Bike cuts out under load?

[mellowyellow]

That's a fair point, but why is the plug temp still in range if it's weak spark?
The chokes could be stuck or leaking anyway, I've had split rubbers in my chokes, fuckin' annoying

for new plugs, they seem to be a litttle dark around the edges. i know that can be cuased due to many things, but the state of the plugs cant rule out a spark issue, imo. dont forget i'm suggesting intermitent spark fault, not consistant (overheating pick up vs cracked coil). though cracked leads probably could cause the coil to overheat, i guess.

sort of, letting it sit allows me to ride again but only for a brief period of time.
Like this morning on the highway, I had just gotten to the top of a hill at 100 when it cut out. I sat there for 20min, started it and rode down the hill. at the bottom it died. let it sit and repeated the process till i got home. - but it tends to die on hills mostly.

that makes sense, it would take mre time for something to overheat from dead cold, from that point on, it would be a much shorter time period for when the problem returns.
heres a senario the old ford LTD's use to have - car would run well for the first 10 min, next 10min the car might loose power. about 20-40min of driving from cold, the engine would die. wait 15min and the car would start and you'd have 2-5 min to drive to saefty (no way you'd wanna push one of these home ), wait another 15min to get another 2-5min of driving. the cause is due to a little piece of electronics on the side of the dissy over heating and preventing the pick up in the dissy from working. good news for the ford driver, the fix was to remove the electronic device, renew the thermal grease and reattach the device.

now im not saying this is your problem or fix, but your issues do fit in with that (and many other senarios i have come across) same type of issue.
loose wire causing overheating in the connector or at the grounding
faulty CDI unit
faulty magneto pickup
overheating electronics
overheating coil/s
cracked or faulty leads
faulty kill switch (handle bars OR side stand)
hairline crack in a fuse
just a few ideas of what could be the cause IF you have no to low spark when the fault arises.

another idea...... when you are testing for spark, if you find you have a good spark, pull out the existing plugs, straight after your test (during the fault, on the side of the road) and see if they are "wet" with fuel.
Just getting back to basics here. checking for spark and fuel while the fault exists

[Lus7]

Awesome, i'll try to get it to fail and test the sparks.
won't it damage the engine if I try to start it without the sparkplugs in?

Also, as far as the choke is concerned. If I cold start the bike it will start with no choke, but if I slide the choke across then it will die. If I start the bike cold with the choke on full, then it will start up and rev hard. When warm i can move the choke across while the engine is on and it won't die. Why's that?

Also, going back to the dirty carb issue. Under the throttle I have a little screw cable extender. When it's screwed so that the cable is as long as possible, the throttle sticks like it did in that youtube video I posted earlier. Does that mean the carb is dirty, or that the cable has too much tension or something?

[Lus7]

lol went to try start my bike with the spark plug out. held it with plyers against the engine. Got shocked as haha, i'll try that again with gloves on or something

[Lus7]

not sure how much electricity should be jumping when the spark plug fires, but there doesn't seem to be a lot jumping the gap. The bike hasn't failed, i'm just testing it in sitting at home

[Lus7]

Alright, so I plugged the holes I made in the exhaust with some cut up bits of cork. Took my bike out round the block.
on the final stretch (which is also the biggest hill), I chucked it in 5th gear and strained it (which i've done up this hill before without problem) half way up no matter how much throttle I gave it, it wouldn't get any faster. I dropped a gear and power seemed to return briefly, 3/4s up the bike started to loose all power. I dropped a gear and gave it gas, nothing happened. Dropped another gear, full throttle, nothing. Bike dies.

I pull over, try to start it. dead, she wont start. cool, recreated the problem successfully. I pull out my tools, take off one spark plug and put it against the engine block. I start the bike and the plug seems to fire fine. same with the other plug. interesting.

She's been sitting for about 5 minutes now. I try to start her, nothing. I turn the choke to full and start her, she starts. I turn the choke off and ride home (15m away)

dafauq is going on?

