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Honda OEM carb info collection
Posted: Mon Dec 23, 2013 6:38 pm
by mousewheels
Before the spring rush of carb questions, We will collect info members have captured in the past as well as new info. Then update the 'wiki as applicable.
--
Some info may be for fun, or to stimulate discussion First topic is one of those.
- Why did some carb bowls support two locations for the bystarter orifice?
- What would trigger Keihin to use one or the other?
- Do you have a carb bowl with the orfice installed in the lower casting location?
- Why did the SB50 move the bystarter orifice lower?
-- Fuel bowls and bystarter orifice placement --
Member lakehouse has been working on an Elite E (SB50) start&run issue. As part of troubleshooting, we got into a question. Is the fuel level in the carb bowl high enough to fill the auxiliary fuel bowl supplying the bystarter? Lakehouse reports a much different bystarter orifice location from models at mousewheels place. Here's photos and measurements:
1) Honda Express carb -- casting shows two possible locations for the bystarter orifice, on this carb, the higher one is used by Keihin.
- Honda_Express_Bystarter_Fuel_orifice_location_1.JPG (33.1 KiB) Viewed 11932 times
Bystarter location from bottom of bowl ~ 0.75"
- Honda_Express_Bystarter_Fuel_orifice_location_2.JPG (32.47 KiB) Viewed 11932 times
2) Honda Aero 50 carb (85-87 series) -- casting shows two possible locations for the bystarter orifice. Again, the upper location was chosen by Keihin.
- Honda_Aero_Bystarter_Fuel_Orifice_location_1.JPG (33.16 KiB) Viewed 11932 times
Bystarter location from bottom of bowl ~ 0.72"
- Honda_Aero_Bystarter_Fuel_Orifice_location_2.JPG (28.64 KiB) Viewed 11932 times
Honda Spree carb (unknown year) -- casting shows only one possible location
- Honda_Spree_Bystarter_orifice_location_1.JPG (37.6 KiB) Viewed 11932 times
Bystarter location from bottom of bowl - 0.55 + 0.10 step up = 0.65"(see pic above, there is a raised floor on the bystarter orifice side of bowl)
- Honda_Spree_Bystarter_orifice_location_2.JPG (33.98 KiB) Viewed 11932 times
Honda SB50 carb (member lakehouse provideds info) --
"Overall, the very inside bottom of the fuel bowl to the opening edge of the jet totals out to be 0.280". That's much different from the sister Spree bowl."
Also -- TODO: Check out 94-2001 Elite SA50...
Re: Honda OEM carb info collection
Posted: Mon Dec 23, 2013 6:47 pm
by mousewheels
-- Bystarter orifice size --
This is a small orifice and is a fuel metering orifice. A few have drilled out the orifice to un-plug, causing a too rich when cold issue.
An exact measurement is not yet made. However as a reference point a 0.010 wire will pass through, and useful to find a wire for cleaning.
wiki link
Re: Honda OEM carb info collection
Posted: Mon Dec 23, 2013 7:00 pm
by mousewheels
-- Dirty float seats
If the seat is irregular, a new float needle may still seep or leak. Here's pics showing dirty seats.
- Carbs_overview.jpg (161.19 KiB) Viewed 11926 times
Pic below illustrates the portion of contact between the float needle and seat
- Float_needle_and_seat_a.jpg (23.33 KiB) Viewed 11922 times
From left to right - these close ups match the carbs above:
- Float_seat_close_up_a.jpg (85.84 KiB) Viewed 11926 times
-- Resurfacing float seats
A popular method quoted is to use a Q-tip and polishing compound. Some use a sharpened wood dowel. What's working for you?
There is an aftermarket tool (note "Made in USA") tool being sold for Keihin carbs. I don't know that it fits our PA carbs, and at $100+ am not likely to 'buy to try'. Yet the idea sounds good. Anyone interested in making a seat reface tool? I'd pleased to pass clean seats to the microscope to present results here.
- Keihin_seat_cutter_2.JPG (59.14 KiB) Viewed 11925 times
Re: Honda OEM carb info collection
Posted: Tue Dec 24, 2013 11:27 am
by ped
thank you for posting this carb info. very helpful.
Re: Honda OEM carb info collection
Posted: Mon Dec 30, 2013 7:56 am
by mousewheels
ped wrote:thank you for posting this carb info. very helpful.
Thanks ped
Carb Body changes:
Early Honda Scooters have rounded venture top/bottom. Later models changed to a 'v' shaped section at bottom and flattened out the top.
For the Spree, this change occurred in the 1986 model. That change led me to look at throttle needle and emulsion tube part numbers to see if a change was made there. None required.
- Spree_Carb_Body_Change.jpg (55.05 KiB) Viewed 11875 times
Throttle Needle & Emulsion Tubes - Spree, Elite E
Part numbers varied over the years of Spree production and on to the similar Elite E. Note there were unique part numbers for 1984-86 restricted Sprees.
-- Part identification
It may be helpful to members (the ones with *boxes of mixed Spree carb parts*
) to collect identification information.
- Needles have unique numbers we can use to id them.
- Emulsion tubes have no markings, but may differ by location, size or number of air holes.
