Misfire

[Solon]

Hello again.
I've recently re-shimmed the valves. Exhaust was  fine, but all intakes were closed, two of them, cyl. 1 were completely closed. Immediately after that, the engine started misfiring, giving short bursts of white smoke in the left pipe.

Cyl. 1, was, just like before re-shimming, showing no signs of stutter when I removed the coil at idle speed, while the other two coils killed the engine immediately when removed. However, the engine accelerated fine with the coil on and stuttered in acceleration without it, so it seemed to be working. I swapped coils between them and took others from the donor Tiger I have, no symptom changed.
New spark plugs +  plug wires from the donor Tiger -  no change as regards the misfiring, but now cyl. 3 shows no signs when I remove the coil, but engine stutters when accelerated without coil. Swapped again coils, tried the CDI from the donor, no change. The tank and tap have been recently checked and cleaned, no chance for water in the system. Readjusted carb settings and synchr. after re-shimming -  no change.
I'm of of ideas, only three options still come to my mind:
1 -  most tempting (!) - setting the Tiger on fire and dancing around it with joy 
2 - ignition pick up sensor - could that cause misfiring?
3 - reopening the engine and closing the valves back to where they were - no matter how absurd this may sound, the symptom appeared immediately after re-shimming the valves, so there may be a connection between the correct adjustment of the valves and the misfiring. Or not?
Help, please, or an innocent Tiger will be burned to death by the fury of its formerly happy owner.

[Sin_Tiger]

Don't take this the wrong way but I would suspect you did something wrong with setting your clearances,  best to open it up and double check the clearances before you totally loose track.

[Solon]

I don't take it the wrong way, but I just don't see what I could have done wrong, just respected the service manual, opened lid, unscrewed camshaft holders, turned rear wheel till each set of cams faced outwards the valves, measured clearances, calculated shim size, fitted new shims, checked clearance again, everything OK, put back the lid.

[rybes]

see my new post Solon

[Sin_Tiger]

Fair enough, got me then, only thing I can think of is what might have been disturbed in that process.

[Solon]

I bought a compress meter and I-ll use it today, to see if it's a valve problem or ignition problem.

[Solon]

Checked compression on all cyl. - 12.5 on all three, quite unlikely that it is related to valves, however, I'll open it and check valves again.
The strange thing is that after the valve job, the problem has moved from cyl. 1 to cyl. 3. Before the valve job, if I removed coil from cyl. 1 at idle, it had no effect on the engine, it only stuttered when accelerated, but it idled smoothly on two cylinders (?). When accelerated with coil, it worked fine. Now it has the same symptom on cyl. 3, but worse, it only starts sometimes when accelerated, most of the time it doesn't work, never at idle, and the engine starts misfiring in 2-3  minutes after starting it, and the misfire seems to get worse as it heats, giving smokey bursts in the left pipe, although cyl. 3 is on the right (!?) .
Only other problem I can think is ignition pick-up sensor, will try to replace it, the other Tiger will be kind enough to donate it. It had symptoms at first, so I have to rule that out.
At my first ride on it, after riding it for a few miles with the choke on, as the carbs were a mess, it heated and started misfiring with short bursts of smoke in the left  pipe and eventually stopped and could not start it again until it cooled. I thought it was just a coil connection that seemed bad, I fixed it and didn't have the same symptoms after that. However, because of some health issues I had (and the Tiger had other issues as well), I've only ridden it for 100 km since, only for short distances -5 to 15 km at once, and the choke was no longer necessary. So I didn't heat the engine again at that temp to see what happens.
Any idea is most welcome - although it seems that a Tiger can raise problems big enough to leave a forum out of answers, just like the local mechanics I took advice from.
Do I have to leak out the oil before opening the cover to check ignition pick up sensor?

[rybes]

ya should be alright to open the cover of the pick up. you might get a little oil dribble out but not much. let us know what ya find

[Solon]

After endless checks and rechecks, I brought a mechanic who sorted out the problem in 5 minutes, now cyl. 3 works, and the bike no longer misfires. He simply played with the mixture, I only played with the air jets between 1.75 to 2.75 turns, while he went on cyl. 3 which seemed not to work all the way to 5 turns.
He finally found the perfect setting at 2.25, 2.5 and 4.5 turns (on cyl. 3). I ran the ike for 30 km on this setting and checked spark  plugs, they seemed ok, neither burned nor whitish.
He had no explanation, he just  told me it's ok and I should ride it and not worry about the weird setting, but to me, it seems too awkward to trust the bike for a long ride.
I checked the carbs and nothing seemed wrong, they were clean etc.
Any ideas what might cause the carbs to run like that? What's the biggest acceptable difference in setting between carbs?

[Mustang]

1. different size pilot jet in #3
2. worn out throttle slide in # 3
3. sucking air somewhere on #3

these would be the three most common faults

[Solon]

Thanks, Mustang. Smth is obviously wrong with it, but I just didn't find the problem. I checked again today, same answer.
So I decided to fit the other set of carbs, the Mikunis. I cleaned them thoroughly, I changed the rubber hoses connecting the air-box with the carbs, as the Mikunis need a different set, and I fitted them to the engine, and then tried to fit the air-box to them - for the next 5 hours -  with no success. Is there any special trick to fit air-box to Mikunis  ? The Keihins are quite easy to fit, while the Mikunis seem very unwilling to receive the air-box. I couldn't fit more than one hose at a time, and while I was trying to fit another, the first one always slipped out, I tried to use the metal collar to fix the first hose, but the other hoses wouldn't fit like that because, with one hose connected, the air-box sits obliquely to the hoses, so they all must connect at once.
Grrrrrr, I 'm seriously frustrated, what's the trick?

[akendall1966]

I find with mine dont put them in engine side rubbers. Fit  to airbox first,  engine second. Liberal silicone grease helps them  pop in. Tighten airbox clamps then seat engine side.

Good luck with it.

[Solon]

Tried that too, still no results. Brought a friend to work with 4 hands - same result. The goddam' thing just won't fit. I just don't get it. Probably the hoses are old and lost elasticity. I ended up fitting the Keihins back.

So I had to take a closer look at the Keihin carbs, I realized that the air jet underneath was fitted badly, the washer was placed first, the O-ring next and than the  spring - only carb 3, so the jet was simply screwing through the O-ring, which explains everything -  the many turns it needed to work properly, the previous misfiring due to bad setting.
The idiots in the service probably misplaced it when I had it there, a fine lesson to do things by myself in the future.

[Sin_Tiger]

So its sorted now?

[Solon]

Sorry, Sin_Tiger, I've been gone for a week to the sea, so I didn't see your post.
Yup, problem sorted, no more misfiring, Keihin carb fully functional after putting the O-ring and shim of the air jet in their natural order, goddam' Mikunis impossible to fit, gave up the idea and realized I only theoretically have a spare set of carbs, in fact the Mikunis are useless because I'll never be able to fit them. I probably need to change the rubber hoses to the airbox, the old ones lost elasticity, it's the only explanation I found for being totally impossible to fit them.