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Discussion Starter · #1 ·
I have a 1972 T120R... It's done a lot of miles now and is pretty tired. I'm thinking of doing a complete re-build of the bike and chassis. The engine is as it came out of the factory, still on STD pistons and the cams/followers are original. I would like to add a bit more performance so rather than having the barrels re-bored, I was thinking of fitting an aftermarket 750cc big bore kit. It would seem that there are two kits that are readily available... the Morgo and the Routt. Is there any consensus that one is any better that the other?
The cams and followers are bound to be worn so I'll replace the lot. Next question... what cams should I fit to complement the capacity increase? Any advice would be gratefully accepted.
John
 

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Hi John,
The routt looks pretty standard, but is USA built, therefore maybe you will need to import + import spares in the future.
The Morgo is UK built so backup is easier, but the cooling fins are wider, mimicking the head fin shape, however this introduces quite a lot of desirable extra cooling area (20% greater area according to the Morgo marketing literature) If you wish the profile to look standard you will need the Routt, if better cooling and practical spares availability is a consideration, then the Morgo is the winner.
A lot of T140 owners have put the T120 cam profiles on their bikes for a power delivery that gives a torque curve that starts lower, making for a much nicer power delivery in road riding. I have removed T140 cams and fitted Hyde half race cams before, these are in reality E3134 profiles (I think they have only added the T140 quietening ramps). Without checking, I suspect you already have this profile on your standard cams (without quietening ramps).

Maybe you will not need a camshaft profile change, followers can be reground to the radius of your choice at reasonable cost.

owners have reported that a T120 with a 750 conversion performs better than a T140.

I believe @rambo has had a 750cc kit fitted for many years and is very happy with the result; hopefully he will post a real life opinion to you.

Regards
Peg.
 

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It's my opinion based on my T140, that the stock intake retimed to 100 degrees lobe center and a 3134 exhaust will pull well through the rpm range...A few years ago I also had a 70 650 fitted with Routt kit and the stock cams..It ran nicely but I cannot say it performed better than the T140. I suppose it depends on the tuning. Myself and others have found stock T140 intake timing to be over advanced making the engine a dog at higher rpm..
 

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What is being sold in the UK is Routt "type", and is actually Aerco, manufactured for Velocette, who own the Aerco brand. They are made in the UK.
Morgo use a slightly peculiar imperial bore size of 2.974" (75.54mm) with +20 and +40 oversizes available and a range of compression ratios (partly through the use of different head gaskets), and can be supplied for 9 or 10 stud heads - oh, and the fins are delta shaped to match the head.
The Aerco big bore is 76mm, same as the T140, but with different gudgeon pin height to suit the 650 "long" conrod, with a compression ratio of 8.9:1. I think there is at least one other head gasket available (I'd have to ask), but of course the Morgo ones fit. Again, the kits are available for 9 or 10 stud heads, but the barrel shape is much the same as normal 650. Incidentally standard barrels for 500, 650 and 750 are also made.
Personally, I have used both types (for different reasons) and have had no problems, others have said different, but in any case I would measure pistons and bores for correct clearance.
Oh, and the Aerco is some £60 cheaper, depending on the dealer you buy from.
Truckedup is right about timing, but as a hooligan road bike I use the T140 profile exhaust cam as well (sold as 71-7017R) with 3/4" radius followers, timed at about 104 deg lobe centre. That basically gives you the same spec camwise as the late Thruxton production racer Spitfire setup.
You pays your money and takes your choice. You do need to know what you are doing in setting up, or know someone who REALLY does, they're getting a bit thin on the ground, many are now sadly below ground.
Cheers,
Mick.
 

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My 750 kit is Aerco using standard T140 piston rings. federal Mogul pistons and it has been on for about 15 years. Nice cylinder as it is round like the original. I bought mine from Tri-supply but many sellers will have this kit. This kit is just bolt it on and ride away. I have had no problems with it at all. Significant gain in low down pulling power and also carrying a pillion. If you compare the bike against a 650, with a pillion, it will pull away faster than a solo rider.
 

