Need help, AF05E engine with 46mm BBK, no power.

[1man8scoots]

If he's using the malossi 16/32 I think it's a 7.83:1 ratio. The malossi bore kit barely pushed them.

[Rogerio]

Thanks you all for the good advices, I'll continue with a T┬║ gauge and check trans dynamically without cover .
What's the head t┬║ range and where/how is the t┬║ sender fixed to the head? Are there any pics in the forum?
After all this I'll become a Spree specialist
Kind regards

[Wheelman-111]

Greetings:

Use the 14mm spark plug ring to compare your temps with others'; who mostly use this set-up. I had one under a headbolt for a while, and it read cooler. The advantage is that you don't have to struggle with the wire every time you remove the plug. A bore kit needs to peak below 375F. to be safe for street power. Push 400 for racing. Pre-ignition, detonation, and Swiss cheese pistons await a bit beyond on commercial Petrol.

[Rogerio]

Hi,
Made my road tests today, trans is working fine/marvel, T┬║ values are normal ~300┬║F after 5Km.
But the engine enters into auto-ignition when hot and running at full throttle (65 Kmh), if I disconnect the ignition with the key, it continues running with less power and out of timing.
Is this a sign of too much compression? I've already a colder spark plug
Adding a 2nd head gasket could be the next test?
Looking forward to yr. advices.
Kind regards.

[1man8scoots]

Pre ignition is scary on a 2t. It's possible your slide is getting stuck or cable also. Too much compression can lead to pre ignition but it's doubtful that's the only thing thats going on. I'd check the carby. It's hard to say.

[Rogerio]

Hi 1man8scoots,
Pre-ignition is one thing (air-fuel ignition takes place before the correct timing) and auto-ignition/self-ignition is another. What I've is the 2nd, the engine runs even without CDI electrical power .
Carb was checked and re-checked. Regards and thanks for yr. help.

Pre ignition is scary on a 2t. It's possible your slide is getting stuck or cable also. Too much compression can lead to pre ignition but it's doubtful that's the only thing thats going on. I'd check the carby. It's hard to say.

[Wheelman-111]

Greetings:

I suggest you pull the cooling shrouds and cylinder head and have a look at the combustion chamber. I suspect you'll find melty bits welded to the head and/or piston crown, acting as Glow Plugs. Then spring for a proper Italian cylinder and make sure this one doesn't run under-jetted and under-oiled.

[patthesoundguy]

Wheelman makes a great point about the metal bits acting as little glow plugs. Had it happen in old cars lots over the years from carbon build up and hot motors. I'd pull the head and have a look at the piston head and cylinder condition before proceeding. Also Check deep in the plug around the base of the insulator for any excessive carbon build up or debris that could cause a hot spot. The heat has to be coming from somewhere to continue combustion. A compression test may also not be a bad idea before pulling the head off.

[1man8scoots]

I've experienced Autoignition on blasters and a tomos ped, both times were from the carb either not being seated or the carb getting jammed open at high rpm. Both bikes were results of carb issues. Also both were fresh built engines. Only way I could get them to shut off was to pull the choke.

[1man8scoots]

Generally auto ignition is from being at a high rpm(fast port timing) and the vapor igniting again under pressure before blow down is finished thus super charging the mix into a volatile state. Pre ignition is usually from what wheels and pat are describing.

[Rogerio]

Hi everybody,

Excellent news, my problem is solved .
Cylinder head was re-surfaced and polished inside. No more auto ignition and on flat road with no wind it reaches easily 70Kmh (I didn't push it more as it was the 1st ride).
Thanks to all the help kindly provided by you (mainly Wheelman,Patthesoundboy).
Attached a pic of the coast 5 Km from home.

Kind regards from Protugal

[Wheelman-111]

Ciao, Rogerio:

So glad you got it to work! Beautiful coastal roads over there to enjoy.

[Rogerio]

Hi Wheelman,
Beautiful coastal roads here to enjoy a decent NE50 scooter, now with plenty of power
But also to enjoy my 4 wheels 73 MGB.

Regards from Portugal

[Wheelman-111]

Greetings:

In British Racing Green, no less! Nice.

[Rogerio]

Coastal road, see Google "Sao Pedro de Moel" / Portugal.
This is where I test my "machines", I don't let me distract by the nice view .
Regards