CM trouble

Snug

Snug

New Member
I have an 81 CM400C that I replaced the ignition switch, and CDI unit on. I have spark now but she still won't start. I have a bunch of the electrical apart, as far as all the blinkers, headlight, brake light, so I'm thinking maybe that has something to do with it? Also, if I put it into 1st pull the clutch in and try to start her she lunges forward a little...... First bike so I'm bummed at this point...... Help?
 
I realize im all over and sorry for that haha in had no spark before I got the new CDI. I got new spark plugs while I was at it. I got the CDI in the mail today, threw it on and nothing. Unfortunately I am driving down to California (from Oregon) so I had to get on the road. Assuming it's a spark issue where would I start? Lol brought my manual along for the trip so I can read up on it. I know CMs are big right now so thought I'd see if anyone has come across this. I'll have to check out "so you bought a cm"thread to next rest stop.
 
I realize im all over and sorry for that haha in had no spark before I got the new CDI. I got new spark plugs while I was at it. I got the CDI in the mail today, threw it on and nothing. Unfortunately I am driving down to California (from Oregon) so I had to get on the road. Assuming it's a spark issue where would I start? Lol brought my manual along for the trip so I can read up on it. I know CMs are big right now so thought I'd see if anyone has come across this. I'll have to check out "so you bought a cm"thread to next rest stop.
 
Just got back from cali. I am getting spark, good compression, and fuel to the carbs. At a loss.
 
Been in and out of town a lot lately, I was afraid it would be timing...... Any good links to rticles or blogs on how to do timing on these? Never messed with timing on cars let alone bikes haha thanks for all the help btw guys
 
Timing is set and not adjustable on the CM's so unless the woodruff key is gone, I'd say your timing is fine. Just to touch on the basics, verify that the battery is fully charged, you have the kill switch set to run and you have the choke closed? Don't mean to offend by this question but everyone has forgotten to do one of these at least once so I figured I'd ask. Also, was the bike running prior to you changing the switch and CDI? Also, how are you starting it? In neutral and leaving the clutch lever alone.
 
I take no offense Lol this is my first bike so I know very little. The bike was not running and had no spark when I bought it. Guy said he thought it might be the CDI. The ignition switch was not making good contact, would only work when you would loosen the bolts holding it on and wiggle it around. I replaced the switch and it makes contact every time now. After the new CDI i am getting spark. The battery is brand new. I have tried starting it in neutral without touching the clutch and choke pulled out, tried neutral not touching the clutch with choke in, tried neutral with clutch in choke pulled out, and in, nothing. I tried to pop the clutch as well but no luck. When I try to start it in gear with the clutch in i can feel it pull a little, but won't start. I'm trying to be the least confusing as possible but realize I might be doing the opposite :-\
 
You're not confusing at all, all good info. Does it sound like its trying to start or is it just basically turning over? After trying to start it, take a plug out and see how it looks, is it wet with fuel? Is the gas in the tank fresh?
 
Try spraying some starter fluid in to the cylinders and see if she kicks over. If she does, then your issue is most likely carbs.
 
Re: Re: CM trouble

Kanticoy said:
Yep.
Click to expand...

nope, it's fixed and electronic advance.
only if you left the woodruff key out of crank can the timing be off
Wasted spark so leads don't care which plug they are on
It's most likely carb issue
 
Alright thanks for all the help guys! Truly appreciate it. Suppose ill be rebuilding the carbs. Updates soon.
 
If you're in Oregon it's doesn't seem beyond the realm of possibilty that it is 45 deg f or below ambient as you work on the bike. I know mine will run the battery down to nothing before starting if I don't choke it at first. Also to re enforce what you've already concluded; if you just got the bike, those carbs need to be cleaned.
 
Hey man,
Total FNG here too, and I copped a cm250 82' a few weeks ago, with it missing some critical parts and the electrical harness strewn out like guts. I bought a clymer repair manual, tagged everything out according to the wiring diagram and after identifying all the participants on the bike I started plugging it all in. But while I did, I had my multimeter out ensuring the battery was grounded and the other components were grounded to the frame like they were suppose to be. I'm thinkin, if your thinkin, if its electrical, just use a mulitmeter to find where the juice is being stopped. Yea this is my first bike, but if you hit start and you hear no noise at all, my first reaction is the electrical system. best guess
-slip-
 
A couple of things to know.
The ignition system on these is independent of the rest of the electrical system. They will run with a dead or no battery. The ignition switch grounds the CDI when in the OFF position as does the Run/Kill switch in the Off/Kill position.
A lunge forward when trying to start the bike in gear with the clutch lever pulled is normal since the clutch plates tend to stick a bit to the steels. Don't do that, start it in neutral.
Since your compression is ok, 165, and you have spark you are left with 2 things. Carbs or timing. First pop the left case cover off and pull the plugs. Using a plastic straw or piece of solder wire rotate the crank until you get the pistons to TDC. The straw will move up/down as you rotate. Now that the piston is at TDC look at the rotor and the T mark should be aligned with the timing pointer cast into the upper case half
It doesn't happen often but there are cases where the woodruff key that positions the rotor shears off and you loose timing. If that's ok then it's time to go into the carbs
 

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