VL front cylinder running hot

[montij]

Just getting my VL running. It’s running well but I’m noticing the front cylinder is much hotter to the touch than the rear after a brief warmup. In Steve slocombes book there is a brief mention of running a cooler spark plug in
the front cylinder. My question is why Is the front cylinder so much hotter? Should I be concerned ?

[T. Cotten]

Just getting my VL running. It’s running well but I’m noticing the front cylinder is much hotter to the touch than the rear after a brief warmup. In Steve slocombes book there is a brief mention of running a cooler spark plug in
the front cylinder. My question is why Is the front cylinder so much hotter? Should I be concerned ?

The front is unfortunately slightly hotter for debatable reasons, Montij,...

But it should be un-noticeable if everything is in order.

Again I must preach: The first diagnostic should be https://virtualindian.org/11techleaktest.html before chasing other loose ends, or masking it with a band-aid.

....Cotten

[montij]

The front is unfortunately slightly hotter for debatable reasons, Montij,...

But it should be un-noticeable if everything is in order.

Again I must preach: The first diagnostic should be https://virtualindian.org/11techleaktest.html before chasing other loose ends, or masking it with a band-aid.

....Cotten

Thanks Cotten I’ll check the manifold with soapy water

[Steve Slocombe]

Dear Montij, the VL front cylinders do run noticeably hotter than the rears. The reason is that the flywheels run clockwise seen from the timing side, so splash oil into the rear cylinder but the front always struggles for lubrication. Harley installed full cast baffles in the front crankcase and half baffles in the rear, on the theory that this would give more suction on the front cylinder and draw up more oil mist. Many VLs have the baffles broken, damaged or deliberately removed, in the incorrect belief that this would help when Harley removed the baffles in 1940 for the recirculating oil bikes. There were also no oil rings on the VLs and I now routinely remove the front oil ring and sometimes the rear. Finally, Harley built the engines on the tight side with a 1000 mile break-in period, which no-one will do today, compliucated by tiny piston clearances specified for the T-slot pistons. With the strutted pistons most people find as replacements, I'd allow 6-7 thou clearance on the front and 5 thousandths on the rear. Check what you've done and it is not too late to take out a little more metal from the bores and remove oil rings at the front. These are fundamental design featrures of the VLs and JDs and nothing to do with the inlet manifold, which you may want to check later.

[T. Cotten]

... These are fundamental design featrures of the VLs and JDs and nothing to do with the inlet manifold, which you may want to check later.

Steve suggests you wait 'til it breaks, Monti!

....Cotten

[montij]

Dear Montij, the VL front cylinders do run noticeably hotter than the rears. The reason is that the flywheels run clockwise seen from the timing side, so splash oil into the rear cylinder but the front always struggles for lubrication. Harley installed full cast baffles in the front crankcase and half baffles in the rear, on the theory that this would give more suction on the front cylinder and draw up more oil mist. Many VLs have the baffles broken, damaged or deliberately removed, in the incorrect belief that this would help when Harley removed the baffles in 1940 for the recirculating oil bikes. There were also no oil rings on the VLs and I now routinely remove the front oil ring and sometimes the rear. Finally, Harley built the engines on the tight side with a 1000 mile break-in period, which no-one will do today, compliucated by tiny piston clearances specified for the T-slot pistons. With the strutted pistons most people find as replacements, I'd allow 6-7 thou clearance on the front and 5 thousandths on the rear. Check what you've done and it is not too late to take out a little more metal from the bores and remove oil rings at the front. These are fundamental design featrures of the VLs and JDs and nothing to do with the inlet manifold, which you may want to check later.

Thank you Steve for this information. I was not able to find the cause after checking many things. This motor is as found and not a new build. I will remove the oil rings in the front as you suggest.

would you suggest a colder spark plug for the front as well?

[Steve Slocombe]

The flatheads are usually very tolerant about spark plugs but something equivalent to a Harley number 4 on the front would not hurt.

[T. Cotten]

Don't look now, Folks,....

Unless there is pre-ignition or it fouls out, the 'heat' of a sparkplug has no effect upon motor temperature.

A 'colder' plug does not make a cylinder run cooler..

....Cotten