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Discussion Starter #1
ok so im building a CB125 cafe. ive just about thrown every new part that i could get my hand on....
new harness, new coil, rebilt carb, new plug, new clutch...ect
but hear lies my proplem....i got new points and am not sure how to set them up right. tryed reading the manual but didnt really get it. had the bike running last week but went to ride it tonight and couldnt get it started. its got spark and got fuel....but no run. how do i do the points the right way? im not shmuck but only just started playing with old toys
thanks for any help


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Discussion Starter #3
part of why i didnt get the manual is that it didnt say anything about top dead.
is there a way that the cam lobe can be ajusted?

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You need to pull the left (I think) side engine cover to expose the flywheel. Pull the spark plug so that you can turn the engine over easily. The manual will tell you which timing mark to use to set up the points base plate to set the point gap, and then set up the timing by adjusting the points. I just use a piece of the thinnest paper I can find, which in my case is the tissue paper between my faceshield tearoffs, but a lot of people use the celophane from a pack of smokes. You just put the paper between the points and adjust the points so that there's tension on the paper till the flywheel gets to the T mark. (once again, check the manual 'cause I can't rememer if it's the T mark or the F mark. Probably the F mark now that I think about it)
You'll also need to pull the valve rocker cover to determine that you're on the compression stroke (both valve's rockers should move).

That's the short version from memory anyway...

FR
 

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Discussion Starter #5
if the cam spins at twice the crank....and the cam has one lobe....why does the spark only fire on one stroke? could i be 180deg out?


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Sorry I missed the post till now. I'm not sure what to tell you, 'cause I honestly don't know if the points fire on every revolution or not. I take it you've got spark but the engine still doesn't run. You may have set the timing on the exhaust stroke instead of the compression stroke, as you suggest, 180% out. That's why you need to check the rockers. That's also why you need to check and adjust the valves and cam chain tension when you do a tune up...
If you need more help, email me direct, I have the manual.

FR
 

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Jaguar,

If the bike ran last week, AFTER you installed the new points, the problem would appear to be something that had changed between those two times. If you didn't mess with the points after it ran, they wouldn't be the problem. If I understand right it DID run after you changed them?

If you changed the points and THEN it didn't run that is a different story. If you moved the points backing plate, and didn't mark where it was you are screwed (I did this with my Ducati 160) unless someone else scribed a line or something at one time--look close for a line on the plate and also on what the plate is fastened too (lucky for me my brother HAD scribed a mark the year before when we were workingon the duc).

I had a vertical 175 that I bought and started to drive home. It ran worse and worse on the way until it died. Ended up the cam bearings or something wore out and it slowly went out of time.

Good luck
 

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Discussion Starter #8
i had the new points and whatnot put on rode the bike and relized that i had no clutch. redid the clutch and now it will not start. could i have moved something doing the clutch?
thanks


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I can't think of anything that you would have disturbed during the clutch replacement. Once again though, you have to start from the beginning when you're diagnosing this. Fuel, spark, timing..

My CB125 can be a bitch to start cold, and I know it's because the carb slide sticks, and the throttle cable sticks too, so I have to get just the right combination of throttle/handlebar position and choke to get it to start. Once it's warm it's pretty easy to start, but it won't idle worth a damn.

FR
 

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Discussion Starter #11
read through the manual and did what it said(still have to do a light test). the F mark lines up and the points open and closed. im gunna pull the tank and seat and go through the wires to see if theres a short. motor has fuel and spark right now. also im gunna charge up the battery. the thing is that i have another CL125 with a dead battery and that one starts on the second kick....so what is the battery for anyway?


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On my CA160, it will run w/0 the battery, but the battery regulates the current. My ground strap broke during the moto giro, so the battery was not part of the system. Pete T noticed my headlight was way to bright for a 6 volt system. Ended up burning out my tail light bulb, and would have done in the headlight if I hadn't noticed.

Wired up a new ground out of some wire I had, and was OK as long as I didn't use the electric start.
 

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Discussion Starter #13
just thought of something. i remember when i wired the bike that it wouldnt start the first time because i hade a bad ground to the rectifer....could that let the motor spark but not run?

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Dude, did you fix the ground? Have you in fact determined that you have, or don't have, spark at the spark plug?
Don't go chasing your tail.
What manual are you using? Does the manual have a troubleshooting section? ('cause it sounds like you've got enough trouble to shoot with a 12 gauge pump action Wingmaster)


FR
 

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Discussion Starter #15
im going to check all of the grounds and what not today. i can see what i think is a good spark using a spark tester. the F mark and everything is lined up. the gap in the pionts is good.
im using the original manual for the bike. i downloaded it


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Spark tester? I don't even have that tool. I'm talking about taking a new spark plug, inserting it in the plug wire and holding it against the cylinder head while you kick the engine over. You want to see a decent spark between the electrodes of the spark plug every time you kick it over. If you don't have that, you need to work back from the plug, checking the plug wire and especially the boot connector, and so on...


FR
 

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Discussion Starter #17
yes a spark tester. its an inline see through tube that you hook up in place of the plug so that you can see the spark but not ignite anything....put the plug agains the head? what are we amimals????

yes i have a good spark

didnt fool around that much today


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thats so safe. you obviously werent around for my lawn mower story a few years back. it invloved my "spark tester" some old dry grass, a flooded lawn mower, and a garden hose.

jc
 
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