flathead front cylinder cold as bike is running

[Streetbobber74]

hello, just wondering is it possible for my flathead to start and run on one cylinder?
i only ask this crazy question because my front cylinder is very cold as the rear is hot to the touch. as well as a small about of oil coming out where the exhaust and front cylinder join. any suggestions please. thanks scott

[Sargehere]

Is the front cylinder firing EVERY time the rear one fires? There are a few reasons for a twin to fire on only one, all ignition: bad plug, bad plug wire, bad coil. Then there are mechanical, like loose plug, blown head gasket, humungous intake manifold leak (you'd hear a blown head gasket, "PFFFT, PFFFT..." or intake leak big enuf for it to not fire at all).

Have you had the timer ("distributor" some mistakenly call it) out of the case, recently? Timing.

[Streetbobber74]

I'm very new to the older bikes, as this is my first kickstart, how will i know if the front cylinder is firing every time, is there a way i can check that? can't thank you enough for the quick response. i just picked up some new plugs gonna try that, tonight or in AM. i have not had the timer out of the case at all.
just got the bike myself a few weeks ago.

[Streetbobber74]

gerry
thank you very much, swapped out the front plug, which was just nasty black, bike fired up on the 2nd kick. sometimes its the obvious stuff right in your face you don't see. thanks again.

[BigLakeBob]

You still may want to keep a watch on the coil, wires or intake leak, it could have just been a plug but something else may have caused it to foul.

[SamJ]

Reviving an old thread here: I recently picked up a 49 WL, and it's running on rear cylinder only. I tried different plugs, replaced coils and wires with Bulldog Bros (great guy to deal with btw), but still only rear firing. Is my next step the intake manifold? Any other rabbit holes to go down? Bike is a mostly-original, mostly-unrestored barn-find. It has all new wiring, coil, plugs, wires & battery, plus carb has been overhauled. Points/condenser are old.

[T. Cotten]

...Is my next step the intake manifold? ..

Your instincts are good, Sam!

https://virtualindian.org/11techleaktest.html

Good Luck!

.....Cotten

[otis71]

Easy to diagnose. Pull the spark plug wire off the running cylinder and it’ll stall if the other isn’t firing.

[SamJ]

Your instincts are good, Sam!

https://virtualindian.org/11techleaktest.html

Good Luck!

.....Cotten

Thank you for the reply, sir. I'll start looking for a testplate ASAP.

[duffeycycles]

pull the front plug & quickly pass a propane torch over the plug hole & clear any fuel from the cylinder
--------------------------
When running,pull the spark plug wire off the not firing, front cylinder.
Hold the wire close to the plug electrode a see if it starts to fire or if there is spark at all.
Sometime a severely fouled cylinder will clear itself.
Right after a severe rain at Wauseon bikes were soaked,My servi had water standing on the heads around the plugs.
Many watched me try to start my servi,making jokes that there was no way it would.
Started on rear cyl only,removed wire to front,held close & it quickly cleared itself & I rode away.

[T. Cotten]

Thank you for the reply, sir. I'll start looking for a testplate ASAP.

If you cannot carve your own, Sam,...

Mine are ABS plastic with a simple nipple, instead of a stupid Schrader valve like ebay gems.

TESTKIT.jpg

It you find a leak, the manifold must be removed, and the inlet nipples tested separately with some sort of plug, and mine are rubber stoppers perforated for a nipple.

Anything that fits will do!:

PATRON.jpg
But it takes three hands.

....Cotten

[SamJ]

Awesome advice, looks like I got my work cut out for me!

[T. Cotten]

I typed a long reply to your personal message, Sam!

Honest I did, but this forum's format sucked it up and it disappeared.

Please feel free to email me direct at Liberty@npoint.net for my test equipment prices, but I encourage you to innovate instead!

(Self-reliance is pretty intrinsic to enjoying these machines.. Computers not so much.)

....Cotten
PS: Re-clicking my email notification brought up the ghost of my attempted reply, but wouldn't let me edit my successful reply. PMs ain't worth it.

[dukekleman]

SamJ,

Have you confirmed the condition of the front cylinder that isn't firing by performing Compression and leak down test?

Duke

[T. Cotten]

SamJ,

Have you confirmed the condition of the front cylinder that isn't firing by performing Compression and leak down test?

Duke

Great idea, Duke!

Can you give us base-line parameters for the leak-down on a 45"?

Thanks in advance,

....Cotten