Ignitor smokes then main 30a fuse blows

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SchoolDaGeek
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Ignitor smokes then main 30a fuse blows

Postby SchoolDaGeek » Sun Jun 02, 2013 5:11 pm

Quick question to the board:

A past trade of mine is contacting me for info, he has been through 3 ignitor units all which puff smoke and then the 30amp fuse blows on his 1979.

I have been trying to help him through email as he is an hour away and it has been many months since the trade, I never experienced any problem with the bike. When I got it it didn't charge, and the black material in the ignitors had already started to ooze. The rotor was junk, warped and cracked, so I purchased a refurb from customrewind.com and everything appeared to be ok, I rode it on a couple of trips with no problems, stored it for the winter, and it started up fine in the second week of March when it was 40 degrees out.

In the first week of April it blew the first ignitor unit and fuse. Since then it has gone through another three apiece.

It is an obvious short somewhere, all the standard checks have been performed, but since I am not there, I cannot verify his work.

Is there an obvious circuit that would take out the ignitor and fuse at the same time? I have it narrowed down to the rebuilt rotor, R/R, solenoid, and ignition circuit, but would like to try and get a definitive answer based on the theory knowledge of the forum.

It is frustrating because he has said that he has gone through the entire wiring harness and found no shorts, so I am limited to those four objects.

Can a shorted ignition coil do that, for example?

Thanks.
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cb650
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Re: Ignitor smokes then main 30a fuse blows

Postby cb650 » Mon Jun 03, 2013 8:39 am

are the lines pinched at the ignitors or the rotor? Easy to do.
Did you clean the tank out?!?!?!?!

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Volker_P
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Re: Ignitor smokes then main 30a fuse blows

Postby Volker_P » Tue Jun 04, 2013 3:06 am

So how do the other fuses look like? Still stock or replaced by stronger ones.
How does the rear side of the fuse holder look like?

Basically the cable to the fuse holder on the handlebars is suspicious.
Also ignition and charging do not use additional fuses.

Do the tail lights work? Tarking light circuit is also something special with regard to the ignition lock/switch, at least for Europe.

As an ignition coil gets its power from an ignitor, I guess a shorted coil will either do nothing at all or kill the ignitor. At least two cylinders won't fire any more.
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Masika
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Re: Ignitor smokes then main 30a fuse blows

Postby Masika » Tue Jun 04, 2013 10:13 pm

I am the new owner of this bike, the problem first started while i was riding bike completely shut off with no power and i noticed smoke under the seat. the black goo the covers the back of the cdi was smoldering, after pushing the bike 1/2 mile home i gave it a once over and notice the main fuse was replaced with a piece of copper wire, was hopping that was the cause of my problem so ordered 2 brand new cdi units installed and also installed an in line 20A fuse because for some reason i thought it was only 20. bike started right up with choke on it revs high at 4-5k rpms just 15 or so seconds into run time bike dies. one of the 2 new cdis was bubbled out and you can see solder was blowing out a small hole. also my in line 20A was blown. this is when i decided to contact previous owner who gave me many many tests to perform including where to buy the proper 30A fuse link. both coils are giving 2.7 ohms not getting any ground outs from any of the 4 hots that run to either of the cdi. i pulled apart the wiring harness from the headlight back and found no burns or exposed wires. did the proper test to check the rotor dont remember the numbers but i remember they were good. checked the resistance on the R/R all 3 yellows were around 54 but the R/R was even removed from the bike for this last start and die. had 2 used cdi ordered from ebay installed them. took out all 4 handlebar fuses, i have a oem 30A main fuse installed R/R removed start the bike with no choke and it ran. just as soon as i start to give it some gas and hit about 4k the bike dies instantly. main fuse did NOT blow just turned white but both cdis are fried. didnt get warm or smoke this time but they are giving me no spark any more.

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Volker_P
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Re: Ignitor smokes then main 30a fuse blows

Postby Volker_P » Wed Jun 05, 2013 3:57 am

Welcome here! :D

Very strange problem.
So possibly the CDI's are not wired correctly, but in this case it would be strange it runs at all.
A considerable overvoltage at the CDI's might be another option.
I also do not know how they would cope with an AC component.

