Modern Vespa

Hey all,

I am sure many of you have read about my trials and tribulations about the DR180 kit I installed on my px125e vespa.

It runs like garbage. The kit is absolute junk and the cylinder head is either warped or defective. I had it machined and lapped and the surfaced mated but I was still experiencing a leak from the base of the cylinder head and a pinging noise that could wake the dead.

A friend of mine had dropped off a LML 150 cylinder set. It has a gasket between the cylinder and the head. So another friend and I took that gasket and slid it between the surfaces of the DR kit. Instant improvement. Minimal pinging noise and no leaking.

So here is my question:

Should I just swap the DR180 kit (with the warped head and unsure if the gasket is safe to use) for the LML 150 and call it a day?

How much difference in performance will I achieve? I will be pairing the cylinder with sip road 3.0.
I have previously read that folks consider swapping their stock px125 cylinder for the LML 150 or the DR180.

Any suggestions or recommendations are appreciated.
Thank you.

N

Hmm I just worked on a DR180 kit on a Stella yesterday. Definitely an improvement over a 150 and no problems with a head leak/pinging etc.

I don't see a problem with the gasket if your squish gap doesn't get thrown too far from spec. 1-1.5mm for a mild engine. Can you measure with and without the new gasket and see what it reads?

Obviously you don't want pinging or a head leak so if it works, run with it till it doesn't and then try the LML cylinder.

I have run DR kits on two occasions and think the cylinder is pretty good. It has the auxiliary exhaust ports and the base transfers can easily be enlarged and matched to bigger case ports. For a budget kit, there is a lot you can do, if you are so inclined. The common complaint with the piston (thick rings) can be overcome with a Grand Sport piston if you can find one, and the other complaint is the sloppy piston to bore clearance which makes it a noisy kit. Most can live with that. I didn't buy the GS piston, but I did run superior 63mm GS rings with my first kit.

As far as the head is concerned, they are junk. I used a Polini 177 head on my first one and a VMC 177 head on my current one. The Polini is cast better and reduced the BIG squish. The VMC is a CNC milled beauty, with a central combustion chamber and long reach central plug, and it allowed me to lift the cylinder to improve the port timing, whilst still keeping the squish sensible.

Whatever you do (DR or LML 150), you will get better performance than a PX125. If I were you, I would invest some Dremel time into the DR kit, then get a better head and the GS rings. There is no need for the head gasket, other than to compensate for poor engineering, which is probably why the LML top end uses one.

Alternatively, there are many other 177 kits available.

Well that's not a reassuring point about the head , but good to know.

The DR177 cylinder kit has to be 30+ years old. It is old technology and in no way produces the power and quality of today's cylinder kits in the market.

Brand new, these sale for $200.00. That's cylinder, piston, rings, and head. That is extremely cheap.

I would figure this: it's near a stock 3-port cylinder with 27 extra CC's. You will not be doing cartwheels with these bad boys.

All that being said, they work and are an okay replacement for any unmodified 3-port cylinder. If you want more in both power and quality, pay more money. It's that simple.

My suggestion: VMC177! best to TIG weld up the cases and match the transfers, but you could also install it as-is. Would work circles around the two cylinders you have referenced.

Might you not try another 177 kit? OK you had bad luck with your DR but how about a Malossi or something recommended on here? The lml 150 bolt on makes very little difference on a 125 performance. I've tried this and got the lml kit still in shed as it was barely noticeable. It has a couple of extra boost ports in it. If you are just looking to get your scoot running again it will be fine and reliable I'm sure but you won't notice a lot of difference.

I like the DR177... what else did you do to the motor?
Squish, porting, carb, crank... ?

They're strong , but a great starting point for modifications.

I ended up keeping with the dr177. It works and has more power than the 150. So that was my deciding factor.
However Its a poorly made, bolt on kit. I bought it as naive first time engine builder. Knowing what I know now, I would have gone a different route. Famous last words I guess.

Full engine rebuild. Including a new mazz crank.
20/20 carb
160/be5/118 main
55/160 pilot
Sip road 3 exhaust.


No porting.

It has some decent pull and loves 80kph with room In the throttle. To get it to 100kph is a stretch and I take my hat off to the folks who do.

Is it worth getting a dremel and giving it a bit of a tidy-up. more of a trim rather than a full on haircut but you might get a bit more out of it with bad castings smoothed out.

Getting to 100 kph with a DR177 is actually quite trivial, even with a 20/20 carb. On that note, your jetting is on the high end IMHO. The jetting of a late PX150 works well with a bigger main. Something like:

20/20 carb
140/BE5/112
45/140 pilot

A lot of people use a 21T clutch gear in place of the 20T (I'm assuming this is what you have in your PX125E), which will give it longer legs for a bit more top end. I use a 22T clutch, but I have the 24/24 carb and my DR is modified from stock as per my earlier response in this thread

I've been running a DR for 10 years and have had no issues with it. That's not to say they don't have defective bits that leave the factory, but I wouldn't say that's a blanket problem.

I will say on mine i have lapped the head, but really you should do that with any kit that has an aluminum head. I also use a very very thin layer of "ultra copper" RTV, of which the vast majority squishes out, I put in on there to just fill any tiny imperfections rather than provide for a total seal around the whole thing.