rear cylinder misfiring help

[cscott]

well I would like to report all fixed but.. replaced the intake seals with peak seals pressurized to 15lbs all good, drained case oil, fired up same thing adjusted carb , no change, have noticed when the exhaust valve stem cover is up on rear there is oil on the stem. thought this was because of misfiring , now starting to think sticking or leaking valves, they were pro re-built so I didn't think so but its looking that way...any thoughts welcome

[tfburke3]

Your welcome.
BTW the Riders Iinstruction book,I have nineth revision for 334, has lots of good info for your bike.Not sure if JG or who sells now,maybe even in the Virtual library.
In "Sources of motor troubles and remedies"#7 Motor misfires-(a)Poor carburetor adjustment;usually too rich. (b)faulty mag (c)ex valve not seating properly,usually tight(d) spark plugs set wrong or in need of cleaning (e)weak or broken valve springs,replace them
have fun
Tom

[cscott]

Thanks Tom, I will give those a try....I have been told many different gaps , good to hear from someone who has the same set-up.chris

[tfburke3]

thanks Tom, could you also tell me the gap you use on the plugs and mag? thanks chris

The riders instruction book says .020 for points but dont say which mag.I run.018-.020.
Spark gap spec is .025-.030.
Tom

[cscott]

thanks Tom, could you also tell me the gap you use on the plugs and mag? thanks chris

[tfburke3]

Hi Chris,you need to drain it before for the sitting leak down and after a run to determine the running sump volume .
Although 1.5 is the factory setting it may be to much and on mine would wet sump,especially on a longer run.TRy 3/4 and if you get oil circulating back dont worry about not enough oil.
The return pump is not able to keep up with supply so you have the pinch off screw adjustment.
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

[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

[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.

[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.

[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]

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

[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

[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

[cscott]

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