Royal Enfield HATZ 350cc RIDER REPORT

I had my head under the bonnet of a Diesel Escort van when Jim Darcy turned up in his Sherpa van to deliver my new Hatz 350 Diesel Royal Enfield. As he wheeled it down a plank from the back of the van the first thing that struck me was how small it seemed compared to some modern bikes. This suited me fine as I am not overly endowed in the leg department.
 Jim, who had travelled down with his wife, wheeled the bike into my garage an started to give me the low-down how to get the machine up and running. It all seemed very straight forward and I watched on eagerly as he turned the ignition key to start the Hatz.
 I must say at this point that I’ve been around bikes most of my adult life and have not been averse to removing the odd baffle in my time. Some of these old British machines just don’t sound quite right unless you allow them to breath properly.
 During Jim’s pre amble he had mentioned that the bike actually had two baffles on the one exhaust.  Closer inspection revealed that the rear silencer was indeed merely for show and the real baffle was the original which came with the engine. This sits slap bang in the middle and up front of the engine. It’s surrounded by a protective grill and has pipe work inside which resembles a zig-zag affair.
 This said I suppose a small part of my brain was subconsciously starting to think that any noise created by the machine would perhaps be less than expected.
How wrong can a person be?

As Jim turned the key and power pulsed into the starter motor I was immediately struck by just how loud that was. With the bike upright on it’s centre stand I was in for a shock when the Diesel kicked in. I was hit by a wall of vibration coming up through the floor and sound coming at me from the bike the like of which, if I’m truthful, frightened me slightly. All this happening in the confines of a small garage only helped to amplify things even more.
 Luckily the looks of shock and awe are not that far removed and I somehow managed to slip seamlessly from one to the other before (I hope) any of the assembled people there noticed.
It was impossible to talk over the thundering knock emanating from the bike and eventually it was switched off.  My God, what had I bought!
 
 Having seen Jim on his way I donned the protective plastic and threw a leg over the machine. I immediately had to un-throw it as I found I could not rock the bike from its centre stand. As I time went by I looked at various ways of fitting a side-stand to this machine but found each time my efforts were to no avail. The new position of the exhaust pipe and the conversion’s new hanging frame made matters worse in that dept.
 After getting bike free of its stand I experimented and found the auto decompression made kick starting relatively easy. One simply had to stand tall, straighten a leg and drop all ones weight down on the lever making sure to follow through. The reward was an ear deafening knock from below and several twitching  net curtains down the street. (I later found out the engine always stops in the same position meaning there is no need to search for compression. You just kick the bike over though half a stroke.)
 I gunned the engine, slipped her into gear and pulled away up the street at a surprisingly smart pace. And yes, I was quite surprised that this little bike proved to be quite quick off the mark making it an excellent little machine for town work. I had only intended to use the machine for commuting and in time found it to be an excellent work-horse. Vibration, of which many things suggested there would be a lot, proved to be virtually none existent and certainly no bother at all.
 But for now, on this first outing, I was experiencing what it was like to ride a diesel powered machine for the first time and differences not immediately obvious soon came to the fore.

A close up shot of the cooling fan - a tell tale sign that this was intended to be a stationary engine.


 The first thing that startled me was the lack of engine breaking. I should have known that with the lack of a carburettor and accompanying slide, shutting off the throttle would have little effect on my mobility but for some reason it never permeated through. Not until I had to stop rather sharpish and found that I couldn't. Yikes!
 The second surprising thing was the bikes reluctance to corner which I (correctly as it happens) found out was due to the square profiled Avon tyres. In time these were replaced and handling improved markedly.  I could also roll it off the centre stand much more easily.
 And so the first and second things combined to make riding the machine a hair-raising experience.
 While clocking up the miles I began to leave behind me any (admittedly faint) expectations I'd had of top end power and concentrate on what was coming from below. On such a small machine (350cc) it was, I’ll admit, hard to gauge to what extent the torque factor would become apparent but I’m glad to say man and machine did finally become as one.
 Things seemed to come together after the bike had warmed up properly and after the engine had been run in they improved still further. At the right temperature the diesel seemed to be in tune with itself and ran like a noisy little dream bike. Small hills and headwinds had less of an effect on me than other machines I’d ridden accept perhaps the Hog I'd once owned. Whatever the conditions this little bike seemed to just barrel on through.
 And another thing. The bike seemed very stable; almost unnaturally so. I can only put this down to the weight of the fly-wheel. This had the effect of making the machine somewhat reluctant to lean into bends but seeing that I’ve always been a cautious rider myself this only served to make me appreciate this eccentric bike more. On reflection this was more likely because of the square sidecar tyre on the rear!
 Top speed was somewhat limited as I had expected and although the engine felt tight, I did as several friends had recommend and thrashed the balls out of it. Drive it slow and it'll always be slow went the advice and so I didn't spare any of the 8 horses or was it 9? Diesel engines are tough as hell and I felt quite confident that I wouldn’t seize it.
  I’d often heard that the original petrol powered RE Bullets weren’t that fast and although the top speed of my bike was limited to about 55-60 mph in perfect conditions it was comparable to the former. Tackling steep hills was another matter altogether and quite an embarrassing one at that. The overly large gap between 3rd and 4th doesn’t help matters either.
The more I rode the bike over the coming weeks  the more I felt it was a good idea to take out the original Royal Enfield engine and replace it with this Hatz Diesel. Original Enfield’s, still made in India, did not have a great reputation as far as reliability was concerned. (This has since improved I’m glad to say).

