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T140 cam timing marks #524552
01/24/14 6:37 pm
01/24/14 6:37 pm
Joined: Jan 2014
Posts: 3
NH
R
Ricky Offline OP
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Ricky  Offline OP
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R
Joined: Jan 2014
Posts: 3
NH
Can anyone verify which timing marks to use for the intake cam on a 1975 T140? I have three manuals that give different answers of various 650 models but none come out and say the info is for the T140. I know about the three keyways and the A and B so that is not an issue. What I'm confused with are the marks on the intermediate wheel. Mine has the two dashes for the crankshaft and the one dot for the exhaust and a dash and a dot for the intake. One book says to use the dot and one the dash. I'm pretty sure I need the dash but would appreciate confirmation before I button it up. What effect would using the dot have? Another question I have regards a Hunt magneto. I take it Hunt mags don't have an ignition advance? How is the timing set with that? Thanks!

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Re: T140 cam timing marks [Re: Ricky] #524596
01/24/14 11:51 pm
01/24/14 11:51 pm
Joined: Nov 2005
Posts: 7,409
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JubeePrince Offline

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JubeePrince  Offline

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Originally Posted By: Ricky
Can anyone verify which timing marks to use for the intake cam on a 1975 T140?


http://www.britbike.com/forums/ubbthread...true#Post441955

Pay close attention to what Pete R says.

Steve


'77 T140J
"Vintage Bike". What's in your garage?

"The paying customer is always right."

Fitting round pegs into square holes since 1961...
Re: T140 cam timing marks [Re: JubeePrince] #524649
01/25/14 12:33 pm
01/25/14 12:33 pm
Joined: Jan 2014
Posts: 3
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Ricky Offline OP
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Ricky  Offline OP
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R
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NH
Thanks for the info but that is a bit more involved than I need. This is a stock bike and I just want to set the marks as per factory. I don't need to fine tune it for max power... I just want to know whether to use the dot or the dash on the intake.

Re: T140 cam timing marks [Re: Ricky] #524654
01/25/14 12:52 pm
01/25/14 12:52 pm
Joined: Dec 2004
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Re: T140 cam timing marks [Re: Ricky] #524749
01/25/14 9:49 pm
01/25/14 9:49 pm
Joined: Jul 2009
Posts: 3,549
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Pete R - R.I.P. Offline
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Joined: Jul 2009
Posts: 3,549
Vic. Australia
If you're using the keyway closest to the "B" mark on the intake,you would line the "B" mark up with the dash (not the dot above it).That will be as it was when new,and the intake timing timing will be about 5 degrees retarded from the actual manual spec of 0.190" lift at TDC.

It will run and cause no damage,but it could run better if the timing is more accurate.

The keyway in the cam faces in the same direction as the drive side lobe,so you don't have to remove the camwheel nut to know where the key is facing.There are 3 keyways in the camwheel,and you must know which one you're using.

I'd be more inclined to use the keyway closest to the "A" mark,and position the "A" mark one tooth ahead of the dash (on the opposite side to the dot).I would then check the timing with a degree wheel or by measuring tappet lift at TDC.If you're out by one tooth,the tappet lift at TDC will change by about 0.049".Intake valve lift at TDC can be somewhere between 0.190" and 0.210",so tappet lift will be 0.169"-0.187".


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