dan williams

Sorry, didn't mean to be cryptic. Your carburator has several "circuits" for controlling mixture at different throttle settings and these all affect each other as they transition from one to the next. By circuit I mean a metered fuel oriface (jet) and various air passages in the carb body. From idle to 1/8th throttle the fuel air mixture is done by a combination of the idle air circuit and the "pilot" jet circuit. From 1/8th to 1/4th throttle mixture is controlled by a combination of the pilot circuit and the angle of the throttle slide cutaway. From 1/4th to 3/4th throttle the mixture is controlled by the "needle" and "needle jet" with influence from the slide at 1/4 and influence from the main jet at 3/4 throttle. From 3/4th throttle to full throttle mixture is controlled by the "main" jet. As you can see a fleck of dirt in one of these jets will affect performance in just one area of throttle. Cleaning with compressed air is really the best way to make sure the circuits are clear. One thing I have noticed about the Keihin is the size of the pilot circuit exit behind the throttle slide is extremely small. Much smaller that the old Mikuni and I have had instances where a bubble of water will sit in and block this exit hole bunging up the way the bike runs off idle. The hole is so small that the water won't evaporate because of its surface tension. It has to be blown out. I now carry a can of compressed air from a camera shop just in case I need to clear a jet in the pits at an event. Even though this is for a Mikuni it is still an excellent guide to carb operation http://www.mikuni.com/pdf/vmmanual.pdf As for the reeds they sit in that square block between the carb and the cylinder. You can take the four bolts off and the assembly comes right out. Just do a quick visual to make sure all the reed petals are in one piece and that there isn't any dirt or debris on the seats that would hold the petals open. Don't worry if they look like they are slightly open. Air pressure closes them so they don't need to lie completely flat to work. Make sure you get a good seal when you bolt it all back together as an air leak can mess with carburation. Cleanliness IS the rule of the day with these fiddly little bits. Happy hunting.

Yeah you probably should have. You can pay the same for stuff made in the millions by Feng Shui manufacturing if it has a fancy label on it. If these are made in the UK I have no problem paying that much. In fact now that I've poked around the website I think I'll see what they cost in the US.

I think it's a 10. It makes 2nd the default section gear and first for crawling. I find the stock gearing makes second a bit too lively and first still too pokey for most sections.

Usually the pilot jet circuit. Clean with compressed air. A damaged reed will also cause a flat spot off idle.

Well Billy, according to Jeremy Clarkson we're fatter in the US (he's right of course) so we probably need to run a bit richer. I'm assuming this is a 250/270? If so a 27.5 pilot runs cleaner on the bottom and gives a crisper transition to the midrange but will also accentuate any lean pinging you get from low octane fuel.

OK so I don't like ATF but some do. I think the better riders who like a faster clutch are more fans of ATF. Then again there are so many types of ATF that I should probably avoid blanket statements.

I find dropping a tooth on the countershaft sprocket makes the 270 much better behaved.

You have to remove the glue in my experiance as I believe it is what causes the sticky. The edges of the tabs should be slightly radiused and polished. On the original bike I did the fix too (guinea pig1) I had a friend replace the main bearings (I didn't have the time) and he, being a Gas Gas dealer, stuck in ATF. The clutch is not working quite as good as before so I may have to crack it open and have a look. In my experiance ATF is not great in a Beta. Not sure about the hypoid gear oils as they are not really meant for a wet clutch if I remember trading friction characteristics for shear strength under load. Oh yeah one other note, too much oil in the gearbox will give you that creeping drag. Not sure why but I've heard it from some of the top mechanics and noticed it myself.

They are supposed to move. Do NOT try to tighten them to stop them from moving. You will bung up your brakes and possibly break your hub. Yes I've seen both happen. The float allows the brakes to be self adjusting which helps them be very strong with minimal throw and much more consistant.

Needs a set of rings. It may seem to run OK once it's going but throw a set of rings in and it will seem like a whole new bike.

