SGX 50 very difficult to start By scut (Read 3,478 times)

[scut]

Hi, have posted previously here recently about my SGX 50 (Honda Sky) and received some good advice on an electrical problem. I now have another problem so I am back for more help please!

Background is that I purchased as a non runner a few months ago. Eventually identified problem as crank seals which I changed then she fired up on second kick. Then had to change the regulator/rectifier as was blowing the headlights. All seemed fine. Took the bike on it's first real run on the road a for a few miles to the MOT test centre.

Passed MOT but garage said they had a lot of trouble starting her up. This seemed strange as she had been started from cold many times, always first or second kick. Indeed she wouldn't start on kick when I picked her up but did eventually on the electric starter.

When she's running and warmed up she seems to run and idle fine. I can turn her off then, within a few minutes , she'll kick first time. Any longer and gets increasingly difficult to start with kick or electric starter

From cold is very difficult to start, sometimes she will show signs of life and others there is nothing at all. On the odd occasion she does start she is fine when warmed up.

Have checked the electric choke, resistance is as per the Haynes manual and needle extends by approx 4 to 5 mm when hooked up to a battery.

I get what seems to be a decent spark if remove plug and lay it against cylinder.

Compression tester shows approx 125 to 130 psi (after about 5 kicks) which I think is good?

Plug is getting wet with fuel.

Have removed carb & stripped but all looks pristine. Air/Fuel screw is set to 3 turns out in accordance with the manual.

Air filter looks like new.

Reeds look fine and look like they are seating properly.

Removed exhaust to check for any blockages, nothing obvious i.e. I can blow through the exhaust with little resistance.

I previously fitted a new plug when originally fixing the crank seals so have tried swapping back between the new & old plugs but with no noticeable affect.

Have even pulled the rotor etc back off to check the crank seals are still Ok and that the rotor had not slipped or broken the woodruff key. There was a tiny amount of oil on the left hand crank seal but this could have been from when I fitted them. Both seals are in place and look in good condition.

Possibly thinking a weak spark under compression (although it looks fine externally) or it is somehow flooding but as I said the choke seems to work OK.

Not sure where to go next, any suggestions would be great as I'm now at a loss !!!

Thank You

[JR]

Man Scut you without a doubt covered a lot of the possibilities as my fisrt thought was choke but your test rules that completely out.

With all the other things you've covered I'll ask did you check the boot end of the spark plug wire? Even though you are getting a spark if that connection is poor or even dirty/rusty it will keep you from getting the maximum spark. Also all grounds to the CDI and coil need to be clean and getting good contact.

Go through the electrical connections in this area we'll and see if they are up to par. And your spark, a good blue strong spark or a weaker yellow/orangish spark? It does make a difference.

JR

[scut]

Thank you for the quick reply.

Have checked main earth and ignition switched earth. Both look good and measure good on the multimeter.


Checked spark plug cap. Measured slightly under on resistance compared to the manual but not by much. Also looked good. cut an inch off the ht lead and reconnected to cap.

No change still difficult to start. Did start eventually but does not seem to be any reliable pattern or routine.

While running I checked the supply from the stator which was approx 25v AC at a fast idle but actually dropped a little when I revved the engine. Does this sound normal? pretty sure this was getting up to about 90v AC previously when I was fault finding the regulator problem.

Do you think the Cdi/coil could be faulty causing the poor start and dragging the stator voltage down?

The stator resistance and pick up resistance is exactly as per the manual.

The spark does look pretty white /blue to my untrained eye by the way.

Sure is proving a difficult little bike to get running properly!

[JR]

What does the manual say is normal? On the typical Gy-6 60Vac is normal. If I were choosing as far as the CDI or coil I would go with coil. In my dealings a CDI is either good or bad, meaning it either works or doesn't.

But here is something to consider though? We know this scooter's CDI is fed from the R/R and not the stator and since your voltage is only 25Vac then that would also mean a weaker R/R output and the same to the CDI.

