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Suzuki GN125 wont start if cold but starts when push started


madmadi
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Hi guys,


I need your help.


Firstly my bike's details:


Suzuki GN125, 2004 year, chinese version, 120,000 km done

Carburettor Mikuni, as it is my first post cannot post any links, but if you need, just google brooksbarn and look for Suzuki GN125 2004- there is a picture of my carb. Mentioning it as I think I have a problem with carb...but you will now better :)


Now the problem. Engine won't start from electric ignition when cold but it does start when pushed and it does start when engine is warm.

New battery, new spark plug, fuel is going to carburettor freely (checked fuel tap filter), there is a good spark (taken spark plug out and touched to engine and pushed the ignition, good spark)

So, there is a fuel going freely to carburettor and there is a spark.


I have cleaned the carb, but to be honest there was no rubbish in it.

There was some white stuff in the rubber hose which is going from air filter to carb, like soapy stuff.

Adjusted a fuel/air mixture as was told by friend that maybe there is too much fuel and not enough air- when cold and rainy outside (live in Scotland) maybe the air filter is getting wet and there is not enough air going to carb?


When trying to start the engine there is an explosion sometimes. Trying to start it with and without choke which is manual of course.


Another thing, the fact is that the engine starts sometimes even when cold, I just observed that there is a problem when is wet outside (keeping the bike outside)


The problem started recently, but as I said it sometimes starts, sometimes not. I use the bike everyday for going to work which is 8 miles one way. After 8 hours of work it starts most of the time, but after night it doesn't. Almost always it starts when pushed and from the 2nd gear.

By the way, I don't know if that's normal but when I start the engine on the choke and it starts the revs are around 4000rpm but sometimes after 30secs, sometimes after 2 minutes revs going down to 1000rpm-1500rpm - does it mean that engine adjusting the choke automatically when warm? Doesn't it suppose to have big revs when choke is fully open, even when engine is warm?

Now few possible reasons (in my opinion):


Wrong fuel/air mixture (even after adjusting it- half rotation on the mixture screw)

Bad compression

Wrong valve settings (gaps)

Ignition settings

Blocked fuel stream from carb to engine (?)

Choke problems


Any ideas???

Thanks in advance,

Martin

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120 000km? is this a typo or has it really done this mileage? If it has covered that mileage you could be looking at loss of compression due to needing a rebore......or at least piston rings. Can you check the compression? If the bike revs to 4000rpm when cold with the choke on and after a bit drops, that could be that the engine doesn't need that rich mixture and is starting to flood.......take the choke off a bit.

Actually....thinking about it.....have you replaced or at least checked the Plug Cap and HT lead?......possibly the coil too? Backfiring is often due to unburnt fuel in the exhaust igniting.

Just my thoughts mate....... :wink:

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I would have thought, if it starts being pushed but not on the button that the starter motor isnt strong enough? Or is that too logical?

So possibly check the wiring to the starter, or get a new one? - but wait till someone confirms (or denies) my hypothosis

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That's a hell of a lot of mileage for a 125.


Sounds to me that the battery isn't holding it's charge properly. Do you have anything else connected to it?


Bikes are a bit funny with the choke on, and they need playing around with a bit, but it's certainly not uncommon for the revs to drop dramatically when warmed up with full choke on, you will just need to listen to the revs and adjust accordingly.


Not sure why you're getting white frothy stuff in the air inlet. Have you checked the air filter is free from water? Not sure what they're like on those bikes but some are just foam that needs to be washed and soaked in oil.


Just realised someone has posted whilst I was typing. It could be that the brushes are wearing in the starter motor or tat the motor needs the carbon cleaning out of it.


What sort of noise are you getting when it tries to start from cold?

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120 000km? is this a typo or has it really done this mileage? If it has covered that mileage you could be looking at loss of compression due to needing a rebore......or at least piston rings.
yeah, sorry, typo error, it is 12,000 km.


 

Can you check the compression? If the bike revs to 4000rpm when cold with the choke on and after a bit drops, that could be that the engine doesn't need that rich mixture and is starting to flood.......take the choke off a bit.

Actually....thinking about it.....have you replaced or at least checked the Plug Cap and HT lead?......possibly the coil too? Backfiring is often due to unburnt fuel in the exhaust igniting.

Just my thoughts mate....... :wink:

 

Don't have a compression meter. Changed spark plug cap to NGK just a week ago.


Just spoken with my friend who is a mechanic, suggested that maybe the float inside the carb is not closing properly and it is too much fuel in it, thats why there is an explosion when trying to start the engine. There is some kind of rubber valve in the float and when is cold this rubber valve is too hard to open/close properly the fuel intake?

