Road Test: Royal Enfield Interceptor

Mk2 Royal Enfield Interceptor

Arranging a bike for a photo shoot isn’t always the easiest thing in the world, there is the weather, the photographer, the owner and the tester to get in one spot at the same time. If you want to test more than one bike, then the problems increase in proportion to the amount of bikes. Which is why, when Allan Hitchcock told CBG that he had three examples of the big Enfield Interceptor all running and rideable and would I like to check them out before they went to new homes, I was there as fast as I could.

The three bikes were in the container load that Allan has recently imported from the USA and were the fruits of an extended trip for the sole purpose of finding decent bikes.

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When I got to the Hen House, moments after photographer John Wilkinson, there, lined up, were a 1965 MkI, a 1967 MkIA and the final 1970 MkII. The thing that appeals to me about these bikes is that they’re straight from the container. In some cases they’ve been sitting for years in barns and outbuildings and while the three model numbers are definitive of the range, they are not exactly sparkling examples. In a way this is better as they are effectively untouched other than Hitchcocks gave them the once over to make sure they would pass an MoT so we could get out on the road. They are all USA export models, so slightly different from their home market brothers.

I’m not going to come Royal Enfield Interceptorsdown in favour of one over the other, it would be silly and after all only my impression. What I’m going to show in this test is that an Interceptor can be a reasonable proposition for a regular and reliable rider in the 21st century. For this reason I quizzed Allan Hitchcock for quite a while and he was brutally honest about the model. Although a fan of the marque, he is he is not blind to its faults and problems, even better he had a section of his workshop devoted to the bits and pieces that go wrong and was more than happy to haul these bits out for our camera. In some cases Hitchcocks can supply certain parts that were considered unobtanium, in other cases he offers advice and says that even blown crankcases can be repaired.

I tend to bleat on about maintenance but it is important as more and more motorcyclists are finding light-speed rocket ships a bit of a yawn and are turning to classics for a different experience. I don’t care what British motorcycle grabs your fancy but they all need more input than just petrol and a wash now and again. We’re talking regular oil changes with the correct oil… proper servicing done by the book, or where a particular marque expert exists follow their advice. Don’t leave it and think it will be OK, it won’t – blow-ups are bad news, even on a bike with a healthy spares situation, as Allan Hitchcock pointed out, some bits on the Enfield Interceptor are unobtainable – break them and you’ve just provided a source of spares for someone else.

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Interceptor owners can go and look at the pictures for a while as the next paragraph or two is for those of us who are new to the big beefy twins. The North American market was of vital importance to the British industry and had the effect of occasionally dictating what our industry did. ‘More cubes’ screamed the Americans and Meriden produce the Thunderbird… ‘more power’ was the cry and Norton produced the Atlas and Royal Enfield went for the Interceptor to provide relaxed cruising at high speed on Interstate highways. They had already the biggest vertical twins in production with the 700cc Super Meteor and the Constellation and the new Interceptor drew heavily on them. Stretching the 70 x 90mm bore x stroke of the ‘Super’ to 71 x 93mm gave a capacity of 736cc and an incredibly torquey engine. It retained the separate heads and barrels that were a feature of the previous RE twins and the oil circulated from a seperate compartment behind the crankshaft.

Royal Enfield InterceptorLooking at the three machines lined up for me and given that there are a number of technical and styling differences that distinguish each Interceptor from the other I asked Allan Hitchcock to briefly talk me through the obvious and not so obvious differences, similarities and which parts are interchangeable. He began with the fairly obvious statement that all models use the Albion four-speed gearbox and top ends of each engine are most likely common too. Though he asked to be quoted as purposely vague here.

This is because when I asked the question of him he wasn’t sure as he’d never been asked this in all the years that he and his charming wife, Jo, have been in business selling Royal Enfield bits. “Go with ‘probably’ on that one please Tim, if we say ‘definitely’ someone will point out that we’re wrong. After all I don’t pretend to know everything about every model,” says Mr Hitchcock. Well, considering how easily he answered most questions I’d say that his knowledge is pretty comprehensive.

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As photographer Wilkinson busily recorded everything for posterity and I scrutinised the bikes and threw the odd question at Mr Hitchcock as he freely gave me the benefit of his knowledge, asking me what I wanted to know. I told him anything that would help a current or perhaps more importantly, a future Interceptor owner. I learned it would be fair to say that they all have basically the same frame and is the 1956 on Bullet one though there are detail changes, certain lugs are on one that aren’t on others and some used different mounting points, but basically the same. It is a robust thing and gives a decent feel when riding along the road. “The MkI US models tended to have longer swinging arms over the UK models,” adds Allan at this point. “They are braced up near the mounting and this gives even better straight line handling.” Continuing with the MkI he told me that it is the only one of the three that has a toolbox mounted on the frame. “It looks like the Crusader type,” he smiles, “but there are enough differences to keep people confused. It would be better to say it is ‘Crusader sized’ to avoid mis-information getting out there. It might be simpler if I start at the front of the three bikes and work my way back pointing out where they changed,” said Allan.

