Now my Steamer won't Start....

[Tigger96]

I have here my 1996 Tiger, california model, with Mikuni carburetors that I've known for just a few months now.  Odometer has 39k miles of which I clocked the last 1K.  The bike had always started immediately, no hesitation until one day when leaving for work.  I had forgotten to switch the fuel on such that the bike died at the end of my street, sooo...petcock on, give it a spell to reach the carbs, then fire it right up (it was already warmed up, choke off and all)....nope, instead WHACK!, WHACK!, WHACKITY WHACK! as it cranked but no love.  I've come to learn all about sprag slap in this forum and I'm guessing that's what I was hearing.  It took a few more tooth grinding attempts before we were up and running fine.  I hadn't experienced anything like this before with the bike, so prayed it was a fluke, and set off.  The situation, however, has gotten progressively worse to where I can no longer rely on it to start nor can I continue to abuse that angry little sprag.  Here's a list of what I've looked into:

Valves:
Exhaust:   (#1).15--.15  (#2).16--.16  (#3).16--.15
Intake:     (#1).10--.10  (#2).11--.13  (#3).10--.15
These are the measurements after swapping 3 shims on valves that where full on out of spec.  I used the special valve tool to pick out the bad ones, but couldn't extract the #1 intake 'cause the slots on the valves aren't facing in an accessible direction (gaps still within spec though), but seems I may need to pop the cam in the near future.

Coils:
It has three nice PVL coils that all bench test fine.  I bought one brand new Nology coil so I could swap it in one at a time looking for a bad apple.  No change.  All plugs get proper spark once the bike is up and running, though the test tool shows no light when cranking to start.
BTW Nology are PVL coils with Nology stickers on them (stamped "PVL made in W Germany.")

Plugs and wires:
Two of the plugs were a bit sooty, but nothing too nasty.  I replaced them all with new, properly gapped, NGKs.  The wires look good and bench test good.

Ignition pickup sensor:
I've read these guys often fail, though I've never witnessed any of the classic symptoms of failure (eg. tach dropping off, or poor running once warm.)  Bench test resistance looks good and there is no performance difference whether warmed up or stone cold.

Electrical:
The battery is new, of high quality and fully charged.  I unplugged, sprayed with contact lube, then reinserted every connector I could locate especially at the igniter box and subharness.  Nothing green, decayed or fuzzy to report.

Fuel delivery:
Gas is definitely getting to the carbs.  The original petcock was a leaker and has been replaced with a nice 'n tight fitting yamaha part.  The problem emerged prior to the petcock swap, so I don't think there's any relation here.  I've tried starting it with the line disconnected from the tank and also with the cap open, but there's no difference in results.  Fresh, soft fuel lines have also been swapped in, replacing the old hard stuff.

Carburetors:
The PO told me at purchase that he had recently done a full carburetor go-through and cleaning, though hadn't done any advanced syncros beyond the bench.  It had run just fine, maybe not the best gas mileage, but fine until this initial incident.  I pulled 'em to check for any funk, but found nothing unusual.  All jets were clean and clear, no deposits or weirdness in the float bowls or elsewhere.  I replaced the three carb-to-head rubbers as one was in pretty bad nick.  The air filter had a small tear/bypass that I patched.  Everything went back together as "easily" as it came off, though I'm not 100% sure the vacuum hoses/solenoid valves are routed properly.

As mentioned, the bike had always started right up on the first flick of the button; never a hesitation.  Now, I get that ugly whacking noise as it cranks with the occasional intermittent hic-cough of combustion.  When/if things catch and the bike starts, it runs quite nicely...blows some smoke 'til warm, but runs and responds to throttle nicely.  I believe I've been through all the basic 'spark-gas-air' check list and am now at a wall.  Here is where I implore the TigerTriple community for advice, knowledge and help...all chime-ins welcome and dearly appreciated. Thanks in advance, good people.

[threepot]

Seems you've done everything but fix the only problem left.....the sprag!! I've only done the one under the 'inspection plate ' on a 93 Trident..But you'll have to strip the bottom of the engine on your bike,96. But apparently its not too difficult. And plenty of knowledge from the guys here. 

[Sin_Tiger]

Engine out and do the sprag before any gets damaged.

Then take your time putting it back together paying particular attention to avoiding air leaks on the pipes and manifolds.

Check the cam chain tensioner, careful not to let the chain slip on the crank.

[Tigger96]

Yeah....classic sprag, right?

The more I learn about the sprag unit, the more it makes sense.  Should that retention spring ever give way, the bike could reasonably go from totally fine to more or less fuct in a blink.

Anyone out there want to make me an offer on this "rolling project" before I start tearing 'er apart and committing myself? 

[nickjtc]

Anyone out there want to make me an offer on this "rolling project" before I start tearing 'er apart and committing myself? 

Now now (easy for me to say because I didn't have to go through this with mine) keep the upper lip stiff and do whatever it takes to keep one of the beasts going

[P3aK]

A few pieces of wood is very helpful to support the engine when it's out. You have to undo bolts from both sides to actually split it, so you'll have to turn it upside down and upright a few times.

When you split the two halves of the engine you'll notice there isn't any gasket there, just left over sealant of whatever was used. This is the way it should be, but I recommend you get the best sealant that you can buy. It took me 5 tries to stop those two halves from leaking. I ended up using some really expensive copper sealant.

Clean all the surfaces properly before putting it back together. Take your time, rushing will end with problems. Document everything, you think you'll remember where everything went, but you won't. So take pictures and keep the bolts and nuts belonging to different things in different bags/bins,. I actually used post-it notes and wrote little directions and what it was for. That saved me couple of times.

It isn't that difficult really, it's just a lot to keep track of.

Oh and before you do anything. Clean, clean the bike, clean the garage, clean/sort the tools. You'll be happy you did. There'll be enough dirt left over even after you clean. Makes it easier to organize and keep track of the pits and pieces.