Just cuts off Please Help

[mshick68]

82 special. I have completed my bobber build and used the tc brothers wiring harness. The bike has been running perfect. Yesterday while riding about 15 minutes it just cut off. waited about 15 minutes and it fired up and i drove home. Today the exact same thing.

Bat voltage is 12.8
voltage at the red/white wire on coil is 12.4

All original equipment the best I can tell. Coil, ignition box and the finned rectifier.

If the voltage at the coil is 12.4 and I get no spark does that mean the coil is bad.

Please help!!

Thanks Mike

 

[5twins]

Yes, it could be. Many times, when coils go bad, they fail when hot but work again once they cool down.

 

[mshick68]

Update so I waited 15 minutes and it fired right up. I took the wires off the plugs and checked the ohms. I put one lead on the red/white wire of the coil and the other on the orange lead with power off. Read 2.9 ohms ??

 

[mshick68]

Another update.. tried another coil fired right up. drove for 5 minutes and it cut off again. Battery voltage when it cutt of was 12.5. I don't get it. What the heck is going on. Please help

 

[mshick68]

Another update.. tried another coil fired right up. drove for 5 minutes and it cut off again. Battery voltage when it cutt of was 12.5. I don't get it. What the heck is going on. Please help

 

[mshick68]

let it sit again for 15 minutes with replacement coil( see above) fired right up. Driving me crazy

 

[deadchef]

since you tried a different coil and got the same results try jiggling some wires next time you get it running, especially around some of your connections. did you upgrade your fuse box when you rewired the bike? could just be a bad connection somewhere.

 

[john650]

Could be the petrol cap breather is blocked.
Had this happen on my first bike, a Triumph Cub.
Lifted the petrol cap as soon as the engine died, fired up again almost instantly.

 

[mshick68]

thanks guys. Yes I did upgrade the fuse box to all spade fuses and soldered all connections. I have wiggled everything but cant find anything.

 

[mshick68]

ok just went out and fired right up. Let idle for less than five minutes and it cut off. I moved every wire in every plug and no difference. I did notice the finned rectifer was pretty hot

 

[Brian902]

Are you getting good fuel flow. When it quits, is there still gas in the bowls?

Pull a drain and see if there is and if it flows good from each carb, test one at a time.

 

[5twins]

I guess there's a chance your ignition black box is crapping out. Sometimes that can be repaired by simply re-soldering all the connections inside.

 

[mshick68]

Plenty of fuel. Each time it cuts off I check for spark, nothing. Can I buy a new TCI box?

 

[XSLeo]

Once in a while new TCI boxes show up on Ebay. Generally around $500. There are several threads on here about fixing the box. Often just bad solder joints on the circuit board. Sometimes some of the diodes go bad, sometimes the tranister.
A bit of a search and you will find the threads about these things.
Getting a used TCI box can be a crap shoot. It may be good or it may not.
Leo

 

[mshick68]

thanks Leo. Just did another test. fired the bike up and let it idle until it cut off. 5 minutes again. As soon as it cut off I checked the voltage of the tci orange wire, nothing. Checked the red wire and had 12 volts. So there was no voltage flowing from the orange wire from the tci to the coil. What do you guys think.

 

[Paulrxs650]

I had the exact same problem, it was the plug wires!

 

[mshick68]

should theer be a voltage reading at the coil, orange side and red side when just switched on and or running?

 

[mshick68]

Paul, Can I change the plug wires? Mine seem to be moulded into the coil

 

[Paulrxs650]

They shouldn't be! Can you post some pics?

 

[5twins]

On the stock TCI coil, they are. The connection usually doesn't go bad at the coil but it can at the plug cap to wire end. Remove your caps, cut about 1/4" off the wire ends to get down to some fresh wire, and reinstall the caps. I like to do this to the wire ends before putting the cap on (or installing into the coil) along with a dab of dielectric grease .....

If your caps are the originals, test them while you have them off because they can go bad. The original resistance was something odd like 9K ohms. When they go bad, that resistance starts to climb, eventually getting to the point where it chokes off the spark.