Dead Cylinder

I'm stumped! 75 Z1B #4 dead. Starts and runs on 1, 2 and 3 nothing on 4. At 3500 - 4000 rpm engine surges slightly like # 4 is hitting occasionally. I think it is hitting at higher speeds, maybe above 4500, Not sure how tell for sure?
-1075 kit
-Cam motion Z2 cams
-Dyna S
-V&H 4-1
- 29 mm Smooth bores 120 main, 22.5 pilot, needles in center groove.

170-175 compression on each cylinder, good spark on all cylinders, swapped plug wire 1 and 4 and still no fire on #4 but # 1 still ran OK, tried 3 different spark plugs (NGK B8ES). Heat gun shows #4 way cooler than other 3 cylinder. At idle pulling plug wire on #4 doesn't effect idle (pulling any other wire stalls the engine.
Disassembled and cleaned carb #4, set float levels with clear tube method, bench synced slides air screw 1 turn out same as others.
Still no fire on #4.

What am I missing here?
Ideas?

Valves adjusted? Clogged pilot?
Steve

Pilot is good, removed jet and cleaned, blew air through all the passages and all were clear. Didn't set the valves as compression was good on the cylinder. Would you check valve clearance if compression was good?

Yes. Routine maintenance.
Steve

Buster wrote: Pilot is good, removed jet and cleaned, blew air through all the passages and all were clear. Didn't set the valves as compression was good on the cylinder. Would you check valve clearance if compression was good?

Yes, because a too tight valve may allow good cold (testing) compression which becomes poor compression at normal operating temp.

As #4 plug wire is able to fire the #1 plug, if the #4 plug wire is old or cracked, perhaps it's leaking voltage to the head when connected to #4 plug but not leaking voltage to the head when connected to #1 plug (which could result from the different routing of the #4 plug wire when connected to the #1 plug).

Is the #4 plug wet with fuel?

Good Fortune!

OK, thanks guys! Will set valves and wires are old enough that they are probably due for a change also.
Any suggestions on where to get a quality set of wires?

Buster wrote: OK, thanks guys! Will set valves and wires are old enough that they are probably due for a change also. Any suggestions on where to get a quality set of wires?

Would test-run the engine with #4 plug wire re-routed so that it's not touching any metal parts such as the valve cover. Possibly by using a rubber grommet temporarily between the plug wire and where it normally rests on the valve cover. Even the stock plug wire clips attached under the cam cover bolt heads can be the source of contact for voltage leakage between old plug wires and the engine head. Could also temporarily suspend the #4 plug wire away from any contact with the engine head.

My old plug wires got to leaking so much that I could feel a buzz when touching the petcock when changing to reserve tank position while riding.

Another fun test is to spray water mist over the plug wires with the engine running in a dark garage. Watch for sparks which may be produced where high tension voltage is leaking from an old hard cracked plug wire to the engine head.

Am a well-satisfied, long-time user of Dyna solid core spark plug wires, which come with caps already built-in, and are available at Z1E.
Click here > www.z1enterprises.com/search?q=dyna+plug+wires

Good Fortune!

When I first got the bike running again in 13, I ran my wires through blue swamp cooler hose until I could get new coils. Worked great and booked sexy too. :lol:
Steve

So my records show last valve set I did all were at .004 - .005 (that was 13 years ago but only about 2000 miles).

What clearance are the smart guys using now days? Cold engine? Exh. same as Intake?

Anybody else getting old and senile and losing their memory? :S

FSM says 0.05~0.10 mm (0.002"~0.004") cold clearance for all valves.

Some pretty smart tuners suggest staying closer to 0.10 mm (0.004") on intakes and up to 0.15 mm (0.006") on exhaust.

Good Fortune!

Could be a failed plug too. Test it or replace it before the other work. R

I've chased my tail many times on whether it was a spark or fuel issue causing a single cylinder misfire. Then I remembered that inductive pick-up timing light gathering dust in the bottom of my tool chest. Clamp it on the plug wire in question and you'll see right away if it's a spark issue or not. Timing lights may be harder to find now a days with everything being being sensor based. Check yard sales, Craigslist or Ebay for a cheap one.