UGH Flooding

10 replies to this topic
  • DaleRidesAll

Posted October 10, 2014 - 07:35 PM


so the story, im picking up a wr400 99 model tomorrow, had one about a year ago. this one says it doesnt idle and only starts occasionaly on roll start, aka runs like shit. engine is still good but it does have a full fmf exhaust system 3 rides old. when i get it im going to check the air filter, if it is clean im going to try to start it, and get back to you guys on my efforts. so i ask what else should i check, does the jetting need to change for a different exhaust? etc.

Cheers, Dale

  • jones.2677

Posted October 11, 2014 - 04:26 AM


Take a can of ether! The pipe change shouldn't make it not want to run at all, but more fine tuning/jetting yes.

  • Krannie McKranface

Posted October 11, 2014 - 05:29 AM


Pull the carb, clean it completely and replace all worn parts

No way to jet a worn out carb....



  • ThumpMe

Posted October 11, 2014 - 10:14 AM


I bet it sat a little to long (which with this "new" gas formula can be as little as 4-5 weeks) and the idle jet got plugged up. I used to be able to go 6-8 weeks without starting a bike up and never had issues with them but NOW I will not go over about 3-4 weeks without running a motor as I have found otherwise you have to cleanout the carb/s. WAY easier to start up a bike, let it warm up and or just ride it a little ways every 3-4 weeks instead of pull apart a carb again!

OR, just turn off the petcock and drain the carb if you will not be starting it up in the near future. Be certain your petcock does not leak at ALL too, or disconnect the hose to the carb as well just to be certain. Been there with a leaky petcock and that too can gum em up over time

On my '99 I can pull the seat, tank, the coil on right frame downtube (to get carb. clearance), pull a little slack for throttle cables on right side of frame and then by just loosening up the front and rear carb boots giving both a little shot of WD40 on top of both boots to help them move I can rotate the carb far enough that I can pull the bowl and access everything without having to remove it. Only takes about 30-40 minutes and a lot faster than pulling it all off. Course you do want to cover the top of the tranny with a rag or towel in case you drop anything, and then lie on your back looking up into the carb jet wells with a flashlight, but to me it is well worth it for the time saved.

If the carb is real grungy, or NEEDS to be thoroughly cleaned then I will just pull it off.

  • ThumpMe

Posted October 11, 2014 - 10:18 AM


Oh yeah......real fast easy rough rule of thumb is that if piping and re-jetting a bike, about 2 steps richer on main (from how bike came stock) SHOULD get you in the jetting ballpark pretty quickly.

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  • DaleRidesAll

Posted October 11, 2014 - 07:20 PM


Alright, leaving to get it in an hour. will clean air filter then try to stat it then ill rip the carby out and give it a thourough clean. as for the jetting, what jett sizez should i be looking at for the powercore 4 with a powerbomb header on the 99 model. place i ride is about 50-150m above sea level in south australia if that changes anything

  • DaleRidesAll

Posted October 12, 2014 - 02:41 AM


okay, so the carby was dirty as hell, went through the whole thing and cleaned it out but it seems with fuel in it, it leaks out the hoses. im pretty sure that means float level is out of adjustment, so my next questions is how do i adjust the float level?

  • Krannie McKranface

Posted October 12, 2014 - 03:25 PM


okay, so the carby was dirty as hell, went through the whole thing and cleaned it out but it seems with fuel in it, it leaks out the hoses. im pretty sure that means float level is out of adjustment, so my next questions is how do i adjust the float level?


It's the float needle and seat you should be looking at. Float height can only make it leak if that float needle stops working, or the seat seal is bad

You need to test to see that the seat seal (oring under the seat) is not damaged too, by mocking up the carb on the bench and putting gas in it

  • DaleRidesAll

Posted October 20, 2014 - 03:32 PM


i seemed to have fixed it but cannot tell until i get a new fuel tap as this one is leaking, it should arrive in a week or so. just wondering if anyone has a digital service manual as i am just scraping by at the moment in forms of money. if anyone has timing specs and torque specs for the top end parts of the engine that would be greatly appreciated.

  • Krannie McKranface

Posted October 20, 2014 - 04:35 PM


Download for free on yamaha's site

  • bobpara

Posted October 21, 2014 - 10:26 AM


Here is an old trick to clean of the float valve seat when that happens:

Run engine down the road and turn fuel valve OFF

Just before engine dies, turn valve back on.

The in-rush of new fuel often times washes away a tiny spec of doo doo on the float vale seat

Takes 2 seconds and worth a try before ripping carb out


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