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I might add, there is a squish band with the new pistons and the gudgeon pin is much heavier duty than the standard one. It does fit the standard small end bush but i changed the bush anyway when i fitted the kit. Mine is supposed to be 8.5 to 1 compression. No more pinking with this kit and a Boyer but i know you have previously fitted some much better ei systems in the last build of your 71.
I use the standard 1971 T120r cams and followers which have done 46,000 miles so far. No wear yet so i just left them in use.
 

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Discussion Starter · #7 ·
Many thanks for your very informative replies, gentlemen and Peg.
Mr Rambo... you have a much better memory than me. My bike is indeed a '71 model, not '72 as I originally posted... not that there's a lot of difference!
When I rebuilt the bike about 7 years ago, I did very little to the engine, other than overhauling the cylinder head. The bottom end wasn't taken apart.as there was no noticeable play in either the big ends or mains. The bore was STD and looked good, so apart from breaking the glaze and a new set of rings, that was also left alone. I did fit an American "C5" ignition system, but after a couple of years I had ignition problems and replaced it with a Pazon system. As it turned out, the C5 wasn't the problem... the real culprit was a short length of MIG welding wire had been left stuck to the frame by the factory welder and had worn through one of the HT leads. I may well re-instate the C5 in due course.
When setting up cam timing, I assume that the "centre of the lobe" is determined with a dial indicator on the cam follower... Am I correct? If I remember correctly, there are 50 teeth on a camwheel and a choice of three keyways... that would give a resolution of 7.2° per tooth and if the keyways divide that by three, a possible resolution of 2.4°. Presumably, that's close enough.
Anyway... I've waffled on long enough 😃
Thanks again
John
 

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I wouldn’t invest in cams or followers until I’d seen the old ones. They may be OK. There’s nothing wrong with the 650 cam profiles for use in a 750.

The shape of the fins will make no discernible difference to engine cooling.
 

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The Routt kit I had was a made in USA old stock. Had to bore it .040 and fitted MAP forged 9.5 pistons. Had some detonation issues but got the tune up right and it was ok with common sense throttle control...Probaly a bit wilder intake cam timed as Mick says might have bleed off some low speed cylinder pressure.
 

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My cam timing is just set up with the dots on the timing gears. The cams have never been removed so they are how the factory installed them. The bike runs very well and mechanically very reliable now. In 23 years, i have had a main bearing failure so rebuilt it with new mains.. Later on, i had the crank snap at deceleration from 80 mph. It just sheared off so rebuilt again. Other than that, just general maintenance now. I plan to replace the head one day and have built one up. The one on the bike has a small crack in it. It is not having any effect so leaving it alone until the head comes off for some other reason. I would never re-fit the 650 cylinders, the increase in pulling power is very apparent as soon as you let the clutch out.
On local club runs, a few riders have asked why the bike pulls away faster than their own despite me having a pillion on the seat.
The bike is always ridden fairly hard and my biggest problem is the oil will not get hot. I have removed the oil cooler i fitted but the oil still remains cool after a 50 mile ride. Nothing i do will raise the oil temperature and i can put my finger into the oil without burning it. The frame is exceptional at keeping the oil cool.
 

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Cam timing on later 650's from what I know is 100 degrees lobe center on the intake and 102 on the exhaust. It may vary a few degrees depending on production tolerances..
 

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Don't forget that big bore kit will increase compression ratio. Blew the head gasket on my old 67 with the nine bolt head using a 750 kit.
 

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Don't forget that big bore kit will increase compression ratio. Blew the head gasket on my old 67 with the nine bolt head using a 750 kit.
My 750 kit lowered compression ratio..Never had a head gasket blow in the last 23 years on this bike. I use copper gasket with a sealant and it is working well.
 

