Modern Vespa

Hi All

I'm new to this forum and have a few questions about a DR177 bore up project that I'm just about to undertake (currently LML PX125)

I'll be using a BGM Big Box Sport and PWK28 with the 177 kit

1. Does anyone have the same or similar set up? If so, can you tell me the carb jetting and settings?

2. What is the recommended degree for timing?

3. It seems like the DR kit comes without a head gasket. Any pointers on this?

4. Any recommendations on porting?

Cheers

The DR does come without a gasket and that is how I and several others run ours.

Thanks for your response

So, are you saying that no gasket but, are you saying that a silicon sealant/gasket isn’t required at all?

I mean, the engine head, bolted directly to the cylinder will work fine?

That’s how I run mine.

I use copper spray head sealer on my top ends. DR heads and barrels are notoriously leaky. Lap them both a little bit before you install. You might be surprised how much variance there is.

The DR is a great intro-to-tuning top end, because it's cheap enough that when you blow it up, you won't feel too bad about it.

As to the PWK 28, you'll need to do a fair amount of porting to see the benefit of that change. Is your LML a reed or a rotary valve?

Honestly, you're better off just sticking with an SI 20/20, maybe a 24/24, with the DR. I built a Stella (LML 150) with a DR 177 and an SI 24/24 that got 14-15 HP a few years back. Eventually went to a big ol' reed block (VForce 4 reeds) and PWK 28, but didn't get that much more HP out of it.

I don't recall what sort of port timings the DR has, although I have some I could measure and estimate, but you'll want to make sure those are spot on, too. People have basically replicated Polini porting on a DR here, but it's a lot of work and at the end of the day, it's still a DR.

Its a reed valve

I've ordered a copper head gasket

I was aware (due to the price and the reviews I've read) that the DR kit is a budget kit, but its kind of a stepping stone to higher quality kits and I didn't wanna splash big cash until I get a good grip of the porting mods necessary for high spec tuning. Also, I'm not bad around the mechanics of a motorbike

The reason I wanna stick a PWK 28 in it, is coz basically I've got one (with the whole jet kit) knocking around. I assume that the 28 will work with correct jetting and barrel porting

I've got other bikes (non Vespa) that I've tuned to high performance with great success, but not at all suitable for zipping around town with the missus on the back, so I decided to get this 125 and give it a bit of a tune up (There are reasons I didn't go straight for a 200)

I've owned plenty of Vespas previously to moving to Japan some 20 years ago, but they were either stock or modified by the previous owner, so never got a chance to go elbows deep into one (however, my housemate was a Vespa nerd and got into mine as much as he possibly could)

Any advice on main and pilot jet sizing for my set up (177, BGM BB Sport)?

All advice on timing, porting and jetting (and any other NECESSARY mods) is very helpful and I appreciate your time

Thanks

Do a search for DR177 and squish, you don’t want to add a head gasket. Normally I’d be more helpful with links, this is my 4th attempt to get this much internet connection is horrid here today.

I'll maybe write up some more comprehensive thoughts on what you can do. Hold tight for later, but you're going to need a dremel with grinding bits and sanding drums

I did a detailed thread of my first serious porting project, Porting 101. It and the linked threads within it get into grinding the cases, cylinder, and piston for an LML with a DR.

First off, replace the stock reed with a fiberglass reed. You can cut out the bar and open it up to improve the flow significantly. These changes alone will get you over an HP right there.

Open up all the ports & windows, then you're looking for port timings of 185 ED / 124 TD / 31 BD. You'll have to raise the exhaust port about 5mm to make that happen, and if you raise the cylinder to get it 2mm above the piston peak, you'll have your 124 TD, but need to get the cylinder skimmed down or get your hands on a recessed head, e.g. from a BGM 177.

For the head, you want copper spray gasket. I use it on the base, too.

For ignition timing, 17 BTDC is what you're going to want. You may lose a tiny bit of power, and tThe kit's instructions say 18, but at higher RPM's, that seems to produce a tendency to seize in front of the exhaust port in my experience and kill the piston after or during long WOT runs.

