yamaha mio /stalling/ bad mechanics/ advice needed

[willfreeman]

i bought an old 2006 115cc yamaha mio to putter around the city on and the bike ran fine, had acceptable acceleration and would do over 80 with me on it and i had it easily over 75 with two people on it, the bike suited the short trips i was doing around town.

However when you would stop at the traffic lights and leave the bike to idle it would run for around 20 seconds before audibly slowing down and down before coughing, spluttering and stalling, i go with a female friend to a mechanic and she explains the problem. He attempts to adjust the carby and then says it needs to be cleaned for 150 baht. My friend picked the bike up later and the mechanic told her it was 'fixed', i think he meant finished as it certainly wasnt fixed and the stalling problem remained.

I go to another mechanic, he adjusts the carby , checks the valves??? ( took of two small caps on the top and bottom on front of motor and cranked something on the side which made them move???, hums and hars and says the carby is no good, He fits a new one for 2000 baht and two days later i still have the problem i go back to him pull up out front he hears the engine slow down splutter and stop - says 'oh slow slow', makes a couple adjustments to the carby and goes on a test ride at which time he never takes his hand off the throttle and doesnt let the bike idle so doesnt actually test to see if the problem is fixed. It wasnt, i go back again and he adjust the carby at the same two points - which i believe are the throttle tension-er - accessed from the top and the idle screw accessed from the side. So i now have the exact same stalling problem as before and im out of pocket 2150 baht.

An acquaintance at they gym tells me he was formerly a car mechanic in england, the subject of mechanics comes up and he says in his ten years here he hasnt found one decent mechanic saying they can replace broken parts but the have no knowledge or training whatsoever in fault diagnosis. i tell him the problem and he said sounds like the carby is no good, i say i had a new one fitted. I take a srcew driver and remove some of the body work and we discover it is by all appearances a brand new carby, i show him the point where the mechanic was adjusting which my friend said was the tensioner for the throttle cable and the mechanic was just winding open the throttle in an attempt to stop it stalling and wasnt actually fixing the problem only masking it temporarily. My friend asked is the bike hard to start after it stalls, i say no, he said well its not flooding maybe you have a partially blocked fuel line and when its at idle it cant suck enough fuel through and runs out of petrol in the carby, he offered a couple other ideas that may be the problem.

A friend tells me of an english speaking mechanic, i head to his shop and explain the issues, he attempts to adjust the carby to no avail and says the carby that has been fitted he believes to be a 'copy' and not a genuine factory carb. He says he has a used but genuine one there he will fit for 1300 baht. I was somewhat skeptical as the bike had the exact same issue as before the new carby was fitted and i believed the issue may be other than the carby itself as my friend suggested. I quizz him and he is certain it this copy carb is the source of my woes, he fits the other craby and i pick the bike up a few hours later. It was fixed, hooray, for about one month i had no problems whatsoever. total cost at this point 3450 baht

Then i develop exactly the same problem as before, the bike unable to idle for more than 20 seconds. I return to the second mechanic he inspects the bike and seems dumbfounded, he and his offsider adjust the carby, start/stall/adjust ect for awhile. He then checks the air filter, finds it dirty replaces it and proclaims this is the problem. He than goes back to the adjust/stall/start/adjust dance and exchanges looks of confusion with his offsider. the bike starts and stalls about four times in a row, on the fifth start it was about to stall before he turns off the engine. I have seen and heard this as i am sitting on a chair not one meter from the bike. He looks at me, smiles his little shit eating green and proclaims, 'better now, its fixed'. I literally couldnt believe but TIT, a 40yr old man supposedly a mechanic has no diagnostic skills other than clean carby,adjust,carby replace carby, and instead of admitting that he didnt know the cause he tells a face saving lie.

I rode the bike home and discover that it still rides fine, acceleration and top speed are fine but the bike will not idle at all now when you stop, would literally conk out in seconds when you come off the throttle. Not only did he not fix the problem or offer a reason for it he actually made it worse.

