dadof2

Th proiblem with a number of brakes is that they have "up loops" in the hydraulic pipes that trap pockets of air. All you do when trying to bleed with the lever / pedal is move the air pocket about but not far enough to expel it. - It floats back to the top of the up loop when the pedal / lever is released. This is usually a worse problem on back brakes. Can you suspend uor bike so there is a continual rise or fall in the pipe or can you remove a compoent and raise or lower it to get the same effect. On some bikes with twin slave cylinders on the same caliper (as most bike now are) the bleed nipple is in some cases on the lower cylinder and the air collects trapped in the upper cylinder. Bck filling with a large syringe or easybleed is the best solution (I prefer not to drill caps)but parking the bike in the right position overnight or for a few hours can get the air to the reservoir naturally. Another thing to check for is corrosion in the slave cylinder seal grooves. This distorst the seals and although they may not leak it prevents them controling piston movement correctly. Cheers

The two riders have in their time either led manufacturers with their development programmes or were a top team rider with a significant infuluence on develoment so it is fair to say they know a fair bit. What they have now come round to is the view that bikes developed with WTC in mind and moderen riding techniques are not in the best interests of the sport overall. As I have said previously I know of a number of riders who are sickened and have retired due to modern bike poor build quality. They bought a Pro - gearbox failed, they moved to BETA then pushed it home several times, then they try a Sherco and the bearings went or the fuel tank split. At this point they say sod it and go off and do something else. Cheers

These geasrboxes were a bit on the weak side, A few of my friends had them hand the majority gave trouble. Slipping out of gear is probably wear on the dogs on the sides of the gears or the holes into which they go. Thee is a pressed on part on the selector mechanism is in primary case which can which can slip or come loose and there are some pawls that wear. All can be sorted with a carefull bit of TIG welding and grinding / polishing if you can't or don't want to get new bits. Cheers

Try Ebay - there used to be a bloke on there who did them on CD, I got a TY 80 CD manual off him and it was fine, only about

Dare anyone answer? Have a look at past posts - there have been plenty on this topic. See if you can get an oweners manual and follow that. Bikes of this era often used mineral 2t at about 25:1. If this is the case consider semi synthetic at 30:1. Cheers

"(i) The machine ceases to move in a forward direction." The rule is quite clear, the problem comes with riders expectations. I as an occasuional observer have been pressured by riders in an attempt to give a 3 or better when it was definitely a five. What is worse (IMHO) is when mature riders attempt to pressurise young (schoolage)inexperienced observers into giving them a better mark than earned. Quite a lot of riders seem to think that a momentary slip back, or dragging the bike sideways with a foot down still count as forwards motion and argue with observers. I always give the benefit of the doubt particulary to riders who perhaps do halt for an intant but keep both feet up. A lenient application of the no stop rule is bad for the sport because it leads to a variety of marking and as scores will be lower will result in sections being stiffened for future events, making them even more difficult, possibly hazardous. What is better - a rideable trial with observers and the odd mark you are not happy with or - harder trials with no or few observers where you can mark yourelves and cheat as much as you like. Cheers

Glad my original post led to a significant number of comments. Laser1. situation may be diffentent in US, my experience is northern England. A weight limit is hardly over regulation - its simple and easy to check / enforce. Manufacturers could still compete by other improvements. The fact is that despite all the development / loss of weight trials bike sales in UK are very low and a cut in price would lead to increased sales (price elasticity of demand) A bit of extra metal on the exhaust system for example would reduce noise - a problem for land access in some areas. As an example from another sport (100 national karting). This used to be heavily price regulated and 3 to 4 grids of 20 to 30 karts were common at club meetings. The price regulations were relaxed resulting in significant cost increases and within a year or 2 entries were down to about 30, ie about 25% to 30% of the previous numbers. I know the general drift of my views is in line with the views of at least 2 top flight riders (Multiple Scott and Scottish six days wins between them) Cheers

Not familiar with this model of bike but if it has a lift up / plunger type enrichment mechanism (not a choke) it coild be dirt under plunger or damaged seal. Wrong float height? Damaged float valve or dirt in float valve? Cheers

As said previously many secondhand 125s have been thrashed. I would go for a 250 and think about putting in some extra cylinder base gaskets or a spacer to soften the power a bit. Cheers

Take the forks (complete with front wheel etc) out at the yokes, front brake off at the handlebars and rear wheel out. You can then easily lift the bits into nearly any vehicle. Cheers

"Dadof2, please don't take this as an attack I realise that this and my previous post could be construed as aggresive but they're not. Anyway, if those points you stated are important to you why not ride twinshocks?" It's fine - I know emails can look a bit "sharp" even when thats not the intent. I am certainly not against progress but as another poster has pointed out, what is progress? Single shocks - excellent move, adjustability, low wear and you don't bend them when you fall off. Water cooling + nikasil - excellent - means a well cared for engine never needs a piston or barrel/ rebore. I think the latest gassers are very good, especially the functional simplicity. However I also know of far too many gassers (and other makes) where a bit more metal would make them more crash resistant / less prone to premature failure and and a change to weldable material would make them easier to repair. I know of quite a lot of people who are less happy with the sport than they could be due to costly bike breakages. I have both alloy and steel framed trials bikes and favour steel, but how long before someone bings out a ultra light / ultra slim dural frame? I think a minimum weight limit of maybe 75 or 80 Kg would be a good move. Cheers

