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1978 CX500 "The Grub", 1983 GL650I "Nimbus"
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Based on this thread, I've ordered some 2mm buna cord. I'll try it next time I find a perforated ACV.
 

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Discussion Starter · #723 · (Edited)
cutting the centre out is no longer an option when the material is thinned with age.

If you are confident of getting a seal at the outer edge though why not?

The couple of old ACVs I initially cut rings from weren't as thick as they once were. I couldn't really feel the cover screws compressing anything.

I also thought of using the new Chinese ones and this would work too but saved them for carbs they may be compatible with - if any. Or I'm just a cheapskate who couldn't bear to cut something I'd paid for.

I will likely do the same with my blue standard soon. It took grinding on the ACV plunger to get that one to stop being rich all of the time. This was trial and error and while improved doesn't seem quite right still - being rich on the bottom end still. Given their intended function I could never work out how a set of ACVs could make a bike run so badly. It should be further back in this thread but this bike was rendered nearly unridable by a set of Chinese ACVs.

I consider this a cost saving on top of avoiding issues.

We have a thickness on the buna material at 2 mm. Next time I'll get an ID measurement on the formed ring and see if there is a readily available O ring that could be used.

Having just measured a carb body I'll tentatively put this O ring size at 26 x 2 mm.

Further observations having just come back from doing the shopping.

EDIT - As well as the idle being better {normal} the bike is now happy to poodle through car parks just above idle in second gear. Previously it needed to remain in first at these speeds as it just wasn't happy at such low revs. It also needs less throttle to get moving off the line. It is simply better all round.
 

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Discussion Starter · #724 ·
I've hopefully just repaired the Finnbox. I'll likely test it on the white 500C tomorrow since that one is stock CDI.

I replaced the burned out diode, repaired the ground track on the board, resoldered a green wire that I think I cut dismantling the unit and rejoined the wire for the high speed stator coil back to the board as it appears to have blown the connection.I missed this before as it was under the wires. It became apparent when I moved the wires to replace the diode.

Wish me luck.
 

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Discussion Starter · #725 ·
Well .... it starts and runs but its behaviour suggests no advance is functioning.

Something else to try to figure out after checking with the timing light whether advance is the issue or not.

I just put the factory CDI box as I have to go and get some groceries.
 

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Discussion Starter · #726 ·
I've been pondering on this Finnbox. When I ran it in the bike today and found there was no advance I swapped the blue and white inputs and hit the start button. The motor kicked back = overadvanced for starting.

The advance circuits work.

It's not switching over to them.

I'll ponder further based on the prior ponderings.
 

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1978 CX500 "The Grub", 1983 GL650I "Nimbus"
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Sometimes, all we can do is ponder. :unsure:
 
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Discussion Starter · #730 ·
Thanks RR. I've skimmed that and will reread it at length and see if it offers a clue as to which component is responsible for switching low to high.

I think it may be the items numbered BT151 - 800R here. I'm not electro savvy but think they may be some type of switching transister. I could also be utterly wrong...

I probably am wrong. Google tells me it's a rectifier....

It's been known to happen.

Font Technology Screenshot Software Games


I need to read up on component functions.
 

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Discussion Starter · #732 ·
Thanks Bob. from the google listing it seems you are correct .... but I may be too.

Purple Rectangle Font Line Violet


I could be wrong but I think this may be the animal that switches high to low speed.

I'll need to trace the circuit board track, do more reading and likely pick more brains.

This stuff isn't my forte.
 

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'84 CX650E that is evolving into a GL500
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You may be right. Partially.
Transistors can be used for switching but the word "transitor" comes from transresistance which basically means that when you vary the voltage between the common terminal and the input terminal it causes the effective resistance between the output and common to vary (there's a lot more to it but that's the basic gist of how transistor amplifiers work).

An SCR looks a lot like a power transistor and both are semiconductor devices with 3 terminals but that's as far as the similarity goes. An SCR is strictly a switch and cannot be used as an amplifier.
 

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Discussion Starter · #734 ·
What I think I need to do is identify the components used on the board and read up on their functions but with my limited knowledge currently I don't see anything else on the board that could do the switching. This may just be a reflection of my ignorance but viewing the things as in the basic form of a mini switching relay it is the only component with more than two connections leading me to believe it to be responsible for switching.

Though .... on second thoughts - maybe this.

Circuit component Font Hardware programmer Electronic engineering Schematic


It has three legs, is a single component meaning it may control both sides of the ignition function. Any idea what the animal is called?
 
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