dadof2

Makes me laugh when GasGas say 200 grams off weight of fuel tank on 2014 models is significant weight saving

I had a 1975 310 MAR and several of my friends had slightly earlier 250s from about 72 to 74 models. Sure the clutches were a bit heavier than modern hydraulics but nowhere near needing stilsons. The standard cables were good quality with oil nipples. I used to use graphited penetrating oil. None of us ever felt the need to modify the clutches in any way. Standard mod was to replace Hex Head sump bung with a tapered hex socket plug so it did not extend below the ally "sump" case.

Lineaway & axulsuv = I cleary implied against re jetting at this stage. The engine is definitely rich and I suggested checks to do. The gasket misalignment would restrict coolant flow causing overheating. This engine is clearly rich / cold. Those bore scratches should not be there - I have seen 15 year old well used bores with less. Thouroughly rinse the barrel, piston and crank cases with petroil mix and pour into a clean bowl, allow to settle, pour off the clean liquid and examine the sediment under a strong magnifying glass or microscope. Check the piston ring end gaps are within specification. There seems to be a bore sealing problem Re assemble engine and check it turns over easily and smoothly. Run in for 10 hours using mineral oil at 25:1. Grey plug can be due to lead in petrol but you should not be using leaded petrol in a 2t, nor do I know where you would now get leaded. and you state you use shell advance unleaded so I can't see that being the cause.

Some time ago I made a post about all sorts of restrictions to cut development and parts costs and got quite a bit of flak for it. I favor a weight limit and would like to see it gradually increased to 75 kg or even a shade more. But what also needs to be done is banning expensive materials like titanium and magnesium and putting minimum thickness limits on bash plates, engine casings, discs etc. The aim being to reduce costs and increase robustness. The problem with what the FIM have done is akin to shutting the stable door after the horse has bolted. Oddly enough If I were buying anew trials bike I would likely buy a Honda, but If I were buying a MXer no way would I buy a four stroke. Not only are they heavier and more expensive to buy but they are noisier (tracks lost) and far more expensive to run and maintain.

Just a thought for those with titanium (expensive) exhausts. Coloration is a sign that the exhaust is hot enough to react with oxygen in the air. As titanium absorbs oxygen it becomes brittle and will crack. If your titanium exhaust colours change your jetting and or riding style.

0007 in reply to your questions Dadof2, just avoid quoting the entire post Thanks for the info, engine testing is very interesting stuff, do you do this kind of work? Not professionally any more - for about 20 years I worked in the oil industry and then after that in engineering with close links to all types of engines from chain saws to turbo diesels and some fuel research We had a 125 HP dyno and oil test equipment. Most of the interesting stuff was picked up from work colleagues who had worked in very specialized automotive fields. I like to see how and why things happen in engines, amazing how subtle changes make radically different results Q: for curiosity reasons, were the engines air cooled? (Chainsaw) Some of the engines were in chainsaws, other variants in motorcycles, both air and watercooled The no problem 32:1 engines ere all hard used chainsaws. On a waterbrake dyno (rpm controlled by load or electronically limited) The production engines are electroInically limited - I think the miss alternate ignition sparks at the RPM limit. I think the dyano was electric generator type Was there any detonation (detonation applies shock wave loads to rings, damaging ring land etc etc) On the test engines as far as I know it was just lubrication film became inadequate at about 12500 RPM followed by galling of the rings and bore. On the warranty claim engines the symptoms were the same. As far as I know the engines have not been modified at all but the oil spec and advice to customers has been. It is not improbable that there was nothing wrong with the engines or the oil but the frequency of failure would have been damaging for the manufacturer if it continued. The comment was made that "UK pump fuels are among the least regulated in Europe" Out of interest I wrote to my MP about fuel and received a very detailed reply with info dating back over 50 years. The variability of what they can put in it is quite surprising if not shocking.

