I've Got A Hunch...

az_slynch · Post by **az_slynch** » Thu Aug 29, 2013 9:43 pm

Recently picked up an '81 Honda Passport as a project to further broaden my queue of projects. Besides, I'm still in OE Zuma Parts Limbo/OE Helix Parts Limbo/OE Vespa GT Parts Limbo and I figured I'd start working on the Passport in the interim. One of the things I considered was swapping out the original 70cc 3spd semiauto engine for a Lifan 125 4spd semiauto engine. 12V electrics and a CDI ignition would be a nice upgrade too.

So, in looking at the Lifan motors, I noticed some similarities with the 4T Stella top end. After poking at some online business journals, I noted that back in 2006, Lifan was looking to buy into LML (Lohia Machinery Limited) to get a piece of the Indian market. Maybe it happened and they did some tech transfer?

I need to do a bit more research, but the bore/stroke of the 4T Stella is identical to the Lifan 150 (crank is most likely different). The cam and cam chain orientation is identical to the Lifan and from parts book views, even the the chain guides look similar.

If the top end "is" Lifan or similar enough, this could definitely move the performance possibilities on the 4T Stella up, as there are larger bores than 170cc and 4V cylinder heads out there. Here's to hopin'!

Drum Pro · Post by **Drum Pro** » Thu Aug 29, 2013 9:57 pm

If you could see me now I'm doing my "Happy dance". It's a step in the right direction for the 4T.

jimmbomb · Post by **jimmbomb** » Fri Aug 30, 2013 1:14 pm

Keep at it,az.....if your research gives us parts for a 200+ 4t stella..then im selling my p200 and getting another stella..
Im tired of the dim headlight and weak brake. .but I love the get up and go.
Keep at it.. find us options! Thanks.

Rusty J · Post by **Rusty J** » Sat Aug 31, 2013 9:00 am

No kidding?!

171cc (or bigger) with a 4V head might be possible with bolt-on parts? That's a game-changer, if there's a clutch that can handle the increased torque.

viney266 · Post by **viney266** » Sat Aug 31, 2013 2:44 pm

is the 4t clutch the same a 2T? If so, then that is covered. I put an SIP clutch in my 2T stella and it works GREAT...not cheap, but worth it.

az_slynch · Post by **az_slynch** » Sat Aug 31, 2013 4:53 pm

viney266 wrote:is the 4t clutch the same a 2T? If so, then that is covered. I put an SIP clutch in my 2T stella and it works GREAT...not cheap, but worth it.

The 4T Stella has a 7-spring clutch like a P200. The difference is in the drive gear, which is a 21T like the 2T Stella. SIP makes a 22T gear for the 7-spring clutches that would give a small (4%-ish) upgear across all four gears, presuming that the cush drive is a 68T gear. Still need to tear down a motor and do tooth counts for all gears one of these days. Collecting gaskets from Genuine has been like pulling teeth so far (buying through my dealer), so I'm holding off until I have everything needed to rebuild afterwards.

Rusty J · Post by **Rusty J** » Sun Sep 01, 2013 2:01 am

One point about the clutch: The 4T engine has similar average torque compared to the 2T engine, but the peak torque is about twice that of the 2T. It has to be, as the same average torque is concentrated in a once-every-two-revolution power stroke instead of distributed evenly between once-per-revolution power strokes.

So we need a clutch rated (in 2T engine use) for about twice the nominal torque of the 4T engine, or it'll slip during the power stroke.

I may be underestimating the effectiveness of the cush drive, however. The 200cc version apparently uses a redesigned clutch; if it's interchangeable, that may be the way to go.

viney266 · Post by **viney266** » Sun Sep 01, 2013 1:52 pm

That is what I have i my 2t. The SIP "house brand" clutch. Its a cosa set up they they make. VERY tough and works like a charm too. It was right around 200 bucks for the whole thing,but worth every penny IMO

viney266 · Post by **viney266** » Sun Sep 01, 2013 1:58 pm

That is what I have i my 2t. The SIP "house brand" clutch. Its a cosa set up they they make. VERY tough and works like a charm too. It was right around 200 bucks for the whole thing,but worth every penny IMO

slotrod65 · Post by **slotrod65** » Thu Oct 03, 2013 1:24 pm

This is great news! I will be following this thread for more....

