177 / Big Box PWK28 Carb setting
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Member
LML Star Deluxe 125 (177)
Joined: 08 Aug 2020
Posts: 10
Location: Japan
Sat Aug 08, 2020 2:42 am quote
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
Molto Verboso
2007 Stella 225
Joined: 02 Nov 2019
Posts: 1676
Location: Rochester, Minnesota
Sun Aug 09, 2020 3:13 am quote
The DR does come without a gasket and that is how I and several others run ours.
Member
LML Star Deluxe 125 (177)
Joined: 08 Aug 2020
Posts: 10
Location: Japan
Sun Aug 09, 2020 3:30 am quote
Thanks for your response

So, are you saying that no gasket but, are you saying that a silicon sealant/gasket isnít required at all?

I mean, the engine head, bolted directly to the cylinder will work fine?
Molto Verboso
2007 Stella 225
Joined: 02 Nov 2019
Posts: 1676
Location: Rochester, Minnesota
Sun Aug 09, 2020 4:57 am quote
Star177 wrote:
Thanks for your response

So, are you saying that no gasket but, are you saying that a silicon sealant/gasket isnít required at all?

I mean, the engine head, bolted directly to the cylinder will work fine?
Thatís how I run mine.
Ossessionato
76 Sprint V, 63 GL, 62 VBB, 05 Stella
Joined: 16 Jun 2011
Posts: 3188
Location: Nashville
Sun Aug 09, 2020 9:44 am quote
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.
Member
LML Star Deluxe 125 (177)
Joined: 08 Aug 2020
Posts: 10
Location: Japan
Mon Aug 10, 2020 8:24 pm quote
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
Molto Verboso
2007 Stella 225
Joined: 02 Nov 2019
Posts: 1676
Location: Rochester, Minnesota
Tue Aug 11, 2020 5:11 am quote
Do a search for DR177 and squish, you donít want to add a head gasket. Normally Iíd be more helpful with links, this is my 4th attempt to get this much internet connection is horrid here today.
Ossessionato
76 Sprint V, 63 GL, 62 VBB, 05 Stella
Joined: 16 Jun 2011
Posts: 3188
Location: Nashville
Tue Aug 11, 2020 6:30 am quote
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!
Molto Verboso
2007 Stella 225
Joined: 02 Nov 2019
Posts: 1676
Location: Rochester, Minnesota
Tue Aug 11, 2020 7:10 am quote
The PWK, jetting, and me
Ossessionato
76 Sprint V, 63 GL, 62 VBB, 05 Stella
Joined: 16 Jun 2011
Posts: 3188
Location: Nashville
Tue Aug 11, 2020 8:02 am quote
oh, yeah, and The Kyajet jetting tool. It's awesome for modeling planned jetting changes.
Member
LML Star Deluxe 125 (177)
Joined: 08 Aug 2020
Posts: 10
Location: Japan
Tue Aug 11, 2020 2:12 pm quote
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, Iíll keep a log and try to update along the way and no doubt need more pointers

