Honda Spree and Elite 50 Forums

OEM bystarters have not been available for years for many scooter models on this board.

Aftermarket bystarters for price/availability reasons are becoming popular replacements.

With the increased popularity have been new questions and requests for operational parameters.
Some examples:

• What are the cold/hot measurements for my scooter?
  How far should the bystarter extend?
  How long does it take to extend?
  My scooter runs rich for 5 minutes before the bystarter closes. Is that normal?
  When taken out of the carb, the bystarter extends, but when installed there is little change from cold to hot. What could the issue be?
  How much power should the bystarter draw?

For OEM bystarters, a cold measurement and a hot measurement of approximately >= 1/8" extension was good.
For OEM transition from cold to hot - around 2 minutes.

How do aftermarket bystarters perform? Why do they perform as they do. Let's find out.

Aftermarket Bystarter used in this test
An example aftermarket bystarter was ordered from a US Seller. The seller states compatiblity with Spree/Aero/Elite 50 models. Also that the seller has sold several hundred with good feedback. So with local/fast ship good reputation and a price of $5.90 a part is in hand.
Bystarter Extension Comparison
This is a comparison between OEM and an example aftermarket bystarter.

Test setup:

• Bystarter is powered by a DC Bench supply.
  The bystarter is used as it would be in a Honda Spree -
  Powered by 12v nominal supply
  5 ohms series resistance with the bystarter
  
  A dial indicator is used to measure extension
  Photos are taken to capture the extension at 30 second intervals

Test Results

What is the minimum required bystarter extension to close the valve?
We have a picture on the 'wiki which details this - it is about 0.10".

Discussion
Putting the test results together with the required travel to close the bystarter circuit, we can determine 'time to close' for various bystarter cold lengths.

For the purposes of fastest time of close, the ideal cold length setting is when:

• The bystarter valve lengh is set exactly at start of close
  As the bystarter cold length shortens from the above point, the time to close gets longer up until the bystarter circuit never closes.

The graph markup below demonstrates the 'ideal' case as well as the extreme limit - where extension starts so low, the bystarter circuit never closes.

-- Graph markup notes

• The lowest horizontal blue line denotes the 'start of' bystarter valve close
  The highest horizontal blue line denotes the 'complete close of bystarter' valve.

Edit: replaced picture

mousewheels.. I've found a number of Honda scooters that have a factory resistor installed in series with the bystarter as in your example. I've assumed that the purpose of the resistor is to slow down the time it takes the bystarter to close. Is this true or is it for another purpose?

vintagegarage wrote:I've found a number of Honda scooters that have a factory resistor installed in series with the bystarter as in your example. I've assumed that the purpose of the resistor is to slow down the time it takes the bystarter to close. Is this true or is it for another purpose?

Yes - that is my belief too.

Honda did tweak the resistor, but only on the TG50 Gyro (3.5 ohms) and 1994-01 Elite SA50 (6.7 ohms)
The 83-85 Aero NB50 has *no resistor*
1985-87 Aero 50 I have found no spec, but have removed a 5 ohm resistor from the frame
1984 Gyro NN50 is also not spec'd, but a friend and I used 5 ohms as a default with no issues.

While working on my new NN50 gyro today and debugging why the alternator isn't working, I stumbled on the spec for the NN50 bystarter resistor on page 15-6 in the alternator section of the NN50 Service Manual. It is specified as 5 ohms.

If I am reading it correctly, this NN50 Gyro Bystarter resistor says 5 Watts and 5 Ohms