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1982 cm450c idle problem

4820 Views 6 Replies 3 Participants Last post by  cbr900racer77
ok so i got a1982 cm450c that i've been rebuilding the last 6 months. I've rebuilt the carburetors completely with all new parts. i have good compression. The bike idles fine on the right cylinder but not the left. If i got to 3000 rpm or beyond it seems to run fine. The carburetors are synchronized. I have been trouble shooting this problem for a week now. At idle i get backfires and slight stalls from the left cylinder. But not on the right one. After extensive work on the carburetors i don't think there is much i can do. so i am leaning more towards an electrical system problem. i've checked al connections and thy seem to be good. i've used two different sets of new plugs and i get spark form both. using the honda factory manual i checked the ohm measurements for the alternator and they are well within range. but as for the cdi module the measurements i got were out of range, instead of getting 10-30 ohms on certain connections i was getting between 6-800 ohms. which is way higher than they should be. So i believe its the cdi. But when i swapped the plug wires, left <-> right, the same problem still occurred. and now im stuck. Has anyone had a similar problem? also if this does seem like a cdi problem does anyone know where to get one, this is a very rare part from what i am seeing. and i cant seem to find anykind of workaround for it. thanks!
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try driving around just looking in the worst looking neighborhoods and i'm sure you will see a few in peoples yards.

if not, i would swap the coil packs out, or if its a single pack with 2 plug recepters, try a new coil all together.

CDIs rarely go bad, one of the best systems honda ever made, you can also try out of state motorcycle salvage yards thru the internet and you might have better luck.
So i got a hold of a new cdi and a coil, going to install them this week. i really don't think its the coil because when i switched the plug wires the problem still persisted on the same cylinder. ill let you guys know when i get it going. Does anyone have any other ideas i can explore though?
So i changed the coil and the cdi and nothing changed. I have no more ideas on where to attack this problem next. Any ideas?
Just curious...Did you make absolutely sure pilot jet is clear? Did you spray carb cleaner through opening for pilot jet and fluid sprayed out tiny hole in front of butterfly? How about removing fuel screw and with a finger covering pilot jet, look for same spray? Not doubting your abilities, just trying to help cover all the bases.
Turns out the carburetors were not synchronized. After 2 months of messin around, a buddy of mine who works on bikes came by, looked down and boom he was like there u go. Half a turn and purrs like a kitty. thanks for the help though.
Cool, glad you got it going. Sometimes an extra pair of eyes helps us see the forest for the trees LOL
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