Scooterotica

Currently running my Vespa cutdown with a reed valve LML125 engine fitted with a 150 5 port kit.As the cranks a crappy LML and I was thinking of upgrading it over winter,how hard would it be to up it to a 60mm one for a bit of extra torque? Would it require a base packer plate or are we talking porting changes also? It currently just runs a normal paper type base gasket and a copper head gasket.

Can't answer your question re the crank but interested in your opinion on the 5 port cylinder as I've had one fitted to the LML 125 engine in a PX I've been doing for my son. I've put about 60 miles or so on it and it's a smooth a silk but too soon to really open it up. Just wondering what sort of speed/performance can be expected?

Cheers

Colin

Hi Coaster,Mine ran ok for 500 miles,gave a lot more torque than the 125 and i even upgeared the clutch to a 22 toothed one as it would pull it no problem.Just had trouble with it nipping up over 50 after a mile or so of riding.Jetting was rich across the range as plug chops were fine,no air leaks and timing was spot on,no pinking or anything.Put it down to a tight bore.
Got a new piston now and going to get the barrel honed and measured next then try again.The 125 is flat out all day long but slow compared to the 5 port!

Thanks for the feedback

The 60mm crank will slot right in. You can either pack out the base or the head 1.5mm to improve the top end or give you a bit more pull off the line. Or you can split the difference if you're feeling cavalier.

If it's a thin ring piston that you're running, you can open up the exhaust port to get more out of your cylinder and take better advantage of the crank.

The last stroker I built was a 3 port Sprint. The cylinder needed a rebore and I was able to get my hands on a thin ringed LML piston. With that piston in mind I widened the exhaust port somewhere in the 65-68% range. I also raised the exhaust port, to approx 50-55 degrees over the transfers, (thanks Darrel!) Finally I packed the cylinder head, which gives you improved low end torque, and with a Sito Plus, and the stock 20/20 carb (albeit fitted with one of these http://shpws.me/CflN), it goes quite well and is a pleasure to ride.

Another fun trick is to drop the steel LML reeds in favor of Yammy RD350 dual stage reeds. It's a straight swap, but I like to cut out the center bridge on the reed block to improve flow.

guygrrr wrote:Another fun trick is to drop the steel LML reeds in favor of Yammy RD350 dual stage reeds. It's a straight swap, but I like to cut out the center bridge on the reed block to improve flow.

I replaced the reeds in my Lad's with Polini reeds and cut out the bridge piece at the same time. Do you thing the RD350 ones would be better?

Colin

I honestly can't say as I've only ever run the dual stage reeds.

What sort of improvement did you see with the Polini reed?

guygrrr wrote:I honestly can't say as I've only ever run the dual stage reeds.

What sort of improvement did you see with the Polini reed?

I wish could say, as I mentioned above, I had an issue where it wouldn't run over about 20 mph and that was following a complete nut and bolt rebuild so I was trying every thing including the Polini reeds.

Are standard RD350 reeds all dual stage? might have a set already if so.

coaster wrote:Can't answer your question re the crank but interested in your opinion on the 5 port cylinder as I've had one fitted to the LML 125 engine in a PX I've been doing for my son. I've put about 60 miles or so on it and it's a smooth a silk but too soon to really open it up. Just wondering what sort of speed/performance can be expected?

Cheers

Colin

Have you done anything else to it? With the stock pipe, it'll stop revving at 90km/h. A little bit more with a SIP road. But not a lot.