- Spree_Elite_E_Needle_Sets.JPG (43.21 KiB) Viewed 11875 times
Re: Honda OEM carb info collection
Posted: Mon Dec 30, 2013 8:57 am
by mousewheels
Aftermarket Jets
Main jets fitting Gurtner carbs also fit Keihin PA carbs. They are available in sizes to 118.
Finish is not as smooth as Keihin, but they are inexpensive. This Naraku set of a dozen (incrementing by '2' from 74 to 96) was just under $23 before shipping at
External link to racingplanetusa.com
- Gurtner_Jets_2_sm.jpg (76.18 KiB) Viewed 11864 times
Re: Honda OEM carb info collection
Posted: Thu Jan 16, 2014 8:32 am
by mousewheels
Bystarter clone comparison
Here is one more clone to compare. To allow direct comparison photo positioning was controlled.
Summary -
Neither clone is same as OEM
- Clone 1's fuel metering needle differs in length and taper.
- Clone 2 is too short when cold, and when hot extended only to about 0.40" at the air valve. Note 0.42" is the cold position for the OEM bystarter. Clone 2 will always be in the enrich state
-- Photos
Reference OEM bystarter: Aero 50
Clone 1 is from Wincycles. It is a couple years old, current model may be different
Clone 2 is unknown origin
- Bystarter_Compare_1..jpg (110.79 KiB) Viewed 11790 times
- Bystater_Compare_2.jpg (75.52 KiB) Viewed 11790 times
Re: Honda OEM carb info collection
Posted: Fri Feb 07, 2014 1:33 am
by mousewheels
Aftermarket carb rebuild kits
Buyer beware: Watch for components which differ from OEM
Kit on the left:
- Longer float needle and a float with a metal hinge.
- User may need to tweak the float level by bending a tab on the hinge
Kit on the right:
- Main jet is a mushroom head (incorrect part)
- Bowl gasket is incorrect
- Float valve is metal tipped, and with use will wear the softer carb body
Re: Honda OEM carb info collection
Posted: Sat Mar 15, 2014 7:41 am
by mousewheels
-- Bystarter closing - time lapse --
This is an AF16 bystarter connected to a 12v dc bench supply. It displays ~20x faster than actual speed, frames were taken 1 every 10 seconds.
-- Over travel
Normally, after hitting bottom, a spring driving the air valve takes up the extra extension. However in the photo sequence, the bystarter is not clamped down. Thus after the air valve hits bottom, the bystarter body is pushed out of the carb.
Re: Honda OEM carb info collection
Posted: Sat Mar 15, 2014 9:04 am
by Wheelman-111
Greetings:
All hail Mr. Mouse, and quite possibly the most comprehensive and helpful post EVER! Cool time lapse, too. You must really, really love these scooters and your brother enthusiasts. Wow!
I am speechless except for the following question: (Spoiler alert - JOKE!!)
You don't have a girlfriend, to you?
Sinceriously, awesome post Dawg. You're the best.
Re: Honda OEM carb info collection
Posted: Sat Mar 15, 2014 11:54 pm
by mousewheels
Thanks Wheelman!
I am speechless except for the following question: (Spoiler alert - JOKE!!)
You don't have a girlfriend, to you?
Mrs Mouse would stop saying 'cheese'
Re: Honda OEM carb info collection
Posted: Sun Mar 16, 2014 12:02 am
by mousewheels
Watching the bystarter makes a person wonder how expanding wax creates the long extension.
For example, a candle burning has wax level with the sides while burning, and only a slight depression once the wax cools.
-- Pic from our 'wiki' of a disassembled bystarter showing the actuator
- Bystarter_Actuator_assembly.jpg (37.99 KiB) Viewed 11677 times
-- Annotated Cutaway
- Bystarter_actuator.jpg (97.5 KiB) Viewed 11677 times
Re: Honda OEM carb info collection
Posted: Fri Mar 21, 2014 10:23 am
by GSX1400
Terrific topic!
In my favourites. Thanks for the research and all the typing.
Re: Honda OEM carb info collection
Posted: Wed Mar 26, 2014 8:40 am
by mousewheels
-- Clone bystarter seal --
OEM bystarters have no seal between the brass air valve and fuel needle. Many Clones do.
An issue may arise from the clone and it's seal. The seal may prevent the bystarter from fully closing. The leaves some of the air path flowing air *but* the fuel section is sealed. This may cause the engine to run lean or die when the bystarter warms up.
The photo below shows the OEM bystarter has a recess between the needle and air valve sides. The clone has a recess, but it's nearly filled by the rubber seal
- Bystarter_front_view.jpg (75.8 KiB) Viewed 11597 times
An issue with this clone is the rubber seal contacts the bystarter fuel pickup tube before the air valve is closed.
- Bystarter_Clone_with_seal.JPG (61.92 KiB) Viewed 11597 times
With the clone's seal removed, the air valve can be observed fully closed
- Bystarter_Clone_after_seal_removed.JPG (47.78 KiB) Viewed 11597 times
Re: Honda OEM carb info collection
Posted: Wed Mar 26, 2014 9:20 am
by GSX1400
That could explain a question or two I was asking...
http://www.hondaspree.net/phpBB3/viewto ... &start=120
Question :
When doing the air pressure test as per the Honda Shop Manual (uploaded here : many thanks for putting this online guys) when the engine is hot (bystarter completly closed), should it be air tight or what is an acceptable leak when doing the pressure test?