Hard Starting, rough idling and loss of power cure

[Tony Smith]

Some may remember that I have had a long grizzle trying to fix a hard starting problem that defied logic - the timing was fine, I even took my carbs off and fitted them to another bike.

You might also remember I was having trouble with replacement ICUs, I had at one time amassed a sizeable collection of "failed" modules, I even replaced the wiring harness to the ICU - all to no avail.

Perhaps if I'd been a bit smarter and actualyl measured the voltage reaching the ICU I would have solved that problem much faster.

Some time ago I bought a new fuse box which aside from using modern "blade" type fuses, also has a few more circuits than the OEM grand total of 2.

In the process of prying the connectorsoff the old fuse box I noted how horridly corroded they were - I gave the connectors a quick dip in acid to clean them and squeezed them up somewhat to ensure that they have a good grip on the new terminals (and I coated them in Petroleum jelly once they were assembled to stave off new corrosion.

Well the rotten thing starts more or less immediately, hot or cold, with or without choke now.

Moral of the story, low voltage will play merry hell with ICUs and not surprisingly, the "old" ICUs will function of somewhat lower volts than the new ones.

Hard starting - clean the fusebox terminals.

[skippyc]

Good advice.

[wilcom]

Hard starting - clean the fusebox terminals.
                   

Good find Tony!   I wonder how many bikes ended up in the "bone yard" because of issues like that, that were never found...................

[Tony Smith]

Well it confounded me for months, on recollection I did test the power to the power pin of the ICU at least once, but of course as we all know, when you have an electrical component that has a fair load you can only really be sure by measuring voltage under load.


I have a bet with myself that I would have been using my old "sweep" multimeter and that as soon as I saw the needle moving in the right direction I would have disconnected and moved on ASSUMING that the ICU was getting 12 volts.

Looking back it all makes sense - the old ICU working OK, although missing a bit when hot and with power sharply tailing off at much over 60mph. The new ICUs I bought wouldn't work because they simply need more power than the old ones.

Once I cleaned the connectors not only did the old tart start beautifully, it now pulls quite happily to North of 80mph (which is as far as my Reagan era speedo goes) I infer that it reaches an interpolated speed of just a bit over 100mph which is what the poor old thing should do.

Holidays coming up - K100 front end to fit and R75 final drive to slip on as well.

[mrclubike]

The ignition system on a stock Bike is not Fused
Very Scary   

But it is on mine now 

[georgesgiralt]

Well, it is not fused for a security reason.
A fuse can fail. And if it fails you are left without ignition and this could be when overtaking a vehicle or at very high speed...
Have you had a rear wheel stop suddenly turning at speed ? Not fun. Not at all.

[mrclubike]

This may have been true for the old German  or glass type fusses for sure but I have converted to the Modern ATC fuses that are no more likely to fail with out a current over load than any other component in the system
 
Like tubeless tires  i guess it is a choice one needs to make for them self
Personally I would rather have a blown fuse than a melted down wiring harness
If you have never experienced it
It isn't pretty
It just doesn't take out one circuit
The shorted circuit melts into the others in the bundle and can cause serious havoc with the whole system 

[Barry]

A physically sound fuse doesn't fail easily. Fuses will take in excess of their rated current for a surprisingly long time. For example to get a fuse to blow within 1 sec you would have to put triple the rated current through it and it could take up to 60 secs to blow at double the current. Sensitive they are not.

[suecanada]

I for one will check for corrosion on the fuse box terminals this Springtime startup time! Still have the VW ceramic 2 fuse box.