quick question
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Novice
Joined: Apr 2008
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From: Eastbourne East Sussex UK
quick question
hi again,after finding out the grinding rocks noise was the cam bushings(post earlier this year)had them replaced and i put things back together, everything lined up as it came apart(timing marks on cams)but i have noticed that when 1 cylinder is on compression stroke the opposing cylinders valves are both open,this is the same for front and rear cylinders is this normal? or have i screwed thing up
Stellar HDF Member
Joined: Feb 2006
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From: Houston Texas
hi again,after finding out the grinding rocks noise was the cam bushings(post earlier this year)had them replaced and i put things back together, everything lined up as it came apart(timing marks on cams)but i have noticed that when 1 cylinder is on compression stroke the opposing cylinders valves are both open,this is the same for front and rear cylinders is this normal? or have i screwed thing up
When the front exhaust valve is fully closed........the rear exhaust is open.
Ditto for rear cylinder valves closed.....then the front ones are open.
I think you are fine with what you have.
As long as you timed the breather notch with the flywheel at the timing mark in the hole......then installed all of the cams with the timing marks aligned (the timing hole mark is not part of that) then you are fine. There is really no way to screw this up..........pg
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Novice
Joined: Apr 2008
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From: Eastbourne East Sussex UK
nice one pg, thanx for the help,i just removed the gearcase cover and cams, and didnt disengage the crankcase rotary breather valve from the oil pump drive gear when i stipped it down ,so should be ok?, didnt want to try starting it untill i knew things were ok, jus waiting for new points and condenser to arrive and will be attempting to start it up,will post and let you know how things go,many thanx again lewzab
Stellar HDF Member
Joined: Feb 2006
Posts: 3,035
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From: Houston Texas
nice one pg, thanx for the help,i just removed the gearcase cover and cams, and didnt disengage the crankcase rotary breather valve from the oil pump drive gear when i stipped it down ,so should be ok?, didnt want to try starting it untill i knew things were ok, jus waiting for new points and condenser to arrive and will be attempting to start it up,will post and let you know how things go,many thanx again lewzab
Cruiser
Joined: Oct 2008
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This probably for Piniongear more than anyone else,When I built my 1970 XLCH (in1971) I had built one other stroker motor the year before for our fuel drag bike (77cu. in.).When I started it it ran fine ,when ever you got on it ,it would blow the oil dipstick out and you had to go back and get it! I racked my brain trying to figure out the problem, fially gave up and had to take a look. I had lined up all the timing marks perfectly, and then PUSHED THE BREATHER GEAR BACK, oops, off one tooth! Retimed the breather, problem solved,DUH!
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Joined: Feb 2006
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From: Houston Texas
gunnut1.......
I agree. The breather has to be timed correctly.
The breather is timed to open on the downward stroke of the pistons.
The lower end pressure developed from the pistons coming down expels the scavenged oil in the crankcase breather oil trap to move to the timing cover via the breather valve.
Now the timing cover has oil and pressure. The oil lubes the cams, gears and generator. The generator has an oil slinger which keeps oil from running out the breather tube (located below the generator) but the excess pressure makes it's exit via this tube.
The oil falls back in the bottom and is picked up by the scavenge section of the oil pump and returned to the tank.
Also, when the breather closes, the upward stroke of the pistons now creates a vacuum in the crankcase and the whole cycle repeats itself the next time the pistons come down.......pg
The breather is timed to open on the downward stroke of the pistons.
The lower end pressure developed from the pistons coming down expels the scavenged oil in the crankcase breather oil trap to move to the timing cover via the breather valve.
Now the timing cover has oil and pressure. The oil lubes the cams, gears and generator. The generator has an oil slinger which keeps oil from running out the breather tube (located below the generator) but the excess pressure makes it's exit via this tube.
The oil falls back in the bottom and is picked up by the scavenge section of the oil pump and returned to the tank.
Also, when the breather closes, the upward stroke of the pistons now creates a vacuum in the crankcase and the whole cycle repeats itself the next time the pistons come down.......pg
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