Is this the stock charging RR system?
Any non-stock parts at the ignition system?

In any case blowing the 30A fuse typically means a considerable short.

Guess I must think a bit about it.
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Masika
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Re: Ignitor smokes then main 30a fuse blows

Postby Masika » Wed Jun 05, 2013 1:00 pm

well the time it did blow the main fuse was when the cdi got hot enough to melt solder and blow it out through the "goo" so i would guess an electrical component getting that hot is shorting itself. I have done allot of tests with key on bike off and have failed to blow the fuse again so I believe the main fuse going is linked to the cdi going first. so my main concern is why is the cdi going. and like i said it only does this once i hit 4k rpms or higher which also led me to believe over voltage but in the last test start the R/R was removed completely.

on a side note- freshly charged battery reading 12.7 when i turn the starter it drops to 10.5 as the starter is turning with no struggle heres the strange part. when i let off the start i can see the volts on the battery jump from the 10.5 up to 15v only for a split second but long enough that my meter reads it and i can see it. then right back to 12.7. I did take the battery in to have tested at advanced auto parts and he said all the results looked good other than a small drop in CCA but the machine said to replace. the guy told me "it will say replace with the smallest problems so its most likely fine"

also if theres anyone here that could sell me a cheap set of cdi units that would be great. cheapest single unit on ebay right now is $40 and i already have $160 spent on these cdi units.

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Volker_P
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Re: Ignitor smokes then main 30a fuse blows

Postby Volker_P » Thu Jun 06, 2013 4:20 am

I agree that melting solder in a CDI asks for a power that may blow the main fuse.
So the question is why both CDI's should blow simultaneously at all. Besides melting out the black stuff, they typically are really inconspicuous.

If you did blow your CDI's with battery power only (no charging because RR unplugged, right?) you certainly have the problem related to ignition.

As written, verify the ignition circuit. E.g. no idea what happens if you mix up the two cables from the pulsers for each CDI.

What about your ground connections?

As SchoolDaGeek experimentet with an electronic ignition (see HEI ignition thread not sure if this was on this bike?) something might have got wrong during going back to stock.
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SchoolDaGeek
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Re: Ignitor smokes then main 30a fuse blows

Postby SchoolDaGeek » Thu Jun 06, 2013 7:28 am

Volker_P wrote:
As SchoolDaGeek experimentet with an electronic ignition (see HEI ignition thread not sure if this was on this bike?) something might have got wrong during going back to stock.


No, the experiment was not performed on this 1979, it was performed on a 1981 Custom.

The only two things I did to this 1979 was to jump the 30A fuse with the copper wire because my screwdriver slipped on the + terminal of the battery and contacted the frame which blew the fuse and I did not have any spare parts at all to put any type of fuse back in there to drive it home. I pulled the 4 10A fuses along with the R/R harness to drive it home on battery power. Once I got it home I completely forgot that I had done that and never replaced it.

The reason I obtained the bike was only a charging issue which ended up being the rotor which I replaced from customrewind.com and fortunately the R/R worked fine with the new rotor installed. I drove it several times with no problems and so did Matt after the trade.

Matt, there are cheap ignitors listed all the time on Ebay. The cheapest set right now I have found is auction:

251126161591 LINKhttp://www.ebay.com/itm/1979-Honda-CB750K-CB750-Four-Igniter-Set-/251126161591?pt=Motorcycles_Parts_Accessories&hash=item3a784920b7&vxp=mtr

The updated part number from Honda is:

30400-MA4-601

If you go to Partzilla, you can get the cross reference to search for used parts on Ebay when you are just using the bike model, which are all interchangeable.

Here is that LINK http://www.partzilla.com/parts/detail/honda/HP-30400-MA4-601.html
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Re: Ignitor smokes then main 30a fuse blows

Postby Volker_P » Fri Jun 07, 2013 1:15 am

SchoolDaGeek wrote:The only two things I did to this 1979 was to jump the 30A fuse with the copper wire because my screwdriver slipped on the + terminal of the battery and contacted the frame which blew the fuse

Thanks. This would be already quite strange. Your report rather would fit hitting a "+" terminal behind the starter relay (with the fuse).

