SRX400 - cuts out at low revs/idle

[andy0405]

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

[Steve H]

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.

[andy0405]

It dies at low revs e.g. stopped at a junction

If you keep the throttle open it runs.

[Andy M]

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

[andy0405]

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.

[guest7]

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

[andy230]

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

[Andy M]

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

[andy0405]

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

[andy0405]

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

[themoudie]

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!

My regards, Bill.

[andy0405]

Thanks for the tip Bill.

Andy

[guest295]

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.

[andy0405]

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 !!!   

[themoudie]

I wish you well.

regards, Bill.