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Discussion Starter #1
any thoughts on why points on a 74 cb200 would open right at the F mark on one turn of the engine, but then, on the next engine revolution, they would open a bit before F?? this keeps happening. every other time the F mark meets the notch on the engine case, the points are dead on. do i need to fiddle with the turning the plate a bit more, or is there something more going on here?? i'm using a test light to determine when the points are opening...
 

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Sensei
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Sounds like the breaker cam (center of the advance unit) is worn on one lobe
 

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Sensei
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Would require making the "good" lobe match the bad one (precision grinding) ....Probably cheaper to just get a new(er) advance unit complete.................
 

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Discussion Starter #5
i had a feeling you might say that! just bought a spark advance unit off ebay...i'll give that a try. just out of curiosity...would the timing being 'off' like it would be in this case cause things like hanging idle and significant hesitation at 0-1/4 throttle?? these were problems that the previous owner described to me from when he had the bike running...
 

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Sensei
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That's more likely from "unbalanced" carb adjustments made to compensate for the timing error.... Fix (replace) the advance and then re-sync the carbs...
 

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Discussion Starter #7
will do--thanks. i thought the previous owner said he had the carbs synced but that it didn't solve the problem, but who knows? i've got one step down--the valves are adjusted dead right. once i get the new spark advancer, i'll get the points dead right, and then see what we got. but i think you're right--the carbs will be the 3rd thing needing work. i've got some new parts ordered for those (needles, seats, slow jets) from honda. once they're cleaned and the new parts are in i'll get to the syncing part. without a manometer, is it enough to sync them by just make sure the slides are lifting at the same time and evenly?
 

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Discussion Starter #8
still waiting on the new spark advancer, but in the meantime i removed the old one. i didn't think until after i had removed it that i (maybe?) should have marked its position somehow? is that necessary, or can the spark advancer be taken on and off without regard to its position around the shaft?
thanks...
 

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ryder.441 said:
still waiting on the new spark advancer, but in the meantime i removed the old one. i didn't think until after i had removed it that i (maybe?) should have marked its position somehow? is that necessary, or can the spark advancer be taken on and off without regard to its position around the shaft?
thanks...

There's a locating pin on the cam that takes care of overall alignment.
The advancer does not come apart as easily as 350/450 do, so it's hard to get the lobes of the sleeve 180 off.
 

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Discussion Starter #10
oh, ok--that's what the notch on the advance unit and pin on the cam are for. glad the person who designed it had people like me (who don't always pay enough attention to how things are coming apart!) in mind.
thanks for the clearing that up...
 

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Discussion Starter #11
well, the NOS spark advance unit i bought turned out to be neither NOS nor even an exact match for my bike. so, i took the cam lobes off another old advance unit i had (the lobes were good but the springs were shot) and fit them to the unit that was currently on the bike (that had good springs but badly worn lobes). it seems to have helped--i'm getting the points to open within a hair of the F mark for both cylinders. it's better, but not as perfect or precise as i'd like. i'm wondering if there's a bigger/different problem than just the cam lobes being unevenly worn? anyway, i got it all back together and it runs much better. the bad sputtering and hesitation are gone and it rides nice. the only ongoing issue is that the idle still doesn't settle down as smoothly as i'd like after a blip of the throttle and after it does settle back down (to about 1200rpms), it rises (to about 1400rpms) and then drops again.

i'm wondering if i've got an air leak somewhere...maybe in/near one of the insulator boots that connect the carbs to the engine? also, is there something i can use to "lube" the carb slides a little? there are some marks on the carb bodies where the slides move up and down that seem to indicate a little excessive rubbing and maybe not real smooth sliding action...
 
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