Starting/Engine Issues Suzuki 125

[smegbrains]

Hi guys,

My Suzuki GX125 (yeah that's GX... import one. Seems mechanically similar to the GN125, but slightly diff. body style) is showing starting/running problems.

It's a 4 stroke carbed 125cc engine.

Symptoms/History:

Bike has been starting fine, apart from issue where you have to really warm it up before you can apply any throttle or it'll cut out.

Fairly recently it's been playing up when hot, seems to be in the upper third of the rev range, from 6k - 9k under accelleration it'll occasionally hesistate, as if it's been starved of fuel, or no spark or something, then pick up, cut out, pick up, cut out, pick up then carry on as if nothing was wrong.

This has happened a few times recently so I was off to the bike shop this afternoon to get them to look it over when it did the hesitation loads then cut out and simply wouldn't start again.

It turns over fine, there's a spark on the plug and I can see the piston going up and down. I can smell fuel around it but not THAT strongly after cranking it for a bit. The carb looks alright on the outside but I've never done one before so don't fancy cleaning it out.

Don't have a compression tester (going to pick one up tomorrow and see)

Wondering if any of you have any ideas beyond test compression then test electrics then fuel or have had this symptom before?

Someone expressed the opinion it could be the coil.

[lonner]

hi m8

the fault sounds intermittent and that is nearly always electrical.

Plug may show a spark but if its playing up you will get this sort of fault so change it as its the most likely and cheapest.

the coil is a good possibility as is the cap ht lead.

unfortunately with intermittent faults its a matter of finding the right one.

check the earth at the coil ie where it bolts to the frame is it clean and do the wires look clean with good connections check battery earth as well.

is the ht lead in good order and has it got a good fit at the coil and the cap.

if its yes to all of these you may need a new or new parts.

i wouldn't bother buying a compression tester as a multimeter is a better bet and one of the best things to have in your tool kit

give these things a try and see how you get on hth

[smegbrains]

Thanks for your advice, I'll give that a whirl first then.

I can get hold of a multimeter but I've never actually used one for diagnosing anything other than broken connections and testing voltage level so I wouldn't have the first clue how to use it to check that.

I'll give the following a try tonight...

New spark plug (only 2 quid 50, worth a punt)
Clean the HT lead and check snug fit/connections
Check coil is connected to frame snugly

Me boss also suggested having a look in the fuel filter and seeing if it's full of rubbish. I think it's some wee white plastic thingy on the side of the bike under the fuel tap, hoping I can just unscrew it, scrub and refit.

Also might give the fuel lines a blow out just in case.

[lonner]

[smegbrains]

Right reporting back after my evening of spannering.

First thing I did was give it a whirl to see if it ran. No dice, turned over but didn't catch.

So I swapped the spark plug out. Started right off the button and idled happily!

Decided I'd take it for a spin round the block a couple of times, warm her up and see if she's fine. Problems...

Once warmed up, it stalls from idle and takes a couple of goes to start, runs roughly then cuts out. It runs fine if you give it some throttle, and drives fine as long as the revs stay up.

I started going through other leccy diagnostic bits from what you said and had a look at the HT leads/coil. Stealing some mechanical knowledge from me haynes manual, I turned the lights out and ran her and there were sparks from the HT lead to the engine, and a sort of bluish electric "haze" around the sparkplug/HT lead area, sort of like an aura between the edge of the HT cap and the plug.

It was also shorting around the coil part, so wrapped the HT lead in some leccy tape in case that helped, didn't do much.

Took the coil off for a look and it looked a bit tatty around the connector areas but the cap itself looks alright to my eyes. Gave it a spray with WD40 to get any damp out, let it dry and gave it a go. It ran for a bit longer then cut out.

Sounds like replacing the coil might be the way to go?

Only problem is I've checked ebay and wemoto, and a couple of parts stores but since my bike is a model that almost doesn't exist I can't be 100% sure it's the right one. Any suggestions beyond taking it down to the Suzuki dealer and seeing if they can get me one?

Thanks for your help so far, much appreciated

[lonner]

hi 8


the coil should be the same as the uk model as usually its cosmetic changes.

before you spend on a new coil change the cap first as that is quit likely the main fault as your getting leakage.

check that the coil earth is clean (where it bolts to the frame)and the 2 connectors are shiny.hth