Edited by madmadi
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Shut fuel tap, remove the carb floatbowl, with carb still on bike if you can. Lift the floatbowl until you feel resistance, open fuel tap briefly and reclose. There should be no flow of fuel. If there is fuel flow the tab holding the float valve in position should be carefully bent upwards slightly to make the valve shut earlier. Repeat test, if fuel still flows, remove float and valve , clean valve tip and clean valve seat in carb with a cotton bud. Repeat test. :mrgreen: :mrgreen: :mrgreen:

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Hi, If as you say it bumps starts easy then l would say the issue is electrical. When a starter motor is engage the drain on the battery can be so big that there is so little voltage left for the ignition circuit to work and for it to make a spark. To check this If possible connect a volt meter across the battery and then press the starter button as see what voltage is left at the battery. If the battery as you say is in good condition check all the electrical connections, starter solenoid and earth terminals, any resistance in these circuits will produce volt drop which could lead to your problem. Hope this info helps

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That's a hell of a lot of mileage for a 125.

 

Typo error, sorry, it is 12,000km :)

 

Sounds to me that the battery isn't holding it's charge properly. Do you have anything else connected to it?

Brand new battery, nothing else connected

 

Not sure why you're getting white frothy stuff in the air inlet. Have you checked the air filter is free from water? Not sure what they're like on those bikes but some are just foam that needs to be washed and soaked in oil.

 

Just FYI, One guy just responded on another forum that: "The white stuff in rubber hose might be emulsified oil (presuming there is a breather hose connected into the airbox from the engine - this is done to reduce emissions). "

 

What sort of noise are you getting when it tries to start from cold?

 

It is normal starting noise, nothing unusual apart from backfire (sometimes)

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Shut fuel tap, remove the carb floatbowl, with carb still on bike if you can. Lift the floatbowl until you feel resistance, open fuel tap briefly and reclose. There should be no flow of fuel. If there is fuel flow the tab holding the float valve in position should be carefully bent upwards slightly to make the valve shut earlier. Repeat test, if fuel still flows, remove float and valve , clean valve tip and clean valve seat in carb with a cotton bud. Repeat test. :mrgreen: :mrgreen: :mrgreen:

 

I think this is the most probable reason, my friend advised me about the same mate, so I will do it today.

Thanks :cheers:

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Hi, If as you say it bumps starts easy then l would say the issue is electrical. When a starter motor is engage the drain on the battery can be so big that there is so little voltage left for the ignition circuit to work and for it to make a spark. To check this If possible connect a volt meter across the battery and then press the starter button as see what voltage is left at the battery. If the battery as you say is in good condition check all the electrical connections, starter solenoid and earth terminals, any resistance in these circuits will produce volt drop which could lead to your problem. Hope this info helps

 

Yeah mate, either this or the float problem mentioned by megawatt. Will do it today and share the output.


Thanks for all of you guys for your time, appreciate it.

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Cold starting is quite a knack. It's very easy to flood the engine at low temperatures. The fuel mix condenses as it hits cold metal.


I tend to spin the motor with no choke or throttle for a short burst and then add choke in small increments. Use short bursts of starter with no added throttle and listen for the motor firing as you release the button and all the batteries power is transfered to the spark. Try to catch it with the throttle at this point.

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Cold starting is quite a knack. It's very easy to flood the engine at low temperatures. The fuel mix condenses as it hits cold metal.


I tend to spin the motor with no choke or throttle for a short burst and then add choke in small increments. Use short bursts of starter with no added throttle and listen for the motor firing as you release the button and all the batteries power is transfered to the spark. Try to catch it with the throttle at this point.

 

Tried to start the engine with and without choke, short bursts and long, nothing...

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Wet plug from the rain :wink:


Seen this on another forum and answered.

The white gunk could easily just be emulsified grease as I had that.


Mrs's YZF packed in when it got a wet plug then wouldnt run right or start easily for a few days after. It needed a push.


If its used regularly id do the easy stuff and tampering with your mixture and carb then to the electrics would be the last thing Id do.

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Are any of your wires exposed? Because you mention when it's wet that it won't start, might be worth a look for any split wires etc. Give it a good spray of WD40 on expose connections just to make sure no water gets in.



+1 check the battery voltage should be just over 13volts I believe and static not dropping slowly.

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Are any of your wires exposed? Because you mention when it's wet that it won't start, might be worth a look for any split wires etc. Give it a good spray of WD40 on expose connections just to make sure no water gets in.



+1 check the battery voltage should be just over 13volts I believe and static not dropping slowly.