So i foolishly venture to a third shop, my friend comes along to translate and the mechanic disassembles the body work and the top of the carby, i think ive found success someone who seemed to know another trick besides adjust the two points on he carby over and over again to no avail. He pulls out a part of the carby that i can only describe as a black rubber cone shaped thing and was using a screw driver at the small end, i was unsure if he was trying to adjust something there or increase the size of the opening. At this point he said something to my friend that she translated to either 'oh this bike doesn't have much power' or 'it wont have much power' - meaning what he was doing may reduce the bikes power. He puts it back together and starts it up and it seems ok, at this point a lady who works in the shop spots a falrng cash cow on the premises and runs out. She spoke reasonable english and starts with oh you should change the oil etc, i agree as it was nearly due. the bill for cleaning the carby, engine oil and i think gear oil was 350. As it comes time to pay she launches into animated conversation, asking where you from etc, talking with me to my friend back to me back to friend etc, as i hand her a 1000 baht note, she keeps jabbering away highly animated and hands me back 150, jabbering away to my friend trying not to look at me and then when i mention the change oh sorry how much you give me. I say 1000, oh sorry sorry

After the oil is drained one of the mechanics goes on a quick test ride, the shop is on a corner and just around the corner there is a rise in the road, he comes back and was talking in thai and motioning about the hill to the other mechanic. I didnt understand at all, got on the bike and puttered off through the heavy traffic, then i realise the bike wont go over 20kmp/hr, he was telling the other mechanic that he could barely get up the rise in the road. He rode it realised whatever they had down had sapped all the bikes power, didnt attempt to rectify it and let me ride off. Of course the bike was still stalling after 20 seconds aswell.

My friend tells me its my fault as i didnt stick with one mechanic, i dont see the point as none of them offered any solutions to the problem other than clean carby, adjust carby, change carby and once the had exhausted that its seemed they had exhausted their knowledge. So after three mechanics and 4000baht i know have a bike that wont go over 20km per hour, I dont know what the third mechanic did to the carburettor but i wouldnt rule out some form of deliberate sabotage to sap the bike off power and make me spend 2-3000 for a full engine rebuild. Ive had to spend 2500 baht renting a bike for the last month before i go home and now have a bike i could have sold for 8-9000 baht that is virtually worthless in its current state.

Can anyone offer an idea as to what was the cause of the original stalling problem, or offer an idea as to what exactly he was doing with the rubber part from the carby that has sapped all the bikes power?

yes i know i will get people saying the problem is its an old bike, well no shit but that doesnt mean a problem or fault couldnt be identified and rectified if the mechanics are competent.

[krisb]

It's the carby.

[willfreeman]

is that a serious suggestion? the bike had a carby on it when i brought it and ive since had two fitted, three bad carburetors??

[billphillips]

As the carb received a lot of attention without resolving the problem ..... I would be checking the throttle cable for lubrication or kinks, in other words that the throttle slide is returning to idle fully and quickly. The other issue would be to check the spark plug or renew it with the correct plug (it's not necessarily the right plug that's in it now). Also check that the cooling system is not obstructed.

Once the cause of the idle problem is identified and resolved, the carb needs to be set up correctly because it sounds from your post that the fuel mixture screw has been incorrectly set on your last outing. Your bike will not run well on gasohol or E20, make sure that you buy the correct fuel.

[willfreeman]

As the carb received a lot of attention without resolving the problem ..... I would be checking the throttle cable for lubrication or kinks, in other words that the throttle slide is returning to idle fully and quickly. The other issue would be to check the spark plug or renew it with the correct plug (it's not necessarily the right plug that's in it now). Also check that the cooling system is not obstructed.

Once the cause of the idle problem is identified and resolved, the carb needs to be set up correctly because it sounds from your post that the fuel mixture screw has been incorrectly set on your last outing. Your bike will not run well on gasohol or E20, make sure that you buy the correct fuel.

sorry i forgot to mention the spark plug was replaced by one of the mechanics

[Marcel1]

Petrol cables?

Also it would be easy to know where in thailand ur at so you might get some dealer recommendations

[willfreeman]

im in ciangmai

[Namplik]

My friend asked is the bike hard to start after it stalls, i say no, he said well its not flooding maybe you have a partially blocked fuel line and when its at idle it cant suck enough fuel through and runs out of petrol in the carby, he offered a couple other ideas that may be the problem.

Fuel line! Didn't any of the mechanics check that?? Your friend at the gym might be right.

[NeverSure]

I don't think fuel line. If it would idle but not run under power I'd be suspicious that it had a fuel restriction. This is the other way around. It had enough fuel to run under power but wouldn't idle. It doesn't sound like a low fuel issue not even the float.

Cheers.

