dadof2

If its going to save you a lot of money buy the 300 and stick some extra cylinder base gaskets in to soften it up a bit, then its easy to get more power again if ever yuu want it. If its the type with changeable ignition run the soft setting, if not retard the stator plate a bit. Cheers

Why dont you run an ordinary 2 stroke oil for engine protection and add a tablespoon of castor oil to every gallon for smell. It won't do any harm and you will get the best of both worlds. Cheers

These engines can be a bit rattly and pink / tinkle on the overrun. I think Castrol (although a good oil) may be a bit thin (SAE 20 ish) - I think it is low viscosity so it can be used in oil injectors as well as pre mix. Try Smith and Allan fully synthetic, Gulf pride 2T or Gulf fully syntheic which are about SAE 50. Putoline MX 5 at 30:1 also quietens them down. Check the squish clearance and keep the piston crown and head well decoked. I would be inclined to take the barrel off and check piston skirt to bore clearance. From memory I think it should be about 0.0025 inch (0.064mm) and will rattle a fair bit at 0.004 inch and badly at 0.006 inch. Hopefully someone with a yam service manual will confirm or correct my figures. BP Ultimate can reduce pinking compared to "standard" fuels Cheers

Spray easy start round all your carb / inlet joints joints. If revs rise you have a leak and the easy start is being sucked in. Give the carb a thorough clean. Cheers

250 Ohms sounds about right for the source (ignition power generating) coil. Check the resistance of the pick up (timing trigger) coil. I would expect it to be 850 to 1300 OHMS. Rig up an electric drill so you can steadily spin the engine. at about 450 RPM you should get about 20 to 30 volts AC from the source coil and 1.5 to 2 volts AC from the trigger coil. If all is as above and its not the kill switch try borrowing a known goog CDI and ignition coil. Check for wire to coil shorting intermittently on frame. Try spinning the engine in a dark garage and look for stray sparks. Cheers

April fool or not, its about time Michelin gave something away. Trials tire prices are a rip off, far more expensive than MX tires and twice as much as a decent 225/60 R16 for my car. Cheers

I would temporarily remove the brather even if a bit of fuel splashes out. Check the fuel inlet (float) valve in the carb. Check the fuel tap and in tank strainer / filter. Ignition HT coil can occasionally give these symptoms. Cheers

Something a bit strange here. What is meant by "pick up". If this is the trigger coil the ignition works or it does not. Since youur bike had a spark it suggests the trigger coil was working and should not have ben changed. Stator *a bit low". Does this mean the resistance of the source coil(s) is a bit low or is the output of the source coil(s) a bit low? I would have a word with Beta UK. Cheers

If the chain is on the same side go ahead, should be quite easy. Nice running motors the mid 70s TY250s

Armstrong? (ridden by Steve saunders?)

Do you mean the play is 2/3 rds mm (0.66mm) or 2 to 3 mm. A Rev3s main bearings may be geting tired by this time. I would not run the engine until the mains have been properly checked, it could ruin the crank, the big end the lot (very expensive). The vibration can vary. As the bearing cage wears or or starts to come apart the balls move, causing slackness at times and overtignness at others. Cheers

Well! Divine wind as they say in English.

Fit alarms such as http://www.responseelectronics.com/ and make sure you have at least 2 PIR detectors overlooking your bikes and each other. Engrave or hard stamp your registration of part of your frame / engine number on all key parts of the bike such as cases, hubs, fork clamps etc. Personalise a few bits - get them anodised or plated in unusual colours Keep photos & records of the above. Cheers

gasgas249uk. On the weight limit I guess we will just have to disagree. Having said that I think it would only make a few kgs at the most to make bikes really tough. Its not just the thickness of sump guards and cases that could do with an extra mm or two, I bet there are hundreds of riders each year strip out M8 x 1.25 pitch threads into aluminium. Moving to M9 or M10 by 1.5 pitch would go a long way to curing this. On the subject of welding magnesium I maybe chose my words badly. Instead of saying I can't weld it, I should have said I am reluctant to weld it for a number of reasons. The American Welding Society states "welding [of magnesium castings] that may contain oil in pores should not be welded" and "the welding of some alloys in the as cast conduition is not recommended because of the greater risk of cracking". Some cast magnesium requires several hundred degrees C preheat and up to several hours at 450 degrees C post weld heat treatment. Cast magnesioum alloys have very high shrinkage contraction on solidification, this leads to high stress levels in the welds which can cause sudden complete component failure at an unknown time in the future. With an aluminium crancase you can get away without pre or post weld heating, usually avoiding the need for an engine strip. With magnesium alloys the need for pre and post weld heat means a full strip is probably essential, especially when the need to try to get oil out of pores is taken into accound as well. Some casting alloys also contain other alloying elements to increase fluidity during casting to enable them to flow into thin sections of the mould, these additions make them effectively unweldable. Cheers

Hi there Paul - not all off same bike / accident. Brake lever was off near new EVO - just dropped it on its side and the span adjusting screw dug in. Rear brake was off about a 2 year old bike - just caught it on a rock going up a stream bed. The sump guard on Rev 3 was removed to weld a small fatigue crack that was starting at the corner of one of the slots at the front. When guard was removed crank case damage became visible - the rubber cushion under the flywheel housing had been punched up through the right hand side crank case. Fortunately it could be welded by just taking engine out of bike and not having to strip it. Had the crank cases been magnesium I would think the bill would be about £600. Cheers

