Flywheel compatibility / ignition problems

[patrino]

Hello, first post to this forum!

I picked up an FZR400/600 racebike last November, and have been working on it over the winter, to get it ready for the 2015 season.

I'm wondering about the compatibility of different flywheels between the FZR400 and FZR600. Are the pickup tabs on both flywheels in the same location relative to the keyway? Are the keyways on the 400 cranks in the same place as the keyways on the 600 cranks?

The bike came with a Yoshimura ignition system (pickup plate and sidecover). Bike started and ran well. I removed the Yosh system because I didn't want to run total loss (I did that on my GS1000 racebike all last season and wanted the "luxury" of all the modern conveniences.)

I mixed-and-matched a rotor & stator assembly from the many tubs of spares I got with the bike. Part number on the flywheel is FL118-13.

I've got spark now but the bike won't run, only pops and farts every few strokes. Sounds like ignition to me.

Potentially relevant details:
- Cases are "3BF" (which I believe are 400 cases), top end is FZR600.
- Ignitor unit is 3HE
- The flywheel is "concave in", and has FL118-13 stamped on it.
- Stator-to-flywheel clearance is good
- Gap between rotor and hall effect sensor is ~4mm. (I couldn't find a spec on this in my manuals or on this forum - any suggestions?)

I lined up the keyways to the Yosh system and the FL118-13 flywheel, and the four pickups on the are in notably different places.

Could a bad CDI box do this, as well? Again, it "ran when parked" so I don't think that that's it.

Any suggestions/thoughts appreciated. I spent a while checking out the forums but didn't find any info on this; my apologies if it's been covered before.

I'll get some photos up if you're interested.

Thanks, Patrick

[DonTZ125]

Hi, Patrick.

You have a FZR400 rotor and crankcase; I assume that since you have been able to install the stator and pickup coil under the rotor that these are also the 400 version. The TCI is from a 600; the 600 box will run a 400 with one minor wiring mod, so that isn't the problem.

The 400 and 600 ignition curves are quite conservative; they have to be able to run on some pretty crappy gas out in the back of beyond without punching holes in the pistons. A VERY common mod is to advance the ignition 5 degrees, either by advancing the rotor with a customized Woodruff key, or by retarding the pickup coil (not hard, but takes a bit of careful grinding). If the timing teeth on the Yosh rotor are more than 5deg, then I would assume that this was designed with GOOD race gas in mind.

Note that stale gas may be simply unable to light off; try fresh gas. If this beast has sat for awhile, the carbs are likely gummed up and full of water, crap, and small animals. Full strip and clean, be prepared to replace some of the gaskets. At the same time, check the leads from the TCI to the coils, and the HT wires from the coils to the plugs to make sure they're in the correct order.

[DonTZ125]

the 600 box will run a 400 with one minor wiring mod, so that isn't the problem.

Actually, the fact that you're getting coughing and sputtering AT ALL says that this mod has been performed, and the TCI is working!

[patrino]

Thanks for the feedback, very helpful!

I will try new gas. The stuff I put in it isn't by any means brand new (a few months old), and the stuff here in Oregon can go bunk pretty easily.

I did clean the carbs prior to trying to light it up, including a clean sweep of the pilot circuit. Also had checked that both coils were getting power, and that the LH coil was sparking #1 and #4.

You mentioned a wiring mod to make the FZR600 TCI work with the FZR400 pickup. Do you have any details of that mod? Based on the fact that the bike had run well prior to my mucking about, I figure he'd done it right, but I want to make sure I didn't screw anything up. There's a 6-pin connector going from the main harness to the TCI, then two wires (the ignition trigger wires) going to the 8-pin connector also on the TCI box (the other 6 pins in that connector are unused).

Also, do you know the ignition pickup to rotor clearance, please? I checked my manual but did not see a spec. I have at least two different kinds of pickups in my spares.

[patrino]

Here we go, for the 3HE box with 400 pickup coil: viewtopic.php?f=7&t=12271&p=99497&hilit ... ion#p99497

That look correct?

Still would like to know about pickup sensor gap if you have info, please!

Related question: did ALL 600 motors have "concave-out" flywheels? (As opposed to the "concave in" 400 flywheel I have)

Thanks!

Patrick

[DonTZ125]

No idea on the sensor clearance. Wiring mod is to ground top-center wire on 6-way connector. This is a racing mod; for street use, replace N/C sidestand relay with N/O version (available in most auto stores).

The FZR600 was fundamentally unchanged through existence.

[patrino]

Took a close look at the flywheel with the starter turning. It's got a pretty significant taco to it! Someone probably dropped it at some point, my guess. At first I thought the crank might have been bent but I checked the runout and it's fine.

Can't help but wonder if that had something to do with the ignition problem. Doubtful, but I believe that the Hall effect sensors like a nice sharp edge to detect a signal from the rotor.

Now looking for an FZR400 flywheel if anyone has one (there's a post in the classified section, or you can PM me).

[DonTZ125]

The FZR series all used a variable reluctor sensor, not a Hall. Given that the VR signal is influenced by metal approaching or moving away, it's certainly possible that a serious dent could confuse the TCI.

Sidebar - Hall sensors and sharp edges is less about the ability to detect the tooth, and more about reducing the possibility of timing jitter. A ramped approach could result in the sensor signalling the tooth before the actual 'tooth edge' is crossed.

[patrino]

Thanks for the info about the VR vs. Hall sensor, good to know!

When the FZR TCIs fail, do they typically just "go"? Any idea what the common failure modes are?