ask greeves

JON V8...Please don't missquote me, where have I said 'dynamically balancing a single cylinder engine is such a waste of time'. Seems to me certain threads like to have a 'pecking order' If your a callow youth or a non-descript sorta person, you'll do fine. Occasionally you'll entertian somebody who upsets that ordley running, by adding (if there allowed to) pertinent imput....call it human nature, self preservation, but you don't like it.( rather have the 'how much oil'/ 'where is my drain plug'), and all because people at the top, feel uncomfortable with criticism.

Thank you for your considered post... I'll work backwards my last project with regard to single cylinder engines was approx 5 years ago, With manx nortons, 7r's and g50's, Perfomance XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX the afor mentioned bikes, designed in the 40's and 50's, although they used state of the art parts for that period, advances in pistons and conrods, mean't a great reduction in XXXXXXXXXXXXXcould be saved. Only trouble is a great XXXXXXXXXXXXXXXXXXXXXXXXXX. Trouble is the engine now XXXXXXXXXXXXXX, although more powerful (through higher rpm) engine XXXXXXXXXXXXXXXXXXX. To overcome this problem, the standard XXXXXXXXXXXXXXXXXXXXX heavy flywheels. The project prior to this was on single cylinder speedway engines, were theXXXXXXXXXXXXXXXXXXXX than historic road racers, in that inertia is required for 'gating' (the start). These 2 projects are what has made me a little conversant with balance factors. Prior to this my only real involvement with single cylinder engines was approx 40 years ago, when i worked at Radials in Watford, who were agents for Alpha who made bigend assembles. My job was to disassemble crankshafts and rebuild with new Alpha bigends and conrods and true. As to your problem, i'll write further in the next day or so....trial tomorrow

Woody, I have no issue with you, so why are you getting involved. No bodies perfect, I would be the first to admit that fact. You want to play....should i search through all your old posts, No...I've got many more important things to do....finish preparing/fettling my bike for tomorrow.

I find it difficult to understand why persons on this particular thread, have to quantify themselves, maybe they are wanting in the self esteem stakes. Auxlove surely your refering to a KIT CAR bugatti (with a Buick type engine)....not a REPLICA bugatti (Ivan Dutton is the only person, I know of that builds replica Bugatti's) , but then again ..if your wanting to impress..carry on. Jon v8 Please don't misquote me, nowhere have I said you were rude, would seem you have problems following the thread, hope you both have a long and worthwhile relationship. Its amusing how people tend to believe anything which is written in print, the many cases of people in the public eye for example, believing thier own hype, Persons on this particular thread quoting Don Morley, a scribe's personal suggestion, as if it's the end all solution, to a comlpex problem. So you don't want to have lessons on how crank balancing is done, you know it all, so you want to go straight from A to Z , if you know it all, then why ask balance factors, if you were completely ofay you would know from the 'hyperthetical model' how the differences effect an engine.

Davetom, Ho I see, your not allowed to reply to a public posting, unless you agree with the content. Where have I said "I don't agree with modern technology" Lets face it PAL you'll probably get loadsa 'backup' to your posting, from people who really don't understand and want to get a life......bring it on. Wide band sensors don't think so.....dynamic balancing of a single cylinder engine, possible,(all sounds very technical, to the uninitiated) but don't think so. Persons with an IQ of one survive as do persons with an IQ of 150...it's just the life style that changes. If you consider a posting childish, surely replying would put you on the same level as the original post, but then again if you consider that 'you need a life' then it becomes understandable for you to reply. I wasn't to keen on the manner and name dropping of the original post and replied ( I consider) in a similar vein, I don't want to join your 'little clique' of yes men, who agree with anything which is posted.

The balance factor takes into account the resistance offered to the flywheel by the piston/conrod assembly, which when rotating at an oblique angle, causes an out of balance situation. The engine manufacturer may produce thousands of conrods and flywheels, these would be made to certain limits, may it be BSA, Enfield, AMC, they would all have there 'own take' on what they considered the best 'balance factor'. The production line would take any conrod and any pair of flywheels and assemble...knowing that they would work, within a certain rpm range. The secret is to have the vibration range higher than the rpm range. We're talking mass production, so similar to 1 in a 1000 winchester rifle, where all the parts just by luck are exactly as per the blue print. Modern day rebuilds are blue printed, so as to get as near as possible to the exact limits. As your rebuilding your AMC, your in the excellent position to get it spotis bolikus....hopefully ! The process would involve assembly without the piston/conrod, but with a weight on the bigend journal equal (plus/minus balance factor) to that of the piston/conrod, then the flywheels are spun and any alterations could be made, then the assembly reassembled complete....is it worth it !