Cheers
Ossessionato
76 Sprint V, 63 GL, 62 VBB, 05 Stella
Joined: 16 Jun 2011
Posts: 3188
Location: Nashville
Tue Aug 11, 2020 2:41 pm quote
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.
Member
LML Star Deluxe 125 (177)
Joined: 08 Aug 2020
Posts: 10
Location: Japan
Mon Feb 15, 2021 9:22 pm quote
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
Molto Verboso
2007 Stella 225
Joined: 02 Nov 2019
Posts: 1676
Location: Rochester, Minnesota
Tue Feb 16, 2021 3:40 am quote
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
Member
LML Star Deluxe 125 (177)
Joined: 08 Aug 2020
Posts: 10
Location: Japan
Wed Feb 17, 2021 8:52 pm quote
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
Christopher_55934 wrote:
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
Addicted
GL, PK, PE200 with hack, Sears Rust Badge
Joined: 24 Apr 2012
Posts: 995
Location: Deep in the heart of Texas
Wed Feb 17, 2021 10:06 pm quote
If youíre 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.
Member
LML Star Deluxe 125 (177)
Joined: 08 Aug 2020
Posts: 10
Location: Japan
Wed Feb 17, 2021 11:19 pm quote
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
chandlerman wrote:
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.
Molto Verboso
Joined: 03 Nov 2011
Posts: 1226
Location: Racing Capital of the World
Thu Feb 18, 2021 2:38 am quote
Star177 wrote:
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
chandlerman wrote:
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.
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.
Jet Eye Master
PX221 MHR, O tuned PX200, PX125 and some motorbikes
Joined: 14 Jun 2017
Posts: 2755
Location: London UK
Fri Feb 19, 2021 2:47 am quote
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!
Member
LML Star Deluxe 125 (177)
Joined: 08 Aug 2020
Posts: 10
Location: Japan
Tue May 11, 2021 12:38 am quote
Right so.........

Back again after the 177 upgrade and went for an Si 24/24 and BGM Sport Exhaust. Upgraded the Spark Plug, set the ignition timing to 18-19 BTDC.
It was going fine for a month or so, but recently its started misfiring, even at low throttle

New NGK spark plug cap/cable, and checked engine ignition timing position (flywheel off), so I'm wondering if its a fuel mixture problem, but why would this happen now??

I went for the 160 38/120 118 stack when I changed to the 24/24 and with the air filter and box off, the fuel screw 8 turns out(!!!!!!) and it WAS running okish (not bogging on accelerator from low revs)

Can anyone gimme advice on my jetting stack, if they are running similar to my set up please?

Also, Ive read a lot of conflicting info about the fuel mix screw
Some are saying anti clock wise for richening and some the opposite on the Si. This, I can't get my head around, so can someone clear this up for me?

I'm not familiar with Si carbs, most of my experience has been with TMR/FCR (Flat slide carbs) and the general rule is that, IF the mixture screw is before the slide = clock wise is rich, but if the crew is after the slide, anticlock wise is rich.


Ps. I don't really want to drill my air box or filter if possible, if I'm running rich Or have I got air leak issues...........this is very confusing!!!!!!

Also, I found out that its rotary valve, not reed valve. Does anyone want an unused carbon reed valve? hahahahaha

Thanks
Hooked
2005 Stella 2T
Joined: 14 Jun 2020
Posts: 124
Location: MA
Tue May 11, 2021 7:37 am quote
A lot to unpack here but I'll give it a shot.

1. For mixture screw, anticlockwise (out) is richer, clockwise (in) is leaner. Eight turns out is nuts. Should be 2 -3 turns out.

2. With mixture screw so rich, could be as simple as a fouled spark plug. Can you post a photo? That is likely to be instructive.

3. You did not say what mixer tube (middle part of main stack) you are using. Hard to give jetting advice without knowing that piece.

4. Your 38/120 idle jet is near the middle of the rich-to-lean spectrum. Might be a little lean, but by itself doesn't explain 8 turns out on mixture screw.

5. Why are you running without air filter and carb box? Again, by itself probably doesn't explain 8 turns out on mixture screw, but could be a contributing factor.
Member
LML Star Deluxe 125 (177)
Joined: 08 Aug 2020
Posts: 10
Location: Japan
Tue May 11, 2021 7:20 pm quote
Let me just clear this up

The 24/24 that I bought was boxed and unused and advertised as p200x/e non autolube (I've been premixing oil/fuel @ 2%).
When I pulled the stack, only the main was sized at 105, but none of the rest of the stack was marked with sizes, leading me to believe that the seller had replaced it for his own benefit, so i ordered what would be the stock px200 stack 160/BE03/118 and idle 38/120

The PX200 stack/idle wouldn't start at all so I chopped and changed with the idle and jet stack that came in the 24/24 I had bought. Image, stack ON LEFT side. It's difficult to say what it consists of but it looks to me like a 160/BE02-03/118. I used a tapered needle to compare hole size with the stamped BE03 on the right. The mixer tube holes on the left (which I'm using), are slightly smaller. I couldn't measure the air corrector accurately, but under visual inspection, look to be the same

I was only running with the air filter/box off as I was chopping and changing the stack, to get the right combo. I usually run with air filter and box

Ah, I didn't replace the filter, so I'm still running the 20/20 undrilled filter. Could this be a factor???