It's time to check the connections on the stator plugs and from the R/R to the CDI and see if you find a bad one. If indeed more than 60Vac is required by the manual and you find not bad wire or connections it's stator time.

BTW are you using the Dutch manual or do you have a English version of one?

JR

[scut]

Well the manual I have is a generic Haynes scooter manual which includes 1 sheet which has values/measurements specific to this scooter. I also have the Dutch wiring diagram which I found on this forum which has been very useful but I would love to find a full manual for this specific scooter!

The manual I have doesn’t actually state what is a normal voltage for the stator output. All it states is the resistance to earth which I have checked (engine hot and cold) and which seems to be OK at approx 0.9 ohms. However, when I was previously fault finding for the R/R problem I can’t recall exactly how many AC volts I was seeing at idle, maybe 20V AC or so, but I am 99% sure that the stator was outputting up to 90V AC at high revs. I have since changed the R/R to fix the blowing headlights problem and have run the scooter properly on the road for maybe 15 miles. Now I am reading approx 25V at idle which drops to about 20V AC at higher revs.

On this scooter the CDI/Coil is a single item. You are correct that it is fed from the R/R rather than direct from the stator but, as far as I can tell, all the R/R does is connect it’s own stator input directly to it’s output to the CDI/Coil i.e. the resistance between the R/R stator input and the R/R CDI/Coil output is zero.

I have checked the wiring between the stator to the R/R to the CDI/coil and all looks fine.

As the stator resistance matches the manual I wonder if the problem could be the CDI/coil. Wish the manual actually stated what the stator output should be then I could be sure!!

Would be great if I had a known good scooter to swap parts with but I don’t so at some point I will just have to jump one way or another and order a replacement part!

Thank you for your advice again, it really is appreciated, I am determined to get this little scooter running properly again!!

[JR]

OK learned another thing about this scooter the CDI/coil combination. I looked for awhile for a manual on the Suzuki AY 50 which uses the exact same R/R and is a two stroker too and there is a good service manuial for it again in Dutch.

Reason was I'm figuring the stator is the same and we could get some of the stator output specs, again haven't found a english version yet. One can join Scooterhulp and use the translator to look if you want, they have this manual.

I'm still looking for info on this scooter, would love it if I could find some stuff in a english version.

JR

[alleyoop]

Have you tried leaning the Mixture some, 3 turns out feeds quite a bit of fuel and along with the enricher feeding it fuel may be flooding it. Try 2 1/2 turns out see if it helps.
Alleyoop

[scut]

Righto, I have spent some time looking for data on what the stator output should be. 

I registered on the Scooterhulp site but all I can find for the AY 50 was a parts catalogue with the owners manual and a wiring diagram so unfortunately no information there on what the stator output should be.

I then followed the links in a previous thread about the SGX 50 R/R which lead me to the Ducati electrical parts catalogue. From there I could see that a number of other scooters use a very similar Ducati stator (i.e. same number of poles and 1 phase with only one output wire), R/R & CDI/Coil arrangement - one being the AY 50 and one being the Piaggio Zip 50 4T. 

I then found the following guide on a UK website which describes how to test the Zip 50 4T stator output. 

.pedparts.co.uk/blog/piaggio-moped-ignition-fault-finding-4-stroke" rel="nofollow" target="_blank">.pedparts.co.uk/blog/piaggio-moped-ignition-fault-finding-4-stroke  

Basically it says there should be a good 8-9 VAC when cranking the engine over.  I measure this and with a good kick I am seeing approx 10VAC from the stator (both with the CDI unplugged and plugged in), didn't try it with ignition on come to think of it. 

Also, in my generic Haynes manual it has a data sheet on the Zip which states 25 to 30 VAC from the stator at 2000rpm.  When I previously checked this I was seeing approx 25VAC at a fast idle which sound about right. 