I'm going to fill her up on gas, last time I did that the problem seemed to subside.
The only reason I didn't want to was because I'm not sure how to stop the tank from leaking everywhere if I take it off to try clean the carb


The spark was firing probably 1/3d as powerful as this one and the electrical bolts were all over the place.
http://www.youtube.com/watch?v=W8V0U...eature=related

If that matters, it seemed to be the same as when the bike was sitting at idle at home before it failed


p.s. it's my birthday today, so i got the day off work to try fix my bike

[ducatilover]

I'm going to say it again
Get owners manual;
Set floats/clean carbs
Check the cokes (will have a guide in the owners manual)
Check the coils.
Check operation of the fuel tap.
Replace fuel filter.

[Lus7]

will do, just some more info. I filled up the tank with gas and it hasn't cut out on me since.
Would that have anything to do with anything?

[ducatilover]

How far have you ridden?
There will be some sort of tank venting under or incorporated in the fuel cap, if you can figure out how it works, clean it.

[Lus7]

3 times the distance it took me to get the bike to fail last time

if it's the gas cap, should it run fine after it fails with the gas cap open?

[ducatilover]

3 times the distance it took me to get the bike to fail last time

if it's the gas cap, should it run fine after it fails with the gas cap open?

It'll run fine with the cap part open or fully open, but with the engine shut off, you have to switch to the prime/reserve on the fuel tap because fuel won't flow without the engine running (that's what the vacuum line is for)
If you can run it with the cap just cracked open and the bike doesn't cut out, there's your problem.
If it runs on reserve/prime and doesn't cut out, your fuel tap, or vacuum line is at fault.
If it does it even after this, I'd be then going with leaking float needles, or still possibly the fuel tap.
I had an issue years ago exactly the same, my VT250 shat the fuel tap (there's a rubber diaphragm with a spring to cut fuel when the engine is not running) and it had a hole in said diaphragm.
Chased my tail for ages on that one, then replaced the fuel tap and I never had an issue again

[Madness]

Hey guys, i have a fairly new bike (14,000 ks) and it rides great.
Recently I've noticed its randomly loosing power. Going up this hill, my bike starts choking till it stalls.
It feels like the bike just looses all power momentarily and jerks until it completely turns itself off.

You have tried changing down gears when going up this hill, aye?

[mellowyellow]

sweet, so no issues with spark. it may be weak but its there. i'm starting to wonder if you have a collection of issues.
choke on full cleared the fault an allowed the bike to start, i would think this was pointing towards a faulty tap too. choke on full would increase the vacuum to the tap and allow more fuel to flow.
if you released the accelerator to drop the gear, you would have had a burst of vacuum to the tap, throttle open and you would have lost the vacuum (guessing normally not an issue on a functioning tap) and float bowls emptied out.
if it were a tank breather issue, one would think it would be worse with a full tank.

ducatilover has had the problem, find out how much a replacement tap is and swap it out if you can afford it. check the vacuum line for cracks.

as for the engine running rich and the darker colour around the outside of the new plugs (and weak spark)
are the plugs the correct type and gapped correctly? you have spark so its not a huge issue.
you could be running rich due to the other hoses flapping about, it has already been suggested one of the hoses could be causing issues with your float bowl level.
the running rich issue could be why people are pointing towards a leaky needle, but a leaky needle isnt fixed with choke on full, not that i know of anyway.

[Lus7]

I'm going to take the hoses connecting everything on the bike off and replace them with brand new fuel hoses from supercheap (or where-ever is cheap)

In the owners manual under carborator it says "Adjusting the carborator is compicated, take it to a yamaha dealers if you have issues"
All I want to know is which line is the vacume line and what the parts do.

I'm going to check the internet for a more comprehensive manual

[Lus7]

a new petrol tap is 30nzd on ebay. can't be far off that at the store

so full tank of gas, just went up that hill 4 times, no cut outs. however every now and then the bike seems to choke/stutter

[mellowyellow]

been doing some reading, your fuel tap has three positions, correct?
"on" "pri" "res"
"on" is reliant on the vacuum pipe and diaphram (apparently)
"pri" is for the primary tank, fuel should flow no matter what the vacuum is doing
"res" is for the reserve tank.

from a pic i have seen, "pri" is between "on" and "res". switch it to "pri" and go for a test ride. this has been suggested before though.

edit: is your fuel pump run with vacuum or electric?
are all the carby and intake mounting bolts tight?