07 wr450 problem

[koxxwasp]

Hi, I was out riding with my son the other day on a hard forrest loop, he found it tough as he is only 11, so as you can immagine I was back and forth picking him up and his bike. As a result of this my bike was running hot.

When we came to a hill climb my bike would get half way up and stop, at first I thought it was not getting any fuel but it turned out to be the exact opposite, fuel was pouring out of the over flow and the bike was flooding, if i caught it in time and turned the fuel off (not easy whilst doing a hill climb i might add) it was fine.

Whenever I stopped the bike I also had to turn the fuel off or it just poured out of the carby and didn't stop!!!!!!!!.

I have moved onto this bike from a xr400 and I am wondering if I have done the right thing or not.

I am sure someone will know what it is. The bike is standard appart from a 175 main jet and the pea shooter removed.

Please help me out......

Tanks. John.

p.s. Sorry it is not an 07 it is an 06, its been a long long day

Edited October 19, 2009 by koxxwasp
incorrect information

[ohioryder]

I would start with checking your float. Sounds like it's sticking.

[YamaLink]

+1

Take apart the carb and just give it good thorough cleaning.

I would start with checking your float. Sounds like it's sticking.

[OUTERLIMITS]

As others have stated, it has to be something with the float or perhaps the float valve is being wedged open. A friend of mine had the float valve on his 650R stuck open and it was due to a tiny piece of loose plastic from inside the tank that got stuck in there. It was tiny, but the fuel just poured from the overflow lines.

[mongial]

I am not sure about the 06's but I had an 02 YZ426 that gave me the same problem. I cleaned the carb, checked the float etc. but still had the problem. Turns out there was a screen above the Float needle that was dirty and wedged the needle open so the float never shut off.

[WR_Dave]

The carb should be checked, but I would also see if the one way valve on the tank cap vent is working. If the tank pressures up due to the heat of the engine, it could force the fuel over the float needle and flood the engine.

[Alternative]

^^^ The one way valve on the tank breather is to let air into the tank as fuel is used, not to let pressure out, the whole point of the valve is to stop fuel vapor venting to atmosphere. That being said, excess tank pressure caused by slow/hot riding could be the issue, and may be cured by heat-shielding the under side of the tank, similar to the inside of the right side cover.

[koxxwasp]

Thanks for the help lads, I am liking the heat and pressuring gig, as I did remove the cap at one point to have a look and it just blew its load all over me! It was a very hot day and very slow going. I am guessing 35 deg +. And the bike was fine 2 days earlier on the same lap but flat out no stopping. I will keep you posted.

Thanks. John.

[WR_Dave]

^^^ The one way valve on the tank breather is to let air into the tank as fuel is used, not to let pressure out, the whole point of the valve is to stop fuel vapor venting to atmosphere.

I realize the function of the valve, that is why I made the statement about pressuring up the tank. I have seen far too many problems with the stock "high quality" plastic valve. Usually it sticks closed and the tank will stop flowing due to a vacuum being created. Keep us posted if it keeps happening or if normal riding cures the problem. WR Dave.

[Alternative]

I appreciate what you're saying about how the one-way valve can malfunction and cause issues by creating a vacuum in the tank, but this isn't the problem here, the problem is (well hypothetically) pressurisation. This isn't an issue that can come about by a malfunctioning breather valve (even if it working correctly it will allow the tank to pressurise) so mentioning it as a possible cause to said problem is irrational.

[WR_Dave]

Thanks for clearing me up on this one ....TT is to here help other riders with possible resolutions to problems, you seem to want to start something to prove how incredibly SMRT you are. I have been forever humbled now that my irrational behavior has been outed WR Dave

[harvmushman]

Despite the New Zealanders most strenuous objections to the gas tank valve theory, I agree it is a possibility in this situation ... if only a slight possibility.

If the one-way valve is working exactly as it should ... and the temperature of the gas tank is increasing quickly due to ambient and engine temperature ... and the bike is using very little gas due to the very slow nature of the described trip (so the tank is not draining to relieve the pressure build up as it would on a normal ride) ... and the carb float valve is not sealing 100 percent (which can easily happen) ... then i think the theory is sound. It would be possible for the tank to over-pressurize the carb. Heck, the man said he had a lot of pressure build up in his tank that day.

And if the carb is working normally now, and not draining gas out the overflow line, then I think tank pressurization is a possible theory.

Another theory if this situation arose only on the hill climb: Float level is not set correctly, a situation exacerbated by the angle of the bike on that hill climb.

[ww44wrf450f]

I believe the gas tank check valves work both way's. They let air in and out of the tank-- don't they? If it got stuck so the tank would pressurize, I would say the gas will vent from the overflow lines! Pull the valve off for now and give it a try with just the hose.

