Spring Mod Full Tutorial

[Joester]

Hi everyone, I figured that I would make a full tutorial for doing the spring mod with pictures and no steps missed. the "the bog!" pinned topic is basically a huge discussion and it took me a while to see that it actually had methods of fixing the bog in it. The spring mod eliminates the bogging produced when the throttle is stabbed that most stock YFZs have. Some people out there are new to the sport and have a bogging YFZ, they want it fixed, but don’t have the money to take it to a dealer. Well here you go, from start to finish.

First, go get a snack, take a pee and a poo, and set up a radio. I do, and it helps me to be more patient when working on my bike. If you even get annoyed just take a break, if you get mad like I do and smash something you will regret it later.

Also, make sure your bike is pretty clean, the cleaner the better. Its worth it to go wash it off, especially around the carb area before you do this, but let it dry before taking anything off if you do wash it. You don’t want water in your intake.

The ATV that I am performing this on is a 2007 YFZ450. other years may differ slightly, but they should all be relatively the same.

The tools you will need are
-10mm socket
-10mm open end
-3mm allen
-4mm allen
-standard screwdriver(s)
-phillips screwdriver
-pliers (preferably needlenose)



First take off the seat. Then using a 10mm socket take off the 4 bolts that hold on the airbox. Loosen the standard screw on the ring that holds the black intake boot to the airbox. When that’s off, I went to sears and got a Phillips screw because the standard one strips easily and is annoying in my opinion.



Then look on the right side of the airbox and you will see a black box and a hose leading to the airbox, pull off the hose and then there will be a small attachment that just pops in the airbox. Pull it off.



Now the airbox is free to come out. Just pull up on the end.



You should be left with the black rubber intake boot, as I referred to it before



Now look on the carb on the left side where the black intake boot meets the carb. There is a 4mm allen hose
clamp like thing holding it on.



Loosen the 4mm blt and the black intake boot should come right out, the same path as the airbox came out. Now you should be able to see inside the carb like this.



Take the left side radiator shoud off to gain access to the plugs you need to unplug to get the carb out. It is 3 bolts and a little plastic rivet thing. The plastic is then able to slide out the front, past the front wheels. Here is what you should see under it.



Unplug the two switches that I am holding. There is a little latch you have to press down and then just pull. I used the little standard screwdriver in the first picture of the tools to press down the latch. Now making sure that the gas petcock is on the off position, get a rag. Use pliers to press the little silver ring that keeps the gas line on the carb and move it up the line. Now the gas line just pulls off, but make sure that you have the rag handy, because a little gas will spill out. Also sometimes the gas line likes to “stick” to the metal and its hard to pop off, then all the sudden it comes off and you fling gas everywhere. If its hard, use pliers to gently rotate the gas line on the metal part of the carb, then pull it off bow that the dryrot has been broken. It should be much easier. Heres what it should look like once you have everything off.



Now go around to the other side and loosen the two bolts on the small boot that goes from the carb to the engine. These ones. Loosen them pretty much, the carb is kinda hard to get off.



Pull the carb off the boot and then the boot off the engine. Set the boot aside and put a clean rag or paper towel in the engine intake so nothing gets in there. Heres the boot I took off and the detached carb in the background. Notice that I took the little hose that goes to the engine off for more room.



Now go the the other side with your 10mm open end wrench and a 4mm allen. take the small rubber boot off the throttle cable and slightly loosen the 10mm bolt the goes into the carb. Now loosen the two 4mm allens on the cover that says “kehien”. The cover should then come off.



Now you will see the “throttle wheel” hook the cable end out of the hole in the wheel and hook the cable somewhere to get it out of the way.



The carb is now ready to come out. The easiest way is to pull it out the left side. It should come out freely, do not force it. Now find a bucket and turn the carb around, unside down and every which way to get all the gas that you can out. Don’t do that inside, that could be bad. Now you have it out and you are looking at the throttle wheel. The spring puts pressure on the black piece which actuates the accelerator pump, which is what we are fixing. Using the needlenose pliers take off the E-clip that hold the black piece of plastic on there, but look out. There is a small washer under the E-clip that you might lose.



now look at the carb and locate this cover. It has 3 phillips screws. Take them off, but be gentle, there are a few small parts and gaskets inside.



This is what is inside. Don’t lose these.



Also look out for these 2 small gaskets, I lost one when I did it, got it all back together and it spewed gas everywhere, took me a few days to figure it out.



Now using pliers again pull on the little metal shaft that is sticking out of where the round black rubbery piece was when you took of the small 3-phillip-screw cover. Just pull hard, it will pop out, to get more of a grip on it, push down on the black piece we were talking about earlier.



It should come out like this.



Now kind of wiggle the black piece out, its hard to explain how to, but you can grasp the small spring with the needlenose to take some tension off of the black piece. Now find the little spring I was just talking about. This one.

That picture is after modification, but it will do. Your spring should have the tab about at the angle of the blue line. Now unbend the original tab and rebend it further down the spring, like in the picture it should be almost parallel to the tab with the “hook” on the end of it, but about a 15 degree angle difference. Just look at the picture. That is good enough. Now clip about 3mm off the end of the part you just bent, or else it will be hard to fit it back into the carb. you are essentially moving the bend a little further down the spring to provide more pressure on the AC pump.


Now put it back into the carb, hooking the spring over the little silver metal piece in the bottom of the throttle wheel “chamber” and using your needle nose get the black plasic piece back in there. Push down pretty hard to seat it correctly. It should look like this.



