What is an AJS Regal Raptor 125 engine?

[lingeringstin...]

I'm talking about the AJS Regal Raptor 125 thing engine. I've got one coming in the post. It was slightly knackered but easily fixable if I wanted to.

The main reason for buying it was that it was cheap and looked absolutely identical to the Chinese Benly clone 250 I've already got so I thought it might be good for spares. Everything looks absolutely identical from the outside and as far as I can tell it uses the same charging system and starter and engine cases, maybe even the same gearbox and other bits but it's not here to take apart yet so I don't know.

The thing is, the AJS 125 engine looks slightly different than the bog standard Chinese 244FMI that I'm led to believe it is, so maybe it's not one of those. I can't really find any info about who made the engine for the AJS. This is the 2008 model and I think it's got plumbing for an oil cooler but everything else looks exactly like the 253FMM engine.

Not being familiar with Chinese shit I don't know if the AJS engine is just a sleeved down 253FMM or if there's some fundamental differences.

I've got a spare set of barrels for a 253FMM engine. It was going to be an experiment to try and squeeze in some much bigger and higher compression pistons just for the hell of it to see what happens. Now I'm wondering if that 250 barrel could be grafted onto the AJS 125 to make a whole spare engine for my bike.

AJS also seem to have a 350 engine that also looks almost identical to my 250, and I don't have a clue if they are all basically the same things with different top ends.

[Teflon-Mike]

Regal-BSAcreated thier own variant of the Benly engine; most notable dfference being a water cooled head abd barel, and revised primary case to take the water-pump....

You say it has an oil-cooler? Are you sure its not a radiator?
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[lingeringstin...]

It hasn't arrived yet but from what little I could gather online this is an early version that claimed to be air cooled although there's a suspicious pair of inlets on the barrel that look to me like oil cooler points. I couldn't see any obvious water pump or radiator hose fittings. There's apparently a 150 kit for them.

I will be interested in seeing what crank it's got.

From the outside it look exactly like the 253FMM engine and not like the 244FMI. I rather suspect it's just a sleeved down 253. Curiously I found a similar 150cc creature online somewhere called a 247FMJ and it looks identical to the one I'm getting and has the same inlets on the barrel:

https://i67.tinypic.com/2zokgo6.jpg

[lingeringstin...]

So this is an early model oil cooled AJS Regal Raptor 125 engine apparently. It looks just like a Chinese Benly clone and is something called a DD244FMI. It also has DADYW stamped on it in places, whatever that means.


https://i63.tinypic.com/2rx9vk5.jpg


https://i67.tinypic.com/xnuoog.jpg



Apart from the barrels it's externally identical to a standard Chinese 253FMM. Looks to me like it uses the same clutch, starter, charging system, intake, exhaust, head, and engine cases. I wouldn't be surprised if it's got the same gearbox in it when I open it up.

The only real difference I've found so far is that due to the shorter throw of the 125 crank and barrels it's altogether about 15mm shorter than the 253FMM Benly clone engine I've got but either one could be shoehorned into the same space without changing motor mounts.

This engine has a knackered tappet doodad which could be due to somebody over tightening the rocker cover bolts that stupidly screw into them or it could be indicative of quality issues with Chinese metal but I've yet to look into that. Anyway there's easy after market spares and old Honda stuff seems to fit usually so I think you could spiff up one of these Chinese engines to be pretty good if you were arsed, which most people wouldn't be because it's probably cheaper to just get an old Honda Benly engine to rebuild.

This is supposed to be low mileage and so far it looks pretty good, apart from the obligatory appalling chrome you get on Chinese bikes that rots off in no time. But I didn't buy it for the looks.

The Chinese 250 engine I just rebuilt actually seemed well enough made although I have doubts about the quality of the bolts that held it together but I changed them for nice allen bolts when I was rebuilding it. I suppose in order to keep costs down they cut corners on certain things but the actual engine cases, gearbox, clutch and crank certainly seemed decent enough. Time will tell, but then that's why I have two of these engines. I want a spare one standing by just in case. And anyway I've sort of been wanting to mess about with a 125 to see what can be done to make it go faster. I might even like it better than the 250.

It will be interesting to see what's inside.


https://i64.tinypic.com/2e3phkl.jpg


https://i66.tinypic.com/152glk4.jpg

[lingeringstin...]

It just got more interesting.