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Many thanks for your very informative replies, gentlemen and Peg.
Mr Rambo... you have a much better memory than me. My bike is indeed a '71 model, not '72 as I originally posted... not that there's a lot of difference!
When I rebuilt the bike about 7 years ago, I did very little to the engine, other than overhauling the cylinder head. The bottom end wasn't taken apart.as there was no noticeable play in either the big ends or mains. The bore was STD and looked good, so apart from breaking the glaze and a new set of rings, that was also left alone. I did fit an American "C5" ignition system, but after a couple of years I had ignition problems and replaced it with a Pazon system. As it turned out, the C5 wasn't the problem... the real culprit was a short length of MIG welding wire had been left stuck to the frame by the factory welder and had worn through one of the HT leads. I may well re-instate the C5 in due course.
When setting up cam timing, I assume that the "centre of the lobe" is determined with a dial indicator on the cam follower... Am I correct? If I remember correctly, there are 50 teeth on a camwheel and a choice of three keyways... that would give a resolution of 7.2° per tooth and if the keyways divide that by three, a possible resolution of 2.4°. Presumably, that's close enough.
Anyway... I've waffled on long enough 😃
Thanks again
John
You don't need a dial indicator, takea look at my thing under the tech information section HERE.
Cheers,
Mick.
 

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I have been wanting to build a hooligan bike lately. Sever departure from my usual thinking of totally stock restorations. I recently saw an 800cc big bore kit for sale for the 650cc triumphs. Any insight into these?

Thanks,
Rob
 

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I have been wanting to build a hooligan bike lately. Sever departure from my usual thinking of totally stock restorations. I recently saw an 800cc big bore kit for sale for the 650cc triumphs. Any insight into these?

Thanks,
Rob
Hello Rob,
Who is selling the 800 kit? The 750 big bore kits leave not a lot of cylinder head contact area, I'd have thought that even bigger bore would start to get really marginal on a 9 stud, not great even with a 10 stud head. I have gone a different route, with a Norton based crank (89mm stroke instead of 82mm) and T140 top end, but still not exactly easy as the rods hit the crankcase without mods.
My cam setup and a nicely done head will probably get up to 60 bhp, not to be sniffed at in a fairly light bike. There are others on this forum who have had dyno results on engine mods, I'm sure they'll chime in.
Cheers,
Mick.
 

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If I remember correctly, it was a Routt Kit (Spelling might be wrong). Came with cylinders (800cc), pistons and rings.

Rob
 

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If I remember correctly, it was a Routt Kit (Spelling might be wrong). Came with cylinders (800cc), pistons and rings.

Rob
AFAIK, Sonny Routt used to do an 800 kit, but as I said in an earlier posting, the "Routt" kits now available are 750 from Aerco in the UK. I think MAP cycle will do pistons for an old 800 kit, not sure!
Mick.
 

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Hello Rob,
Who is selling the 800 kit? The 750 big bore kits leave not a lot of cylinder head contact area, I'd have thought that even bigger bore would start to get really marginal on a 9 stud, not great even with a 10 stud head. I have gone a different route, with a Norton based crank (89mm stroke instead of 82mm) and T140 top end, but still not exactly easy as the rods hit the crankcase without mods.
My cam setup and a nicely done head will probably get up to 60 bhp, not to be sniffed at in a fairly light bike. There are others on this forum who have had dyno results on engine mods, I'm sure they'll chime in.
Cheers,
Mick.
Dyno info is always suspect, you cannot compare dynos...But my 650 land speed racer made 57 rwhp at 7000 rpm with a peak torque of 46 foot pounds at 5100 rpm..That would be crowding 66 or so crank HP. The engine has not radical Sifton 390 cams, 10.5 compression, 34mm Mikuni flat slide carbs and a moderately modfied head with raised intake port floors. It starts on one kick and settles into a 900 rpm idle...It held several national speed records.The bike weighs 315 pounds and I have ridden it on the back roads a few times, yes, scarey fast for a Triumph with no front brake...
My 79 T140D has the cylinder milled for .032 piston to head squish , retimed stock intake cam, 3134 exhaust, 32 mm Mikuni flatslides, no head mods other than a good valve and guide work, the stock two into one exhaust with a Supertrapp muffler. It gives the Norton Commandos a run for the money..
My opinion based on hot rod cars and bikes that a moderately built engine is best for the street and generally is easier to tune....
.
 
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