Typically hitting the battery "+" terminal with some tool makes some marks on your tool and may even heat it up to red heat if it slips there without someone noticing it. But then the bike circuit would be completely bypassed and the battery voltage would be low, so no chance to blow a 30A fuse this way at all (guess there is nothing capable of a that considerable inductive pulse).

Did not check in the diagram, but possibly a poor ground connection could make the current flow through the starter so it blows the main fuse when you hit the terminal.
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SchoolDaGeek
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Re: Ignitor smokes then main 30a fuse blows

Postby SchoolDaGeek » Sat Jun 08, 2013 1:29 am

It is strange.

The standard practice on charging systems is to remove the offending unit and test the rest.
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80chopper
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Re: Ignitor smokes then main 30a fuse blows

Postby 80chopper » Sat Jun 08, 2013 12:57 pm

On my bike the ignition modules are insulated from the frame with a rubber grommet so I assume that they should not be touching the frame. Are your cdi's insulated or bolted directly to the frame? maybe the grommet is melted and arc-ing?

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Re: Ignitor smokes then main 30a fuse blows

Postby Masika » Mon Jun 10, 2013 1:16 am

@80chopper grommet is fine and i think its just for vibration purposes anyway.

i removed the complete harness from pulse gen to the cdi found no burns pinches or shorts. is there any way a bad pulse gen would short the cdi? if so can i test them?

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Re: Ignitor smokes then main 30a fuse blows

Postby Volker_P » Tue Jun 11, 2013 3:03 am

Pulser coil resistance should be around 530Ohms.

As both circuits are affected, I would start with the common components.
It is quite unlikely that two components show the identical fault in this case of such quite untypical behavior.
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SchoolDaGeek
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Re: Ignitor smokes then main 30a fuse blows

Postby SchoolDaGeek » Tue Jun 11, 2013 8:39 pm

Volker_P wrote:Thanks. This would be already quite strange. Your report rather would fit hitting a "+" terminal behind the starter relay (with the fuse)...

... so no chance to blow a 30A fuse this way at all (guess there is nothing capable of a that considerable inductive pulse).


Sorry, Volker, I may have misstated that particular aspect. You are absolutely correct. Now you got me thinking... Don't you mean bridging the "-" terminal in front of the 30a fuse? Going to full ground once the + is hooked up?

My memory is only that after the purchase, I chained it up and pulled the battery to charge it at home while I got the title and license plate.

Upon getting back to the bike and installing the charged battery, a tool slipped on me and the bike blew the fuse. I just cannot remember what the combination was, it slipped, it popped. I didn't think much of it because the tool fell so fast, I jumped and blinked. I would have needed a high speed camera to catch exactly what it did. And yes it did mark the tool.

I know the '79 has a somewhat strange battery setup with the hinged seat. Maybe the negative was already connected and I was playing around with the + terminal cable to the starter solenoid, but it survived when I pulled the battery but the mishap blew it with the charged battery.

I totally understand though that the fuse could not have blown unless it was in front of the + (LEFT) terminal of the fuse, and grounding out from the - (RIGHT) side.

Just don't know. Still trying to figure out other than a worn short in the insulation of a wire somewhere why the bike is blowing ignitor units and the main fuse, especially when the RPM climbs to 4k.
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Re: Ignitor smokes then main 30a fuse blows

Postby Volker_P » Wed Jun 12, 2013 1:35 am

SchoolDaGeek wrote:Just don't know. Still trying to figure out other than a worn short in the insulation of a wire somewhere why the bike is blowing ignitor units and the main fuse, especially when the RPM climbs to 4k.


Just to track the facts precisely:

The bike will start with the bike battery. Chaging is deactivated (probably RRR plug pulled?). It will start and run for a while but as soon as you exceed 4000rpm it will kill both ignitors simultaneously and also blow the 30A fuse?

Are these details correct or did I mix up something?

Did you observe if the engine was still turning when the fuse blew or did it blow at a later time?
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