Electrical timing bogs out at 5500RPM???

[Guest]

My '83 katana 650md has been at the local tuner and he's found it is bogging/erratic spark after 5500RPM. It runs good on the dyno up to 5500 RPM and then it just backfiring and running poorly. Carbs have been cleaned, synced, and tuned. New spark plugs and Dyna coils but everything else is stock (save the coils themselves).

Anybody know what to test next?
How to I test the cdi box/brain box?
Are the pickups adjustable to advance timing? It wants to stop at 20degrees before TDC but that's as far as it will go.

[roeme]

First order of debugging electricals: Thou shalt test voltages.

Looks like the electric power supply of your bike cannot sustain the power demand of high rpm sparks.

Confirm that the following components are healthy; in this order:
1. Battery
2. R/R
3. Stator

Do the stator quick test (available at http://www.thegsresources.com/statorpapers3.php) and report your findings.

[Steve]

Testing the "CDI box" is easy. You don't have one, so it's not possible.

What you are calling a "CDI box" has nothing to do with CDI, it is called the "Ignitor". It is just a box of transistors that switch the current through the coils. A true CDI system does not even have coils.

That said, your ignitor also has the ignition advance built into it, rather than the mechanical advance found in earlier years. That part might be faulty, you will need to replace the ignitor if the advance is not working.

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[tom203]

The stock 83 650 ignitor should be the same as what my 81 has...ignition advance is all mechanical.. The advancer starts at about 10btdc and goes about 25 degrees more , so maybe 38 degrees bdtc. I'd remove and clean/ inspect advancer.

[Steve]

The stock 83 650 ignitor should be the same as what my 81 has...

Good to know. I know the larger bikes had the electronic advance starting mid-'83 and early '83, I figured the rest of the bikes did, too. I guess I figured wrong.

I did a quick search on the parts fiche, it seems that all the 650s used the same ignitor and the same centrifugal advance.

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[Rocket66katana]

Oh ok I'll see if the stator is pumping out the right voltage on all banks. 3 years ago I replaced the whole wire harness, the harness was used but looked in good shape. Is there a certain banks of the starter that sends its power to the ignition? By the roeme what is R/R? Also I believe after 83 650s went to igniter boxes.

[Steve]

Oh ok I'll see if the stator is pumping out the right voltage on all banks.

"Banks"? I think you mean "Phases". The standard test is to remove the three wires from wherever they connect, so there is NO load on the stator. Arbitrarily label the wires A, B and C, it does not matter which one is which. Run the engine at 5000 RPM, measure the AC voltage from A to B, B to C and C to A. They should all be over 75 volts and within a volt or two of each other. The second test is to again run the engine at 5000, check AC voltage from A to ground, B to ground and C to ground. You are looking for ZERO volts there.

Is there a certain banks of the starter that sends its power to the ignition?

Again, you are using "banks" when I think you mean "phases". You are also using "starter" when I think you mean "stator". BIG difference between the two, so make sure you use the correct term. To answer your (apparent) question, NO. All phases of the stator work together to provide power to the bike. Some will be used directly, the rest will charge the battery. Together, they work to charge the coils, which will provide spark to the plugs. You are thinking "small engine" stator that has an ignition coil, these are REAL ignition systems that use batteries, coils and (the electronic version of) points.

By the roeme what is R/R?

The R/R is the Rectifier/Regulator. The rectifier portion converts the Alternating Current (AC) from the stator to Direct Current (DC) to run the bike and charge the battery. The regulator portion is designed to limit the voltage to about 14.4 to keep from frying everything.

Also I believe after 83 650s went to igniter boxes.

You will have to change your belief. ALL the 650s have ignitor boxes. In fact, ALL of the GS bikes have them, starting with the 1980 model year. The last bikes to use mechanical points were the 1979 bikes. And please don't think there is anything "magical" about the ignitor. It's just a box of transistors that replaces the mechanical points.

Because it is transistorized, and different forms of electronic ignition were popular in the cars of the time, "CDI" was mistakenly attached to the description. The term "CDI" stands for Capacitive Discharge Ignition. In a CDI system, a large capacitor is charged at a high rate of current, then discharged to provide the spark at the plugs. The GS bikes use a standard coil and points arrangement, meaning that it is still an INDUCTIVE discharge system. It just happens to be triggered when the transistors in the ignitor open up, stopping the current flow through the coils.

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[Rocket66katana]

thanks steve for the info, in been a few years since i bought most of the electrical for the bike. i forgot the name of the igniter box till you told me. i just wanted to get the post up quick, it was the end of the night and i was using my phone and i didnt see it auto corrected some of my words my apologizes. do you know if there is any aftermarket igniter box that i can replace mine with, instead of buying another used one?

[Steve]

I think the only option for an aftermarket unit would be a Dyna. Usually used to replace points, but I see no reason why it shouldn't work to replace your stock signal generators and ignitor.

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[tom203]

The dyna will work...you have to make a cutout in dyna mounting plate to clear oil sender.
i have two spares of these ignitors..p/n 32900-34210 both tested for half hour plus on my bike into the 8000 rpm range.
if you post a $65 "bond" , I send you one to test on your bike...send it back to me and I will refund the money less my $6 shipping cost. This particular ignitor is very durable, !'d suspect that you have a wiring issue...or voltage dropoff at high rpms.

[Rocket66katana]

I took it for the first long ride today. it running smooth threw the lower rpms as what the dyno shop told me. sometimes off power take off it sputters the same way it does on high rpms. the way it sputters isnt like hitting a rev limiter type. its like the spark plugs are firing on the wrong spot, like bad carbs. the dyno guys are for sure its not the carbs its the ignition. is it possible when i wired up the bike with the used harness if i wired the stator wires wrong, are all the 3 wires the same or do certain colors have to go certain parts of the bike like the battery then the ignition ext. this weekend im going to go ahead and test the stator and check the the connections.

[OldVet66]

There is no color code order to the stock stator wires that matter and the new stators usually come with three yellow wires. If you are using an old stator it could be breaking down with load because of previous damage. These bikes were famous for electrical problems primarily due to the R/R design and issues at terminals plugs and switches. Going through the entire harness at all connection points would be a good first step to eliminate any high contact resistances Refitting the bike with a reliable Series type R/R would eliminate stator damage if you don't already have it. Your best bet is to save your money at the tuners and learn how to do it yourself. The information and expertise is on this site and in the end you will have a better experience with your old bike.

[tom203]

Yes,it's possible that stator and/or its connections are breaking down at high rpms and causing system voltage drop. Fully charge your battery, get to someplace where this rpm issue occurs: unplug the stator from r/r ,take a spin,and see if things improve. With headlight off, you got a good half hour of running with a 14 ah battery (and still enough for restart)

[Yozzer74]

Any luck sorting this issue sounds similar to the problem I'm having .

[posplayr]

Any luck sorting this issue sounds similar to the problem I'm having .

It is usually low voltage to the coils which can be a combination of poor charging or just bad connection to the coil. It is unlikely an igniter problem despite all the discussion. Usual fix is gnition or coil relay mod.