Carb questions???

I know there are plenty of threads on jetting, I can track those down fine. My question is a little more basic though. I don't think I have any problems with the jetting (but since this is my first bike I have no baseline for acomparison), but I want to at least figure out what jets, clip position, etc I'm currently at to see if I can make it even better at altitude, in winter, etc. My question is, how big a process is it to get to all of the jets? Can someone give me a quick idea of what to do to get the carb accessible the fastest way. I have a Clymer manual for it, but it looks pretty involved at getting it apart. The way everyone fiddles with their jets, I would think it would be easier (or maybe you guys are all just awesome mechanics)...Anyway, any help would be great as to how to get started.

Thanx

nobody??? :)

First off there are LARGE improvements you can make to your 98 carb. The first thing is to remove it.

You want to know the easiest way to do it? I would say pull the subframe. Pull the seat , side panels, loosen the boot that attaches your carb to the airbox, remove the subframe - pull off the three bolts holding it on.

You will have to remove the retaining bolt for your silencer on the end of your exhaust.

When you pull off your subframe, you will have complete access to your carb.

Remove the throttle cables from the carb, loosen the front rubber manifold boot and slide your carb back.

With the carb in your hand, you can flip it upside down to access the float, accelerator pump (this thing gets FILTHY on the 98/99's), main jet, pilot jet and whatever else is in there.

:) A WORD OF CAUTION :D

When you flip it upside down, gas WILL go EVERYWHERE. You can flip it upside down and continue to roll it, the gas WILL come out your vent and overflow lines onto your shoes, pant legs, etc.

When you are satisfied the gas is out, FIND A CLEAN, EASY TO SPOT THAT DAMN O-RING, OPEN AREA TO DISASSEMBLE IT!!!!!!!

There are two o-rings in your accelerator pump that LOVE TO FALL OUT, ESPECIALLY IN TALL GRASS!!

Check out one area of the carb at a time. DO NOT disasemble it all and toss the parts in a bucket. If you have never done this before, you may sell the bike for parts being unable to re-assemble your carb. :D

You can make great strides in performance by doing a bastard BK mod to this bike. There is the KL method (mine - which resembles the R & D P38) and the Taffy mod. Both involve the actuation rod on your accelerator pump. By altering the length of the rod, you can adjust the actuation point and stroke time of your AP (accel pump). I shortened my rod, and drilled and tapped the AP cover for a set screw. This set screw is used to set the squirt duration of your AP. My stock AP squirt time was > 3 seconds!! :D:D:D The average corrected time is < 0.5 seconds. The AP accounts for a bit of the bog associated with this bike. It FLOODS the carb initially, before engine RPM and vacuum can handle the DELUGE of fuel squirted into the venturi fo your carb.

If you want more, feel free to PM me, otherwise you can do a search on everything I have mentioned.

Glad to see you want to jump into this!!

Congratulations! :D

[ July 19, 2002: Message edited by: NH Kevin ]

Thanks Kevin-I'm going to tear into it for sure, just not sure if I want to right now (in the heart of my riding season). Sounds like there is a bunch I can do with it-though some may be beyond my mechanical ability (or better yet beyond my ability to utilize as a rider). I may do it and just give it a good cleaning at least to start with. I appreciate all the info for sure!!!

I should mention this: You have two throttle cables, one is a pull, the other a push. Make sure you mark which one is the TOP cable, the other being the bottom.

Ya getting the throttle cables backwards is embarrassing, even when nobody is around. I did it, and Ive had mine apart 15-20+ times. Once you get the throttle cables off, the rest is easy. I dont have to remove my airbox to get the carb off my bike. I can just loosen the clamp and push the air boot back. Once ya get it out, its a peice of cake.

Perfect, thanks a lot guys!

Would you do this modification on an 2002?

If you simply want to change jets for experimentation purposes, you can access them fairly easily from the plug at the bottom of the float bowl. Turn off the petcock and open the float bowl drain screw. Next, using a 17mm wrench, remove the plug at the bottom of the float bowl. From here it gets a bit tricky. I would suggest that you buy one of those little automotive mirrors from an auto parts store or sears. Use the mirror to look up into the carb and locate the main and pilot jets. The main jet is very easy to remove with a 6mm socket. The pilot is a bit harder since it is recessed deeper and needs a small flat blade screwdriver. With a little patience and perserverence, you will get much quicker at changing these jets. I can change a main jet in about 5 minutes. Less if things go perfectly. It takes longer for the pilot jet simply because it's difficult to get the blade of the screwdriver in place quickly. I have to kinda feel my way with the pilot jet. As a piece of advice, resist the urge to tighten the jets too tight. They are only brass and will strip easily. Snug them gently.

If you simply want to change jets for experimentation purposes, you can access them fairly easily from the plug at the bottom of the float bowl. Turn off the petcock and open the float bowl drain screw. Next, using a 17mm wrench, remove the plug at the bottom of the float bowl. From here it gets a bit tricky. I would suggest that you buy one of those little automotive mirrors from an auto parts store or sears. Use the mirror to look up into the carb and locate the main and pilot jets. The main jet is very easy to remove with a 6mm socket. The pilot is a bit harder since it is recessed deeper and needs a small flat blade screwdriver. With a little patience and perserverence, you will get much quicker at changing these jets. I can change a main jet in about 5 minutes. Less if things go perfectly. It takes longer for the pilot jet simply because it's difficult to get the blade of the screwdriver in place quickly. I have to kinda feel my way with the pilot jet. As a piece of advice, resist the urge to tighten the jets too tight. They are only brass and will strip easily. Snug them gently.

Boit obviously has a newer bike. On a 400, the bolt is 14mm and only covers the main jet.

It's a little tight but you can take the seat and tank off and get the top of the carb off (two 3mm allen bolts). Looking into the top of the carb you will see the top of the slide with a 4mm allen on it. If you're not sure, twist the throttle and the slide will come to the top. The needle is just under this 4mm allen. You will need tweezers or girlfriend sized fingers to get it out. Needle code around top, count clip position down from top.

If you only want the main jet size, just unbolt the 14mm Boit was talking about and use a 6mm socket to unscrew main jet. If it is closer to 3 inches long than 1 inch, the needle jet came out with it (if it did replace needle jet and tighten it with 8mm socket a little tighter than the main jet). Size is on side.

To get the pilot jet, you have to remove the bowl. It is as easy to remove carb but there are 3 (4 on 2001 and up) 3mm allen bolts holding on bowl. Pull bowl down and pilot is the more deeply recessed jet beside the main (other is starter or choke jet). Clean it, they are almost always plugged.

The air jets are between the joint to the air boot and the carb. Pulling carb or lifting subframe is the way to get to these.

The fuel screw is just barely in front of bowl in a deeply recessed hole. Count fractions of turns turning it in until seated, then turn those same fractions back out.

Good luck,

mwc

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