“The forks and wheels are fairly obvious, in that the two earlier bikes had Royal Enfield components but the MkII got Roadholders and a Norton wheel, this one on test has a tls plate in there so it’s a decent stopper. The other two have the 7in sls. Though for some reason the UK spec MkI has a twin sided 6in version.” At this point Allan gives a wry grin adding the two earlier models didn’t perhaps have the meatiest brake for the performance expected, but then again the traffic wasn’t as bad in those days.

Warming to his task he tells me that the MkI came with a twin clock casquette fork crown, the MkIA however has a more stylish type where the clocks are separate. Then the final MKII has Norton type to suit the Norton forks. As my pen flashed across the notepad he glanced over and said, “just say if I’m going too fast” – which I actually wrote down before I realised what he’s said. When the MkI was introduced in late 1962 for the 1963 season it came with 6v electrics and magneto ignition. Though this was soon changed to 12v electrics, just like the rest of the industry was doing. The MkIA had a coil ignition with its own special distributor and the MkII had a proper points-in-the-timing-case coil ignition that made it a piece of cake to set up. Luckily at this point a tray of coffee came on the scene and I could take a breather.

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Royal Enfield InterceptorAs we supped Allan fielded a stream of queries from his dedicated team, and told me that most of all the Interceptors are twin carb bikes apart from a few to special order that came with only one and the first interceptor came with handed Monoblocs supplying the fuel to the cylinders. After that they all wore Amal Concentrics. “Early  MKIAs are supposed to have Monoblocs as standard,” says Allan, “but I’ve not come across any, which isn’t to say that they won’t turn up now.”

Coffee and biscuits out of the way, I learn that the MkIA version was never actually released as a home market model. The factory were busily producing 250ccc models for us and had reserved the 750s for export. An all-encompassing statement is to say that this model is a tuned up MkI, it might be harsh but that’s the top and bottom of it. It’s reckoned that under 1000 MkIAs were produced in total, though the factory found time to make it in two variants – a road scrambler designated the TT7 and road racer called the GP7. As far as anyone is aware the only differences between the two are the petrol tank, silencers and shrouding on the rear shocks. And the one that Biffa got his grubby paws on was the interceptor GP7. By the late 60s Enfield themselves were going through turbulent times and it is impressive that they could even produce bikes let alone virtually redesign the Interceptor to such an extent that the bottom end is completely new. Now a much truer wet-sump engine, with proper oiling and filtering to suit this type of engine, it is probably the strongest of the Inters. The whole concept of the MKII is a much fresher and more modern-looking motorcycle, it is sad that the company couldn’t manage to produce more earlier when it didn’t have things like the CB750 Honda or the Z900 to compete with.

OK, so what are they like to ride then? Well, despite having to make allowances for the totally unrestored and as-found condition of all of them, they weren’t too bad. Of the three I’d have to say the MkII was the best to ride and the MKI the worst as it had obviously had a much harder life before being laid up. None of the bikes had any problems firing up though as ever the later coil ignition was the best in this respect and the magneto equipped MkI was the one that needed a bit of technique. This isn’t to say it was difficult, just that magneto-powered bikes need their own technique and when it was new all riders would know the procedure.

With all three bikes fired up we headed into rural Warwickshire so that the gentle art of posing for the camera could be done. It would be gentle too as of the three only the Mk1A had anything like decent tyres on. The good thing was that all three bikes ran very well and considering they’d only been fired up the day before for an MoT test after years of inactivity. In fact Hitchcock’s in-house engineer, Charlie, had merely changed the fluids and checked the timing and clutch adjustment on each bike before topping up with fresh petrol. Yes, the MkI smoked a bit but so does my Triumph and that generally gets quite a bit of use.

Royal Enfield InterceptorFirst to suffer the joys of the Biffa right hand was the MkIA and going through the twisty bits was pleasant enough, engine pulling strongly, not a great lot of vibration and the twin Concentrics well balanced. It certainly felt as though power would come in strongly the more I tweaked the throttle. Balancing this against an unknown quantity in the front brake which, while working ok, meant I made sure that the traffic in front was a long way in front so I didn’t have to do any panic stops. The back one on the other hand – or foot, depending on your viewpoint – was fine especially when the Biffa Size 11 stomped on it.

