Apparent Fuel Starvation

[BLUEJEEPLAB]

My XT 500 thumper was acting as if it was fuel starved the last few times I rode it last summer. Fuel flow from the petcock was normal so I figured it was a case of Crap in the carb (Blonde punch line - "So how often do you have to do that?")

I finally had time to remove the carb and look into it. All vents and jets appear to be clear (Hate the taste of unleaded, but how else you gonna know a passage is clear than to blow through it?). I pulled the plug and it's a nice roasty brown.

My first thought on finding the carb passages clear was a vacuum leak, but the brown plug doesn't back that up. What am I missing? The bike was so fuel starved that it would actually bog out,stall and not start again for several minutes.

My next thought is to remove the petcock from the tank and check for floating garbage.

[Ken Talbot]

Try checking the fuel cap vent. If it is plugged, you'll build up a vacuum in the tank and eventually kill the fuel flow.

[GNEPIG]

The bike was so fuel starved that it would actually bog out,stall and not start again for several minutes.

cavitating
.. gino, the floating trash is a good place to start, but if that doesnt help with your problem then try taking the gas cap off or opening it a little bit the next time it starts to act up, if the vent in the cap is not working then the fuel wont go down as fast as your bike will use it
. hope this helps

[strom]

Make sure your fuel filter (what fuel filter?) is turned the right way (they usually have in/out ends)

LP

[BLUEJEEPLAB]

Initially the first thing I did was check the fuel vent hose and lo and behold, it was clogged. Yippee, I says to myself. I replaced it and took Old Shaky out to the curb, fired him up and still rn into the problem (yeah, I also checked the vent hole in the gas cap, clear there too)

One other thing that leads me to believe it may be a vacuum leak was that for a period (not anymore), it would only run when choked, but then I have that nice brown plug. Can a plug that has been running well retain it's color when running lean or will the high temperature always clean it up? It has been running like that for about two tanks of fuel (about 130 miles, XT tanks are even smaller than XS tanks )

[LoserShoes]

Could also be electrical, something getting hot. Vacumn leak will usually start right back up. Either a flow restriction or electric.

Plug takes quite a while to clean itself, try a new plug to get a good reading.

Steve

[xsivebiker]

Remote Possibility

First, let me say that I work 3rd shift and I'm staying up WAY too long.
Next, on Keihein carbs, i.e. early Gold Wings, they have Micro-Screens/Filters , one per carburetor. The therory is that what ever passes thru the in-line fuel filter will not plug up a needle jet.
On my 'Wing I removed the carbs, removed the float bowls, removed the floats, then take out the float valve assembly. On the top of each float valve assy. is a small micro-filter/screen that is hard to even blow thru. Discard it! Re-assemble.
'Made a BIG difference to my Gold Wing. It was acting as if fuel-starvation was going on until I did this. Consult your service manual to see if this might apply to you. 'Just a thought.
Ride Safe,
Greg
'80 XS1100-G "Christine"
'87 GL1200-I "The Queen"
'93 KLX650C1 "Back Roads Beast"

[BLUEJEEPLAB]

No micro screen, but there is a screen inside the petcock, I am going to pull that out tonight after I re-assemble the carb. If there was crap in the carb, there is probably A LOT of crap in the petcock.