Modern Vespa

Hi all


I rebuilt my GTS 300 engine following a blown head gasket using Robots 3 rebuild videos.

Now I have the bike all together the engine is not starting. It has a brand new battery. When I turn the ignition on the petrol pump comes on and the orange engine light goes off and when I press the starter button nothing happens at all.

I have added a Gemini alarm to the bike during the rebuild. I checked the spark plug is connected.

The earth wire is connected, and all the plugs are tight.

What is the most logical place to start investigating? Do I disconnect the alarm ?

How do I tell if the key is being recognised?

Many thanks


Paul

Yes, disconnect the alarm. Go back to square one and see if it will start.

If the code LED goes out and stays out after you've switched on, then the key has been recognised.

Wind back on the alarm install first, and check all fuses.

Check the fuel pump 'whirrs' for two seconds after you switch on. If not, chase that...

Check the brake light comes on when you operate either lever.

etc, etc...

OK I have checked the code light and it goes out with the correct sequence (the same as my other bike). The fuel pump whirrs and the brake lights come on. The headlight is not working which could be a bulb but I will check that out too.

I will need to take to the toolbox panels off to get at all the wires to disconnect the alarm.

OK - and the headlight won't come on until the engine has started and is 'happy' - which can be a second or so after starting.

This now sounds suspiciously like a kill-switch problem - which would tie in with the recent alarm installation.

As it backfires I'm going with a cam/cam timing issue.

waspmike it won't engage the starter motor so no backfiring at all.

jimc I disconnected the alarm harness from the back of the ignition barrel and still the same correct light sequence but no starter motor.

I checked all the fuses and they are all OK.

So if its possibly a killswitch issue do I replace the handlebar switch or is it more complicated than that.

The oil light was on too. It's not the oil pressure sensor is it?

Um user error.. because I wasn't sitting on the bike I wasn't putting the brake on.

Doohh thanks for your help..

Thanks for reporting back - we've all done it once!

Well a bit of an update. After realising my error and reconnecting the alarm it is all working.

I decided to use gloss black super decals so now the bike is complete. It's not perfect but was fun resurrecting it after years sitting in the corner of the garage.

Now just need to insure and MOT it and I'm riding it again.

https://youtube.com/shorts/5SuVXSL9gRQ?feature=share

I managed to get the bike MOT'd which is the safety inspection done every year and before you can register a vehicle over 3 years old here in the UK.

The bike passed the MOT fine including the SIP Smoked LED indicator set and rear light kit with the linked brake lights. The inspector said that unlike cars here in UK LED conversions are OK so I think I will also install the LED conversion globe I bought too.

After a week of riding the bike is good. A little rough when cold but nice and smooth after it warms up a little. I need to adjust/bleed the rear brake a bit more so it comes on quicker too.

I am amazed it works after pulling it apart to replace the water pump and blown head gasket. It was my first attempt to do that level of work on a bike so pleased it's all running.

Ooh, that's nice. Excellent job!

Well done

Good job! Did you replace the piston and cylinder with larger or just replace all the gaskets?

No left the piston and cylinder as-is, new gaskets and got the head machined, put on a new water pump assembly as it had seized and done the head in which I am told was common.

It got some new goodies such as MP3 rims, frando brakes and bitubo shocks to go with the LED lights. I cant go very fast in London so don't really get the benefits but it was fun doing it. I think the bike feels a lot lighter than my other GTS as it doesn't have a top box and crashbars.