I would like to see the minimum weight increased for 3 main reasons 1) Cut the cost 2) Make bikes stronger / more reliable 3) Heavier bikes would mean sections could be eased and made safer. I would also ban the use of non weldable (magnesioum alloy?) components Cheers

I agree with NZRalphy, OSSAs from this period could suddenly have their motoplat ignition fail. It's a fair bet the problem is due to ethanol in your fuel, it could attack alsorts, seals, fuel pipe etc on a 1972 bike Cheers

Any of these older 4 strokes tend to be a bit jerky just as you open the throttle, can shove the front wheel out in tight turns. Look out for camshaft wear, often evidenced by misfire at higher revs. Rest of the bike , judge condition as you see it. cheers

Yep, this topic certinly does come up time and time again and causes a fair variance of opinions. I note there was a poll a while ago and certainly the majority expressed a preference for leaner ratios. I suggest that those who have posted since my first post, read my first post again carefully. You will see I made no recommendation,just pointed out the alternatives which did include 50:1 and leaner ie 70:1 ". I can't see how you'd get more power from a motor burning so much surplus oil" was then in the following post so I gave an explanation. Excess oil can have implications for the exhaust on a poorly jetted bike, but if your jetting is correct 25:1 burns off no problem. As for gassing your mates queuing at the bottom of sections, I can only point to the popularity of trials in the 1970s when every one ran 25;1 on much smellier oil than today. From previos posts "Be warned trials bikes don't handle that kind of treatment at all well and you'll probably kill it in a year" - I would agree, you probably would at 80:1. Cheers

Perhaps you should ask the question why "we" went to 50:1. Was it on knowledgable scientific research, or was it because of what it says on the bottle or in the handbook and gossip in the paddock? The reasons more oil gives more power even at low RPM are: It provides a more complete oil film reducing frictional losses It Provides a better piston ring seal, raising compression, reducing gas loss on the power stroke and reducing contamination of the crankcase mixture by reducing ring blow by. It lowers piston temperature and distortion as the greater quantity of oil provides more medium to conduct heat from the piston to the cylinder wall / cooling jacket. Lower piston temperature increases charge density giving more power. Over the last few years I have seen quite a few engines with premuture wear and the common factor is that they are very dry / unlubricated inside having been run at lean oil ratios. Remember 2 that if you are mixing at 75:1 and you get it slightly wrong you can soon be at 100:1, get it slightly wron at 30:1 and you will still have adequate lubrication. Also remember that manufacturers are going for lean ratios to reduce emissions, they may not be that interested in engine longevity - they do have spares to sell & profit from. Cheers

If you want your engine to run clean but wear faster go for a lean ratio of 50:1 upwards If you want more power and less engine wear go for a leaner ratio between 25: and 32:1 Choose a fully synthetic or semi synthetic oil that meets JASO FC specification and never go leaner than oil or bike manufactuer recommends. Cheers

Beta UK did (and probably still do) have a list of chassis numbers on their website Cheers

"contrary to common opinion more oil can do more damage than too little oil" That statement just is not true - too little oil WILL cause rapid wear and probably wreck the whole engine. The most likely worst thing too much oil will do is foul the plug or make the bike hard to start. Cheers

Compress your rear suspension until the rear axle, swing arm pivot and gearbox sprocket shaft centres are all in a straight line. At this point your chain will be at its tightest. At this point it should have about 20mm play mid way between the sprockets when the tensioner is held away from the chain. Some people set it a bit slacker to keep the tensioner up a bit away from rocks or accomodate mud build up on the sprockets. Main thing is not to have it too tight or it wrecks you gearbox bearings as well as increasing chain wear. Nor should it be so slack tensioner touches swing arm. Cheers

0.12mm sounds slack and I would think a shade over the limit. I would expect clearance when new to be about 0.0025 inch (0.64mm. The maximum taper or out of round of the bore is 0.05mm. my guess is you need a rebore + os piston.

I would be inclined to stick to a full face until he is a bit older / wiser, preferable to a mouth full of handlebar for instance.

I am well aware of the different stress levels in different engines having run karts, MX, grasstrack, and trials at various times over the last 40 years. Modern mineral oils are nothing like the mineral oils of old, they burn much cleaner and contain much less ash and suphur. Go to any trial from world to club level and you will see riders giving the engine a good rev at times to clean it out even when they are on lean oil mixes. As I said in an earlier post " sure with modern oils and engine materials you are unlikely to seize even at 80:1" so I accept synthetic oils do work at lean mixes and if riders are happy to use them fine. Richer oil mixes do produce more smoke and exhaust deposits. A rich mix improves cylinder to bore sealing, heat transfer and compression and reduces blow by which contaminates fresh mixture in the crank case. However it is my belief that taking all factors into account, wear, performance, oil costs etc then 32:1 and richer offers the best compromise. The most significant factor in a good running responsive engine is jetting, slide cutaway and ignition timing, not oil mix ratio. Cheers

Is it an electrical misfire or is it "fourstroking" due to running rich? Turn the fuel off and keep running it - if the misfire dissappears as fuel in carb runs low then it is richness which could be float level, dirty air filter or jetting. If it does not seem to be richness try running the bike in the dark with the flywheel cover off and tank lifted - look for stray sparks paticularly in the HT coil area. Stray sparks are much easier seen in dark than in daylight. Cheers

Set it so that is has about 19mm free play at end of lever, this is same as diameter as ball on end of lever. Is clutch still drags suspect something internal or still air is oil. On most trials bikes it can be hard to find neutral once stopped. Cheers