cdi or rectifier problem?

short story:
riding bike bike broken down with a red hot battery,
changed battery bike turns over but will not start
new battery fine, power at coils but no spark on both coils
either the rectifiers gone or cdi unit isnt working
iv been told its very unlikely its the cdi because there pretty reliable
however the rectifier sends signal to cdi then cdi will send signal to coils,
is this true?
and what is your opinion?

cheers guys

[timwilky]

The R/R Rectifier/Regulator has two purposes only.

Purpose 1 is to rectify the AC current from the alternator at about 70v to a DC current.
Purpose 2 is to regulate that voltage down to ~12v suitable for a 12v electrical system

There is no interface between the R/R and the CDI. You only need lok at the R/R connections, 3 off to the alternator and 2 to the battery.

So what would you sugges the reason for the bike to not have a spark? On both coils the cdi unit? Or the rectifier isnt changing the voltage to 12v?

[jambo]

You have 2 issues:
1) Why did the bike stop working, leaving the battery so hot?
2) Why will the bike not run now.

The answer to issue 1 MAY be the reg/rec. This can't be proven until the bike starts. But it CANNOT be the answer to issue 2 for the reasons Tim has laid out. It has nothing at all to do with the timing of the spark, the ignition pick up sends a signal to the ignition unit. The Reg/rec takes ~80V AC from the alternator and changes it to 12V DC. The 2 items are completely separate.

You can actually start and run a bike without an alternator & reg/rec, it'll just stop when the battery gets low. This is known as "total loss" and sometimes done in racing but I'm wandering away from the point.

Jambo

Edit: If the reg/rec failed and started putting high-voltage into the bike's electrics, bets are off on what components may, or may not have failed as a result. Be methodical.

So im kind of leaning back towards the cdi not sending a pulse to the coils

[jambo]

It is one possibility. Do you own a Haynes manual? Where are you based?

You may find buying a new ignition unit (it's not technically a CDI) fixes the issue, but if not you've bought a part that you didn't need.

When you do get it to start make sure you test the charging circuit to make sure it's not over-charging (this may well be an issue) or you'll be back here again.

Jambo

I have a suzuki workshop manual, i am based in nottingham

[Sid Squid]

It's likely the battery got red hot 'cos the regulator-rectifier err... didn't - which is because it's knackered and the battery has been grossly overcharged. Another possibility is a properly duffed and highly resistive battery - they also get hot when charged.

My money's on the first possibility - if only because the likelihood of a dud reg-rec is higher than that of a battery that badly stuffed. But bear in mind both are entirely possible.

Assuming goosed reg-rec, the resulting excess voltage might possibly have damaged the ignition unit, (it's not a CDI - that means something quite specific), but until you're sure of the charging system don't go connecting any new bits to it - or they may go the same way as the last ones.

Get a new battery, if it's not already dead your present one's days are numbered if it got charged highly enough to get that hot, then make sure it's fully charged off the bike, disconnect the reg-rec unit and test out the ignition, it will run fine for more than long enough without the charging system as long as the battery has plenty in it. Substitution with known good parts is the best practical way to test in these circumstances.

PS. The ignition unit may have escaped unscathed - uber high voltages occasionally pop the pick up coils first. Maybe.