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Two T140 inlet cams
#798748 02/19/20 9:30 pm
Joined: Jun 2013
Posts: 90
PEH Offline OP
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Has anyone fitted 2 T140 inlet cams to a 750 motor T140/Tr7, as opposed to the common mod of just fitting a 3134 exhaust profile cam, i would be interested to know is there still a decent midrange, or is it all up top,

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Re: Two T140 inlet cams
PEH #798756 02/19/20 10:44 pm
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I'm running T140 profile inlet and exhaust cams in my 1973 TR7 powered T140. Everybody I talked to and everything I read online told me I'd have a miserable peaky engine that only made power from 5K RPM on up but that's not the case. It easily pulls from 3K in the lower gears and maybe 4K in 5th, though that's getting close to ticket speed in California and not the kind of riding I like to do.

Eric


1971 T120RV (R.I.P.)
1973 T140V/TR7
1993 Ducati 900 SS
Re: Two T140 inlet cams
PEH #798757 02/19/20 10:51 pm
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That sounds like a nice ride Eric. Did you time the cams to any particular numbers? And what carb are you using?

Re: Two T140 inlet cams
PEH #798760 02/19/20 11:19 pm
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I no longer have my assembly notes but my target cam timing was a 100° intake lobe center and 105° exhaust, I'm sure I'm within a couple of degrees of those numbers. The late forum member PeteR said one could advance the exhaust cam to 110°, knock 5° off the overlap, for a smoother idle and better low end. My idle is pretty ropy and more low end is always nice, but I'm not going back into the timing chest to try 110°. Carburetion is an AMAL 930 with a 60's style pancake air cleaner, exhaust is full 1971-72 T120 reproduction with a crossover tube, pistons are Taiwanese 0.020" over 8.6:1 compression with the cylinder base gasket omitted for about 0.040" squish and a few more points of compression and topped off with a really nice low hour TR7 cylinder head rebuilt by MAP Cycle.

Eric


1971 T120RV (R.I.P.)
1973 T140V/TR7
1993 Ducati 900 SS
Re: Two T140 inlet cams
PEH #798781 02/20/20 3:34 am
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...hello; I have that set up in a 79 bike. Do not know about lobe center. Do not know if its more or less than a std T140 really.
I ride on the road mainly and very briefly into towns.
I commute at strong cruising speed. Normally at 120km/h. The range mostly is between 115 - 140km/h This range put you between 3800 - 4800RPM or so; between 1 - 3 hours riding.
2 Mikuni 32mm.
Valve clearance 0.008 both.

Re: Two T140 inlet cams
PEH #798792 02/20/20 10:25 am
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Originally Posted by PEH
Has anyone fitted 2 T140 inlet cams to a 750 motor T140/Tr7, as opposed to the common mod of just fitting a 3134 exhaust profile cam, i would be interested to know is there still a decent midrange, or is it all up top,

The T140 cams works well from 5000 and up and are nice for road racing og fast road use.
On a twisty road you'd feel the lack of low down power. On a smallish dirt oval you'd likely be chasing the power or fighting for traction while the field is long gone.
Very different on the open road of course, which is why I like my Trident there.
In the twisties I struggle hard to keep up with the wife on her Street Twin "Hi Torque" out of the bends, even when I'm on my Daytona 900.

But why not try, nothing beats your own experience. You might prove me dead wrong, and I'd be happy to learn from it.

SR

Re: Two T140 inlet cams
PEH #798794 02/20/20 10:43 am
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Like Bike Vice, I believe timing is the key here. 100-101* LC for the intake and 104-105* exhaust will result in a torquey motor.
Be sure to check intake valve/ piston clearance. These numbers can make things a little close.
My race bike has a 750 intake and 650 ex, timed at 101.5 and 104. It's got a bit more compression than stock and a few other things.... on the dyno the torque curve is about the nicest ridable curve I've seen. On the track it's easy to ride- important with the clunky slow shifting 4 speed.

Re: Two T140 inlet cams
Mike Baker #798834 02/20/20 6:40 pm
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Do you mean a 3134 Exhaust Mike. Any chance os seeing that Dyno curve?

Re: Two T140 inlet cams
Stein Roger #798835 02/20/20 6:41 pm
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Im still juggling SR, But the plan is slowly coming together,

Re: Two T140 inlet cams
PEH #798870 02/21/20 1:05 am
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I haven't learned how to do photos on this site. Lazy, I guess.
PM me and I'll text or email it to you


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