Surging and Stalling

AllNewbie

AllNewbie

Member
Hello all! I recently became the owner of an 03 Pitbull.

Took it out for a ride today and it was running great. About 20 miles in, the throttle became touch and go, meaning it felt as though I was pulling the throttle and letting go over and over (while open throttle). Pulling the throttle didn't give an immediate go, then it would surge and buck wildly. Backfiring and surging until it stalled out.

Took the bike home (limping) and took apart the carb (being a new owner I was unsure of its last cleaning. it was already spotless) cleaned it and put it all back together, changed plugs and went back out for a ride.

Same issue. About 20 miles in it started to misfire and surge/buck wildly until I made it home.

It's odd that it runs perfectly until about 20 miles in. Where should I look to next?

Thanks!
 
chubs

chubs

Guru
You might also try loosening the gas cap and see if it helps. Sometimes, as the gas is used up in the tank, it builds up a slight vacuum and affects the flow of gas from the tank. (just a couple ideas)
 
AllNewbie

AllNewbie

Member
chubs said:
You might also try loosening the gas cap and see if it helps. Sometimes, as the gas is used up in the tank, it builds up a slight vacuum and affects the flow of gas from the tank. (just a couple ideas)
Click to expand...
i was reading about that in the forum here. Not sure if my vent cap is working properly or not. A lot of the old forum topics have broken links and pics so I'm unable to look into taking mine apart.

My right side gas cap comes off fine, the left didn't come off at all, rather the chrome top just spun off leaving a cap in place but it looks like only the right side one vents anyways?

Ìve tried to look up the petcock filter but again, all the old posts have broken links so I'm having trouble locating any info on it
 
S

Sven

Well-Known Member
Way:
1. I remove fuel hose off tank. Have gas can ready. Have a full tank of gas for this test. Turn fuel to on position and let it flow.
a. Continues to flow and stream is constant = Not gas cap.
b. Continues to flow but the stream begins to slow down = Gas cap vent hole is clogged.

2. I remove the fuel hose off the carb. Still a gas tank topped off with fuel. Turn petcock on.
a. Continues to flow a steady stream = Not a swollen/kinked hose.
b. Continues to flow but starts to slow down = Fuel hose inner liner is collapsing causing a flow to block as it flaps inside.
 
HMAN

HMAN

I just like my Freedom
AllNewbie said:
Not sure. Is there a way to check that? I'm still learning where everything is on this bike. Any diagrams to help me locate?

Thanks!
Click to expand...
Your petcock filter is inside the tank. It can be removed for cleaning if needed. It is attached to the on/off gas petcock. Shine a flashlight in the tank and look for pieces of tank liner floating or sitting on the bottom of the tank. When it starts to act up, do as chubs suggested and loosen the gas cap. You may have a venting/fuel issue. With the gas line off the carb, turn the petcock on and check fuel flow. Report what ya find and we will try to narrow it down.
 
chubs

chubs

Guru
The left gas cap is probable reverse thread than the right cap. ( my 02 pitbull is that way ) the petcock filter is up inside the tank attached to the top of the petcock. Turn the fuel valve off, attach a piece of fuel line to the petcock and then turn the valve on to drain the gas into a gas can or other container, (ya might need 2 if both tanks are full) After the fuel is emptied, remove the petcock and gently pull it out of the tank. Might have pieces of tank liner clogging it. Or maybe not.
 
S

Sven

Well-Known Member
AllNewbie said:
Same issue. About 20 miles in it started to misfire and surge/buck wildly until I made it home.

It's odd that it runs perfectly until about 20 miles in. Where should I look to next?

Thanks!
Click to expand...
Then again:
1. Heat related.
a. Can't bet a petcock/gas cap/kinked line = 20 minutes in.
b. Gas cap surge/flows fine/surges again; is not some 20 minute deal with a full tank heading out.
c. Sounds like, feels like... fuck the test, just buy a cam/crank sensor and shoot the craps just for crapsake.
 
AllNewbie

AllNewbie

Member
Sven said:
Then again:
1. Heat related.
a. Can't bet a petcock/gas cap/kinked line = 20 minutes in.
b. Gas cap surge/flows fine/surges again; is not some 20 minute deal with a full tank heading out.
c. Sounds like, feels like... fuck the test, just buy a cam/crank sensor and shoot the craps just for crapsake.
Click to expand...
Going to check petcock right now. I'll give my findings in a few min.

