ET4 Evaporative Canister Delete
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Addicted
2010 S50 Modified "Punkin"; 2003 ET4 150 "ISO"
Joined: 18 Feb 2017
Posts: 536
Location: Deepinnaharta, Texas
Fri Oct 09, 2020 5:47 pm quote
Greetings:

Even with a brand-new Keihin carb, ISO was hard to tune. Startup has always been prompt, but reluctant to take throttle before fully warmed up. A bit of surging at steady part-throttle opening was another symptom. Idle mixture screw needed to be 3.5 or more turns out and idle speed adjusted to 2000 RPM or there would be stumbles. All pointed to a vacuum leak, which did not manifest itself when spraying brake fluid in all the usual suspect places.

I had sort of resolved to keep it "Stock", but enough is ENOUGH! Set to work deleting the evap recapture system, taking care to keep everything intact in case of a need for reversal. Turns out there was a vacuum leak, in an inaccessible place. See pics.

Idle speed now steady at 1800, mixture screw only 1.5 turns out. Will report again after first full-cold start.

EvapDeleteComponents.jpg
The parts removed, fasteners retained.

EvapVacLeak.jpg
Cracked 20 year-old lines letting extra air into manifold port?

EvapDeleteCompletion.jpg
Cleaned-up and lightened, lines neatly routed to lower frame.

Hooked
lml 2t 150 with sidecar, Vespa ET4 150cc
Joined: 21 Jan 2018
Posts: 284
Location: Wales
Sat Oct 10, 2020 2:25 am quote
Wow lot more restrictive than my ET4 here in the U.K. with evap system.
Addicted
2010 S50 Modified "Punkin"; 2003 ET4 150 "ISO"
Joined: 18 Feb 2017
Posts: 536
Location: Deepinnaharta, Texas
Sat Oct 10, 2020 4:46 am quote
Smog Police
Greetings:

How different, Graham?
Hooked
lml 2t 150 with sidecar, Vespa ET4 150cc
Joined: 21 Jan 2018
Posts: 284
Location: Wales
Sat Oct 10, 2020 8:29 am quote
Wheelman-111 wrote:
Greetings:

How different, Graham?
On my two ET4's from around 2000 they have what's called the sas system. None of the system you have with the charcoal canister etc. I will try and find a diagram of it and post.
Hooked
lml 2t 150 with sidecar, Vespa ET4 150cc
Joined: 21 Jan 2018
Posts: 284
Location: Wales
Sat Oct 10, 2020 8:40 am quote
Pipe 8 comes out of the head exhaust side part 14 goes to the air filter with the other bits in between.

I copied and pasted this below from another forum

The Secondary Air System (SAS) has been developed to
reduce carbon oxide and unburnt hydrocarbon emissions in
vehicles that are not equipped with a lambda sensor. Natural
air (which is rich in oxygen) is channelled into the exhaust
stream to trigger a post-combustion process that raises the
temperature of the exhaust gasses for a quick light-off of the
catalyst.
The secondary air system is especially useful when the
engine is idling and during warm-up, as the catalyst alone is
not capable of triggering post-combustion under these
operating conditions.
DESCRIPTION OF THE SYSTEM

The secondary air system operates on pressure fluctuation
in the exhaust system. During depression stages, the
exhaust takes in oxygen-rich air from the secondary air
system so unburnt gasses in the exhaust stream can
complete the combustion.
During overpressure stages, the secondary air reed valve
cuts air supply to prevent backflow.
On 4-stroke engines, the reed valve is equipped with a cut-
off device that shuts down additional air during cut-off
stages, as exceedingly lean exhaust gasses would lead to
exhaust blowing, resulting in exhaust valve and catalytic
converter damage.

C__Data_Users_DefApps_AppData_INTERNETEXPLORER_Temp_Saved Images_Secondary-air-box-VESPA-VESPA-SCOOTER-150-ET4-Other-year-Vespa-ET4-150-Leader-45.png

Addicted
2010 S50 Modified "Punkin"; 2003 ET4 150 "ISO"
Joined: 18 Feb 2017
Posts: 536
Location: Deepinnaharta, Texas
Sat Oct 10, 2020 12:27 pm quote
Greetings:

Whoa! Interestingly different approaches to the emissions issue. AFAIK no Catalytic Convertor on the U.S. Models, certainly none in my Sito Pipe.

I'm pretty sure that cracked hose or the loose-fitting rollover valve was admitting air. Kit deleted, the idle is remarkably smoother, without needing to back out the mixture screw like 4 turns!

Idle starts to stumble only when Mixture screw is turned in to less than 1/2 turn out, suggesting the pilot is rich. Testing throttle response, it seems 1-1/4 turn is all it needs, but richening further changes nothing. Still has a bit of a bobble if the throttle is opened quickly. The accelerator pump is working correctly. I had a 38 "Short" Pilot, and this afternoon swapped it for a Keihin 38 standard length. It's flush with the tower when screwed in. The other was sunk in 3mm.

I'm not seeing much difference with the new long jet regarding the throttle-stab hesitation, but runs acceptably. I may try to see if I can find a #36 pilot to split the difference - Stock was 34.

KeihinLong_Short.jpg

Addicted
2010 S50 Modified "Punkin"; 2003 ET4 150 "ISO"
Joined: 18 Feb 2017
Posts: 536
Location: Deepinnaharta, Texas
Mon Oct 12, 2020 8:19 pm quote
Strange Startup Behavior
Greetings:

This is mostly for my own future interest, since nobody else seems to care...

