Vespa SS180 update 2
I’m still running in the SS180 so every chance I get, which isn’t as much as I’d like, I take it out for a spin. It’s got nearly 300kms on it now so only a couple of hundy to go.
Whilst riding a couple of weeks ago, I pulled up to a busy roundabout, sat in neutral waiting and went to take off in first but only to find I was reversing into the car behind me. In to neutral again then back into second and try another take off – same thing. Up until now the scoots been starting and running really well.
I had to push it off to the side of the road and got on the phone to Mike Salmon who owns Not a Motorcycle Shop in Upper Hutt. Although he had heard of this happening but didn’t know anyone that had experienced it. Apparently my timing must be too retarded, which didn’t mean much to me, but it was time to check it out. He recommended 23 degrees BTC (before top dead centre) for the timing.
The scooter started up fine – no reverse gear – and ran good all the way back to the shed. Mike had suggested a timing light would be needed and I found a good article here – http://www.scooterhelp.com/tips/timing/electric.timing.over.html . They also have a degree wheel that you can download and attach to some card or laminate.
If you haven’t done this before it can be a little confusing and as I have had a crap run with CDI units, I wasn’t too keen to stuff anything up. The guts of it is that the flywheel turns clockwise via the crankshaft in relation to where the piston is, so to set the correct timing we need to find out where the piston is at the top of its travel in the cylinder. This is called TDC (top dead centre). There is a tool you can make on the scooterhelp site to do this with or just use a pencil or something similar – be careful you don’t drop it down into the cylinder or get it caught. This is how I did it:
- Remove the fan shroud and the spark plug. You should be able to rotate the flywheel easily. Shine a torch into the plug hole so you can just see the top of the piston. Adjust the TDC tool (as per the arrows, 10 to 15mm) and screw it into the spark plug hole.
- Rotate the flywheel slowly clockwise until you can feel the piston stop in the cylinder. Put your finger on the TDC tool and feel for the piston making contact with the threaded part of the tool in the cylinder to make sure.
- Line up one of the cooling fins on the flywheel with the edge of the housing your fan shroud attaches to – use a ruler or something straight and make a mark on the housing. Mark the edge of the cooling fin as well. Be careful to not move the flywheel. Now rotate the flywheel anti clockwise until you can feel the piston stop in the cylinder and make another mark on the housing. You should now have two marks on the housing. TDC is in the middle between the two marks you have made. The mark on the flywheel cooling fin will become your timing mark.
- Put the flywheel back on and the spark plug back in and attach the timing light to a battery and your HT lead. You may have one that just attaches to the HT lead and doesn’t need a battery. Start the motor and point the flashing light at the mark you made for TDC on the housing and look for the mark on the edge of the cooling fin. The strobe effect should show the two marks as the flywheel rotates. The mark on the flywheel should appear to the left of the mark on the housing, which it did on mine.
- To get the flywheel timing mark to line up at 23 degrees before TDC we need to measure the 23 degrees with a degree wheel. Take the spark plug out again and rotate the flywheel until your timing mark lines up with TDC on the housing. Place the degree wheel on the flywheel, centre it, and use a magnet to hold it in position. I used a ruler to be able to extend the mark out to the housing. Turn the degree wheel, not the flywheel, anti clockwise until 23 degrees lines up with your TDC mark on the housing. Where 0 degrees now is on the wheel is where you need to make a mark on the housing. So you should have your TDC mark on the housing and to the left around the housing a bit will be your other mark which is now at 23 degrees before TDC. Put your spark plug back in, set up the timing light and start the motor.
- When I did this the mark on my flywheel was about half way between 23 degrees and TDC so that meant I had to physically move my stator, as per the picture above, anti clockwise or advanced. To get at the stator you have to remove the flywheel.
- Once you remove the flywheel the Stator is underneath that. Don’t lose the small metal key that keeps the flywheel located on the crankshaft. If it looks dodgy, go and get another one as these do wear. The stator is the heart of your electrical system and is attached to a housing by 3 screws in slots that can be adjusted as per the picture. Loosen the screws and advance or retard by turning the stator as required. I turned the stator anti clockwise until there was no more adjustment and then tightened the screws back up. You may have to do this a couple of times to get it right. Put the flywheel back on and check the marks with the timing light.
- My marks lined up so I was quite happy with that.
I took the scooter for a ride this afternoon, while there was a break in the crap weather, and it seemed to start better and run well. Once I have a few more km’s on the clock I will check the timing again and then look into the fuel system and spark plug to see how they are going.