This dropped to approx 20VAC when revving the engine which I am really not sure about - is this correct? I really thought this should increase as the engine revved?  This is one of the reasons I am suspicious of a fault in the ignition system.  I have double and triple checked for wiring/earth faults but can't find anything. 

On the above link it also talks about testing for a strong spark by making the spark jump a larger gap.  I improvised a set up with 2 screws in a piece of wood set 10mm apart, one connected to the engine earth and one to the spark plug cap.  At first I couldn't get a spark, now I am not sure if this highlights an intermittent fault with my ignition or if I had a bad connection in my improvised test set up.  Tried again however and was getting a good strong blue spark jumping across the gap between the two screws which indicates that at least sometime my ignition is working OK. Having said that - sometimes the scooter will start! 

I have tried varying the mixture screw but this doesn't seem to make any difference (3 turns out is as per the manual).  The needle clip is in the middle position, have thought about raising that a notch to lean things out but my understanding is that this wouldn't have any affect on starting which is mostly about the pilot and the choke circuits. 

I am starting to run out of ideas?  My suspicions are still around the ignition and am thinking about purchasing a replacement CDI/Coil. Does this sound like a reasonable next step or is there something I am missing?

Thank you for your time as always!

[travler1]

idont know if this will help, im a mc exp not scooters they are small mistries to me but try this
get a can of quick start give it a couple shots into the air filter and start it, if it starts vary easily and warms up fine start looking for cracks in the intake gaskit at the head or any small cracks around the carb gaskits or intake between carb and head letting extra air in after the carb these small cracks will appear when the motor is cold and makes for vary hard starting, but they disapear as the engine heats up and starts to expand and the motor starts to run smooth again, but then will reapear as the motor cools, and the longer it sets the cracks open again and back to hard starting a couple of shots of quick start and your back in busnessn this happens a lot on the bigger cycles ive had too change many a gasket and intake conectors to correct hard starters,,
travler 1

[scut]

Have spent some more time today double and triple checking for good electrical contacts and any possible vacum leaks.

I am as sure as I can be that all the above is good.

Still the same issue with difficult starting. Sometimes from cold or hot she will start repeatedly on the first kick. Other times there is nothing using the kick start. I have established a pattern with the electric start which seems to work reliably. This is a 3 or 4 second attempt to start with no throttle. Pause for 5 seconds or so. Repeat. Then on the third go she will splutter and I can catch that with the throttle to keep her running.

There has then been the odd occasion where she is ticking over reasonably well then will stop suddenly. More like the ignition has been turned off suddenly rather than a spluttering stall.

I do still suspect the ignition. I wonder if there is an intermittent fault which needs the above start pause start pause procedure to overcome and build up some charge or energy in the cdi/coil.

I'd love to know if the stator voltage drop with increasing revs is not normal. I have spotted a cheap used cdi/coil on Ebay so have ordered that to see if it makes any difference. Also ordered an iridium spark plug to see if that helps the ignition any.

Will keep you updated.

If any of the new info above Sparks any new ideas or thoughts please let me know.

Thanks
Scut

[JR]

Scut I also believe you're on the right track with all you have done and I'm anxiuos to see what this CDI will do for it?

We've got several bits of information on this scooter too, even if a lot of it's in Dutch. I'm going to start collecting it and putting it in a sticky thread for futur use because this is a popular scooter and every little bit helps.

JR

[chimnies]

hi scut im a new member here just got a sgx 50 ran great 2 days now same prob as you, did u get it sorted in the end

[geffers]

Same problem - when I cover the air intake grill with my hand she fires ok on electric. Can't rev her for a few minutes unless the intake is covered. Anyone know a cure for this please?

[alleyoop]

To much air not enough fuel, what your doing is cutting off the air and that gives it the right mixture of air to fuel ratio to ignite.
So turn the fuel mixture screw Counter clockwise 1/2 turn at a time from where it is at and try to start it after every 1/2 turn.
Alleyoop

[geffers]

Thanks Alleyoop - I will try this over the weekend and report back