I can’t really suggest a one size fits all mixing ratio, there are too many variables. Firstly the type of oil is a compromise in itself. Ideally the rolling bearings, mains, big and little end need a low volume of heavy oil (SAE 50) whereas the piston needs a much greater supply of lighter viscosity (SAE 30) oil. Oil lubricity / quality also varies greatly, some synthetics are less than £10 per litre whilst some are about £30 per litre. Research shows that whilst idling a ratio between 80 and 100 to 1 is adequate whereas at high throttle openings between 20 and 30 to 1 is needed, hence the development of pumped oil systems. Some riders use good quality oil, keep the air filters clean, the carburation correct and don’t work the engine too hard (avoid high sustained RPM) and never have any problems at ratios over 50:1. Others tend to buy whatever oil is handy, are a bit careless on carburetion and maintenance and work their bikes hard and their piston / bore is worn out or mains fail in a season or two. They would have been far better at 30:1. Many years ago I used mineral 2T at 25:1 in trials and 20:1 in MX. Never had any wear or seize problems but did get hard carbon build up. Then along came synthetics that supposedly could run at 50:1. On my local dealers recommendation I used them at 40:1. For several years I persevered with 40:1 but noticed significant increase in rate of bore wear on both MX and trials and even had a big end fail at less than 5 months old. The above applies to 3 well known brands. Colleagues using Castrol’s synthesised versions of castor oil at between 30 and 40 to 1 fared much better wear wise but did get some coke sticking of exhaust power valves. I reverted to mix rations of 32:1 for trials and 20 or 25:1 for MX using mainly semi synthetics and the wear problems ceased. I understand at least one of the reasons Yamaha developed Yamalube R (now 2R) was because of the variable quality of synthetics being sold. Air filters do not stop all dust, (nor do they stop water which has a severe negative effect on synthetics) the smaller the particle the more likely it is to get through. A thick oil film and good supply of lower specification oil is more effective at stopping wear due to dust than a thin layer of high specification oil. There is a lot of rubbish talked / written about the supposed disadvantages of using rich mix ratios such as poor pick up, smoking and carbon build up that are putting it bluntly a pile of crap. Good quality oils and petrol contain cleaning additives and don’t produce deposits, poor oils and cheaper petrol don’t contain sufficient additives and produce deposits. Carburation is also important – take a look at Souwesters “Beta tar factory” despite running fully synthetic at 75:1. Some of the cleanest pick up bikes I have ever ridden were during the 25:1 mineral oil / tubed tyre era when clutching was not used and precise throttle response was key to adjusting speed and finding grip. Detonation and piston temperature. One of the main functions of 2t oil is to transfer heat from the piston and piston rings to the cylinder wall. A thin film of high lubricity oil may prevent metal to metal contact but there just is not enough of it to transfer heat out of the piston and high piston crown temperatures then cause detonation (pinking). This is perhaps the main reason why high revving kart engines need 15 or 20:1 oil ratios and why 4 stroke engines spray the underside of the piston with oil. I have seen trials bikes correctly jetted and running on Putoline MX5 at 40:1 suffer quite severe detonation and overheating problems when pulling hard on sustained climbs (about 60 to 75% throttle). Switch to mineral oil at 25:1 and even with no carburation adjustment the detonation and overheating problems disappeared. I would always advise to mix at least as rich as the engine or oil maker recommends, whichever is the richer and use the recommended or known better oil, not some uncertified brand. Jon – I hope I have at least to some extent answered your question and end with the following thought. James Dabill’s Beta seized at the Scott when he dropped it and the throttle stuck open. Perhaps someone will post exactly but I guess he was running at between 50 and 75:1. Would it have seized if oil ratio was between 25 and 32:1 ? I have seen several bikes at these ratios rev their b------s off until the carb ran out of fuel in the same circumstances but not seize.

# 69 yes i do read posts. Veterinen had a substantially lightened bulto and then added weight to the front forks to keep the front end down on steep gradients. Also some of those bashplates were not aluminium ally, stainless steel was experimented with to increase weight low down as in some circumstances this improved handling characteristics. That bantam is an abomination - Totally pointless - If a manufacturer wants to prove themselves do it in the modern world as Jotagas are doing. Don'y hijack and push up costs in classic trials.

Hi again, firstly a bit more on the ring failure I mentioned. The problem was not down to acceleration forces on the rings, it was due to the breakdown of the lubricant film between the ring and bore. The evidence suggests this was a lubrication rather than an engine material problem but it is not as clear cut as that. Once the lubricant film breaks down friction causes heat and the ring or bore expand more locally increasing the contact pressure and irreversibly damaging the ring and bore. The symptoms were that the engines would seem to loose power and once stopped would be difficult or impossible to restart. The problems occurred on engines using manufacturers recommended oil (fully synthetic) at the recommended ratio of 50:1. There were doubts about the fuel quality, the time it had been mixed and the accuracy with which the 50:1 had been consistently adhered to. Engines run on Texaco Motex 2T (a mineral oil) at 32:1 did not have any problems despite the oil not meeting the manufacturers specification, however in these cases it was known that the mix ratio was adhered to and the fuel was used within 24 hours of mixing maximum and that the fuel was Texaco or Gulf and used within 2 days of purchase. I suggest having a look at http://www.rotaxservice.com/rotax_tips/rotax_feed2.htm which makes interesting reading for those using high mix ratios of fully synthetic oil in infrequently uses engines or where there is water about - both of which are common factors in trials bike usage. Synthetics oils when used correctly do have very high film strength / anti seize properties and it it probably this coupled with a desire to reduce emission that has led to the adoption of high fuel to oil ratios. Modern engine materials are pretty good so generally these ratios work but that does not mean they give optimum performance or lubrication (engine protection)

The plug on the photo looks way too rich, the base ring (the bit next to the threads) looks like tar, it should be tan to chocolate brown. The fact that the centre and earth electrodes are much cleaner suggest the plug is hot enough to burn the deposits off, perhaps too hot. I am always reluctant to suggest leaning off the mixture via the internet because of the consequences of going too lean. I would start by checking the carburetor float valve, float level and that the cold start enrichment is seating / sealing properly. There is a lot of misleading advice about carburation / plug colour. The carburation is mainly judged by the colour of the base ring and the part of the centre electrode well up inside the plug (hard to see - needs magnifier and strong light). The heat range of the plug is judged by the colour of the electrodes and insulator near the spark area.