Pressing it down allows room for the washer and e-clip to go back on, which you should do now. Reassemble everything, and now there should be very little to no bog. It will still bog some in neutral, but when in gear, there was a noticeable difference.

When reassembling, make sure to

-reinstall and tighted down the throttle cable, put the rubber boot back over the bolt. Now press the throttle to make sure everything is still smooth.
-put the cover back on the carb
-tighten all intake tract bolts and make sure everything Is seated securely.

Here are the parts that I had to take off. Along with the airbox, intake tube and left side radiator shroud.



some people like doing the zip tie mod, which is when you put a small ziptie around the metal arm and the black plastic arm. this works fine, and is easier, but i have heard of the zip ties breaking. the spring mod takes only another few minutes and is much longer lasting. some people buy and install a size 35 leak jet, which further helps. here is a picture of the leak jet. it is in the carb bowl


also, as a disclaimer, i do not guarantee that this will fix your bike, so dont get mad at me if it doesnt. it fixed mine, and will probably fix yours, too. also, if you are still unsure about your mechanical abilities, dont do this. you would probably rather have a working bike and the bog than a non-running bike with crisp throttle response.

oh and credit goes to my brother (Jimmy Hoffa) for teaching me... weather he got it from someone else i do not know.

[2004yfzrider05]

good work, should really help some people.

[YFZER359]

PINNED!!!

[Joester]

QUOTE (YFZER359 @ May 5 2009, 05:42 PM)

PINNED!!![/b]

lol, i sure hope so. i spent all day on this. i even shed some blood! a new guy was too afraid to do it by himself and he said if i made a tutorial with pics he would do it. lol.

by the way... shed some blood = scraped finger on footpeg. =P

and hopefully it will stop the thousands of people creating the "my YFZ bogs" thread every other day.

[SyKo450]

To make my life easier when re-installing the carb back on the engine, I just loosen the allen screw that's closest to the engine and keep the boot on the carb

Also, don't smash your gas line when taking off the hose, be gentle, it's aluminum

Good post noob
;)

[Joester]

QUOTE (SyKo450 @ May 5 2009, 06:17 PM)

To make my life easier when re-installing the carb back on the engine, I just loosen the allen screw that's closest to the engine and keep the boot on the carb

Also, don't smash your gas line when taking off the hose, be gentle, it's aluminum[/b]

thanks for the suggestions, and yeah, keeping the boot on the carb works fine, just it makes it easier to slide the carb out if you take the boot off. you can really do it either way.

[jwfab1]

Thanks for the write up, excellent job!! I may now consider doing this, thanks.

[zadjali]

Great write up :D

[blaknblu]

Excellent job

[Joester]

QUOTE (BlaknBlu @ May 6 2009, 06:53 AM)

Excellent job[/b]

yay! thanks. =) =)

[YFZER359]

Congrats Joester, got er' pinned!

[yfz450allday]

lol nice one...I will probably do it this weekend, im just unsure about trusting myself - but I will be fine. Thanks man
btw congrats on the pinned!

[fast450yfz]

good w00ter very detailed and clean

[fever2ride]

I found this thru the search.. :D

This was EXACTLY what I was looking for!!! Acc pump adjustment, and leak jet adjustment.. I did a pump cover a while ago, but I'm pretty sure I didn't do the adjustments properly, if at all...

One question tho.. On the final pic of the Leak jet; what do I do with it? Replace the jet with the 35?


And I found out earlier, that it's easier to take the throttle cam cover off while the boots are still attached.. THat way the carb can't move too much.. Those two allen bolts were wicked tight for me..

[Joester]

QUOTE (Fever2ride @ May 8 2009, 10:13 PM)

I found this thru the search.. :D

This was EXACTLY what I was looking for!!! Acc pump adjustment, and leak jet adjustment.. I did a pump cover a while ago, but I'm pretty sure I didn't do the adjustments properly, if at all...

One question tho.. On the final pic of the Leak jet; what do I do with it? Replace the jet with the 35?


And I found out earlier, that it's easier to take the throttle cam cover off while the boots are still attached.. THat way the carb can't move too much.. Those two allen bolts were wicked tight for me..[/b]

yep, all you do its unscrew it and put in a 35 from your local dealer (if they have it..)

and the allen set i use is bulky (see picture) so i cant get in there, but if you have one of those sets that each wrench comes out individually then its probably easier to take that cover off first.

[planemaker501]

Excellent job! I will be doing this mod. first thing tommorrow

[usafEODguy]

Is the leak down jet only available at a dealer? Also is the leak down jet the accelerator jet? That is the only thing I could find in the repair manual in that general area.

[planemaker501]

Thanks again for the great writeup! Heck that was pretty dang simple to do! The hardest part for me was getting the spring bent to look like your picture:)

[bansheeslayer]

QUOTE (Joester @ May 5 2009, 06:58 PM)

lol, i sure hope so. i spent all day on this. i even shed some blood! a new guy was too afraid to do it by himself and he said if i made a tutorial with pics he would do it. lol.

by the way... shed some blood = scraped finger on footpeg. =P

and hopefully it will stop the thousands of people creating the "my YFZ bogs" thread every other day.[/b]

my yfz bogs...lol

[ae13291]

whats the purpose of the leak jet? and should we adjust that spring loaded screw more out? the screw that is pushing on the black plastic piece