OzVMX Forum
Clubroom => Tech Talk => Topic started by: Quicksilver on August 10, 2008, 05:18:12 pm
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Spooky Elsinore. This going to sound really strange, unbelievable even spooky. I tell you all now its 100% true. Not a joke, not bullshit. I have 3 other people beside myself who witnessed this.
Today my son and I took out one of CR250M's for a spin. We got to the reserve, unloaded and I set off for a fang. I spend about 20 mins on the bike then pulled over next to ute to hand over to my son Derek. I jumped off bike and Derek climbed on. Derek popped the clutch and bike stalled. No problem Derek kicked her and she fired right up again only now the bike was doing about 4000rpm. My son let go of the throttle as you would expect but the bike kept revving. I hit the kill switch but nothing, the bike just kept on revving I raced around to right side to check for jammed throttle but it was fully closed? Derek couldn't let clutch out for fear it just flip over or take off. So in desperation I reached down and unplugged the wire from the stator to the coil "THE F^*KEN BIKE KEPT" revving. No power from stator to the coil and bike is still going? I was completely shocked. Dumfounded. This cant be right. Now what can I do.....thinking, thinking, thinking fearing my bike was gunna pop any second it dawned on the put choke on which in about 5 seconds killed the bike.
All shocked we sat and looked at the bike for about 10 mins and discussed what had happened debating if we should call it day, bugger it I thought I'll give it other go, stuck the bike in forth gear so I could pop the clutch and stall the bike if it happened again. I kicked the bike up and it ran fine. Tried the kill switch and it stopped dead. Kicked her up again and handed it to Derek who rode it for another 20 mins with no problem. I rode it again no problem. Took my daughter for a double, again no problem. Bike behaved completely normal for next 2 hours till we loaded up and came home.
Now I am no engine expert but it seems logical to me that if the stator is unplugged then the bike has no power to the coil. Can someone please explain to me how this bike kept running with that wire completely disconnected for at least 20 to 25 seconds after it was unplugged.?
Has this happened to anyone else? Where did coil draw power from to keep firing the plug? As amazed as I am this happened its also of great concern. Whats going on with the bike. Why or how did it react that way.? Will it happen again. The whole thing is just plan strange.
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hot spot in the head combined with an air leak
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Had it happen a couple of times and the first time is a bit spooky. The bike starts "dieseling" and just keeps going. Stalling is the best way to stop them. Whatever you do , DON'T turn the fuel off and wait for it to run out. The one I did that to grabbed the piston when it finally ran out of fuel at about 15000 rpm! I learnt an expensive lesson that day.
Cheers,
M.H
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Had it happen a couple of times and the first time is a bit spooky. The bike starts "dieseling" and just keeps going. Stalling is the best way to stop them. Whatever you do , DON'T turn the fuel off and wait for it to run out. The one I did that to grabbed the piston when it finally ran out of fuel at about 15000 rpm! I learnt an expensive lesson that day.
Cheers,
M.H
M.H
Whats the cause of dieseling and can it be prevented from happening again? Oh, and yes turning fuel off was one thing I did do about 15 seconds before I choked it ::) ::). Spose im up for rebuild now?
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I remember the first time it happened to me........ an apprentice rebuilt this TS250 fired it up and it went straight to 100000rpm.
He freaked out, so I cruised over, all calm, and flicked the plug lead off and it made no difference......... :o :o :o
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That usually means there is a poltergeist living inside your engine. Contact a Holy man before your next ride :o
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Priest is booked and will be at your door for 10am tomorrow. ;D
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Pulling the coil and getting zapped big time is bad enough and it dont fookin stop does tend you make you do the double take. Last time was on a 750 water bottle and your head doesnt think choke it as its in WTF mode.
If its running on for a while on revs with the throttle body seated id be checkin out the bottom end seals
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Quicky, the cause of mine was the throttle cable kinked and holding it open after a crash. I don't know how to prevent it, but I'd imagine you have an underlying problem somewhere. Happy hunting.
Cheers,
K
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Dirttracker above, has the one to follow up Quicky. Look for that air leak, and pop the top end off inspecting for Chernobyl effects.
