Dying At Low Rpm

[gen1aus]

Having an issue with my turbo Gen 1 not wanting to idle below about 2500, and stuttering slightly up to around 5000. Seems to run ok in the 5-7000 range, but I haven't pushed it as there's clearly a problem.

It will run for a moment at lower engine speeds (e.g. 1300rpm) but then abruptly die, usually within 10 seconds or so, sometimes nearly immediately.

Running between 4000-5000 sounds slightly stuttery like it's missing on a small percentage of spark cycles.

Initially I thought CKP sensor, as I changed to a high output stator roughly around when the problem began. The CKP coil resistance is in spec though, and I'm reading just over 5v from it while cranking (spec is over 3v), so it seems fine.

Coil resistances are ok. Fresh and newly gapped plugs (smaller gap for turbo). Fuel pump was changed for other reasons very recently, so no concern about it being bad or clogged filters. Adjusted TPS. Checked all connectors and vacuum lines.

The engine seems to die suddenly and totally rather than struggling first, so I'm thinking electrical rather than fuel.

Sidestand switch works properly. Tipover sensor and bracket look fine. Haven't yet tried bypassing them though.

Frustratingly the ECU isn't throwing any codes to help me track down the problem.

Any suggestions would be much appreciated.

 

[gen1aus]

After checking everything I could think of, it turns out the problem is being caused by the high output stator, though I haven't yet figured out how it's doing it. I suspect it's somehow interfering with the CKP sensor circuit (and therefore the ignition system).

If I unplug the stator leads from the reg/rec, the bike runs fine (and it ran fine on the standard stator beforehand too). Plug the stator leads back in and it immediately begins to stumble, then will die shortly after. It will still die from 2000rpm so it isn't just mechanical load, and the battery is fully charged at 13.1v so any stator load should be minimal anyway.

I've tried both the Shindengen SH847 MOSFET reg/rec that's currently on the bike, and a standard Hayabusa reg/rec - it happens with both of them. There is also no detectable AC voltage on the DC side of the system.

I've sent an email to Rick's Motorsport Electrics, where the stator is from, and am waiting to see what they say about it.

 

[gen1aus]

Emailed Rick's, they asked me to change back to the standard stator to see if the problem went away.

Went to change back to the original stator, and noticed a mark on the engine case inside the stator cover, where the solder on the forward wire of the crank sensor on the high output stator harness had been touching it. There is a protrusion in this spot of the Hayabusa engine case that makes the clearance between the case and the more forward of the two sensor connections quite small.

It seems the crank sensor on the harness I was sent has at some point been removed and re-soldered. I'm not sure if that is part of their process when making the high output stator, or just the state of the core I happened to get. The solder protruded a couple of mm higher than the Suzuki factory soldering (comparing it to my factory stator harness), just enough to make faint intermittent contact with the engine case and ground out the sensor momentarily. The oil on both surfaces made this intermittent.

It was such a light contact that it seems to have been influenced by the tiny amount of flex in the stator cover and gasket from magnetic force when the stator coils were being energised compared to when they weren't.

Having re-soldered the sensor using less solder, the bike now seems to be running fine.

Have let Rick's know to check this on the harnesses they send out.

 

[jermzfree]

Glad you figured it out. How many electronic accessories did you add to your bike for the need of a high output stator?

 

[David Offor]

Glad you figured it out. How many electronic accessories did you add to your bike for the need of a high output stator?

 

[jermzfree]

View attachment 1572919

I wonder would water/meth pump, electronic gauges, second fan etc.. can push the stock stator/rectifier a little to hard.

 

[David Offor]

I wonder would water/meth pump, electronic gauges, second fan etc.. can push the stock stator/rectifier a little to hard.

Sounds like he's fitted a drugs lab to the bike to me, so in that case, it's probably powering a 240v mains generator, in which case, yes, he would need a high output stator and some large panniers too, I'm guessing

 

[gen1aus]

It's a turbo with a big fuel pump, a front mounted air/air intercooler, and dual cooling fans (which spend more time on due to the intercooler reducing radiator efficiency).

The combined draw of the headlight, fuel pump, and fans previously meant that it would slowly drain the battery while idling.