I took the 125 top end off. No damage to the valves or pistons or anything. It's a 360 crank. I could just replace the broken rocker gubbins and make it a 125 again.

Then I took a 250 barrel and to my surprise it just slid right on. The 125 head even fit on the 250 barrel although it is designed with a smaller combustion area to be on a 125. I think the valves might even be the same size as the 250. The inlet ports are certainly the same size as the 250 and although I didn't check I'd bet the exhaust ports are the same as well.

If I could use the 125 head on the 250 barrels it might create a really high compression engine. I'd have to fit a 250 crank and cam chain and maybe but maybe not some longer studs. With a rebore and some oversize pistons this could be fun.

But I was also wondering what would happen if I used the short throw 125 crank and fitted the 250 barrel and pistons. I reaslise I'd probably have to shorten the piston skirts, and I'd have to have Mr Geezer at the machine shop take about 15mm from the barrel, but it could be done. It would be a short stroke 250. Anybody know what happens if you shorten the stroke on an engine?

So far all that sort of adds to my theory that the whole AJS 125 bottom end is probably the same as a 250 only with a different crank. I have yet to actually take the bottom end apart so there's still a chance there's differences down there but I doubt it.

[lilredmachine]

Technically it would make it a revvier engine. More 'oversquare' motors tend to spin faster. Unfortunately to make use of this you would need to port the head, run a hotter cam with more lift and duration, use larger valves, enlarge the intake etc. A less torquey, revvier motor needs to spin faster to make power and to do that it needs more air and fuel to do it, without the extra breathing it will simply spin at the same speed, with the same power band but make less torque and therefore horsepower at a given RPM.

Just for example one of the 'hot swaps' in the day was an xl185 barrel/head, crank, rod and piston in a cg125 bottom end as it gave you more power and torque but with an extra gear.

What I'm getting at is that unless there are differences in the bottom end that give you an advantage over using the vanilla bottom end, then it is ultimately pointless. Same for the head. You would be better off using the 250 head and tuning that for shits and giggles.
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Bikes: too many, too much for one man to maintain anyway.

[lingeringstin...]

I only stumbled across this engine when I was looking for a spare clutch. I like to have one handy just in case and this whole engine turned up for peanuts so I just had to go for it.

I took a chance that if it looked the same as the 250 on the outside then it was probably much the same on the inside, and that turns out to be true. The engine cases even accept the 250 barrel without any trouble whatsoever, so basically it's a 250/300 bottom end with a 125 top end bunged onto it. Now what to do with it.

It's complete all but the broken rocker thing and I found some old Honda ones that are a perfect match so I could easily just fix what it is and keep it around as a bodge in case I break my 250. It would bolt right in. Problem is now that I know the 250 barrels fit on it I want to make it a 250 engine.

In 125 form it claims about 11hp which is probably about right for what it is. However there are also 150 top ends for these engines, or I could rebore it and put in some pitbike pistons of appropriate size. I don't know how much horsepower can be squoze out of it as the liners look like they can only be bored out to about 50mm or so. I don't know what that would make it but I doubt it would be as powerful as my 250, but it would be cheaper than getting all the stuff to change it over.

To convert it to 250 I'd have to get:

crank
pistons and gudgeon pins
cam chain
full head with cam and valves
probably a rocker cover
longer studs
cam chain tensioners

...and of course all the gaskets, but 90% of them are interchangeable between this 125 and the 250/300 so that's not really a big deal.

By the time I sourced all that and maybe even a rebore it could be getting a bit expensive for what it is. I should probably just fix it as a 125 and wait until local Ebay regurgitates yet another dead Chinese bike for £40 and do it up for sale to the L-plate crowd.

I've been wanting to make a green lanes bike but I want a kickstart single for that. Perhaps I could swap it to somebody for an old CG125 or something.

[lilredmachine]

Reboring and using larger pistons tends to increase torque on these small engines. IIRC a 150 kit on a 125 cg clone means it is able to trundle up hills at 50 rather than 45mph. There will be a small horsepower bump for it, but law of diminishing returns and all that.

Pitbike motors are a good thing to look at for reference, a hoopty 160 might make 20hp, but it does it with a trick 4 valve head. A 160 barrel kit on a 2 valve head won't make anywhere near that, it will act like a torquier version of the 125 stocker.
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Bikes: too many, too much for one man to maintain anyway.