"The first (and only) real problem I had with the machine occurred just after the first week was out..."

 The frame on the other hand seemed more than up to the job. Sure, small parts could have done with being finished off better but on the whole it was quite a solid bike.  During the first week I only had one minor problem to deal with when the hooter decided to drop off at a rather annoying moment. Strangely, it even succeeded in over taking me for a brief period, honking as it bounced by. Was it mocking me in some way? I almost didn’t stop to pick it up.
 The first (and only) real problem I had with the machine occurred just after the first week was out, when I broke down on the far side on my housing estate not 100 yards from a Motorcycle shop.  I repeatedly started the machine only to have it fire about four times and then stop. In the end I suspected some sort of blockage in the injector was the cause of the problem and called it a day.
 I was then forced to walk it home and as I started off I noticed the owner of the Bike shop peering out from his doorway. What would he know about Diesels!
 Having finally made it back I positioned the bike in the centre of the garage and retired for some refreshment. Small the bike might be but light it most certainly was not!

Your's truly with the then new Royal Enfield Hatz diesel motorbike.


 What followed was a frustrating week during which I tried to find the cause of the bikes ills. Several friends popped in during this time, several of who know a thing or two about diesel’s, and none were able to turn up a solution.
 Eventually I removed the injector, swung it out from the bike, and, keeping my leg out of the way kicked her over. Poof! Well, the spray pattern looked OK to me.  More through frustration than anything I phoned the main Hatz dealer and ordered a new injector. If for nothing else I figured it may come in useful in the future.
 While I was awaiting its delivery I phoned Charnwood and spoke with Alan, the man behind the diesels. He too was at a loss as to what could be the matter and suggested I phone Hatz themselves.
 Before doing this I decided to have one more go and armed with my tools took a closer look at the fuel supply side of things. First stop was a small square bloke of metal that housed the solenoid. This is just visible and goes in and out as the key is turned. And yes, it appeared to be working fine. Finding an Allen key I loosened off it’s fixings and removed it completely. Imagine my surprise when the plunger fell out onto the floor! I had found the problem!
 The plunger can be best described as closely resembling a brass matchstick with a spring fitted down its body. And it had snapped clean off! Further investigation showed the spring to be rather crushed and I rapidly deduced that the whole affair had not been aligned properly from the beginning. Kicking the machine over started it fine but the flow of diesel soon forced the loose plunger into its hole and cut the supply dead.


 It's true to say that these engine have been modified slightly from the original and that this key operated device was probably fitted only to the engines used in the bikes. But, that being said, more care should have been taken in squaring it off properly. I have since talked to other diesel enthusiasts and it seems none have ever come across this problem before. On phoning Hatz I was able to give them a good description of the fault and they agreed to replace the part under guarantee. I was told they normally wait until they have received the old/broken part back before dispatching the new but seeing as this would mean me being unable to ride my new machine they kindly waved the rules and go the part to me in rapid time.
 It was good to get back onto the road in record time and continue the experience of riding the Hatz. After a few more trips out I decided to check my oil and found it to be very low. These engines have very small sumps which have a capacity of 1 litre and the fact that the rider has to use the engine at full bore it comes as no surprise to find that the it’s not long before the Red Oil light comes on.
 Filling is easier said than done as the position of the hole is at the back bottom of the engine. Charnwood have extended this up with a thick rubber pipe and secured it in a more accessible area but it’s still not the easiest thing to get at.  Allowing for the top to be screwed on I found I had to take the Full level with the metal cap sat on the top.

Hats off to Charnwood for going ahead with this motorcycle build.


As time has gone on I have tinkered with the bike and succeeded, I believe, in making it more responsive and slightly faster. First to go was the cardboard air filter. This was replaced with a free flow foam effort that produced a noticeable improvement. I purchased it from the RS (Radio Spares) catalogue.
 Now, several years later the bike has done almost 19,000km and is still going strong. It’s done 2 trips to Germany and has only threatened to break down on one other occasion. I say threatened because it never did. I’d fitted a new rubber fuel hose with a pair of long nose and must have creased the pipe. Anyway the diesel had wasted no time in getting into that crease, if that’s what it was, and eating through to the outside.
 We'd just got off the ferry from France and were heading down the motorway when I had a 50% loss in power. Turns out it was sucking air in through that pipe and injecting it. I managed a quick bodge and we limped home safely.
 I'm currently wondering whether to sell the old girl and get ready to purchase a new diesel KLR but given the price of them ($18,995) I think I'll hold on a while.  If nothing else, riding a diesel bike has taught me to be patient!

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