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Cut-Out Problem
Hello everyone. I have had this problem for a while but never sought to resolve it as It does not happen that often. My bike is Derbi 125cc, with an air cooled four-stroke Yamaha engine. The petrol tank holds 8 Litres with a reserve of 1.5 Litres. Now when the bike uses about 3.5 litres something strange begins to happen:
1) I twist the throttle and have a delayed response. 2) The bike jerks so I knock down the gears. 3) The bike continues to jerk and loose power until it cuts out. 4) It takes a while to start it again. Sometimes I choke the bike and it recovers. I have wondered about this, is it the petrol? Battery? It seems to happen after its been raining, when its cold or really warm but this is not exclusive. Spark plug is OK, air filter is OK, engine oil is OK, chain is OK, throttle cable is OK. As I said not really a massive issue for me, as 3.5 litres can take me 80 miles. Any help/advice ot there? P.s. hope you all had a good weekend in Dent, I froze my a**e off on top of holme moss. |
must be fuel problem
Filter in the petcock clean? Any other filters, fi. in the carburettor?
Must be the issue, since you are sure it is only after using 3.5 litres. Auke |
while the petrol is going out of the tank , air has to com in . otherwise you create unterpresure in the tank and the petrol stops flowing . for tad reasen the fuelcap has a smal hole . if the problem starts , open the fuelcap . if it is beter after thad ,then you have fond the problem
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sounds about right...
thanks samson, that makes a lot of sense. il give it a go next time it happens. cant see it being the pet cock valve or carb filter (not sure if i have one of those) auke but il bear it in mind, thanks.
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Keep the forum informed as to the progress you make and good luck. |
Hi Tommy
I had the exact same thing with mine, and it did turn out to be the breather hole in the fuel cap. On mine it breathes through the lock barrel, so of course over time this fills up with tiny bits of key/lock/dust/grit you name it. I found this solution on a Spanish Derbi forum, so it's obviously something fairly common. I soaked the whole lot in petrol and general prodded, brushed, blew up and down it. And no more problems. For a while after I stuck tape over the key hole, but now I don't bother and I'll just clean it out as and when. Give it a try first, it's the simplest place to start. |
Thanks dave, if it comes to a strip down Il let you know but looks like Alex is on the money. Il give it a wash tomorrow and have a go. Makes sense too as a lot of crap will get in after its been raining.
Cheers guys, I feel a bit happier now, no, a LOT happier :thumbup1: (positive thinking n all that) |
cut out.
Hiya bud.
Did a repair on one of these a while back and it turned out to be a dodgy fuel vacuum tap, just in case it's not your breather on your filler cap. All the best. Dave. |
cheers rob. latest news, I did what Alex said. There was a small hole at the top of the filler cap that led to knowhere, i couldnt even get a needle into it. The lock itself is covered with a flap so next time it starts to happen Il open the flap. I cleaned with petrol all around, this must have loosened the low grade glue that held the outer ring onto the fuel cover as it then fell off. got my UHU stick out and fixed, fingers crossed.
tom, very light headed at the moment and feels a bit sick :D |
oh wait...
...nope, the culprit is a dirty pitcock valve! wont even run on the 'on' position has to be on reserve. strip down this weekend (not me, the bike...terrible joke) and we shall have a look see. :rolleyes2:
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Keep on sniffing that petrol and glue!!!
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if anyone cares...
...dum dum duuuummmm...it was the starter motor all along!!! the swine :stormy:
on the plus side im now first hand when it comes to bump starting a bike. lets hope its just a nest of spiders clogging the brushes or some solidified oil (straws and grasping, I kno, I kno...) At least II get to spend tmrw morning looking at shiney new motorbikes at scooter crazy in huddersfield, tis the season after all :clap: |
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I had exactly the same problem with my 4 stroke 125c bike a while back. Exactly as you descibed your cut out. The breather hole sounded like the correct diagnoses.
My bike has not cut out again yet. Like Dave said the starter motor is a different problem and would not cause your bike to stall while running. Happy riding ... |
Just got the report, its the battery thats buggered. Turns out the spark plug was "too high" (I presume the electrodes had moved apart) and its drawn too much power from the battery. The cut out is fuel related, dirty pit cock valve but I can live with that. Getting it back on friday.