[paulchiangmai]

Some mechanical problems are very difficult to pin down for even the best mechanics. In such a case you must look at the three things an engine must have to run properly, compression, ignition, fuel. Compression must be checked first, if ok then you have eliminated burnt valves, valves not seating, piston and rings, head gasket, insufficient manifold vacuum, etc. Secondly ignition, you must have a good spark all the time, at the right time [timing], correct plug etc, lastly is the fuel system, correct fuel, no blockages, no stuck choke, carburettor adjustment, no air restriction,[remove air filter temporarily for this test], fuel pump if fitted delivering sufficient fuel at the correct pressure etc etc. Can be a lot of work but a good mechanic should do all these things reasonably quickly providing he has the right tools, compression tester, vacuum gauge, timing light and so on. You may need to check or temporarily disable a device [if fitted] that cuts the fuel off should the bike fall over.

[NeverSure]

I suspected a plugged/dirty idle jet until I learned it's had 3 carbs on it. I also suspected a low float level until then.

The next thing I would check would be voltage to the plug at idle. If the battery was weak and so was the charging system it might not develop enough spark to idle. Of course I would also want to know if it's trying to idle too slow. Any of that could do it.

He reports that it would run fine under power but not idle with 3 different carbs until the last guy did something to the carb. Now he may have two different problems.

He doesn't report that it ran rough but rather that it died shortly after returning to idle. I'm suspicious of spark at idle. I'd replace the plug (again, they can be defective or get cracked) and the wire and carefully check the plug gap if it has enough voltage.

Does this rig have electronic ignition? I don't recall any talk of points and condenser.

Edited July 20, 2015 by NeverSure

[ktm jeff]

Will , you have a small problem with the bke , but a bigger one , trying to find a good mehanic . I found one! . His name is NUNG, and his workshop is on the 108 to Hang Dong road . The shop is behind a "frontage" shop sellig Spirit houses , and it opposit the NORTH Chiang Mai university . You will have to go past and doule back , as he is on the North bound side . Could be water/dirt in fuel or an air leak between carb and engine . Good luck .

[willfreeman]

i will take it into a yamaha dealer tomorrow or wednesday, can anyboy shed some light as to what he did to the carby thats sapped it off power? I saw him working with a black rubber coney shaped thing from the inside of the carby, at the bottom end of it he was either adjusting an adjustment point there or was enlarging the opening im not sure. Is there an internal adjustment on the carby? not the external idle screw or the throttle tensioner

[paulchiangmai]

i will take it into a yamaha dealer tomorrow or wednesday, can anyboy shed some light as to what he did to the carby thats sapped it off power? I saw him working with a black rubber coney shaped thing from the inside of the carby, at the bottom end of it he was either adjusting an adjustment point there or was enlarging the opening im not sure. Is there an internal adjustment on the carby? not the external idle screw or the throttle tensioner

The 'black rubber coney thing' regulates the fuel flow into the bowl, it is known as the needle and seat,the float raises or lowers this to keep the fuel at the correct level. The seat it sits in must be perfect or it will not make a seal when the bowl is at the correct level.

Edited July 20, 2015 by paulchiangmai

[ktm jeff]

Will , whever you take it ( Nung , as suggested in post 12 ) , or a main Yamaha dealer - where the mechanics should be trained to a higher level - it will be better than a shop , where the owner , who likes bikes , decided that alone was enougth to "qualify" him to open up a bike shop .

[desmondspencer]

I've got an old wr400 up in ubon and it does exactly as the op's mio.

Firstly it's a beach to start up but once it does, it runs well and pulls great. Only thing is when I need to rev down, the bike just cuts out as if it's not getting enough fuel & quits. I've changed the lines, plug, slow jet and filter but no joy..

Now that some have mentioned, it could very well be the coil that's causing the problem...!

[losworld]

Could be a weak battery. Or a weak fuel pump. Apparently even some of the carbed models have some sort of pump I understand. Maybe a clogged filter or fuel line.

I would not be filling up with bottled gas or at PTT. I find the gas at Texaco or Shell much better. I think bad gas much of the time. I also sometimes run 95 through the bike (half tank) which I find helps clean the lines.

[willfreeman]

thanks for all the advice i will try the yamaha dealer as its a lot closer to me than nungs shop, hopefully i can putter off down there at 20km/p hr.

[willfreeman]

returned to pick up the bike today, the english speaking guy didnt appear to be there. Get ushered inside for the bill - wow a paltry 285 baht, ride off and the bike and its running fine again full of power and acceleration, so he undid whatever the last idiot had done ( and im not ruling out him doing it deliberately so i came back and he charged me for a full rebuild) Ride the five minutes back to my condo stop in the parking garage and find the bike still wont idle for longer the ten seconds.

