Friday, February 27, 2009

Enfield switches gear for new UCE motor

The Indian engineer helping disassemble a prototype of the new Royal Enfield motorcycle engine paused a moment and held up a pretty metal gear. He had just pulled it from the cam array deep inside the unit constructed (UCE) motor.

Now he wanted to draw the attention of his audience, American Royal Enfield dealers gathered Feb. 12 for a training session on the new engine.

"Only metal in the prototype," said K.S. Sarveswaran. "In the production bikes it is plastic."

The dealers literally gasped. A plastic gear near the beating heart of a Royal Enfield motor?

The dozen men had watched the disassembly of the UCE motor with obvious approval. Although the prototype engine had been used hard (it had served about 20,000 miles they were told), it still looked great. UCE motors like it will power the new Royal Enfield G5 and C5 motorcycles when they go on sale soon in the U.S.

But a plastic gear inside the motor, where it turns the oil pump? The dealers couldn't believe it.

"We'll be making those out of metal," one commented, to general agreement.

Sarveswaran, a senior manager for Royal Enfield engine design and development, seemed a bit bewildered by the reaction. "In production, only plastic," he repeated, explaining that "it does not take any strain." The dealers were skeptical.

Watching, Kevin Mahoney of Classic Motorworks, the U.S. importer, seemed to realize what they were thinking.

"Is it a cost issue?" he asked the three Indian engineers present. "Is the gear made in plastic because of the cost?"

No, he was told: it's not a cost issue. The gear is made of plastic to reduce noise in the bottom end. Sound was a priority in designing the new motor. While the traditional Royal Enfield Bullet exhaust "thump," beloved by Indian riders, was to be saved, the noise from gears and push rods was to be curbed.

The dealers nodded. That might be OK, although one spoke about getting some of those gears made up in metal -- just in case.

The disassembly manual dealers were given shows the gear in white plastic.

It drives an oil pump that is said to deliver four times as much oil as the spindle gear arrangement of classic Royal Enfield Bullets, and to do it without maintenance.

That has to be the case, of course, since the unit constructed engine encloses all its bits deep inside, whereas the classic Bullet oil pump can be pulled out roadside, if you have to.

My guess is that few dealers and even fewer owners will ever see the plastic gear.


  1. How long can a plastic gear last? That question, combined with making it much harder to get to.... I'm no engineer, but it seems like that was a poor choice. Glad the engineers came and demo'd the engine though!

  2. Your reaction is exactly what everyone was thinking! Still, this was the only plastic piece in the engine, which suggests the engineers know something; it must be for a reason. Perhaps noise, as they said. Or perhaps there is the thought that rather than have all the gears strip in a catastrophe, let this single one take the hit. My guess is: it will be OK.

    1. I guess the same. I suppose is a kind of "mechanical fuse"

  3. Anonymous2/27/2009

    We have been running around with plastic timing gears in our cars for years, I ain't scared of it.

  4. If only it were a timing gear... this apparently is the drive gear for the *oil pump*!! if this baby goes... your gonna blow that motor. I haven't seen anywhere that there's an oil pressure indicator, no?
    I have no doubts that under normal, *proper* circumstances it will last a good long while... but how long before some dude dumps a couple of quarts of straight-50wt oil in the tank "cause' that's what we used back in the day" and trips that sucker bare on the first sub 40* morning?

  5. Interesting how the term "Plastic" makes us think of weak. F1 cars are made of plastic! OK carbon fiber composite. However many industrial gears are made of plastic and never wear out even with high load. Plastic tends to self lubricate, damp noise and vibration and deform just enough to share the load over multiple teeth.
    I would bank on that gear never failing.

  6. Anonymous3/05/2009

    I would rather have the noise of a metal gear than the silent but WEAKER plastic gear. Yes, they have been using plastic timing gears and sprockets in cars for years. And that is usually the first thing to go bad in the engine. THE JUNK YARDS ARE FULL OF THEM! I have NEVER seen an iron timing sprocket wear out. I will stay with my old iron barreled maintenance and mechanic friendly 350 Bullet. With proper maintenance and tinkering I intend to make it run forever.

  7. Anonymous3/07/2009

    Hi Guys,

    I am Amit an owner of a Royal Enfield, a UCE equipped Thunderbird Twinspark. I have taken a trip of 1320 Kilometers(approx 819 Miles) through the roughest terrain possible to my destination in the Himalayas. I have not come across any issues with the new motor. 2 years back I had done the same ride on an Electra (Non UCE) and I had a ton of issues with the rear brake link and the clutch cable snapping frequently. The ride on this baby by was great, It even breathes fine in the thin air conditions up in the himalayas I must say the new engine is fine if it can function well in the extreme heat and extreme cold, I have already clocked 45000 Kms on this bike and no problems, I came to know of the plastic gear only via this post, but I am not worried. The only thing I had to replace till date were the worn clutch plates. Kudos to RE.

  8. The main concerns in plastic would likely be size and physical makeup of the material used.The gear appears robust and much use has been made of these in many applications.It actually looks over engineered.The plastic should produce less wear in the whole pump system.IF they have done it right,it should be fine.

  9. Anonymous4/20/2014

    Howdy, name's Joel, got a G; had Guzzis, Triumphs, Jap bikes, a Penton, an Ossa, even a Hercules Wankel. 44 years experience. Until I discovered the GT and followed it from its Bullet-modified showpiece to the crate at my dealer(shameless plug time)Killeen Power Sports outside Ft.Hood, I've never seen or heard of a bike company going to such lengths to overhaul, revamp, and re-imagine their product. The plastic gear is progress, it is obviously rolling along in a non-stressed task, unlike a timing gear. The frame was engineered by British performance frame designers.It is basically a Featherbed construction. It also has a Head to Frame gusset plate that sends more vibes to the rear shocks and strengthens the frame even more, supplying Norton-like handling. Brembo floating brakes, Pirelli tires, aluminum rims. Paoli shocks and fork internals with the forks by Gabriel. Keihin fuel injection. Lightened crank and almost square bore. Unit construction. I really don't think that Sid Lal is going to make all of these improvements in a brand new huge facility and hang the entire future of Royal Enfield on whether a critical piece of engine is going to crap out or not, maybe. That is juuuuuust ridiculous.

  10. Interesting read, here we are 9 years later and no horrible stories about failure in the UK. I have a cast iron barrel year 2000 500 and the oil feed quill deal came adrift toasting the big end, a bonded rubber seal to replace the original cork yup CORK design. Japanese bikes have had nylon oil pump drives for years with few problems bar the Kwak gpz305. Nice little bike the Enfield and suits brit country lanes a treat.


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