Also, I think that you are saying that I'm running too lean? I thought bogging and misfiring on acceleration are caused by over rich mixtures, No?


Using stack on the left


NEW Spark Plug after 30 mins running time


Im using right side (Unknown) air corrector. Looks like 160?


20/20 undrilled filter

Hooked
2005 Stella 2T
Joined: 14 Jun 2020
Posts: 124
Location: MA
Wed May 12, 2021 6:48 am quote
Thirty minutes may or may not be enough running time for a valid test but, as it stands, that plug reads very lean. That plus the fact you felt the need to go 8 turns out on the mixture screw suggests an air leak. My advice is to address that before going any further.

Nonetheless, I will add that I think a 118 main jet is going to be way too big for a rotary valve motor unless you have modified the timing. As an example, the Malossi 177 kit I am most familiar with only calls for a 105 main jet with an uncut crankshaft. Did the DR 177 kit come with any instructions on this?

Once you sort the probable air leak, I would try an AC140/BE5/MJ105 main stack, assuming youíre still running stock intake timing and the kit's instructions do not say otherwise. Keep the 38/120 idle jet for now.

That mystery mixer tube appears to be the equivalent of either a BE1 (one step richer than your BE3) or a BE5 (one step richer than a BE1). A BE1 might actually be OK, but it would be nice to know exactly what youíre dealing with.
Molto Verboso
2007 Stella 225
Joined: 02 Nov 2019
Posts: 1676
Location: Rochester, Minnesota
Thu May 13, 2021 2:49 am quote
Star177 wrote:
Let me just clear this up

The 24/24 that I bought was boxed and unused and advertised as p200x/e non autolube (I've been premixing oil/fuel @ 2%).
When I pulled the stack, only the main was sized at 105, but none of the rest of the stack was marked with sizes, leading me to believe that the seller had replaced it for his own benefit, so i ordered what would be the stock px200 stack 160/BE03/118 and idle 38/120

The PX200 stack/idle wouldn't start at all so I chopped and changed with the idle and jet stack that came in the 24/24 I had bought. Image, stack ON LEFT side. It's difficult to say what it consists of but it looks to me like a 160/BE02-03/118. I used a tapered needle to compare hole size with the stamped BE03 on the right. The mixer tube holes on the left (which I'm using), are slightly smaller. I couldn't measure the air corrector accurately, but under visual inspection, look to be the same

I was only running with the air filter/box off as I was chopping and changing the stack, to get the right combo. I usually run with air filter and box

Ah, I didn't replace the filter, so I'm still running the 20/20 undrilled filter. Could this be a factor???

Also, I think that you are saying that I'm running too lean? I thought bogging and misfiring on acceleration are caused by over rich mixtures, No?
In reference to that spark plug it looks very lean, the bogging could be the motor starting to seize up. Plug porcelain should be a chocolate color not white. Black soot is better then white on a two stroke. Lean is to little fuel which burns hotter and less oil for lubricant. I'd be curious if you activate the choke (AKA enrichment circuit) while riding if it actual bogs down from to much fuel or runs normally or better even.

Also don't think of it as just running rich or lean overall, think about each throttle position. You can be lean at idle, rich midrange, perfect wide open throttle. When tuning you usually mark throttle positions at 1/4, 1/2, 3/4 and WOT, then tune each stage.

Also each circuit is additive, so if your lean at idle that carries over to less fuel midrange and less fuel WOT.
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