After deletion of the Evap Recovery system, the effects of a huge but imperfect vacuum reservoir were apparent:
1. Idle speed became much more consistent, even at lower (1800RPM) revs.
2. Balky behavior with the "Short" 38 Pilot was apparently completely resolved with the K38 Long Pilot.
3. Startup from cold previously resulted in idle at ~3000 RPM, the same as my untouched S50/78cc scooter. The 50 keeps a fast idle for about a minute before settling to its 1800 RPM idle speed. By contrast the 150 would only fast-idle for about 15 seconds before resuming a stumbling, inconsistent idle with the mixture turned to 3-4 turns out. Very fussy to take throttle until fully warm.
4. Now it starts easily, but idle remains low, ~1550RPM until it warms. It's as if the bystarter is having no effect. Once warm settles at around 1900.
5. I tried to Chill the bystarter, literally, with an ice cube, without much effect. Still went to about 1950 briefly, then hung around 1550 until warm.
6. Balky throttle response and lean "hangup" is gone! Takes throttle enthusiastically and returns to idle with no delay.

I Believe the EVAP system was admitting air. Deletion has cleaned up the irregular inconsistent idle. Installing the K38 Long pilot improved throttle response significantly. But I can't figure out why the idle on Cold Start remains so low. Nevertheless, I can now ride off without fussy throttle, so happy for now.

Thoughts and comments welcome.
Enthusiast
Derbi Boulevard 125 4t
Joined: 05 Feb 2020
Posts: 72
Location: Lithuania
Tue Oct 13, 2020 1:25 am quote
Hi,

try disabling bystarter circuit (use tape between carb body and bystarter bracket to block bystarter passages ) and you will see that actually it has effect on idle after startup, but it is not huge. When outside air is warm, bystarter ads ~200 RPM to idle and when it is cold i get maybe 400RPM increase. I noticed bystarter works way differently on 2T and 4T: on 4T RPM increase is not so big and it shuts off very quickly compared to 2T.
Addicted
2010 S50 Modified "Punkin"; 2003 ET4 150 "ISO"
Joined: 18 Feb 2017
Posts: 536
Location: Deepinnaharta, Texas
Tue Oct 13, 2020 4:33 am quote
Greetings:

Two things remain a mystery:
1. The HUGE increase in idle speed before removing the canister, etc, from the 150. Now not so much...
2. The 50 - also a 4-stroke - holds fast idle for at least a minute, even in hot So. Texas weather.
Enthusiast
Derbi Boulevard 125 4t
Joined: 05 Feb 2020
Posts: 72
Location: Lithuania
Tue Oct 13, 2020 9:29 pm quote
I think it is due to too little air is passed to bystarter without canister.
My scooter never had canister and never had high idle when bystarter is on. I have noticed that i can get high idle with bystarter removed and using my finger sticked into bystarter bracket to dose air/fuel.
You could try enlarging air passage to bystarter, but i am not sure if it is worth the effort.
Addicted
2010 S50 Modified "Punkin"; 2003 ET4 150 "ISO"
Joined: 18 Feb 2017
Posts: 536
Location: Deepinnaharta, Texas
Wed Oct 14, 2020 4:33 am quote
Greetings:

Thanks Isdee! I'm still not sure - other than a large vacuum "reservoir" - how the presence of the canister affects airflow on cold start so much, but your observations would appear to be correct.
Addicted
2010 S50 Modified "Punkin"; 2003 ET4 150 "ISO"
Joined: 18 Feb 2017
Posts: 536
Location: Deepinnaharta, Texas
Wed Oct 14, 2020 8:16 am quote
Greetings:

I thought I was clever in attempting to swap my Walbro bystarter into the new Keihin carb, but no dice. The sizes of the sealing surfaces are too different.

SO, I'm wondering if I should try to connect the small-bore line from the carburetor port under the float bowl to vacuum via a T-fitting. Looking over the discarded parts, it appears that the carb port was under vacuum(?) before. Will report results if/when I try it.
Addicted
2010 S50 Modified "Punkin"; 2003 ET4 150 "ISO"
Joined: 18 Feb 2017
Posts: 536
Location: Deepinnaharta, Texas
Sat Oct 24, 2020 8:32 am quote
Upshot? HEAT!
Greetings:

So, forget about the little vent line under the diaphragm dome. It's just a vent and was connected to vac only for emissions capture reasons.

The first half-decent cold(-ish) front finally descended into South Texas last night. Rarely gets super-cold here but there was a nip in the air outside, and my garage temperature, thoughtfully extra-warmed with a gas water heater, was below 85 degrees for the first time since March.

Fired up the ET4, now with semi-Modern Keihin CVK. Instead of a 1550 RPM idle, it settled at around 2500, stayed there for about 40 seconds before dropping to a steady 1890, at which I had set it. Apparently the Keihin bystarter thinks the engine needs NO enrichening at temps above 80, and provides none. Ran sweetly all the way through my morning errands.

In fact, all my scooters are running about as well as I deserve right now. Life is good.

F7Garage.jpg
This was the 7th Incarnation of Honda SA 50 with a Fabrizi 79 cc kit, pipe and Polini 24mm flatslide. Over 70 MPH. Ms. Wheel-person disliked the Drama and had me tone it down .

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