It seems to be two opposite methods here but people are really in agreement. When they say put the naughty bits on the tank they really mean to lower your center of gravity to help keep the front wheel down on climbs. Think about the angle of your center of gravity vs the contact patch of the rear tire. When you move forward you increase that angle but it tends to unweight the rear wheel which causes spin. Sqatting down allows you to increase that angle while keeping pressure on the rear wheel.

The clutch fix does help but Beta's are notchy as a matter of course and neutral is always elusive.

Well there are a million ways to do this but you only need one since you only have to do a set of clutch plates once. I thought of lots of methods and they were good mental exercises but in the end picking up a set of files and just going at it got the job done faster/cheaper.

Sorry but the only way to get rid of a stupid rule is to enforce it exactly as written. Just like the only way to get rid of a bad law is to enforce it. When something like this is let slide by most then the people who do try to follow the rule are considered jerks.

Brilliant!

I remember reading about Ossa having titanium frames for some of the factory bikes.

Have a look at your reeds as well. You may have a damaged one. If they are just slightly open though it's not a problem as they are forced shut by air pressure not the springyness of the material. Is springyness even a word? Actually I should add the question does it rev properly when slowly brought up to full throttle?

Basically the bearings sit flush in the hub and the spacer should be an exact fit between the inner races. The spacer is really just a bare tube. I haven't had the wheel apart on a Beta in a long time but I don't remember it looking like what you found. It almost looks like what was in your wheel was some random piece of tubing just stuffed in the wheel. The sole purpose of the spacer is to allow you to torque the axle without any side force being absorbed by the bearing.

The Beta Mikuni is a VM26-208. It's sort of a special setup so you won't find any parts places stocking parts for that particular model outside of a Beta dealer. I don't remember if that particular year had the "noodle" on top. Basically a right angle tube held into the top of the carb with a snap ring sort of deal so the cable doesn't foul coming out the top of the carb. This is a good place to start. Remember some parts are not specific to a certain carb so they may have very generic part numbers. http://www.motorcyclecarbs.com/VM26-VM44_Spigot_Mount_Parts_W192C1420.cfm

The Bernie book is rare as hen's teeth these days. I had an autographed copy but gave it to a lad I thought had potential. He quit after a year. Dammit I want my book back!

Did you or a previous owner replace the wheel bearings? This sounds like what happens when bearings are replaced with the center spacer (tube that fits between the inner races of the bearings) left out. If the spacer is left out you can tighten up the axle and everything seems fine but the side loading on the bearings causes a quick and usually catastrophic failure and the whole hub assembly can be destroyed.