Your quite right Dave, the bike wouldnt start at all yesterday and thats a different problem to the cut out. Essentially I fixed the cut out when I ran it on reserve. The starter motor ticked over less and less when I tryed yesterday, until it didnt move at all. This is becasue the battery is boobed up due to not looking after my spark plug. Apperently motorcycles need "regular servicing" :blushing:....... |
The spark plug will NOT ruin a battery ! A large gap may make it run shite, but if the charging system & battery are OK, the plug gap won't effect it. Battery was probably on its way out, coz they don't seem to last long now-a-days.
Gl;ad you seem to have it all sorted though. |
Tommy, I believe a knackered battery would also give you the cutting out problem, I once had this on a Triumph which first corresponded when I touched the brakes, its suprising how much power brake lights use, it once happened at night and I had to ridr home on side lights and once near home NO lights at all just to leave enough power to trigger the electronic ignition!.
Similar problem last year on my BMW:blushing:everytime I touched the brakes the GPS went 'dim', now in this case the battery was GOOD but flat due to problem with the rotor which was failing to keep the battery charged. Buy yourself a cheap AVO meter thats Amps,Volts and Ohms, set it to 12v and link across the battery now and again test to see how many volts the battery is holding, then you can test the battery with the engine running to confirm the bike is charging. We will make a 'bush mechanic' out of you yet!! Now get yourself booked for the HU meet at Ripley in June......You know it makes sense!!! |
Good call Dave, will try and make it.
Another confession I hesitate to make, I may have used a car charger on my battery, twice.....:oops2: This isnt a very clever thing to do apparently, as the charging rate is different. |
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I use a car charger ALL the time, its not really the end of the world, being your bike is electric start I assume its 12v, the main problem is if you try charging a 6v battery with 12v charger:nono:. If you want to learn about mechanics quickly, buy an old British bike! I started off at 16 on Jap bikes, and knew next to F.A. about mechanics, then at 18 brought my first Triumph, within 3 months I could remove the barrels pistons, rings etc in my sleep! If we meet up at Ripley I will introduce you to a couple of mates and fellow hubbers who live up your way(I'm in South London) who I'm sure could help you out with advice etc, I learnt a few things from them when we were offroading in the Pyrenees last summer. It just goes to show that YOU can teach an 'old dog new tricks!. pm me your mobile so we can meet up. Dave ps, never hesitate to give every symptom your bike suffers however trivial it may seem, this helps others to try and diagnose the faults. |
Late Reply
Sorry Dave forgot to check back. Just PM me if your ever up north, usually better then a text for me as my phone has legs. Id love to buy an old and do it up, and I have made my first new years resolution that I will have a go next year.
In the end it was the spark plug that was way worn down and the battery was cooked trying to compensate. Plus it hadnt been charged or topped up in quite a while. Bike smooth as owt now tho, had great fun riding it home in the snow on friday, although a bit too cold on the old fingers! Merry christmas to all and a happy new year, I got one present and someone had already opened it....:rolleyes2: |
Hi Tommysmithfromleeds,
Hi Tommy,and all others Heres wishing you a Merry Xmas and Happy New Year :Beach: although a little wet at this time of year its good times here in OZ I know there are many bikers out ther that probably know more than I do about bikes and their problems but I hope you and others might find the following information helpful it is only basic information but may be a logical explanation on fault diagnosis My information is written in good spirit :D Simply put if you have a lawn mower or simple industrial engine that is a simple single cylinder engine with no starter motor it starts by a pull cord and has no headlights .so doesn’t require an alternator or back up power system such as a battery, which is what a battery is for so logically let’s put it this way. If the charging system is not working the battery will eventually run out of charge and the lights wont work and the engine will die. Batteries have a short lifespan and there is no such thing as a cheep battery you get what you pay for so look for one with a three year or more warranty. I know that some cheep batteries do last a lot longer but it is good luck like winning the lottery. The engine has several systems and each is separate to the other and can be seen as such although they all work together and are interrelated but need to be separated to be able to diagnose problems , there are three main electrical systems :- 1. The starter circuit :- battery and starter motor to turn the engine 2. Charging circuit :- once the engine is turning provides electric current to recharge the battery and provides power to operate the next system which is the ignition system 3. Ignition Circuit :- power supplied either by the Battery or the Charging system operates the spark which ignites the compressed air and fuel in the engine For the engine to start it must have: - fuel… compression…. ignition When trying to diagnose an engine fault think of everything as a separate system. The clutch has nothing to do with the battery and the fuel has nothing to do