[willy_fitz]

If we are talking about the inline check valve in the vent line coming off the gas cap the theories stated above are incorrect. The function of the check valve is not to stop vapours from escaping from the tank. The function of the valve is to stop liquid fuel from escaping if / when the bike is dropped. The carb takes its fuel from the tank by gravity. It is therefore important that the tank stay at atmospheric pressure at all times so that the pressure differential between the air intake and the fuel jet nozzle stay within design limits. When the check valve gets stuck closed the pressure drops in the tank as fuel is used and then the venturi effect of the carb cannot draw enough vaccuum to overcome the negative pressure in the float bowl and tank.

No fuel to motor = no go.

Vapours are constantly being released to the atmosphere past the check valve but I would NOT recommend checking this with a match.

The initial problem described in this thread is almost guaranteed to be a problem with the float valve and or seat not sealing correctly when the float level rises in the carb. Disassemble carb and check carefully for damage or foreign material.

[ww44wrf450f]

If we are talking about the inline check valve in the vent line coming off the gas cap the theories stated above are incorrect. The function of the check valve is not to stop vapours from escaping from the tank. The function of the valve is to stop liquid fuel from escaping if / when the bike is dropped. The carb takes its fuel from the tank by gravity. It is therefore important that the tank stay at atmospheric pressure at all times so that the pressure differential between the air intake and the fuel jet nozzle stay within design limits. When the check valve gets stuck closed the pressure drops in the tank as fuel is used and then the venturi effect of the carb cannot draw enough vaccuum to overcome the negative pressure in the float bowl and tank.

No fuel to motor = no go.

Vapours are constantly being released to the atmosphere past the check valve but I would NOT recommend checking this with a match.

The initial problem described in this thread is almost guaranteed to be a problem with the float valve and or seat not sealing correctly when the float level rises in the carb. Disassemble carb and check carefully for damage or foreign material.

ok, I know its to prevent gas from spilling on a tip over, and yes it's probably the carb -- but that valve will let air into the tank or out, but not liquid. And yes I know about that suction theory I'me not that old yet.

[harvmushman]

Thanks for the help lads, I am liking the heat and pressuring gig, as I did remove the cap at one point to have a look and it just blew its load all over me! It was a very hot day and very slow going. I am guessing 35 deg +. And the bike was fine 2 days earlier on the same lap but flat out no stopping. I will keep you posted.

Thanks. John.

How did he get pressure build up in the tank if the fuel vent line check valve was letting air out?

[wondermuscle]

Thanks for the help lads, I am liking the heat and pressuring gig, as I did remove the cap at one point to have a look and it just blew its load all over me! John.

John, I bet after you took a shot of gas from your tank and put the cap back on it ran fine for a few minutes. Am I right

Boiling gas..... I have experienced this same phenomenon. This is a quick fix, no need for two pages of nonsense. The tank is pressurized and is forcing fuel though the main jet past the needle, thus causig the carb to SHOW a stuck float senario. It is not a carb problem.......

If you have a one-way valve in your tank vent tube, remove it and run a single hose. If you have one of those fancy aluminum vent valves drill a hole in the bottom where the tube attaches so it can breathe both ways. I have two vent valves, one for the summer when boiling gas is a possibility and one for the winter which only breathes in.

Another solution, but not a sure fire fix, is to get some metal sided duct tape and apply it to the bottom of the fuel tank, it never stays on for long though.

Pulling your carb apart will not fix the problem.

Good luck

Edited October 28, 2009 by wondermuscle

[koxxwasp]

Right lads here goes.

I went out on Sat with a faster rider, yes I took the carb to bits again!!!!!!!! and I found nothing untoward.

However I rode the bike how it was meant to be ridden for a full tank of fuel, so a fair test I am sure you will aggree. It was very hot again and yes the bike did get hot i am guessing, but as I said I rode it hard and fast and it ran like a dream!! Never missed a beat, never pissed fuel out and started first time every time.

So what ever the trouble was it certainly wasn't there this time so I can only presume that it was a build up of pressure due to the riding style and temp but the jury is still out on that one e?

I am forever greatful for all of your help with this one even if a couple of you had a little spat with each other. (Nothing wrong with healthy debate)

I will continue to moniter it and will keep you posted.

My next challenge is the "free mods" are they worth doing???if so at what cost to the overall rideabillity of the bike??

My friend has a KTM530 he rode mine this week and said it made his feel sluggish and numb!!!! So i don't want to loose that all round good bike thing.

Thanks again groovers.

One very happy John.

[CORider63]

In my opinion, the Free Mods are a must to make the bike more predictable and enjoyable.

[tribalbc]

The bike was built expecting the free mods to be done. That is why they're so easy to do