Scooterotica

i seem to remember a few years back in scootering, sticky was putting a cr250 motor in a lammy (project baastard) and also managed to get that running backwards.
also ive read somewhere that big singles have a tendency to do this as older models run with alot of retard and high compresion, cant remember where tho

Same problem here.
New engine with RB20 + AF head.
The ignition is a BGM 120W with 2Kg flywheel and Ducati Regulator and CDI, in 18º.
I have NGK B9 sparkplug.
I only drive two days and have the problem of the Lambretta goes backwards two times. Then i restart the engine and goes well.
Do you think that i must recheck the ignition if this 18º are correct?
Thanks!

firekdp wrote:I would say the timing was too advanced, not too close to TDC.

This is what I was thinking, too much advance reversing the piston while still on it's up- stroke sending it back in reverse motion. Only ever seen this on over advanced engines or failing ignitions.

Agree with above, either the timing is too advanced or something else is causing pre-ignition.

Hi again.
I strobe the ignition and the arrow is in 28º-29º and i timing in 18º.
I have the TDC two times with piston stoper and my marks are ok.
Then i turn the stator in the maximun that i can and the arrow is in 25º-26º. I cant go lower to this.
What is wrong? The flywheel is a 2kg with welded center and the stator is a 120W one.
Thanks for your help!

hi all,reading this thread,throws my memory back about 28 years,my mate had a early yamaha dt175 twin shock,anyway for some reason diesel had been used instead of 2-stroke oil.he came out one morning,kicked the bike off dropped the clutch and promptly reversed into the garage wall,when he told us what had happened in the pub,we all fell about laughing, we all thought he was having us on,but sure enough on starting the bike it would set off backward,even if you bumped it off forward,pulled the clutch in,it would go backwards,we stripped the top end and found the cylinder head heavily carbonised,also the exhaust port was half closed due to carbon build,we cleaned it all up and the bike was fine,thinking now that the heavily sooted head,had little hot spots acting like glow plugs,causing the mixture to detonate earlyforcing the piston backwards,anyway we all had a good laugh and told him to get something reliable like a lambretta,which he did,cheers all.