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1260

SH125 is reluctant to start

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1260

Hi guys 

Thank you for my welcome.

Any ideas please?

My boys SH125 is reluctant to start. Once running will only tick over with throttle half open, will run but cuts out.

We've changed throttle body, no change. Cleaning out the injector and will try again later also changed plug for a new one.

Would really appreciate any further ideas Cheers

Mart

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dave

It could be the sign of a tight tappet, easy to do on the SH. make sure the plug cap it pressed fully home.

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MatBin

Air filter? Plug condition/sooted up?

Edited by MatBin
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1260

Dave and Mattb thanks will try each.

👍

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SteveThackery

This is such a difficult question, because in reality it COULD be dozens of things - diagnosis over the Internet is really hard.

 

The proper way to address any fault like this is to follow a logical sequence of diagnostic steps, which would include looking at any fault codes recorded. Without having the bike in front of us all we can do is throw out suggestions.

 

It has fuel injection, you say?  Sensor malfunctions can lead to this kind of fault.  I know nothing about the SH125, but ones to check would be the throttle position sensor (TPS), the engine temperature sensor, and the manifold absolute pressure sensor (MAP).  However, mostly (but not always) you'd get the MIL (malfunction indicator light) lit on the dashboard.

 

Mechanical problems which can cause similar problems are low fuel pressure, and this is certainly a possibility.  You should check the fuel pump and the pressure dump valve for correct operation, and also check the fuel strainer to see if it is blocked.  All of these are inside the fuel tank.

If you can get a Haynes manual, or the official service manual, they should contain the information you need to check the above things.

 

Finally, if there are any pipes or tubes connected to the intake manifold, check that none have fallen off or split.

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Tex

 

48 minutes ago, SteveThackery said:

Finally, if there are any pipes or tubes connected to the intake manifold, check that none have fallen off or split.


Actually, do that first. An air leak will give you all sorts of problems and can be a bugger to find. 

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dave

Good post Steve. I assumed the the light was not on. Being a scooter problems  sometimes are caused by motorcycle shops not wanting to work on scooters.

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trisaki

Valve clearances and a good check over for split vacuum pipes 

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Defender
5 hours ago, Tex said:

Actually, do that first. An air leak will give you all sorts of problems and can be a bugger to find. 

Yes, oh so very true, I had that issue on an XJ600 (1st generation) inlet rubber had gone porous! It was weakening the mixture, so it would start with some help from damp start (or similar) but once that was combusted it needed a lot of throttle ie. fuel for it to run?

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