Fuse rating for kill switch kickstart only

[pablohoney]

Well the title pretty much says it all. I recently redid my 79xs650 special and I have made it kickstart only, removed the safety relay, turn signal canceler, starter solenoid, and light checker. It starts right up and everything works but after about a minute of running, the kill switch fuse blows. I have looked and can't find a short and it has done this several times at about the same time intervals after starting. Should I still be running the 10A fuse, or because I have removed so much I should put in a 15A? Thanks

 

[XSLeo]

The main fuse on the stock system was a 20 amp. You should still run a 20 amp main fuse.
With the main fuse between the battery and key, having a 10 amp to feed the lights and a 7.5 for the ignition won't hurt.
Just checked a diagram. Your bike came with the four fuses. If you are feeding just the ignition with the Engine Stop switch a 10 amp should be fine. If your blowing the fuse you have an overload situation. A short or something drawing to much power.

 

[pablohoney]

ok, How do I solve an overload issue? And wouldn't a short blow it right away?

 

[retiredgentleman]

No, you don't want to increase the fuse size. A larger fuse could cause the wiring to heat up and melt the insulation....................even cause a fire

By "kill switch" fuse, I think you mean the Ignition fuse. I don't know what type ignition you have.............points or Pamco or Boyer?? Regardless, something downstream of the Igntion fuse is drawing a large current. Spend some time checking all the connectors and wires, looking for bare wires etc.

You can use a VOM meter to measure the current flow.

If you are using those old style glass fuse holders and fuses..................they can have high resistance and cause problems...............replace them with blade type.

 

[pablohoney]

Ok, That is what I thought.

Yeah, the ignition fuse, pamco, I am using a new glass fuse holder, so I will switch over. Thanks for the help.

 

[retiredgentleman]

When I referred to glass type fuse holders, I meant 30 year old ones. If yours is new, it may be fine. I just don't trust that type of fuseholder.

 

[XSLeo]

I don't trust the glass fuses. The element can break down in the cap and you can't see if it is blown. The element can come unsoldered from the cap. Again you can't see that.
I have had way to much aggravation late at night, on some lonely back road, trying to tell if the fuse is blown.
The blade type have no caps and on many you can see the entire element. The element and the blades are made from one piece. Can't come unsoldered. Much more reliable fuse.
On the fuse blowing, depends on just what is causing the trouble. A short may need the heat to expand the bare parts to get them to touch.
I see you have the Pamco. What coil are you using. It may have an internal short that only shorts after the coil warms up.
Generally if you remove parts the load decreases, so a lower amp fuse can work. Like on the turn signals, with the stock bulbs the curent draw with two 27 watt bulbs is somewhere around three amps, so a 5 amp fuse would work on them. Convert them to LED and the current draw is somewhere around .5 amps so a 1 amp fuse would work.
When the fuse blows start checking the system as soon as possible, before it cools off. Or perhaps with the meter hooked up, warm the parts with a hair dryer.
Leo

 

[gggGary]

If you still have a stock headlight shell and harness shorts up there are not unusual. Does the fuse blow happen about the time you start to head for the street?

 

[pablohoney]

I got the Pamco electronic ignition kit from mikes. Part #14-0901. But I have had that for a while and didnt have any problems before.

I will switch to those fuses soon but I don't think that is causing the current problem. And I have switched the fuses while the bike is hot and it still waits a minute before blowing.

 

[retiredgentleman]

For my Pamco, I use a 7.5 amp fuse ( the pamco coils draw less than 2 amps).

Since you have 1 minute to look at the problem, I would use that minute to measure the current flow to the ignition coil. Use your VOM meter selected to "Amps" on a 10 amp scale if you have that (or 20 could be used). Remove the ignition fuse and connect the meter in series to the connections where the fuse was previously. Use a 10 amp fuse also in series with your meter leads to protect against a short circuit. You might have to switch the meter leads if the polarity is wrong.

Start the engine and monitor the amps reading. Should be less than 2 amps, actually closer to 1 amp. Is the amp reading steady until the fuse blows, or does it gradually increase over the minute??

 

[pablohoney]

Wow, that is a great idea. I will do that once I get home.

 

[pablohoney]

Here is what I found out. With the ignition on I am getting, like .4A through that fuse and with the bike running it is like 2A. But I am getting continuity (with no fuse) between the fuse holder that goes to the coil and the frame. And with the wire that goes to the kill switch I get a quick crazy reading then infinite. It doesn't seem to matter if the ignition is on or not. This one is a head scratcher.


It also backfired through the carb while I was checking the idling amperage and now it won't start

 

[retiredgentleman]

OK, it seems like you have an intermittant short. If you are still wired as per stock wiring diagrams, you want to look at the path from the ignition fuse that goes to the kill switch and from there to the coil and the Pamco.

I would suggest you disconnect the Pamco red and green wires so that the Pamco is removed from the testing area. Remove the ignition fuse and use your VOM meter on the lowest ohms scale. Connect one lead of your meter to a good ground (bare metal). Now use the other lead to test for shorts to ground. Clip the testing lead onto the fuse terminal the feeds toward the kill switch. Operate the kill switch many times to see if the meter shows a short to ground. Also wiggle the wiring (red/white) that goes to the coil. This may find where the short circuit is.

 

[pablohoney]

Ok, thanks a bunch RG I will get right on that.

 

[pablohoney]

I tried checking the the amperage through the circuit and at 2.4A with just the ignition on and between .2 and .8 with the bike running. This normal?

Also I am not getting any continuity through the circuit with the battery disconnected and the ignition and kill switch on closed. Although i get amperage through there when I connect the battery. How does that make sense?

 

[pablohoney]

I taped whats going on. This was the second fuse in a 5 minute time and there was still the delay so it doesn't have to do with heat. It was running for about a minute before this:

 

[pablohoney]

I checked the coil and that is fine, and the charging system doesn't have anything to do with it cause I disconnected the reg/rec and it still blew. What else could it be??