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had a similar situation with a blown base gasket on the rm400 in the forestry. It took off while I was riding. Killswitch failed, yanked plug lead, it zapped me bigtime and then simply arced back across to the plug and kept revving it's tits off. Only way I could stop it was dump the clutch in 5th with the brakes fully locked. It still tried to pull away under full brakes and I was really shitting myself. Thankfully it either ran out of fuel or simply 'gave up the ghost' but whatever it put the fear of god into me for the next few rides after replacing the gasket. so much so I had a string from the plug cap that I could yank if the need arrose again :D
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the best way to stall it is to put it in gear and let the clutch out as it will be all revs but it wont be making any power.
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the best way to stall it is to put it in gear and let the clutch out as it will be all revs but it wont be making any power.
After thinking about their could of few ways we could of stopped the bike. At the time confusion ruled. After disconecting the stator and bike was still going did my head in big time. Couldnt think clearly after that. :o No one thought to pull on both brakes and pop the clutch ::). Panic had set in. ;)
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drew
my it400 did that once and i pull the plug lead off still ran so i just dumped the clutch with both brakes on and it stoped.sticky cable.back at the car lubed the cable never happened again.at home i retensioned the head as well.
cheers
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Quickie - couple of things - the bike running on is not unusual - have heard of that before where they basically become perpetual energy but I am not good enough technically to explain the whys and wherefores. However I did have my 250M lock WFO recently - was all traced back (hopefully as still to take out) to either a piece of the stranded throttle cable or a piece of the inlet "nozzle" on top of the carby had come adrift and went inside and jammed the slide in the body. Replaced cable, nozzle and cleaned everything and it seems OK - I think I would be worried about what caused it intially rather than the running on. Mine did it at the end of the long straight - when you back throttle off and bike doesn't slow things get messy!
Rossco
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my first experience with a full revving bike was in 1974 when I bump started a Can-Am and it started revving,lucky I pulled the clutch in but that just increased the revs so i pulled the plug cap,no effect,so i turned the fuel off and let the clutch out(I was up against a hedge by this time)and let the thing buck and jump whilst digging a huge hole until it ran out of fuel.
I know from that experience that when something is making that much noise and is out of your control,then your train of logical thought is somewhat scattered ;)
the next episode was when a complete motor fell off a twin engined competition kart and tumbled into the infield revving flatout untill it self destructed due to excessive revs and a diet of dirt and gravel.
The officials stood back in fear and when it stopped they walked up to it and prodded it carefully with a flag.
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Spooky? How's about a bike running backwards? Is this common?
No...common is the wrong word but has it happened to anyone else?
I was 16 so it was spooky to me at the time.
My YZ125C ran backwards but it only did it on one afternoon. I'd dropped it in 'Dead Horse Creek' and when I kicked it back into life it travelled backwards.
Each and every time it started for the next half hour it did the same thing.
I eventually gave up and started pushing it home along the road.
This resulted in being chased and caught by Sgt Peterson from the Woodridge Police Station... but that's another story (you try outrunning a Cop car whilst pushing a YZ).
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Used to do it is a fun trick on our old RT360 outfit. Looks you got in the pits when you let out the clutch and started going through the gears in reverse............ :D Caution you always eased the clutch out after starting her just to see.... And NEVER rolled backwards on a hill!!!!!!!!! Lost that fun when we removed the points and fitted a DT360 Electronic set up. :P
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When I was a young boy I was coming home on my AT1, just about stalled it as i stopped at the traffic lights but managed to whip in the clutch lever and saved the situation. The bike sat there and idle for the 2-3 minutes but when I went to do the normal 'drag bike like' 125 take off the bike moved backwards :o, at a good rate of knots :o. Again I whipped the clutch in without damaged to me, the bike or the car behind. I sat there in disbelief as I tried the clutch 3 or 4 more times - same result. Eventually turned it off and kick started the beast without a prob.
Two strokes, especially those of mild tune that fire near TDC, run happily in both directions. I believe BSA Bantams were particular proned to it - they would just hestiate while idleing and end up running backwards.
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I had a ts400 do it at the levin vmx meeting 3 or 4 years back.Just about ate the bars.When i was a kid the local gun use 2 crash start his old suz backwards
and ride the whole school feild that way.
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Sgt Peterson asked me why I was pushing the bike so I told him.
He didn't believe me... and neither did Springwood Suzuki when I gave it to them to 'exorcise'.
"Mate, we rode it for an hour and couldn't get it to go backwards!"
I thanked them for trying and coughed up the dollars for one hours riding on my bike.
I'd always assumed it was something to do with dropping it in the water.