Edited July 24, 2015 by willfreeman

[ktm jeff]

Will , now the bike is rideable , take a trip to Nung . I susspect an air leak , or a weak diaphram , causing it to lean out at idle . Weak battery can be elimitated by hooking up a charger whilst bike is ticking over . ECU normally works , or doesnt .

[willfreeman]

is he open on saturdays?

[Vogele123]

im in ciangmai

If you are in Chiang Mai take it to Tony's Big Bikes, ask for Pikey. Seriously these guys are pretty good, up front and dead honest, they are not the cheapest but their work is top notch. They gave my old XLR a good going over and solved a lot of issues with clutch, valves etc.

Sounds to me (I don't know the bike you refer to) like it might be the idle jet is dirty, clogged or something if it is a carb. bike rather than EFI.

Here is the link, it will cost you nothing to take a look and check them out.

http://www.chiangmai-motorcycle-rental.com/

[Turkleton]

These bikes usually have a "vacuum" fuel outlet/cock, which is connected to the intake Manifold through a vacuum hose.

If this hose is broken or porous, etc., the fuel outlet probably doesn't open at low RPMs, so that the Carb doesn't get enough fuel.

Additionally, the engine pulls "false air", which can increase the bad idling.

PS: The old Mio doesn't have a fuel pump.

[ktm jeff]

Will , sorry for late reply , been out . Yes , he is open Saturdays , EDIT = ( and Sundays , when he often leads off-road / track ride-outs ) . I have heard about Tonys professional set-up , but never been . I would feel 100% at ease , leaving my bike with Nung . If you Google NORTH Chiang Mai University , the spirit houses are opposite , with Nung behind .

Edited July 24, 2015 by ktm jeff

[llp]

I've had the similar problem on a 2008 honda click.

It would shut off when ideling sometimes, but more so shut off right at the moment when you try to give it gas after idling. Usually this happens when the stoplight changes from red from green. Most of the time can start it up again, but it got to the point where it wouldn't start back up. Sometimes have to wait till the next day to start it again, or maybe it won't start up at all and has to be pushed to mechanic.

Used my local mechanic who kept cleaning the carb, and adjusting the two screws (i think one screw is for idle and the other screw is for the mixture of fuel/air). This would fix the problem temporary, a few days or a few weeks. Eventually gave up with him, and went to Nat Motors in Chiang Mai. And 1 month later the bike would shut off and I'm left stranded. Repeat this process three times, go to Nat Motors, fix the problem temporary, and bikes shuts off again in a few weeks time.

Eventually I just gave up and switch to 95 benzine fuel, and haven't had the problem come back. So now just have to keep track of which gas stations have this fuel.

[ktm jeff]

will , any progress with the bike ?.

[speedtripler]

Stop taking it to every somtam eating knucklehead you can find to have a go ,

a main yamaha dealer should have the mechanical knowledge, correct tools and the experience and also the catalog to order spare parts if necessary

The price quoted will be the price you pay, the work will be guaranteed and if not to your satisfaction of the problem persists you can then you keep going back until it is, you can complain to yamaha service centre manager or even hq of the owner if a dealership is unable to fix a simple issue on a bloody 125

[Lena5295]

Hey everybody!

This thread was very helpfull!

I am also located in Chiang Mai and have bought a 2012 Yamaha Mio with 44k km for 18.000 baht.

I have JUST bought the scooter and after 5 days the same problem occured to me.

It turns off everytime when it's on idle and even as soon as I get lower than 20 km/h. I cannot drive it anymore, it just shut off almost 10 times on a 2km distance.

 

I have been to the Yamaha main dealer 4x times now. They have changed the air filter, the spark plug and cleaned the carby. It works fine when they showed me but as soon as I drive off it happens again after 10 mins of driving.

 

So dissapointing, please tell me I have not just put 18.000 baht to waste. How did you solve the problem - or did you ever?

[ktm jeff]

Lena. This could be fuel starvation. The fuel cap should have a small hole in it to allow air in when fuel is used. Try blowing through the hole. Or see my previous posts , and find Nung in Hang Dong , near BIG C , but opposite , on the North bound side , returning to town. I dont have the co-ordinates for his workshop , and im now in England so cant take you - sorry.