[lingeringstin...]

What ARE those things for?

I was looking at the 125 head from the engine in the pictures above and started to wonder about the oil cooler fittings. I couldn't tell where they fed to and from, so I put the snozzle of a WD40 can in one of them and gave it a big long squirt waiting to see where it came out. I was expecting to see it dribble out from around one of the stud holes.

It only bloody came pouring out of the exhaust port!

Upon investigation I found that those weird little things on each side of the head that I THOUGHT were where the oil cooler lines connected have nothing to do with the oil. I have no idea what they're for, but each little inlet just has a really small straight channel directly into the exhaust port on that side.

What on Earth is this shit for?

Whatever it is, if I decide to use that 125 head (possibly on top of a modified 250 barrel and pistons) I just intend to block them off.

[Evil Hans]

Some sort of EGR / emissions thingy?
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Triumph Sprint ST 1050. And it's Red.

[lingeringstin...]

Jesus tap dancing Christ...

Apparently those little fittings on the sides of the head are for some completely idiotic bit of snake oil called an EGR, which allegedly does something "by recirculating a portion of your exhaust and running it through the combustion process again."

WHAT??????????

NO. Just fucking NO, NO and NO! I do not believe what I've seen. Has the world gone utterly fecking stark raving MAD? There is absolutely no way the "recirculating" of exhaust gasses can possibly do ANYTHING of any value to a 125cc motorcycle engine, or any other engine for that matter. It's complete bollocks. Absolute shite. I am insulted that anybody in the universe has actually invented such a stupid thing, and I am outraged that any motorcycle engine, ESPECIALLY a 125 twin, has such a device. It is utter, UTTER stupidity of the highest order. Just no. Absolutely screaming NO!

Absolute shit. Stupidest shit I've ever heard in my life. Total rubbish.

NO.

[Bricktop]

[lingeringstin...]

However, it's EFFECT is to add more complication, weight, expense and potential FAIL to a tiny little engine that already gets about 300mpg that will spew out so much less pollution than ANY car, Chelsea Tractor or urban tank that Mrs Nump uses to ferry her two ugly children the quarter mile to their exclusive school.

Given the fact that most people using 125's are probably not great natural bike mechanics then one can only assume that such a failworthy and idiotic addition to any frugal 125 will after only a short while very probably spend much of it's time either not working correctly due to the owner's lack of attention, either by ignorance or just plain teenage lethargy, or failed altogether, both of which won't help with emissions AT ALL and will only worsen the toxicity of what comes out of the exhaust due to bad running even though what comes out of a 125 exhaust if you ran it all day long is still less environmentally toxic than one car ferrying one moron to and from their pointless civil service job in heavy rush hour traffic.

It is in my mind highly questionable whether the addition of complication, weight and expense to a 125 engine can serve any practical purpose whatsoever. If anybody's worried about noxious emissions they should just fart less and the fat lazy bastards should stop using their stupid obnoxious, overpriced, overcomplicated cars to go EVERYWHERE, all the time, taking up THAT much valuable space on the overcrowded road system stuck in traffic with only ONE PERSON per car. How many scooters can you get in the footprint of a Range Rover, and how many of them will be permanently stuck in traffic?

It is an absolute fact that (and I am a self proclaimed rocket scientists so I know these things) a 125 ridden like you stole it through city traffic would still pollute less than any car in traffic, including "hybrid" or electric vehicles the size of a house that still has to be recharged by getting it's coal fired and nuclear electricity from some spewing power station hundreds of miles away where you can't see it so it doesn't exist in your tiny little closed minds, and cost a whole lot less in Earth's resources to manufacture and maintain in the first place.

In short the stupid little addition of a regurgitating thingy valve to a 125 engine is just some snake oil insanity proffered as an unrealistic knee jerk response to pacify the braying hippy-dippy twats who think polar bears and whales are dying because a patch of rain forest the size of Wales disappears every five seconds due to the fact that MY little 125 engine doesn't have a bloody-whatsist fitted but it's still OK for everybody else to drive about in two tons of metal just to go get a pint of milk at the shop at end of the road.

And I'm also giving everybody the James Finlayson squint who thinks a bike isn't a bike unless it's got an enormous spewing engine and can go 200mph on the pothole encrusted public roads of Great Britain and beyond.

In short... NO. Just absolutely NO, NO, and NO.

NO!