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#227191 - 12/08/08 8:40 pm Timed Breather on Comets  
Joined: May 2006
Posts: 148
TriVin Offline
BritBike Forum member
TriVin  Offline
BritBike Forum member

Joined: May 2006
Posts: 148
Warrington, Cheshire, UK
Hello

This question follows on from my last post concerning excessive oil in the primary chain case.
Twin Pot Phil mentions that the timed breather might not be aligned correctly. Now one thing I do know is that when the dots on the timing gears are aligned as per the illustration in Richardsons book then the bike will not run. So when my mate and I assembled the timing gears we had to put the cam wheel in so that the lobes were both 'on the rock' so to speak, whilst at TDC. The breather gear was then assembled as shown in the illustration. The assumption being that for some reason the cam gear had moved on its shaft at some time in the past and had been welded up by a previous owner with the relationship of the dots and the cams buggered! So, is my assumption correct in believing that if the other dots on the idler gear, half time pinion and breather gear are as shown, at TDC, then the timed breather at least should be correct relative to the crank position?
I should add that the bike runs fine. Starts easily etc. Although not having ever ridden another Comet I cannot make comparision on performance, I'm certainly happy with it at the moment except for the excessive oil in the primary.
It has a had a new piston and rebore so the clearances should be OK in terms of crankcase pressure, I'm just not 100% sure about this breather gear position.

thanks

Dave


Dave
Tiger 100SS 1966
T120V 1972
Vincent Comet 1952
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#227470 - 12/10/08 3:18 pm Re: Timed Breather on Comets [Re: TriVin]  
Joined: Nov 2007
Posts: 112
Twin Pot Phil Offline
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Twin Pot Phil  Offline
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Joined: Nov 2007
Posts: 112
Birmingham, UK
Personally I NEVER take any notice of any marks EVER, stuff has had too much of a "life" previously to be trusted.
I always time up (cams, ignition and breather) to a dial gauge and timing disc - never fails and shows if the cams are good (or not).
The standard timed breather should open 35-41 degrees after TDC and close 2 degrees before BDC. The result of this is that you should hear it "blow" when the piston is moved down from TDC on the kickstart (holding the valve lifter in while doing this helps!).
Hope this helps

#227505 - 12/10/08 5:48 pm Re: Timed Breather on Comets [Re: Twin Pot Phil]  
Joined: May 2006
Posts: 148
TriVin Offline
BritBike Forum member
TriVin  Offline
BritBike Forum member

Joined: May 2006
Posts: 148
Warrington, Cheshire, UK
Hi Phil

Thanks very much for that information, just what I needed. Is there any special kit required to hold the dial gauge in place when checking the valve opening and closing or will a mag base do it?
I notice you are in Brum. Although I'm in Warrington now I grew up in the Weoley Castle/Bartley Green area. In fact the rest of family are still there.

thanks


Dave
Tiger 100SS 1966
T120V 1972
Vincent Comet 1952
#228241 - 12/15/08 9:11 pm Re: Timed Breather on Comets [Re: TriVin]  
Joined: Nov 2007
Posts: 112
Twin Pot Phil Offline
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Twin Pot Phil  Offline
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Joined: Nov 2007
Posts: 112
Birmingham, UK
When I time the valves I make sure the Dial indicator pin is bearing vertically on the end of the valve stem (with the tappets adjusted to give 10 thou "nip" on the valve) and I have an "adjustable" bracket that firmly holds the Dial in the same position when it is clamped up (usually clamped off one of the cylinder bolts (others adapt a series "D" breather to hold a DTI and then this just lightly screws on at the valve spring cover (but only with the UFM off).
The breather opening (and closing) event can be checked visually by checking the slot position in the pinion relative to the slot in the spindle all against the timing disc.

I know Weoley Castle and BG (my side of town), I live in the area that used to make cars (until very recently) - drop in for a brew if you are ever in the area .
If it helps, I may be passing the Warrington area (going to Bury) over the Christmas period, it's your call!

#228316 - 12/16/08 5:59 pm Re: Timed Breather on Comets [Re: Twin Pot Phil]  
Joined: May 2006
Posts: 148
TriVin Offline
BritBike Forum member
TriVin  Offline
BritBike Forum member

Joined: May 2006
Posts: 148
Warrington, Cheshire, UK
Hi Phil

I just PM'ed you. Never done it before so we shall see if it works.


Dave
Tiger 100SS 1966
T120V 1972
Vincent Comet 1952

Moderated by  John Healy 


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