Firstly XK 150's never came with webber carbs, so i consider 'it's a load of crap' Then again Jay Leno has a vehicle with an 1920's aircraft engine, to which he had fitted twin turbo's.....so it's whatever ring's your bell...go ahead an do it. When you've been through the whole cenario...been sold aftermarket equipment, which in reality, is inferior to the proper article, you can become very cynical, to a large majority of what is said on this web site. Isn't this a motorcycle trials site...how can xk 150 or alvis or 4.4 range rovers have anything to do with trials bikes, unless of course your trying to impress the reader ! Laird 387 has given us valuable insight into the history of motorcycle trials, a picture is worth a thousand words and his information excellent, the advance/ retire trick was used by many riders, your never going to be able to do that with a modern crankshaft ignition, but then again i'm a purest. The majority of the modified bikes (in my opinion) haven't been made better, they've just got caught up, in a 'modern day' money making exercise and it's great...because that means there's going to be less proper trials bikes, who's value will most likely increase. 'Teardrop tanks' a prime example of modern crap, they look nothing like anything which was ever produced, but slap a triumph or james or anything badge on it and in the beholders eye...he is the dogs danglers...yes i'm cynical.

In bygone days there used to be machines called 'Krypton Tune' people would say 'i'm going to have my car Krypton Tuned' This was the start of taking away the 'human feel' to the mundane, low power, gas guzlers of the day. If you can't use a timing light and haven't got 'the touch' to be able to twist a distributor or adjust a carburettor...I think your lost. Or maybe all you need is a kick up the aristotle and read up on basic engine technology, or why 'uneven' engines and dual plane engines (modern V8's) need a balance factor. So your going to fit a pair of wide band oxy sensors, I assume its a 6 cylinder engine, why not fit 6, monitor each cylinder, or maybe just fit one further down the exhaust...2 carbs maybe, dual afr gauges...so then you'll need some kind of data aquisition gizomo, to record over the full rev range, to make your adjustments, otherwise your just going to 'get it right' over a very small part of the spectrum. Sounds like an excellent way to spend somebody elses money.

I was always of the understanding, that the distributor drive was not strong enough to withstand this conversion. During the 60's there was a guy named Barry Worman (spelling maybe wrong) in the South Midland Center, who trialed a B 40, this particular bike had special side covers that allowed the magneto to be placed similar to the earlier B31/goldstar.

Sounds like your a fastidious dude, Don Morely 60%....why not ask Sammy Miller...maybe he'll be 61% or even Kieth Duckworth. Why not include an external counter balance shaft, also some guys use methanol on trials 'old timers'...the father of a famous trials rider definitley uses alky in his HT5. Probably your going to use a Carrillo with a super tick Piston..so's the combined weight would probably be nowhere near stock so you will need a balance factor....do the maths...work it out yourself, unless you want to add some providence, or name hinting to the speel, when you sell either machine, lets hope there's a scrap of bygone trials heritage, left to saviour.

Hello Ian, straight in fit, you'll need the 305 exhaust, first inch or so, to replace the same on the 300 exhaust, the head steady may need modifying slightly to fit the 305 engine, and the carb rubber (carb to airbox) will need slight tweek. Hope the 305 engine's a good-un, pistons distort and become noisey and new pistons are becoming rare.

303 engine will bolt in, might have problem with the large 303 flywheel case, touching the frame, where the c shaped tube flywheel protector is. The exhaust will fit straight on, although the outside diameter of the 303 exhaust port is 38mm, compared to 35mm for 240's and 300's. You would have to fit the inlet manifold from the 240 maybe or a 300, as the carb position is different. 303 engine (249cc) last of the piston controlled ports, probably the best motor, should have 'high exhaust port (which allowed it to rev) and some had a squish cylinder head, just like a 240. The clutch is bigger on the 249cc engines(and 241 onwards 212cc engines), the extra power, needs to be respected (to control wheelspin)but the larger clutch allows plenty of clutch control.

Often referred to as 'helicopter tape' this super tough tape was developed to protect the leading edges of helicopter blades.

Breagh has given you the 1st premis of looking after your clutch...but unfortunately you seem to have dismissed it. OK buy new clutch plates, these will be thicker than used items and give you clearance, if lack of clearance is your problem, BUT have you adjusted your old clutch first, given it free play ! or maybe your paticular design of clutch doesn't have any facility for manual adjustment and it's all compensated for in the hydraulics. I always find it's difficult to repair something, if your not aware of exactly how it works..think it's called 'shooting in the dark' Then again, if you've 'burnt' your clutch, through either bad maintanance (not enough free play) or general wear and tear, the plates will be knackerd anyway, so needing changing.

