Board index Flathead Power-Technical Questions, Answers, and Suggestions K-Models How much air puff out the vent?

How much air puff out the vent?

Moderators: Curt!, Pa

Post Fri May 05, 2006 4:23 pm

Posts: 330
Location: north central Ma.
How much air puff out the vent?

Got my 52 k running well (sort of) again noted it puff a lot out the vent i had cut some wood in the drive way and drove over the chips it will blow them away.

The more i run this bike the more it smokes out the exhaust on start up and when revved and a puff on throttle closing. It didn't do this 400 miles ago when i got it.

I'm thinking rings with the amount it puff out the vent but normally i'd say valve guides cause it heavy on start up but it a flat head so how would it pooling the intake tract?

So much to learn.......so little time...............

44dwarf
"Smok'in the competition NOT Tobacco"
"Transplant organs, Don't bury them!"
Why dwarf? 5/8 scale race cars! http://www.dwarfcarracing.com

Post Fri May 05, 2006 11:34 pm

Posts: 640
Location: Wisconsin, USA
The only way it could be valve and guide related is if the oil return slot in the tappet guide is plugged with carbon and the valve cover is full of oil. They do puff a bit out the breather tube, are we talking oak chips or balsa?

Post Sat May 06, 2006 7:05 am

Posts: 330
Location: north central Ma.
Pine chips from a chain saw ~1/4 x 1/4 1/8 thick from a big husky and a 24 bar so chain size is big. It puff out the vent allot more then i thought a dry sump would but I'm not an expert on HD's.
All my dry sump work has been on sealed crank cases with vented tanks in race cars where you pull a vacuum on the lower end to aid in ring seal and anti ring flutter.

I don't buy the guides worn my self gravity always takes the easy way out.

44dwarf
"Smok'in the competition NOT Tobacco"
"Transplant organs, Don't bury them!"
Why dwarf? 5/8 scale race cars! http://www.dwarfcarracing.com

Post Sat May 06, 2006 7:26 am

Posts: 1050
Location: Greenbackville, Virginia, USA
44dwarf, i'm guessing you K model has sat for a number of years? If so, the rings have probably gummed up and are letting some compression past. Have you tried a compression test? A leak down test? They'll give you a good indication of what shape your rings-valves are in. In the past i've freed rings by squirting KROIL in the spark plug holes and kicking the engine through a few times and then letting it sit for an hour. Squirting again, plugs in, then starting it. The valve covers/lifters on my KH get a LOT of oil, so a puff of smoke when you snap the throttle closed, if the rings are OK, is not unusual, and means oil is getting to the valve stems. Just my $0.04 G 8)

Post Sat May 06, 2006 12:45 pm

Posts: 330
Location: north central Ma.
Yes it sat for ~5 years at least twice. I've been running a pint of marvel oil in the oil tank with valvoline 50 and changing it offten (every 100 miles or so) a slash in with the gas to.

Been looking for my dual gage leak down tester but no luck i must have let it out. :cry: but to who?

44
"Smok'in the competition NOT Tobacco"
"Transplant organs, Don't bury them!"
Why dwarf? 5/8 scale race cars! http://www.dwarfcarracing.com

Post Sun May 07, 2006 7:28 am

Posts: 1050
Location: Greenbackville, Virginia, USA
44, like Kyle said, some puffing out the vent on a K model is normal, and necessary. The oil in the crankcase is pushed out by the air pressure from the downstroke of the pistons through a timed breather into the camchest where it is eventually picked up by the scavange pump and returned to the tank. When the pistons start the upstroke the timed breather is closed. If the breather is incorrectly timed it will cause excessive oil consumption, leaks (you'd be amazed at some of the places a K type can leak) and loss of power. G 8)


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