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Engine performance of classic Interceptor #766732
02/28/19 12:47 pm
02/28/19 12:47 pm
Joined: Jan 2009
Posts: 886
QLD, Australia
R
RetroRod Offline OP
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RetroRod  Offline OP
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R

Joined: Jan 2009
Posts: 886
QLD, Australia
I am interested in the performance of the '69 650cc RE Interceptor.

I have been told this model from 1969 had comparable power to the Triumph T120. Is that the case? I'd certainly like to know.

Anyone care to comment.



'72 Bonneville
"He who praises you for what you lack wishes to take from you what you have." - Don Juan Manuel
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Re: Engine performance of classic Interceptor [Re: RetroRod] #766737
02/28/19 1:46 pm
02/28/19 1:46 pm
Joined: Aug 2001
Posts: 7,748
scotland
triton thrasher Online content
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triton thrasher  Online Content
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Joined: Aug 2001
Posts: 7,748
scotland
It was 735 cc.



Amateur Loctite enthusiast.
Re: Engine performance of classic Interceptor [Re: RetroRod] #766746
02/28/19 4:36 pm
02/28/19 4:36 pm
Joined: Aug 2006
Posts: 177
USA
oilyamerican Offline
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oilyamerican  Offline
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Joined: Aug 2006
Posts: 177
USA
If by comparable power you mean horsepower, the general HP rating given for the 750 (736cc) Interceptor motor was approximately 52 from what I've seen. Some sources claimed 55.
RE's claim to fame was having the longest stroke of any British twin, which was supposed to give the motor gobs of torque.
In actual practice, I'm not sure if that long stroke was a blessing or a curse ?
And you must consider power to weight ratio. I don't know what a T120 weighs, but the Interceptor comes in at about 425 lbs.
Of course it might be helpful to take the time to read period road tests, then you will see the mixed impressions that magazine riders had of it.


Will work for Guinness smile
Re: Engine performance of classic Interceptor [Re: RetroRod] #766754
02/28/19 6:10 pm
02/28/19 6:10 pm
Joined: Dec 2008
Posts: 233
Rossland BC Canada
C
Chris Overton Offline
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Chris Overton  Offline
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Posts: 233
Rossland BC Canada
By 1969, do you mean the 1968½ Series 1A, or the 1969 Series II? Distinguished by IA or IB on the crankcase, as well as the dry or wet sump feature.
Horsepower figures in the magazines were provided by the distributors who paid for the advertising. Actual outputs were variable because of manufacturing tolerances, but the factory was happy if the dyno showed 49 hp. This from someone who was there at the time, and told that to me, gREgg, and maurice about a decade ago. Peak horsepower is only one indicator; the area under the power curve is a better measure.

Last edited by Chris Overton; 02/28/19 6:13 pm. Reason: additional info
Re: Engine performance of classic Interceptor [Re: RetroRod] #766830
03/01/19 12:21 pm
03/01/19 12:21 pm
Joined: Aug 2001
Posts: 1,568
Jordan, NY
Al Eckstadt Offline

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Al Eckstadt  Offline

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Joined: Aug 2001
Posts: 1,568
Jordan, NY
Seat of pants comparison: '67 1A Interceptor not as quick at back road acceleration as a '69 Bonneville. Handling is very good but not as light as the Triumph. At 60-70 mph the RE engine is working a few hundred RPM lower than the Triumph making cruising at that speed very pleasant. The Triumph starts to get bothersome when approaching 65. The Interceptor feels about the same at 90 as it does at 60, which the Triumph definitely does not. The Triumph has better brakes, even with my RE upgraded to the Indian twin leading shoe. Hope this helps.


Al Eckstadt
Re: Engine performance of classic Interceptor [Re: RetroRod] #766988
03/03/19 1:45 am
03/03/19 1:45 am
Joined: Jan 2005
Posts: 977
Ontario Canada
Don Leaming Offline
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Don Leaming  Offline
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Posts: 977
Ontario Canada
Yup, you are right on Al. The Interceptor has lots of torque, especially in the mid range. You can feel the difference in pulling power compared to my 69 TR6R. The Triumph is more fun to ride on 2 lane blacktop though. Both are shod with new K70 Dunlops, 3.50X19 on the front of the Inter and 3.25 section on the TR6R. Both with 4:00X18s on the rear.
As aside note though, way back when I had my 59 Costellation with that big 10TT9 carb, that old Conny had even more fearsome grunt than any of my 65, 66, 69, or 70 Interceptors.
That’s my story and I’m stickin to it!
Don


1965 Royal Enfield Interceptor
1969 Triumph Tiger 650
Re: Engine performance of classic Interceptor [Re: RetroRod] #767233
03/05/19 3:19 am
03/05/19 3:19 am
Joined: Jan 2009
Posts: 886
QLD, Australia
R
RetroRod Offline OP
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RetroRod  Offline OP
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R

Joined: Jan 2009
Posts: 886
QLD, Australia
Thank you one and all. Informative and useful info here. RR


'72 Bonneville
"He who praises you for what you lack wishes to take from you what you have." - Don Juan Manuel

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