Clean the carb out. I am not familiar with this carb but asume it has a cold start enrichment system. Make sure this is closing off properly when not in use. Float level? dirt on or damaged float valve seat? Occasionally faulty HT coil gives same symptoms. Run the bike with the fuel turned off and see if problem goes as the carb empties - if it does you know flooding or similar is problem. Cheers

Find someone with a multimeter that measures ohms. Your stator will I think have 4 coils - three with thick wire and one with fine wire. Measure the resistance of the fine wire coil at the terminals that plug togeter at the top of the radiator. Should probable be about 250 to 300 ohms. Try measuring a good bike if you can. If resistance is infinity (open circuit) coil or a wire to it is broken. If resitance is well over 300 wire may be thinning / about to break and won't flow enough current. If resitance is much lower than 250 windings are shorting and wont generate sufficient voltage. Try bradford rewinds or west country windings - cheaper than whole new stator. Cheers

In the last few weeks I have welded the following Beta parts - front brake lever, rear brake lever, sump plate and crank case. Over the years I have welded crancases on Yams, Hondas & Gassers. Had these been Magnesium I would not have been able to. A quick look on Beta website shows crancases to be about £300 (Yams & gassers are a lot more) and I guess the new Beta magnesium case will be.a lot more than £300 also. Is this realy progress when you pay a lot more to shave off a few % of a Kg and render the part un repairable. I watched the WTC indoor trial from Spain on saturday night and more or less only the top 3 could make a decent attempt at the sections. What is the point of this expensive weight shedding excercise when only the top few in the world can make use of it and its just an added cost for the rest. The sooner the FIM bans magnesium and ups the minimum weight limit the better. Bou & Co would be just as spectacular with an extra 5 or 10 Kg and as a prevous poster says the rest of us should keep further from the table. Over the years I've seen quite a few riders spend a fortune to lighten their bike, and judging by their girth and riding ability they have spent even more at the pub! Cheers

Just out of curiosity anyone remember the Cumberland County MCC trial at Milburn in the 1976 / 77 winter, (dancing on ice?) or the Barrow club trial at High Newton in about 1983? (2 foot of snow). Then there were the wet and foggy Scotts of 1990 and 96? or 97? when quite a few riders found themselvs swiming the section and some bits in between. Then there was the Lakes 2 day in January 76 - part of it was like Scott of the antarctic - freezing riders on their hands and knees in snow trying to drag there bikes along. Cheers

Hi there - glad to be back - had trouble getting on since forum upgrade. The oil issue is a bit more complicated than what burns off at high revs / heat. Also its easy to state generalities that are not true in all circumstances. Its pretty true that more oil gives more power when the engine is pulling at whatever revs. However if the large quantity of oil in a rich mix reduces the rate of burning of the fuel outside the expected range when the ignition advance curve was determined power may be lost. This is neither the fault of the oil ratio nor the ignition timing - its just the fuel burning rate is no longer matched to the ignition timing. More oil generally means less friction - so more power More oil generally means a better seal betwen piston / rings and bore so more compression and less blowby = more power More oil provides a better heat path between piston and barrel (cooling jacket) resulting in lower piston temperature. This reduces piston distortion (hence friction) but also increaes charge density because the incoming mixture is kept cooler for longer. A cooler piston also reduces heating of the mixture in the cylinder before ignition, reducing pre combustion pressure meaning less power loss on the compression stroke. Going back to the original subject of Castrol A747,(which I regard as synthetic rather than castor although it ontains castor) from memory this has a flash point of about 270 degrees C. More modern fully sunthetic Castrol power 1 racing has a flash point of only 73 degrees C and burns much faster and cleaner. Most of the moderd synthetics are designed to burn fast and clean at the temperatures / conditions found in lightly loaded water cooled barrels to enable them to meet the clean burn specs such as JASO FC and FD. Many years ago I saw a Bultaco 250 sherpa big end wrecked after very little gentle use over 4 years. The owner was also a grass tracker and used the same shell sport R (a castor racing oil) in the Bult. The oil had turned to varnish and gum all over the underside of the piston, the con rod and big end. The gum was so thick it blocked the lubrication slots in the conrod meaning the big end ran dry and uncooled as it was shielded from the incoming mixture by gum and varnish Cheers

"what it means is that you can run leaner fuel / oil mix to effectively burn more fuel unlocking power from the engine whilst still maintaining protection and minimalising engine wear." That statement is simply just not fact. Engines make more powrer at 20:1 fuel:oil than they do at 50:1 - ask any professional tuner. More oil in the fuel = less wear Moving from a ratio of 25:1 to 50:1 increases wear by a factor of 200 to 300%. Cheers

How do you know its overheating?

http://www.shell.com.au/home/content/aus/products_services/on_the_road/oils_lubricants/advance/product_range/racing/ Have a look at the above link and the mix ratios. These oils and castrol as well have a significant additive packages that won't burn off in normal trials usage. Running them at lean ratios compensates for this to some extent as it lessens the amount of additive. Why buy an expensive oil for hard use lubrication then throw much, maybe all of that benefit away by lean oil to fuel ratios? Cheers

http://www.clarkforest.com/shop/chainsaw/2-stroke-oils/oregon-2-stroke-oil-5-litres If you are looking for decent oil at a good price try the above - it meets the latest/ highest specs as regards lubrication and cleanliness. Also when you see the hammer these small two strokes get day after day with little wear you know its a good oil. As for Castrol A747 - yes a superb lubricant but as it is based on castor you probably should use it within a day or two of mixing - not leave until next weekend. Cheers

Ask around at nearby trials and local trials shop and see if you can find some riders to practice with. Cheers