Stilts · Post by **Stilts** » Thu Oct 03, 2013 3:25 pm

Yes, yes, and oh, YES.

Keep that great eye of yours looking, az_slynch!

slotrod65 · Post by **slotrod65** » Fri Mar 21, 2014 1:37 am

Any update on this az-slynch?

az_slynch · Post by **az_slynch** » Mon Mar 24, 2014 11:01 pm

My colleague with the injured 4T (collapsed inner valve spring) has refused any work on it until his modern-Vespa-of-miscellaneous-and-sundry-bits is reliable as well as rideable and there is available garage space to take his 4T over and drop the motor. I have all the gaskets, just want to tear it down and get the spring specifications so I can find performance springs for it (since he winds on it like it was a 2T).

My 4T is still in a box at my local dealer. Been waiting for a work performance bonus payout for about four months now so I can get it paid off and take it out of the carton.Tax refund should be coming soon too. I'll break it in, buy new top-end seals and then crack it open to see what's what.

BuddyRaton · Post by **BuddyRaton** » Tue Mar 25, 2014 2:40 am

viney266 wrote:That is what I have i my 2t. The SIP "house brand" clutch. Its a cosa set up they they make. VERY tough and works like a charm too. It was right around 200 bucks for the whole thing,but worth every penny IMO

I'm not a fan of the cosas. I had one asplode after 1,000 miles on CBR 2012. Yeah I ran the snot out of it but still. The MMW basket is much beefier.

slotrod65 · Post by **slotrod65** » Wed Mar 26, 2014 1:40 am

Thanks, I am very interested to hear what you find...

Neurotic-Hapi-Snak · Post by **Neurotic-Hapi-Snak** » Mon Jun 23, 2014 8:39 pm

So, any word on if Stella 2T/Vespa PX/P200 transmission parts fit in the 4T? The 4T, IMHO, needs an up gear and even stock has the torque to pull slightly taller gears.

az_slynch · Post by **az_slynch** » Mon Jun 23, 2014 9:37 pm

Neurotic-Hapi-Snak wrote:So, any word on if Stella 2T/Vespa PX/P200 transmission parts fit in the 4T? The 4T, IMHO, needs an up gear and even stock has the torque to pull slightly taller gears.

The gear stack is essentially the same as the 2T. If you want slightly taller gearing, you could try a 22T, 7-spring clutch gear. That would net you about 4% taller gearing across all four gears. Easiest upgrade.

Neurotic-Hapi-Snak · Post by **Neurotic-Hapi-Snak** » Tue Jun 24, 2014 6:55 am

az_slynch wrote:
Neurotic-Hapi-Snak wrote:So, any word on if Stella 2T/Vespa PX/P200 transmission parts fit in the 4T? The 4T, IMHO, needs an up gear and even stock has the torque to pull slightly taller gears.
The gear stack is essentially the same as the 2T. If you want slightly taller gearing, you could try a 22T, 7-spring clutch gear. That would net you about 4% taller gearing across all four gears. Easiest upgrade.

That's what I was thinking, a 22 tooth clutch gear with everything stock. Maybe the Malossi upgear kit or a custom gear stack if I ever put in the 165 kit.

Neurotic-Hapi-Snak · Post by **Neurotic-Hapi-Snak** » Wed Jun 25, 2014 6:59 am

So what size clutch basket does the Stella have? Isn't it 115mm like the P200E, not 108mm like the older PXs? I know it uses the newer PX EFL transmission. Also the Malossi upgear kit would be a 16% upgear on the EFL transmission with the 21T clutch/68T primary, not the 8% on the P200E with 23T clutch/65T primary.

SIP sells a DRT 23 tooth clutch gear that works with the 68 tooth primary. Maybe I should try that, it should be about an 8% upgear, correct?