with the handbrake keep everything simple. · Battery :- engine wont turn over so battery is flat or there is an open circuit to the starter motor or the starter is not working , this part of the system has nothing to do with the running of the engine except to get it started. · An indication of the battery being undercharged or in poor condition is that the headlight lamp will not glow…. It will have a dull glow …if it is bright and healthy looking but the starter wont turn over then this would indicate that the starter may have a problem · Attaching a car charger ……… small trickle charger to your battery should enhance the charge in your battery and would be advantageous if your bike has been sitting for a long time without use/startup. · Battery charge does take time · You can bump or push starts the bike …. this indicates that the alternator is working because it is supplying electrical charge to the ignition system, once the engine is turned over · If you push the bike and you finally fall with your face in the mud and it still wont start then there is no ignition or spark you may have another problem. I would have given up after the third push and put the battery on charge and come back to morrow. In a bike shop they would have a set of jumper leads and possibly connected a heavy duty car battery as a starting aid remember Connect + to + terminals and – to – terminals or you will rapidly discharge the battery. If the Starter is working this provides a good place to start the diagnosis. NOTE WELL Clear area of any flammable liquid ensure there is no fuel leaking or lying around the engine, If fuel has been spilt clean it up. · If the spark plug is burnt out or defective the bike probably won’t start and Plug should be replaced …. Test remove plug ,check to see if if it is wet from fuel and oil this is probably an indication that the plug or ignition system isnt working..... get a par of insulated pliers and hold the base of the plug against the engine and crank over the engine there should be a bright spark and if not then test the lead …… by putting a screw driver or piece of wire in the plug cap and holding it near to the engine this should provide a visible spark. · If there is spark and the plug is wet the engine may not start …..Clean the plug or replace with a new plug , on hand you should have some aerostat or similar product give the engine a mild squirt in the air cleaner and see what happens. · If there is an indication the engine is trying to start but won’t after the second try remove the plug and go have a cup of tea or lunch and ponder the situation, don’t rush into anything.allow the time for the engine to dry up some of the excess fuel that hs been sucked int ti by continuing to crank the engine. Put the plug in when you return and give it another go. Unless you are a very unlucky chap and have burnt out a valve when the bike has been shut down then you should have compression. Unless for critical tuning purposes you may not possess a compression gauge …… Simply remove the plug and hold your thumb or finger over the plug hole and crank the engine the compression should push your thumb away and release the built up gas from the engine if you can’t get your thumb over the hole then improvise. Around 100psi is ok up to 160-170psi if real low there is a possibility of an internal problem. specifications can be checked and it may be possible to down load a manual from the internet. Even with years of experience technissians do read their manuals · Fuel to the Carburetor:- firstly prepare a clear bottle or jar that you can run fuel into collect the fuel and examine for contaminants check this by removing the fuel line at the carby end the fuel should flow freely. · If the system has a vacuum tap or diaphragm remove the vacuum line and provided that the fuel is not coming out the vacuum line suck it gently and fuel should flow from the main line siphon the fuel into a clear bottle and check for water or other contaminant …. Remember disconnect the fuel line from the carby and don’t have fuel running all over the engine a spark may ignite the fuel and destroy your bike. So that’s the basics of the whole thing, now experience cuts in and things out of the norm happen like:- · blocked holes in fuel caps creates a vacuum in the fuel tank and fuel will not flow check and clean suck the hole and see if it blocks off · Burnt out plugs replace if bike has intermittent problems
· Check wiring to coils and look for loose fittings · Have battery tested by the local battery shop and replace if necessary. They should also be able to test your charging system and if not up to scratch seek advice from an auto electrician. He will probably do a comprehensive test and advise of any fault · Bikes that run ratty often have air leaks so things like inlet and exhaust manifold gaskets need to be replace as periodic maintenance if bike has O rings in inlet manifold make up some paper manifold gaskets and use these. O rings or notorious for going hard and leaking. Replace flexable carby mountings if they are hard and inflexable · Starter motors don’t go for ever the brushes and internals wear again seek advice from auto electrician. It is not an expensive exercise to replace a starter do it at the first opportunity it may save you a tow job at an inconvenient time. I wish you all the good things in the coming New Year and look forward to hearing of your adventuers and if you are in OZ please call, in there is always a good feed and a place for the night Cheers Champ:mchappy: |
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