 

Checked all the cables yesterday, but no major flooding or something. I have just charged my new battery overnight as it was flat after trying to start the moto, took out the HT cable and the electric module to home for night so it can dry out properly, adjusted a little the float in the carb and will try to start the moto today. Will see. Fingers crossed!

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Gentleman,


I would like to thank you all for your help and time you have spent for replies to my post, really appreciate it.


My bike is working now, it seems that there was a problem with the spark and moisture. I have dried the electric module and the HT cable, charged battery over the night and it is fine now. Also changed the fuel/air mixture a little (half screw turn) so there is less fuel, more air.


Now, the only two things which changed comparing to before the fault is that now at high revs it doesn’t have the power (slightly only, above 9000rpm).

as I have bended a little the carb float part so it closes the fuel flow earlier than before, so I think I will bend it back to the original position.

My “neutral” revs should be 1800rpm and it is fine, the thing is that when I stop at lights and revs are going down they are going to 1500rpm for around 2-3 seconds and then going back to 1800- it wasn’t like that before- will it be carb float level or air/fuel mixture? I think the latter.


I tried to close the carb float and see if the fuel is leaking but no, it is fine.


So, so far so good, I am covering the bike for the night and outside work because it was all about the moisture.


Thanks again for all your help

Wishing you wide roads and rubber trees!

All best,

Martin

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Gentleman,


I would like to thank you all for your help and time you have spent for replies to my post, really appreciate it.


My bike is working now, it seems that there was a problem with the spark and moisture. I have dried the electric module and the HT cable, charged battery over the night and it is fine now. Also changed the fuel/air mixture a little (half screw turn) so there is less fuel, more air.


Now, the only two things which changed comparing to before the fault is that now at high revs it doesn’t have the power (slightly only, above 9000rpm).

as I have bended a little the carb float part so it closes the fuel flow earlier than before, so I think I will bend it back to the original position.

My “neutral” revs should be 1800rpm and it is fine, the thing is that when I stop at lights and revs are going down they are going to 1500rpm for around 2-3 seconds and then going back to 1800- it wasn’t like that before- will it be carb float level or air/fuel mixture? I think the latter.


I tried to close the carb float and see if the fuel is leaking but no, it is fine.


So, so far so good, I am covering the bike for the night and outside work because it was all about the moisture.


Thanks again for all your help

Wishing you wide roads and rubber trees!

All best,

Martin

Good news :up: Just make sure you get that mixture sorted, Being that its such a small engine they tend to be worked hard ie reved to death lol. A weak mixture could end up with you getting a holed piston not nice :roll: and further more, you will not notice this until its to late :crybaby: . Well done in thinking the fault through, Not sure how far you travel everyday to work and back but being that your turning a cold engine over and running with the lights on all the time you might want to think of getting an optimate charger and keep that battery right on the top line. Stay safe

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http://i2.kym-cdn.com/entries/icons/original/000/005/165/PFFFFT.png


So it was the easy thing?


These threads always crack me up. :lol:

I see you put this thread on quite a few forums, the answers coming back, some of them by "experienced people" had me in stitches.


Glad its sorted, always remember to check the easy things out first. In this case a clean and dry, then lubing the right parts and WD40 I find leaves you in a better position to find a problem.

When my battery died I got told it was "definitely" the reg/rec or generator. It was just the battery and my bike has been fine for over a year. So I find when asking for help, start with the easy bits then work up. It wont do harm :thumb:

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http://i2.kym-cdn.com/entries/icons/original/000/005/165/PFFFFT.png


So it was the easy thing?


These threads always crack me up. :lol:

I see you put this thread on quite a few forums, the answers coming back, some of them by "experienced people" had me in stitches.


Glad its sorted, always remember to check the easy things out first. In this case a clean and dry, then lubing the right parts and WD40 I find leaves you in a better position to find a problem.

When my battery died I got told it was "definitely" the reg/rec or generator. It was just the battery and my bike has been fine for over a year. So I find when asking for help, start with the easy bits then work up. It wont do harm :thumb:

 

yeah, posted it on 4 different forums as needed to fix it ASAP- I am commuting and cannot stand the buses...


As you can see, there was a lot of different suggested solutions from many guys, but at least if someone in the future will have the same problem I hope he will find it here.


Thanks again

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1800rpm sounds high for tickover to me unless thats with the choke on most bikes tickover at about 1000-1100rpm

 

nah, under 1500rpm it dies, 1600rpm is absolute minimum and it is doing good on 1700rpm. I have setup 1800rpm as at the lower revs the headlight is dimming so battery is used.

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