Thumper Club Forum
Technical => Bike Problems/Questions => Topic started by: andy0405 on December 11, 2007, 08:32:12 AM
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Bike starts on choke in the morning and I leave it for upto 5 mins.
Close down choke and set off.
Ride for less than 1/4 mile, pull up at junction and engine cuts.
Start bike and set off again, to next junction, engine cuts.
Coughs and splutters sometimes at low revs.
I've not tinkered with anything like idle settings this just started on Monday morning.
Did a 60 mile run out last Sunday and didn't have any problems.
Any help appreciated.
Andy
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My mono suffered from carb icing. It had different symptoms though, instead of running rough at low revs, it would just cut-out and die for a short period.
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It dies at low revs e.g. stopped at a junction
If you keep the throttle open it runs.
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I don't suppose the bike lives outside or was down to the dregs of the fuel tank on Monday morning?
I'm thinking water in the fuel or **** from the bottom of the tank blocking the idle jet? I'm not familiar with the SRX carb, but most have either separate jets that don't block at the same time, or circuits that produce a mixture that'll burn almost anything. If you are on reserve stick a tank full of fresh petrol through and maybe think about cleaning the fuel tap and carb in the near future? Also look at the filler cap.
I'd also take a look at the plugs and air filter while you are about it. It's the season for water & oil to turn the filters to mush (like having an old fashioned choke on all the time which the enricher choke can work with) and make the coil/HT leads do odd things as it steams. The electrics can be WD-40'd, oil and water on the filter needs to be investigated further to see it it's coming out of a breather, or from the outside.
Good luck
Andy
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I don't suppose the bike lives outside or was down to the dregs of the fuel tank on Monday morning?
I'm thinking water in the fuel or **** from the bottom of the tank blocking the idle jet? I'm not familiar with the SRX carb, but most have either separate jets that don't block at the same time, or circuits that produce a mixture that'll burn almost anything. If you are on reserve stick a tank full of fresh petrol through and maybe think about cleaning the fuel tap and carb in the near future? Also look at the filler cap.
I'd also take a look at the plugs and air filter while you are about it. It's the season for water & oil to turn the filters to mush (like having an old fashioned choke on all the time which the enricher choke can work with) and make the coil/HT leads do odd things as it steams. The electrics can be WD-40'd, oil and water on the filter needs to be investigated further to see it it's coming out of a breather, or from the outside.
Good luck
Andy
Kept in brick garage.
Full tank of fuel in on Sunday.
Air filter changed 2 months ago when serviced.
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Are you sure it's not carb icing? One of the things about it is that you can hold higher revs, but it will cut out at low revs.
I reckon icing is getting worse and more prevelant as the quailty of our fuel changes. My XBR suffers badly from it.
Failing that, it could be electrical, but I'm nowhere near qualified to offer an opinion on electrics.
GC
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Failing that, it could be electrical,
My twinshock ran like a pig when hot, fine cold.
Traced it to a faulty stator coil. Check yours against the data in www.srx600.net ?
Prolly not this, I've never heard of anyone else having this bother, but you never know. It drove me nuts for weeks!
Try changing the plug too. Another funny one I had was rough running traced to a spark plug "unwinding" and the electrode disappearing up the thread. You can imagine that it doesn't do combustion any favours!
Next, make sure the tappets aren't closing up? Maybe the locknut could have worked loose from the service?
And run it on "prime"; this just bypasses the silly fuel tap. (not sure about mono's tho)
good luck!
andy
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Are you sure it's not carb icing? One of the things about it is that you can hold higher revs, but it will cut out at low revs.
I reckon icing is getting worse and more prevelant as the quailty of our fuel changes. My XBR suffers badly from it.
Failing that, it could be electrical, but I'm nowhere near qualified to offer an opinion on electrics.
GC
I'd check the physical condition of the plugs, make sure there is the famous "fat blue" spark, do the resistances of the HT leads, coil etc. look for any corroded connections and WD-40 the lot. Also, check the battery with the engine off and with some revs on, it's a long shot (would tend to refuse to start) but the battery could be at fault. The stator coil is a fair bet, but if it only breaks down when hot and at idle you'll be lucky to find it except by swapping parts which is an expensive way to find a probelm.
Carb icing as suggested by GC and Steve H is cured by putting an additive in the fuel. Silkolene proFST is the usual suggestion. Before you get into that, does the problem go away if you sit still for 5 minutes and keep the engine going on the idle? The idea is that the engine warms the carb and the ice melts. You then get the idle back until the ice builds up again. GC knocked up a fairly useful heat deflector for the XBR to heat the carb if I remember correctly, my Bonneville requires electric heaters in the carbs to prevent it below 10 degrees C!
Andy
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Didn't seem as bad on the short ride home tonight. Bike has been stood in the sun all day so maybe the carb has thawed. I'm going to get some proFST anyway but can't do any real tinkering till Friday, will have to use my other bike till then. Thanks to everyone who commented, I'll let you know the outcome soon.
Ta.
Andy
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And run it on "prime"; this just bypasses the silly fuel tap. (not sure about mono's tho)
The mono does have prime, I'll bear it in mind tomorrow morning.
Cheers
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Aye Andy,
Instead of firing the old girl up and then letting it 'tick over' for 5 mins + :(. Start her up and then ride her, easing the choke after you have progressed. Much kinder to the engine providing you don't rev the nuts off it whilst still cold. Engine warms up quicker, you save on fuel and the oil circulates and heats through preventing the emulsion 'mayo' syndrome with less internal engine wear.