“What d’you think of it?” asked Allan, when I pulled into the lay-by we used as our parking point. “It’s right enough, everything seems to work well and there are no nasty noises,” I said. Allan thought so too and as a dealer and Royal Enfield nut – not fan, but nut – he’d been listening very carefully to the sounds the bike had been making as I went past.

Next up for the treatment was the MkII for no other reason than I’d parked the MkIA behind the MkI and both would have to be moved before I could ride the MkI. I didn’t like the look of the bars on this one, they are not original, and much too ‘apehangery’ for my sensitive eyes. However once on the bike I changed my viewpoint, they were comfortable enough, though I might have changed my mind after a few hours the 80-90mph the Interceptor was designed to cruise at. Chugging round the lanes they were no problem and gave a bit more feel when doing U-turns. Handling was good and I pushed this one a little harder than the other two, maybe the Roadholder forks and a tls brake plate had something to do with this but it certainly felt sure-footed. It was certainly quick and no need to flick up and down the gears as the power and the torque just pushed it into the distance.

'Handling was good and I pushed this one a little harder than the other two, maybe the Roadholder forks and a tls brake plate had something to do with this but it certainly felt sure-footed…'

By the time I got back to our lay-by the MkI was ready for a spin. To be honest this one was a bit of a disappointment as on the face of it what will be a nice machine really showed what a hard life it had had. I’d have to say that it was quite brave of Hitchcocks to put up three unknown motorcycles for such a warts-and-all test as even in the heyday of the Industry it was rumoured that test bikes were specially prepared. Having said that it didn’t do anything badly, it started, ran and stopped quite acceptably and there were few vibrations that you wouldn’t expect with a big vertical twin, it is just that everything was tired and it would be best to say that it will be a good starting point for an Interceptor fan.

OK, all three bikes are quite big physically, all three feel acceptable on the road and I’m going to stick my neck out and say that there is enough knowledge about them to make them a practical proposition in today’s motorcycling environment. These particular three would need to be restored, but it isn’t the point of this test to denigrate a machine because it’s had a hard life but to look past that and see what the designer had in mind. In the case of this classic muscle bike it was effortless cruising at something like a speed. In this respect the Interceptor will do very nicely and the technology exists to make it do it even better.

Top tips: head steadies
Ensure these are tight and rigid. With the traditional Enfield separate cylinders and heads, the crankcase halves can move and chafe the top mating surfaces, causing oil leaks. Fit a one-piece rigid plate over the four studs between the head steadies and head. Alternatively, go one step better and fit one-piece alloy cylinders.

Royal Enfield InterceptorCrankshaft
Make sure the clearance on the timing side is not worn. This is the first journal to receive the oil and, if the clearance is too great, very little oil will reach the drive side with potentially devastating results. When regrinding, grind the timing side journal a little less than the drive side. This will force oil to lubricate both journals. For the serious rider, there are ways to increase the oil flow!

Breathing modifications
You can modify  the Series 1 to the Series 1A version but, if everything is working correctly, this should not be necessary. On Series 1 engines make sure the disc valves in the crankshaft rotor bolt and the crankcase neck are working correctly.

Ingition timing
The K2F magneto on the Series 1 works well so long as it is in good condition. Remember these are 40 years old so are likely to be tired. The cam ring can wear unevenly so check your timing on BOTH cylinders. Do not use suppressor plug caps with magnetos.

Clutch
The clutch can give problems owing to the sheer power of the Interceptor. Enfields offered the vastly improved ‘splined’ clutch for the last few months MKII production but these are all but impossible to find. You need to make the best of what you have, ensure the steel plates are totally flat, and fit the modern ‘Surflex’ friction plates. Make sure that the clutch centre and basket have grooves that are smooth with no jagged edges. Use automatic transmission fluid. Correctly adjust the clutch pushrod with the gearbox adjuster and not the cable. Or fit a belt-drive system, which will give many more benefits.

Gearing
Standing gearing is considered too low; fit a 22t gearbox sprocket.

Front brake
Use modern linings and nylon-lined cables. Set it up correctly, especially if you have the dual brake fitted to the early UK models.

Gearbox
The Albion selector mechanism cannot cope if you have an amount of wear. Replace the entire selector assembly – it is not expensive. Ensure the neutral pointer and lever are not binding on the cover. This will allow you to get the adjustment spot-on.

Centre stands
The alloy centre stands have an unfair reputation of being weak. Normally when a stand breaks it is because the engine plates are worn, allowing the stand to go too far over centre. This puts too much strain on the stand.

Cross rings
The Interceptor cross ring is an excellent invention. The cylinder head must tighten down on the cross ring and not the cylinder. You should aim to have a couple of thou between the head and cylinder once torqued down; also make sure you use the correct size cross ring for your bore size. If you have +20 pistons, you need +20 cross rings! bike

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