The 240 (212cc) was Fantics all build engine (forward kick), the engines prior to this were minerali (back kick) with Fantic head barrell and piston. The 240 was a 'stand alone' engine, the bore/stroke and rod length were excellent to be able to rev/pull with little vibration. No major parts of a 240 are interchangable with a 300 (249cc). With the introduction of the 300, with its larger clutch/straight cut primary gears and aluminium clutch basket. The next year saw the 1st mono's 301 and 241 and now the 241(212cc) had the same clutch gears as the 301 . But remember, not much else is interchangeable between a 241/301, the 212 has smaller internal crankcases, the 249 has bigger flywheels different rod. As for the 125/156 forward kick Fantic engine, very little is interchangeable with either the 212 or 249, but interestingly the Fantic head/barrell from the back kick (125/156) will fit. Without getting into infinite detail, that's about it.

Mr Hewson, Exactly right, great pics. No cutaway original twinshock, cut away mono

We live in strange times, if for instance, you had a Francis Barnet, the only 2 items that could be original could be the gearbox case and the mainshaft, everything else could be new, and maybe £6,000 worse of. Simarly tigercubs and bantams, but at least, the unit construction crankcase and the mainshaft would be original and maybe £7,000 worse of. I can't really see what's wrong with wanting to make a bike, as it left the factory. Seems to me there's plenty of screwed up people out there, willing to spend thousands on competitive non descript trials bikes. I forsee these type of non decript bikes becoming quite common and valued at a lot less than they are now, wereas an original old bike could have more intrinsic value and still be able to compete, but of course, not good enough to win, but then again, i'm not personally young enough to be able to win. Maybe i'm just putting the knockers on an industry which has been created to cater for those individuals that want to imagine, that they will set the standard and win, with thier non-descript expensive 'not really real' trials machinery.

My only reason for replying to this thread, there maybe somebody considering buying (at great expense) a 247 Big Hub Montesa, which they may consider to be 'as came out of the showroom' only for some anorak, such as me, to say....very nice bike, but unfortunately...not right, been changed etc etc. Certain items on any bike, make it a 'dating feature' and in this case big hub montesa's never had aluminium top yokes

Mr Sparks, I am in complete agreement, being very old and having gone through the cenario of buying a SHM top yoke for my bultaco (at very great expense) in the early 1970's. It was the 'way to go' tiller action, dirty great big piece of cast aluminium, and guess what 1st time out with my super trick top yoke....it broke. Getting back to the Cota top yoke, if I was judging a concours, I would mark down considerably a none era conversion, in this case the later top yoke. The other conversion of the era, was to fit the later front wheel spindle, which is approx 1 inch shorter, required the bottom sliders to have approx half inch machined of the bottom fork sliders, to allow the spindle to fit flush with the outside of the forks.

Stephano is correct, Ducati did sell the rights of thier 125 to Italjet, this was originally the basis to the Italjet two stroke Trials 250/350 engine. OK Italjet may had an associaton with Berni S, but thats as far as it goes, nothing about an Italjet is Bultaco. It's like saying a Zak-of-kaki is the same as a Honda, just cos Freddy Spencer rode both marques. The question is, did Ducati originally design the 125 two stroke as a fourstroke or visa versa as used in four stroke guise in the Italjet Scott. I love Italjets...got a 350 greeny, 250 feather, and a Scott.

Hello Woody, Yes the 250 will fit directly onto the 350. If your doing the conversion because of lack of 350 piston and knowing a bultaco piston will fit, be aware the original 250 italjet bore (actually 238cc!) was chrome, so would need iron rings. Also bultaco small end smaller, but can be sorted with different caged roller small end bush.

The easy way to tell wether original engine, the rear engine mount where the engine sits on the swing arm spindle, if the engine is from a 201, the centre of the engine mount will be machined (elongated half moon shape) to accept the mono rear suspension, wereas the 125/156 original engine has no cut away. The same applies to 240 and 300's

The clutch side oil seal needs to be very carefully fitted, because of the sharp edge on the crankshaft, the factory used a taper tool that fitted onto the crank shaft, allowing easy placement of the steel collar and oil seal. I personally use a very thin feeler gauge and carefully roll the feeler gauge round the inside of the seal, to pass the sharp edge.

You might have to 'bite the bullet' and buy a piston complete, have seen them on e-bay £300 squidish. From recollection aftermarket pistons made by omega, doubt wether thier rings would fit a geniune piston though....so probably a case of payup and look big for a complete piston assembly.

Been watching this thread since the beginning, nobody noticed in the original picture, the bike has the wrong top yoke, big hub 247's should have a steel top yoke. Not an aluminium as in the photo.