rear cylinder misfiring help

[cscott]

1934 chief with magneto, can't figure out why my rear cylinder is missing. checked spark, valve gaps, compression, out of ideas. when it misses I get some oil out of the exhaust port? help thanks chris

[T. Cotten]

Diagnostic #1, Chris!

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

Please use a constant, regulated air supply,

Then you can go on to other things..

....Cotten

[hairynob24]

sounds like it may have wet sumped ?

[cscott]

well I made up a pressure test fitting and gave it a try found a few very small bubbles, don't think this is it cause front cylinder runs fine , open to other ideas thanks chris

[T. Cotten]

well I made up a pressure test fitting and gave it a try found a few very small bubbles, don't think this is it cause front cylinder runs fine , open to other ideas thanks chris

No leak is an acceptable leak, Chris!

If you saw any bubbles at all, fix that first (or fix a lot more later).

....Cotten

[tfburke3]

Was it ever running good?
did you check the ignition timing of each cylinder?If say the front( #2) cylinder is timed with rear #1 mag cam shoe the timing would be right only for the front timed cylinder.
When I had my 34 apart I put some center punch marks 1/2 btdc for both cylinders centered in the oil vent line hole. Then set up the mag with magneto induction timer.Makes timing and check mag a lot easier.
Tom

[cscott]

what does anyone think of kiwi composite cones for the intake manifold ? thanks

[cscott]

when at idle or running slow it misses when I ride and speed up it smooths out at higher rpm, the mag is a baby bosch and the gap I tried at 15 and 20 cant get alot of info about this mag, with plugs out and spinning there is good spark at both plugs

[T. Cotten]

what does anyone think of kiwi composite cones for the intake manifold ? thanks

Not familiar with them, Chris,..

Unless they are Endfield Racing's mass-produced PEEK seals.

Or perhaps Mike is properly custom-cutting PEEK?

If they stop the bubbles, they work!

...Cotten

[Steve Slocombe]

A wrong degree magneto would take a lot of diagnosing...

[cscott]

hi steve, this is what I have a ffvrs 53 the interrupter is 42 degree and it is set up for counterclockwise rotation heres some pics maybe iam missing some thing100_1967.jpg100_1971.jpg100_1968.jpg100_1969.jpg

[Steve Slocombe]

We must have members more expert than me on magnetos. Over here we had a 50 degree motor fitted with a 45 degree mag which had rear cylinder problems too. A 45 degree mag on a 42 degree motor would also run unevenly. It must be worth one last check before moving elsewhere.

[TechNoir]

I am no expert by any means although I have been chasing a fault of my own recently.

You say it misfires at low revs but is OK at higher revs?

First fix the intake leak that you mentioned.

Then get the ignition right. I have always been told that most fueling problems are really ignition problems. Measure the firing point BTDC on both cylinders in case, as Steve mentioned, the mag has the wrong timing.

Do those two things first before moving on.

John.

[tfburke3]

The position of the points in pic is about where you would be timing front cylinder,with front wire to front plug.
My mag timed the rear cylinder slightly late even though its also 42,so I had to take a little off the front cam shoe.I doubt the motor would have misfired though.
Thats a beautiful mag,I wish my rubbing block showed as little wear.
Also the suggestion about wet sumping is a good point and easy to eliminate by draining the sump after a run and see how much oil is in the sump.
Tom

[cscott]

hello Tom , if it sits around awhile it will wet sump , I drain it from the upper plug before I run it. What do you think the cause of the wet sumping may be as when running the return line does have oil coming back, I have the supply screw at 1.5 turns , could that be to much? thanks chris