'89 Radian engine into an '85 XJ600/FJ600?

Hi guys!

Long-time lurker, second-time (I think?) poster. I recently dropped an '89 YX600W (Radian) engine into my daily driver, an '85 XJ600/FJ600. Before the heart transplant, the bike was in great running condition save for an oil-burning motor - I live in a crowded area and the smelly smoke was a daily embarrassment.

Anyway, unbeknownst to me, the late-model Radians have slightly different electricals, namely a flywheel mageto at the end of the crank and a single pickup coil, whereas the FJ uses dual pickup coils and a stator that sits under a different cover. I should've noticed the bigger bulge on the left side of the crankcase - doh!

I figured I'd try rewiring the bike. I'm using a period-correct Radian CDI and rectifier/regulator. The ignition and charging systems are wired as per the late-model Radian wiring schematic. I get spark and fuel and all my timing marks are correctly aligned. Valves are within spec.

My issue is - while I get spark on all four plugs when outside the motor, only cylinders 1 & 2 fire under compression. 3 & 4 simply get wet, and the condition stays the same if I swap spark plug wires (swapping 1 with 4 and 2 with 3).

I suspect an electrical gremlin but am at a loss as to what that could be.

So my question is - has anyone else here done a similar transplant? Late-model Radian engine into an earlier model XJ600/FJ600/FZ600? If so, I could certainly use your insights to get my baby back on the road.

Halp,

-Matt

 

For context, the new engine is a fresh rebuild that allegedly ran flawlessly for about 50 kms before it was pulled out of a Seca 550. Guy who sold me the engine has a small fleet of old Yammies and I have no reason to doubt his word.

Compression (measured dead cold) is 145-150 PSI across all 4 cylinders.

Here's what she sounds like running on 1&2:

 

Sound like you have eliminated ignition issues but it might be as well to ohm out your coils and change to new plug caps. Are 3 & 4 headers getting warm at all?
Did you swap carbs too or still using the xj/fj BS 32s ? In any case could be time for a strip and clean..
How about valve clearances (always a favourite topic on this board )?

 

I can't comment on the electrical but you might want to check the offset of the drive sprocket. I was told the output shaft was slightly longer to clear the wider rear wheel on the Radian. I put an FZ in a girlfriend's FJ many years ago and a guy told me that. Never did verify this. The bike and the girl are long gone.

 

Rule#1 - never trust a PO's word
Rule#@ - refer to rule#1

 

Unless you have plug wires hooked up wrong, it sounds like a tci issue. Or 2 bad plugs......

 

..except that it works on 1 & 2 and not on 3 &4 and yet 1 and 2 are on different TCI output 'channels' aren't they ?

 

The coils fire 2 leads per coil.... Should be attached to 1&4, and 2&3. If those are attached correctly,and still only getting spark on 1 &2, then something else is causing 1 lead of each coil to be bad. Could be a bad plug cap on each, could be the tci, could be half of each coil is bad.

But, if one coil is good, then both leads should fire. That's why I said " unless wires are hooked up wrong".......

But with only 1/2 firing, it seems at first glance like there is a tci issue

 

I recommend double checking the period-correct TCI. What is happening sounds like you have an earlier TCI.
I haven't studied the 89 ignition change but are you able to install the entire ignition system from the FJ on this newer crank case? If that is a possibility I would do try that.

 

One other thing is that the lettering on the pickup rotor and the TCI should match. That's another easy first check..

 

Still using the stock 32s with the stock airbox. I cleaned the carbs in April of this year and the bike was fully functional before the engine swap.

Thanks for the heads up! Good to know. The mechanic who did the engine swap didn't mention anything to that effect, but then again all he cared about was dropping the engine into the frame. I've got a shimmed front sprocket after doing a 520 conversion so I may need to remove the shims from the front and add some to the back.

Yeah it's looking more and more like I've got a faulty CDI.

It's definitely the correct TCI - TID14-79.

What do you mean by "the entire ignition system from the FJ?" I can't move the FJ's dual pickup coils over since they are at the end of the crankshaft, and on the newer crankcase that space is also occupied by the flywheel magneto and the stator. So right now I've got Radian CDI/TCI + rectifier and FJ starting circuit which uses a sidestand relay and also another combo relay that includes turn signal function and part of the safety interlock switches. The Radian uses no sidestand relay and only a flasher relay. I'm thinking that's where a wiring conflict may be happening, but have no idea where to start to even test that hypothesis.

Interesting, will go check that and report back.

Thanks all for the assistance, I'm at my wits' end with this thing.

 

So no markings on the rotor/flywheel. The TCI's Yamaha 3-letter model code (3LT) does match that of the engine case, so I got that going for me.

I suppose the next step is to try a TCI that's known to be good. There's one on eBay right now but the price tag is a little steep, especially after converting to Canadian tomatoes. Ugh.

If anyone sees a TID-79 (3LT) TCI on Craigslist or else, please do ping me! I'm told that a TID-78 (3KM) would also work but would rather use the very same unit to begin with.

 

Oh, another bit of info that is probably relevant - the '89 Radian uses a different diode block that has no Yamaha part number (!) The part doesn't even show up in the official microfiches. I only have a barely legible wiring schematic in my Haynes manual as reference (see the attached.)

 

Engine swaps often also require wiring harness swaps, or modification. I doubt that the TCI is at fault.

 

As per my original post, I did modify the wiring harness to accommodate the different components and pinouts. The one area I have not touched is the diode block since I can't find a part number for the '89 Radian. I'm fairly handy with a soldering iron and can try to make my own, I would just need some guidance as to what type of diodes, resistors and whatnot are commonly used in these things.

 

BTW here are both the '85 FJ and '89 Radian wiring schematics, should an amenable soul want to play along.

FJ: http://i.imgur.com/SYk1xRz.jpg

Radian: http://i.imgur.com/mqkL8Qn.jpg

(The Radian's schematic is just as borderline-unreadable in the actual hard copy I scanned.)

 

Wait, I found the part. What's described as a "diode" in the Haynes manual, Yamaha calls a "relay assembly", part number 2UJ-81950-00-00.

We're making progress here.

 

So did you wire the L/Y wire on the TCI through the side stand switch so it has a path to ground?

 

I wired the sidestand relay to the L/Y on the Radian TCI. I figured that when the sidestand relay is energized, it's the same as connecting the sidestand switch directly?

 

Your likely correct on that as you do have spark. I was trusting the Hayne's manual that states the side stand switch contacts close when up and it does not differentiate between models on that test. Could be on the YX it opens to remove ground, which is ultimately what the side stand relay does.

It appears to have a relay mixed in with the diodes and resistor, I guess that was their logic. That's going to be a challenge to wire since they don't give wire colors for it on the wiring diagram.