I was thinking either TPS or Cam/crank sensors.

To go back to the tank venting issue, wouldn't it be feasible to think that the tank builds pressure after a certain amount of time that would stop the vacuum, also slowing down fuel pressure. After the bike sits for a little while the pressure is dissipated(I also pulled the line earlier when I cleaned the cam sensor), and the bike runs normally again?
 
S

Sven

Well-Known Member
No. Gas cap is instant. Can't even run down for the mail it would cutout that quick... especially with a full tank. A tank vent does not close off 20 minutes later.

No fuel to carb: Gas tank cap/petcock filter/kink in line.
No fuel to injector: Gas tank cap/filter/fuel pump no longer meets set pressure.

After the bike sits: is more heat than vac related. You more relate heat rather than flow. Whereas, my experience has always been a clogged cap is to have as little air in between the gas to cap difference so you don't wait those few extra 'seconds' not minutes if the tank is low.

Say for argument sake, it takes a mile to empty the float bowl. Take that volume of gas and add it to the air gap in the tank. Now think of taking it away every mile out of the tank. If a few seconds of riding with a full tank was the road test, and then it took less for me to leave the lot and head to the first stop for a test ride, it's not a fuel vent problem is my guess. Too much assfactor on my end.
 
AllNewbie

AllNewbie

Member
chubs said:
The left gas cap is probable reverse thread than the right cap. ( my 02 pitbull is that way ) the petcock filter is up inside the tank attached to the top of the petcock. Turn the fuel valve off, attach a piece of fuel line to the petcock and then turn the valve on to drain the gas into a gas can or other container, (ya might need 2 if both tanks are full) After the fuel is emptied, remove the petcock and gently pull it out of the tank. Might have pieces of tank liner clogging it. Or maybe not.
Click to expand...
Your were 100% correct. It was reverse threaded.

The petcock filter looked pretty clean to me
0506201910.jpg
 
AllNewbie

AllNewbie

Member
Sven said:
Way:
1. I remove fuel hose off tank. Have gas can ready. Have a full tank of gas for this test. Turn fuel to on position and let it flow.
a. Continues to flow and stream is constant = Not gas cap.
b. Continues to flow but the stream begins to slow down = Gas cap vent hole is clogged.

2. I remove the fuel hose off the carb. Still a gas tank topped off with fuel. Turn petcock on.
a. Continues to flow a steady stream = Not a swollen/kinked hose.
b. Continues to flow but starts to slow down = Fuel hose inner liner is collapsing causing a flow to block as it flaps inside.
Click to expand...
Ran this and the flow was steady.

Where can I order a cam/crank sensor from? And where is it located on the engine? I'm happy to give this a try if you think it's the next feasible option
 
S

Sven

Well-Known Member
I think there are jobbers on line here so support the crew... if they have replacement parts for the BD.
 
HMAN

HMAN

I just like my Freedom
Curtis @ Wild Steed Worx should have what you need.

WSW, Rule Your Ride!

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www.wildsteedworx.com
 
S

Sven

Well-Known Member
Steed would know by year change if it's cam or crank. Unless you can see a sensor harness wire near the cam area? That's, follow the pushrods to see where the cam lifts the pushrods. If not, then the crankcase area for a crank sensor harness off the case.

Seems like it's pretty common for these. Some sensors will show good when checked with a meter and measured against the resistance specs in the book. But a new one solved it. That's one variable I've noticed on these. Or say, sensor wise again, this one bike would run fine, but as soon as it reached its running heat range, where the engine is fully warmed up, it stopped. Waited for it to cool down, and it started again. Replaced the sensor and solved. So his was 15 minutes, yours might be 20 minutes and shows ignition curves jumping all over the place is my [binary fed] guess.

These are computer bikes so the one sensor that stops the bike from running is a bad crank/cam sensor. Let's recap.
20 minute window:
Compression; Can't be this. The bike starts right up again.
Fuel; The bike starts back up so two are out of the loop.
Spark; Can't be a coil, nor a black box, nor new plugs; it keeps firing back up until the 20 minute window kicks in.
Crank/Cam sensor; Magnetism~you cannot separate heat from the chemical reaction. The sensor makes magnetism; is the form of a wave length. Heat times 20 minutes equals wave my length any other way but square. Then there is no other choice to square away but the sensor.
 
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