1999 YZ400 Carb flooding?

[ezirydr]

Bought the bike 2 weeks ago, starts fine, took maiden voyage in the mtns. and had maiden spill (on ice).  Question.....the bike was difficult to kick over after being on its side.  Was it flooded and is there a way to quickly remedy this so I can go out and injure myself again?

[grayracer513]

Yes it was flooded, no there's no quick fix.  In fact, short of converting to fuel injection, there is no fix whatever; it's normal.

 

The float in a carb controls the level in the float bowl, where the jets get their fuel. The float hinges horizontally so it swings vertically, shutting off the fuel into the carb when the level is where it belongs.  Laying on its side, the float can't rise with the incoming fuel, and the bike floods.  That's just how it works.

 

If the bike won't immediately restart by using your normal hot engine starting procedure after a fall, assume it's flooded.  To clear it, pull the compression release, if still so equipped, hold the throttle at least half way open to let air flow through without lifting any more gas from the carb, and crank the engine several times.  Close the throttle and attempt a restart in the normal manner.

 

The "hot start" on these bikes is essentially a designed air leak, allowing a small amount of air to bypass the carb throat and flow directly to the intake.  This creates an artificially lean condition with the intent of helping a hot, flood prone, or flooded engine get going again.  On the 400F, they were originally bolted to a frame tab near the air boot, and ran a hose from there to the intake neck on the head.  It's a simple open/shut plunger, same as the choke, mechanically, except that it controls air only.  Be sure yours is working, and give it a try when you next run into this situation.

[Mike15870]

99' YZ400F - I have, I think the opposite problem.  Bike will start and idle only with the choke out.  I push the choke full in and the bike immediately dies.  Good gravity fuel flow from the tank to the carb.  Pilot screw tried at 1.5 turns and 3 turns makes no difference.  Leg about ready to fall off from kicking this POS over and over...   Any  idea's

 

BTW - I have had the same flooding issue on the trails after a crash, and Hot start is your friend !

 

Mike

[grayracer513]

99' YZ400F - I have, I think the opposite problem.  Bike will start and idle only with the choke out.  I push the choke full in and the bike immediately dies.  Good gravity fuel flow from the tank to the carb.  Pilot screw tried at 1.5 turns and 3 turns makes no difference.  Leg about ready to fall off from kicking this POS over and over...   Any  idea's

 

BTW - I have had the same flooding issue on the trails after a crash, and Hot start is your friend !

 

Mike

 

You have a plugged pilot jet.

[Mike15870]

Well GR I took the carb off and pulled every jet, blew out (compressed air) every orifice, jet, and hole I could find.  Reset pin clip to 4 from 3, have pilot jet 48 from stock 45, 175 main, and 65.  Set pilot screw to 1.5 turns.  Reassembled.

 

No dice.  couple pops like it wants to start but Nuthin!!   Really starting to remember why I hate these '99 FCR's.   Pulled choke to see if it would start and idle like before and still no dice.  Even pulled the hot start, just in case it was flooded and low and behold the bike fired up and idled for about two seconds and then died.  Tried the idle adjust at all the way out (zero) and then about 1/8" open, didn't really make a difference.  The hot start trick worked twice.

 

Kicked it over another 40 or so times before I had to quit.  Think I will start a new workout DVD "You To Can Lose LBS with FCR workout"

 

Looking for wisdom!!!

 

Mike

[Mike15870]

Still have my eye on a 2005 WR450 carb.... another $200 in to the YZ .....

[RocketRoss57]

Still have my eye on a 2005 WR450 carb.... another $200 in to the YZ .....

Do it. It will relieve many headaches in the future

[grayracer513]

DON'T use the carb from a WR450 or YFZ450 quad.  They're set up with a more complex and problematic pilot air circuit so as to deal with the air injection system that bike runs.  Stick with one from a YZ450F.

[Mike15870]

Hey Grey Racer - Mike again. Well in the process of taking the carb apart and talking to a guy at work I found a few other issues that led to getting the bike started.....  The slip on muffler 'gasket' was very loose, as was one of the header bolts.  Replaced both header gasket and the slip on packing or gasket.  That got the bike started at least, but still only with the choke out.  Pulled the carb again for like the 100th time and literally pulled every jet I could put a wrench or screwdriver to, cleaned with carb cleaner and numbered drills.  reassembled and the bike still starts on the 2nd or 3rd kick with choke out, idles and then dies immediately when the choke is put in.  Still sounds like a pilot jet issue, but damned if I can solve this one.  Running a 48 pilot jet, 175 main and on the third clip setting for needle jet.  pretty much ready to put this carb into the furnace!!!!  Actually proud of myself for getting the bike even to start consistently !  Bike seems to rev well with 1/2 - full throttle, very little back fire, runs but still dies without choke.

 

As far as purchasing a 05 - 09 yz400 carb. for this '99, I am guessing but need confirmation that any carb purchased should be gone through to confirm stock jetting and clear passages as well as replacing standard gaskets, right?  Saw a few on the net, $200 +, plus carb kits.  Hard to find any with attached hot start cable....Sound about right?

[f150jokerstyle]

I'm not positive that the 400's had this piece but if there is a removable piece/cover on the slide make sure it's not up side down. I did it once and I killed my self trying to figure it out.

[jakeh_16]

Well GR I took the carb off and pulled every jet, blew out (compressed air) every orifice, jet, and hole I could find.  Reset pin clip to 4 from 3, have pilot jet 48 from stock 45, 175 main, and 65.  Set pilot screw to 1.5 turns.  Reassembled.

those jets are big for this model bike, are u at high altitude?

check the fuel screw has seal intact, should have a seal first, washer second, and spring third

 

when engine is running with choke on, spray some engine starter (ether) around ur carb, if rpm increases u have an air leak somewhere.

if not likely the valves and seats are worn and damaged

[Yz400f Jeff]

Did you try to push fishing string or anything up into the passages?? I had the same problem when I first got my 400f. I was doing everything you did and nothing seemed to work till I got the string out and gave it a shot. In another thread I read awhile ago a guy took the upper and lower part of the carb apart and the gasket between them was blocking the pilot passage. Iv heard not to do this because a new gasket is hard to come by but someone apparently supplies them but not to sure don't quote me on that. Try pushing some string up through there and see of it comes out the other end.

[grayracer513]

Contact JD Jetting about the body gasket.  Have one in hand BEFORE you open the carb at that point, because you will not be able to reuse your old one.