Also, get a CHT. Trailtech makes a good, cheap one. It'll make jetting testing much easier, and also act as a warning system if things go awry, such as a head nut loosening and causing a head leak leading to a rear wheel lock seize at 60 MPH. Ask me how I know...

Finally, you have 2mm rings, so you're not going to get past 7,700 RPM's, which means you're gearing is going to be low, so you can get a little bit of a top end bump with a 22t clutch, like from 60-62 MPH up to like 65.

Good luck and keep us updated!

oh, yeah, and The Kyajet jetting tool. It's awesome for modeling planned jetting changes.

Thanks guys for this valuable help so far

The DR is in transit to me and enough at the moment for me to get prepped

If I Initially restrain from doing the porting mods, will the pwk28 choke out even with smaller jetting?

As and when I get underway, I’ll keep a log and try to update along the way and no doubt need more pointers

Cheers

The PWK will be too much carb and you won't get enough flow through it without the porting, which will make it damn near impossible to dial in.

On the LML, you're better off sticking with the (I assume) stock 20/20 and keeping the auto-lube. It will be plenty of carb for a bolted on top end and make life easier until you're ready to get more aggressive.

Right, so all of the necessary tools and Haynes manual/workshop service manual arrived in the post this week (ordered in August)

I've done as much research on the recommended threads of porting, reed valve and carb settings etc and feel confident to start attacking this project

I'm gonna attempt the PWK 28 carb (it previously worked fine on my KSR-80cc), but if it is a nightmare to dial in, I'll revert back to the stock carb and up-jet it til I have a chance to get at it properly with the grinders and try the PWK28 again


Still got a couple of things I can't find and will probably come across as a 'DUH!' kind of noobie things:

1. Is it possible to leave the engine as it is or is it better to drop the engine out, as I will be upgrading the sprocket gear and the top end?

2. I'm gonna port the reed valve and change to a performance reed. Can you recommend which reed would suit and if I the stock reed valve frame is sufficient?

If I can get any advice on these points in the mean time and I'm sure I'll have a few more as the project develops

Cheers

What intake did you purchase to fit the 28mm carburetor? Going from a 20mm to 28mm carburetor your doubling the intake area. 20mm = 314mm and 28mm = 615mm. The factory only has two reeds and barely has the same flow area as a 20mm carburetor. Before I bought a P200 motor I was looking at one of these. I planned on splitting the cases, porting everything cleaning it up and installing a MRP vforce intake.


https://www.mrp-racing.de/MRP-Reed-Valve-System-for-LML-engine-case-36mm-complete-set-with-VForce4-and-carb-rubber

Thanks, but that MRP set is way above what I was thinking

I was under the impression that I could adapt (chop out) the stock reed frame and fit a carbon/fiberglass racing reed

I've got a 28mm Polini intake manifold set and I understand that the flow for a 28mm is a large increase, however apart from it being a bit of a pain in a**e to get it tuned in, I'm confident it'll work without major porting. Im not looking to create Ducati performance, just give it enough grunt for me and the missus to paddle round town and I'm not brave enough to have the same argument with her about who needs to loose the extra kilos AGAIN

Back to question 1. Will I need to drop the engine out completely to remove the clutch, to upgrade the sprocket gear (I know its better to ask that waste a load of time and effort)

Thanks

If you’re just changing the gear on the clutch no need to pull the motor. Just remove the clutch. If you want to change the primary gear that interacts with the clutch you will need to split the cases.

Saying I stick with the 20/20 (for the mean time), with the DR 177 kit and BB Sport, what would you say that the carb jetting will be?

Vespa parts aren't freely available here so will have to order direct from abroad, so would like to get near enough the exact jets straight off the bat

Thanks

You can try that 28mm carb, but more carb then needed. Can you even get it to run right? Who knows.

20.20 with BOX exhaust. Get mains from 110-117. That cylinder is very old technology tbh.

PWK will jet in but won't be easy. Not worth moving away from autolube for something not really needed. 24/24 and a P200 carb box/pump would be a better option.

Nothing wrong with a DR kit when it has a BGM head and a GS piston. Bolted on they go ok but feel quicker than they actually are. You'll barely break the speed limit, even in Japan!