SOHC.co.uk Forums > SOHC Singles & Twins
CB200 carb issues
Johnwebley:
after much pondering,playing,testing
Ihave come to the conclusion ,it an ignition issue,
all my other bikes have electronic ignition,this still has damn points,one set and two lobes on the cam,rub at half engine speed.
set the gap at the lower end of the range,massive improvement,
need an electrical engineer to explain how the gap/dwell etc works with a twin plug coil.
K2-K6:
Dwell is the overall descriptor for the amount of time the points are closed, which is filling the coils with energy.
The "time" element is what the coils see as it's just the amount of time it takes to replenish that coil at that resistance, with the volts available.
Dwell is expressed in angle/degrees rotation of cam, setting the points gives a specific angle of geometry that the points are closed for.
Now it gets more interesting as when that angle is set, then when revs go up the angle remains the same but with time now shorter the faster you go. Meaning the coils fill less, because they only "see" time connected to supply.
Closing points gap makes dwell too long technically, but lengthens the time available to fill the coil, at the same rpm.
Good electronic system can just control the time only, and regardless of rpm. So coil saturation is constant from low to high.
If you close the points gap to minimum and set plugs also to absolute minimum spec gap, then it should have the best performing spark output for that system.
K2-K6:
It can be seen also a different result by use of different coil primary resistance to change characteristics, usually to the detrimental though.
If our systems use 5 Ohms resistance it requires a longer time to fill than a 3 Ohms coil. Putting a 3 Ohms coil into a points system may have advantages at constant high rpm (as the dwell time shortens it can still meet the fill requirements) but at constant low speed the coil is now reaching saturation and then some, causing too much draw and potentially overheating the coil.
So you're stuck with aggregated performance over the rpm range in reality, works OK usually though.
Full electronic in concisely controlling the "dwell" characteristics in fixed time only can make use of whatever their system's designer specifically incorporates.
As example;- a V8 with single coil and firing 4 times a revolution can use a 1.5 Ohms coil with attendant dwell characteristic provided by the electronic switching to help with fill and replenish cycle that are overall shorter to fit in with that firing demand.
Bryanj:
Works exactly same as a single output coil, on a single output one end of the secondary is grounded the other to the plug, on a twin both ends go to plugs
Johnwebley:
thank you gentlemen,
it is a new coil listed for the CB200,
using 25thou plug gap,
a great improvement on before,
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version