I'm not discounting crap fuel and ice forming in the carbie, also draining the tank fully of all liquid, cleaning the filters and then re-filling will ensure the removal of all condensate lying in the bottom of the tank.
I hope you can sort it out as a dying motor whilst in the outside lane at 60+ can give a queezie feeling! ;D
My regards, Bill.
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Thanks for the tip Bill.
Andy
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A bit of alcohol [meths, etc] in the petrol will absorb water and prevent freezing. It's a good idea to add some to every fill. And like the man says, cold idling will kill your engine: specifically, gum up the rings so they stick in the piston grooves. If your carb has an idle mixture screw [usually under the body, hard to get at], turn it out a quarter turn to enrich the idle mixture. That usually stops it quitting when you pull up at the lights.
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Bike was not better on Friday morning so I set about doing a bit of tinkering.
Air Filter Ok
Plug & Spark OK
No breaks in fuel line(s)
battery good
Same as before bikes start but wont hold idle.
So head off to local Yamaha dealer to see if they do ProFST, which they don't, but recommended Putoline fuel conditioner and said it would do the same thing. Put in the required amount and now bike wont even start. :(
So currently draining tank, then putting in fresh fuel tomorrow after cleaning tap etc in the hope that I can at least get back to where I was when the problem started !!! :-\
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I wish you well.
regards, Bill.
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For what it is worth, when things like this happens I eventually find it is something I have done.
The one thing that sticks out is that it ran ok before but you filled up with fuel.
My first port of call is was it crap or water in the fuel. When I'm in this position I try and reverse what I have done to when it last worked ie think rationally. In this case drain the tank and try fresh fuel and empty the carb float chambers of old fuel.
If your like me I would already have decided the worst case scenario is the problem and have costed a full engine rebuild.
goodluck
beeman
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The ProTST or equivalent I think will reduce the amount of energy in a given amount of petrol. The fact that it won't even start with it in there is saying to me that with only the idle jet open there is just enough go to make it start, or it's flooded. Reduce the fuel quality and it won't even burn. I assume you held the throtle open to try and make it burn, in which case it shouldn't IMHO be flooded. This is saying not enough fuel to me which brings us back to blocked idle jet, gummed up float etc.
Replace the fuel for sure. Any luck with the colour of the plug tips? Maybe try looking after a few minutes at idle and see if they look lean? Try some carb cleaner?
This assumes of course that simply dumping potentially iffy fuel does make it all go away.
Andy
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Well, my preference, for what it's worth..
1. cr&p in the carb....they are bu55ers to get off and clean, but worth the effort
2. Carb icing up...but if you are running standard carbs with the standard airbox and filter..this is not the most likely reason, as you say that it is the same after you have done a mile or two and then come to a stop.....if the engine then stalls, and it is left for a few minutes before restarting (it takes very little time for the ice to clear when the engine is hot) it should then idle ok if the problem was icing.
3. you filled up on the Sunday...and the problem started on the monday? mmmm....you could have taken on a load of sh1t with your petrol....so draining tank (if you remove the tank you can then remove the filter as well) is a good idea, then clean out the lines and tap assembly, and the carb...it really does help if you have access to an airline......these carbs have more holes..pipes..jets etc than a half decent life support system!....only person I know who has any idea how they work is SteveH
Good luck
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The carb cleaners in a can work a treat and shows you where the passage ways are in the carb but...... if you get it in your eye, life gets very exciting for a few minutes. Don't ask how I know but if you try to clean a hole which you presume goes somewhere but is only a dead end you too will know. However the carbs went like new afterwards.
If the tank is letting rust through an inline fuel filter might do the trick.
beeman
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I did have a similar problem with a sticky/pinched choke cable. Though I did have trouble re-starting, it would run fine until warm, 1st stop it would die.
Good luck!
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Back on the road again :)
I managed to clean out the tank and strip/clean fuel pipes and tap all the way to the carbs, and then Xmas and work took up my time so got local Yamaha dealer to strip and clean the carb for me, hey presto running like a dream again.
Thanks for all the help.
Andy
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Pleased to read all is now better with the wee beastie.
Healthy 2008, Bill
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The old girl has been running great.... up until last week. Took her out of the garage, tried starting, no joy >:(
To cut along week short in the little time I have had to look at her I have discovered that there appears to be no fuel getting to the plug... hence no starting. After paying the local Yammy shop last time I have decided to strip and clean the carbs myself (gulp). Any tips and tricks would be gratefully appreciated. :)
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Hi, a bit of a poor show on the part of yer local shop if they supposedly stipped and cleaned it only a couple of months ago. Are you sure there's no blockage on the way to the carbs?
There's a drain screw at the bottom of the float bowl, if nothing comes out of that then yes its dry.
If you do want to get the carbs off my top tip is loosen the airbox first. Ie take the screws out so you can wiggle it backwards. Then undo the carb boots, you might need to fabricate a tool to do this if they're held with allen bolts - a cut down allen key should do. After disconnecting all the cables, fuel lines, jubilee clips etc you should be able to pull the carbs out upwards and backwards with the boots still attached.
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yeah not happy at all, however need to save some cash so am gonna have a go myself this time (maybe even do a better job).
Thanks for the tips on getting the carbs off, I've not attempted it yet but did look and wonder what the best angle of attack was, a snug fit if ever I saw one :)
Fuel is getting to the carbs as i have checked the carb drain plug several times and each time it was full. Now I'm not a mechanic but I'd expect the spark plug to be wet (or at least showing signs of liquid) but its bone dry. I've even checked with the HT lead off in case it was timing.
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The carbs on the monshock are easier to remove than the twinshock. You should be able to remove the top of the airbox along with the carb trumpets, before you start on the carbs.