your tail on this and wasting a lot of time.

My .02.

Jim.

The reason I was gonna do the #170 main is because In the JD instructions it says to use the 170 with further air mods such as backfire screen, exhaust, and air box, all of which are done to my bike. And I want to try the needle thing first just because I’m curious and it won’t take long to try out, and if it works I can get some money back which I kinda need now haha. If not I’ll be happy to install the kit. 

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11 minutes ago, DanielX450 said:

The reason I was gonna do the #170 main is because In the JD instructions it says to use the 170 with further air mods such as backfire screen, exhaust, and air box, all of which are done to my bike. And I want to try the needle thing first just because I’m curious and it won’t take long to try out, and if it works I can get some money back which I kinda need now haha. If not I’ll be happy to install the kit. 

 But keep in mind that the recommendation is made based on their setup, meaning with the needle they provide and the clip position they state.   It might not be correct with a different needle.

 At 2200' chances are a 170 will put you in the ball park, but a 165 or 172 might work better.

Jim.

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7 minutes ago, Jim Dettman said:

 But keep in mind that the recommendation is made based on their setup, meaning with the needle they provide and the clip position they state.   It might not be correct with a different needle.

 At 2200' chances are a 170 will put you in the ball park, but a 165 or 172 might work better.

Jim.

Ah yes. I misspoke earlier. What I was trying to say in my post is that when I install the JD kit with their needle and everything I am gonna try the 170. I’m not gonna use my needle for that. Sorry for the confusion there. 

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Hey all, I installed the JD kit and now the main issue (backfiring and lean conditions when I hold the throttle steady at any rpm low mid or high) is gone!

only issue now is that off-idle cracks on the throttle bog or kill the engine sometimes. When I had it apart I did adjust the AP timing so I think it’s the leak jet. I was gonna install a #50 (one I have now is a stock size #70) and see if that helps. Let me know what you think. Should I go even smaller? 

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