0007 and others - I will do a lengthy post when I have a bit more time. The information is commercially sensitive as it involves warranty claims so I can't give too much detail Briefly, yes, the engines are smaller than typical trial engine and I should perhaps have downgraded RPM to give comparable piston speed. The engines were electronically limited to well short of 12,500 RPM yet suffered ring failure as a result of inadequate lubrication. Tests using control fuel, recommended oil and 50:1 ration show that these problems should not occur under 12,500 RPM. The suspicion is that variable fuel quality may be the cause or something about the fuel was degrading the oils ability to lubricate adequately

Yes methylene chloride is rather nasty stuff, but caustic soda is none too pleasant either. I get mine from Smith and Allan and the safety data sheet is on their website. Metylene chloride will not harm metals or other exhaust packing materials, It WILL rapidly wreck rubber, plastics and paintwork.

Probably the best way to clean out an exhaust is to plug the end and fill it with methylene chloride (about 3£ per litre). Shake it once in a while or leave it overnight. Pour it oil and if you keep it in a tin (not plastic) container it can be reused several times. If the methylene chloride does not shift really hard burned on deposits in the front pipe near the barrel try spray on foaming oven cleaner, leave it to work then part fill the pipe with chippings, plug the ends and shake it.

I have quite a bit of respect for Jon Stoodley - but it does not mean he is always right nor do other tuners always agree with what he says. The comment about gearbox makes as much sense as ignoring manufacturers advice. Why spend a lot og £££s on a bike then risk damaging it due to lack of oil? Some recent research has shown that at 50:1 a good / top quality synthetic oil starts failing to protect piston rings at about 12,500 RPM so in theory at typical trials bike revs an 80:1 mix should be fine. But then add in some variables like water droplets, a bit of engine wear, poor carburation, variable petrol quality etc and 80:1 looks nowhere near a safe bet. I stripped a 2010 gasgas recently (gearbox fault). Run on Motul at 75:1. Rings, piston, barrel all damp with oil, some wear but still within tolerance. Quite a bit of oil in the bottom end but little end far too dry for my liking. The piston, bottom end and even the reeds were covered in dark brown deposits caused by blowby. It would seem 75:1 was providing adequate lubrication but nowhere near enough piston cooling and ring sealing. There is a serious drawback to advising 80:1 - You do't know what sort of use the bike is going to have, I have seen a beginner stuck in a peat bog rev the bike till the exhaust glowed dull red just outside the barrel. Try that at 80:1 and see how long the piston lasts.

Glad to see you got it off. I hold the pinion with stillsons using aluminium between their jaws and the pinion to avoid damaging it. Never use heat on a pinion (or any other gearbox component) as it only takes about 250 degrees celsius to start undoing the heat treatment that gives the pinion its strength and wear resistance.

Rub some soap on the lever and heat it until the soap chars / blackens then allow it to cool or quench in water before bending it. Repeat the heat treatment (annealing) if you feel the lever stiffen again whilst bending it.

A poll is not only unscientific, lots of germans voted for Hitler but that turned out to be unwise. The words Lemmings and cliff spring to mind. As I said previously if you think nearly halfing the manufacturers recomendations for the cylinder lube is a good idea, why not cut the gearbox oil by the same amount? A correctly carburated bike will not oil the plug at 20:1 fuel : oil, let alone 50:1

Well done the FIM. Hopefully minimum weight will be increased further. The drive to reduce weight has only resulted in increased cost and decreased reliability. It would be relatively easy to run a chain inside a swinging arm / oil bath with epicyclic gears in the rear hub. No chain wear and no pollution

#3 since handbook says 50:1 and yet you think 80:1 is OK I presume by the same reasoning you would recommend ignoring the other manufacturers instructions and only putting 2/3 required oil in gearbox or your car sump?

A worn or turned tyre can give more grip in certain circumstances than a new one. Its down to contact area and effective space between knobbles.

Is it Beta who do a tank that fits on the forks? probably fit other bikes.

Does it have formula brakes - if so the whole system may need stripping and flushing out, some have black dirst and aluminium swarf in them from new. I think there are other posts on this.

I think Cal has gone to Ducati because there was nowhere else to go and it is reputed to be well paid. Manufacturers sucess tends to go in cycles and it may be Ducati's turn next. Audi (who now own Ducati) will have more direct influence and will get rid of some of the traditional design elements that may be holding Ducati back. As I said - Roll on next year - it could be vintage. Anyone see BBC 4s programme on the NW 200 last week - Sammy Miller beat Mike Hailwood.

I really have to laugh at Ossa, same as gassers - why not just make a reliable gearbox in the first place? Casette gearboxes are for rapid / frequent ration changes as in road racing

Have they got and always had the correct and clean fluid in?