Bog Bog Bog

9 replies to this topic

Posted September 10, 2008 - 12:38 PM


I have a 98' YZ400F. It is stock jetting, pipe ,everything. I just rode it about 3 weeks ago and it ran great. Now it takes longer to warm up and there is a bog off idle that has never been there. Anyone know where to start first? Right after idle when the throttle is applied it bogs for a second or so and then runs great. It starts easy and idles well too.Thanks.

  • grayracer513

Posted September 10, 2008 - 12:41 PM


Did you wash the bike 3 weeks ago? Look for water in the fuel. If not that, there's something stuck in a jet.


Posted September 10, 2008 - 12:59 PM


Yes, I washed it. Changed the oil and cleaned the air filter. Do you think it's probably in the pilot circuit? Thanks.

  • grayracer513

Posted September 10, 2008 - 01:16 PM


That's where I'd go with it. Start by removing and inspecting the jet access plug for water.

  • nicogc

Posted September 10, 2008 - 04:41 PM


it could be the AP also. I have found the rod for the AP stuck (rusted) on those carbs.

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Posted September 10, 2008 - 07:19 PM


Thanks for the suggestions. I went ahead and changed my plug and cleaned the petcock. Never cleaned the petcock since I built the bike. The plug had been in there over a year. Just thought I would start fresh. I'll try these suggestions tommorrow. Thanks again.


Posted September 16, 2008 - 05:57 PM


I have just now had an opportunity to look at this carb. Once I had it off the bike I found that an o-ring on the plastic T for the vents was rotted. I can't find a part number or any breakdown that shows the o-ring. Anyone know what to call this o-ring or where to find it? I also found that the AP rod would not move until I forced it. I'm still going to take the carb apart and check everything over. Since I have it apart I figured I would replace anything that was worn out. The area where the o-ring is at is where the two black plastic tees are held in by a rod that snaps over them to hold them in the holes. I can probably post a pic if need be. Thanks. :excuseme:

  • grayracer513

Posted September 16, 2008 - 09:07 PM


Google: Sudco


Posted September 17, 2008 - 05:46 AM


I think I found the o-rings, but what is the model of carb I have? On top of the carb it says CR Flat. The only other numbers I find are 5BE1 00MA12. Thanks for the Sudco site. They have basically everything. Thanks.

  • grayracer513

Posted September 17, 2008 - 05:49 AM


The latest one is the FCR-MX. I believe yours is the FCR, the one just before that.

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