Fixing 02 426 bog

I have been scouring the forums and read the sticky, just need some advice for my situation. I read the 426 doesn't have a leak jet, so I want to get a r&d bowl with the leak jet, a 40 to be exact. Then replace the spring on the ap with the one from Tokyo mods, but I can't find a diaphragm upgrade kit other than the one on crfsonly.com. Is that the correct one I need even if it's made for Hondas?

Oops. Posted this in the wr forum. My bad. Please delete.

You don't need the leak, really.

That motor likes a 35 leak, so you are about that without one.

If you have a FCR/MX/CR carb, the CRF's only diaphram kit will fit.

It won't fit on the earlier model, which some WR's and YZ's came with, but I think that was only the 400's.

 

The R&D float bowl will noticably improve the throttle response and eliminate cavitation on rough terrain, so it's still worth it.

The adjustable leak jet portion is not going to do anything for the bog, on it's own. It's just less restrictive and better made.

 

You need:

 

  • Short rivet diaphragm and longer push rod  http://www.crfsonly.com/catalog/product_info.php/cPath/138_147/products_id/393
  •             This will give you a harder and farther squirt
  • Tokyo mods or R&D linkage spring upgrade
  • Verify the nozzle is not clogged or corroded, or squirting oddly (you can ream it with ultra fine copper wire, like from speaker wire)
  • Verify the squirt is always missing the slide, just barely
  • Double check your throttle cables. The pull cable can get loose without you noticing, and that can lead to stuck throttle
  • Slide plate seal: you need good vaccum or the squirt will land in a lean environment on uptake

 

I wrote some posts about the fine details:

 

http://www.thumpertalk.com/topic/1053317-06-crf450r-still-bogs/?hl=%2Baccelerator+%2Bpump#entry11143305

 

http://www.thumpertalk.com/topic/1093495-fuel-screw-and-jetting/

You don't need the leak, really.

That motor likes a 35 leak, so you are about that without one.

If you have a FCR/MX/CR carb, the CRF's only diaphram kit will fit.

It won't fit on the earlier model, which some WR's and YZ's came with, but I think that was only the 400's.

The R&D float bowl will noticably improve the throttle response and eliminate cavitation on rough terrain, so it's still worth it.

The adjustable leak jet portion is not going to do anything for the bog, on it's own. It's just less restrictive and better made.

You need:

  • Short rivet diaphragm and longer push rod http://www.crfsonly.com/catalog/product_info.php/cPath/138_147/products_id/393
  • This will give you a harder and farther squirt
  • Tokyo mods or R&D linkage spring upgrade
  • Verify the nozzle is not clogged or corroded, or squirting oddly (you can ream it with ultra fine copper wire, like from speaker wire)
  • Verify the squirt is always missing the slide, just barely
  • Double check your throttle cables. The pull cable can get loose without you noticing, and that can lead to stuck throttle
  • Slide plate seal: you need good vaccum or the squirt will land in a lean environment on uptake
I wrote some posts about the fine details:

http://www.thumpertalk.com/topic/1053317-06-crf450r-still-bogs/?hl=%2Baccelerator+%2Bpump#entry11143305

http://www.thumpertalk.com/topic/1093495-fuel-screw-and-jetting/

I'm sure there are threads about checking the squirt from the accelerator pump, but can you give me a quick rundown on that? I appreciate the info! I'm going to pull my carb tomorrow and clean it again, and see what my jets are. It hasn't been cleaned in about a year, so it needs it anyways. Plus it gets me outside!

Also, the carb has a quick shot 2 on it, but I was just going to put the stock back on and go the r&d route. Is this the best plan or should o just leave the quick shot and do the spring and diaphragm upgrade?

And just to ensure you saw my above post that the bike is a yz not a wr, I accidentally posted in the wrong section. Not sure if it makes a difference or not.

Edited by 0BigBlue7

Quick shot is the same thing, but you should use all R&D.

Again, the apump cover does NOT CURE bog, it fixes other problems.

https://www.youtube.com/results?search_query=fcr+carb+apump+squirt

Ok, I will plan on getting the r&d bowl at some point, and the r&d Spring, and the diaphragm upgrade kit. And get my jetting proper. Thanks for the info!

Look at the O-Ring mod.  This cured my low end bog once and for all.  Of course, proper jetting is key as well.  I had tried everything else, to varying degrees of success, but the bog never really went away, until I put in the O-ring.  Still make sure your AP squirt is timed so that it just misses the slide, and then buy a new diaphragm, or just grind down the existing one so that the linkage stays in contact with the plastic throughout the entire throttle opening.  Once you've got the diaphragm ground down properly,  you can then use safety wire if you prefer.  The O-ring will stretch, allowing the linkage and the plastic to separate if the diaphragm isn't exactly perfect.  Lastly, check out disabling the ACV.  This requires a new jet, as well, making it set up exactly like the YZ carb.  I found tuning the bike to be a lot easier without the ACV.  

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now