Normally about 70% of the stopping power of your brakes is from the front brake. On a downhill it goes up considerably. If you look at the top riders on steep down hills their rear wheels are just barely touching the ground and acting more as a stabilizer than any kind of control. You have to use the front brake. One of the things that greatly affects comfort on drop-offs and down hills is bar position. It seems counter intuitive but having your bars too far back makes it more difficult to get positioned for a downhill. Check your bars to make sure that they are at least vertical when the bike is on level ground. You'll see a lot of guys with their bars even more forward but that may make the steering too twitchy for you as a beginner. The key to the up hills as with most things in trials is centering. The Bernie Schriber book is still one of the best references on this basic concept. You probably find that you lose a lot of points in slow turns, always to the inside. This is a common problem for trials riders and is due to not bending the knees and arms to provide a stable platform. Let me 'splain. As Bernie describes it you should be standing on the bike the same as if you were standing on the ground. As a demonstration find a slope and stand perpendicular to the fall line, i.e. with one foot higher up the hill than the other. You may be on a hill but you are still balanced. It’s how you are balanced that is important. If you look down you’ll see your uphill knee is bent. You don’t think about it you just do it naturally. That is exactly how you should feel on the bike. You stay centered and the bike moves beneath you. Here is where most new riders get into trouble. They don’t bend their knees to compensate for the raising and lowering of the pegs as the bike is leaned. Instead they keep their legs locked and spin their torso to compensate. This works OK on an enduro bike at speed but it doesn’t work well at all on a trials bike. Try it standing on the hill and you’ll feel the difference. Have a friend try to push you off balance in both modes and you’ll see that bending the knees is a much stronger position than compensating by twisting your body. So the point of that exercise is this, keep your body upright in turns and let the foot peg and bar end come up to you by bending the outside knee and elbow. Now apply the same rules for uphill and downhill. Let the bike come up to you on the uphill. Don’t anticipate and lean forward because that will just unweight the rear wheel and cause it to spin. Maintain pressure into the pegs and if you feel the rear wheel spinning pull back on the bars. This is another important point from the Schreiber book, don’t think weight, think pressure. When you start thinking about weighting a peg or bar or wheel you’ll displace your center and lose the strength of being centered on the bike. Instead think of applying pressure to do what you want to do. Use back pressure on the bars to load the rear wheel for traction, forward pressure on the bars to load the front wheel for braking. Use pressure on one peg and bar end to initiate a turn or hold an off-camber. Use opposite pressure to stop a turn and return the bike to a neutral position. Try to always be balanced. Bernie said you can learn the basics in 5 minutes in a driveway but spend a lifetime perfecting them. On the down hills let the bike fall away from you. Don’t lean forward but do maintain pressure on the bars. You'll find that you will crouch into the correct position naturally. This helps weight the front wheel more which helps braking. One finger on the brake. If you need more have them serviced. The rear brake is more dangerous and must be treated with great respect on a down hill unless you’re really keen to watch the back wheel pass your front wheel on the way down. I’ve done it. It didn’t end well. Find a nice little hill and practice using just the front brake, using just the rear brake and a mix of both. You can throw in some turns and get used to the transition from up hill to down hill to up hill while maintaining your centering. Believe me the first time you do it properly you will go. “Whoa!” Then you’ll spend a few hours trying to repeat it, and then a lifetime trying to perfect it. One more note on up hills, when you have to dab maintain pressure on the foot still on the peg. Most new riders dab and plunk their whole weight on the dabbing foot. Instant rear wheel spin when you do that. On your practice hill practice dabbing on the way up keeping the back wheel loaded. It has to be a reaction so practice helps the muscle memory. A final tip is to watch slow motion video of some of the older non-trick riding sections. Watch body position and you'll see how the top guys stay centered. You can watch modern stuff too but you have to look around the dynamic trick moves to see how they all start and end the tricks from a centered position.

I figured as much. Nobody in the motherland would cancel a trials for mud.

Trials has an odd (and unsustainable) business model. In most manufacturer/importer distributer/dealer relationships the distributers/dealers serve an essential function not usually known by the customer. That of buffer/storage. For most manufacturers/importers it would be financially impossible to stock all the parts necessary to serve demand. By each dealer keeping a small stock of parts that are paid for up front the manufacturers can maintain a larger footprint than they would be able to if they had to pay themselves for all the spare parts necessary to support a market. That's the way it works in the semiconductor business. The distributers place large orders from manufacturers and by marking up the parts the distributers can handle the smaller orders at a profit and the manufacturers can service the large accounts directly. In trials every novice rider has the phone number of the importer on speed dial and will bypass the local dealer to save a few bob and there'll be hell to pay if they don't get it at the same price as the dealer. This Walmart effect is a relatively recent phenomenon made possible by the internet. It has in many ways damaged the sport as most dealers who were barely scratching enough money out of trials now find it impossible to afford being a dealer. The main problem with this is most trials riders are very close to their dealers. They see them at events, they ride with them and as a courtesy they buy from them. Unfortunately when the local dealer has to undercut the importer price or the price of a more aggressive dealer they go broke and quit no matter how much they love the sport. That means the loss of the major recruiters for the sport, the small dealer.

You need to get the Top Gear lads out there with the Snowbine. Actually it looks a bit odd to me to see bare ground since the guys I ride with are usually shoveling out sections this time of year to practice. It's actually better with snow as bare ground just freezes and makes for variable traction. Good on Stratford-Upon-Avon Club for giving it a go and then having the smarts to know when it was dangerous enough to pull the plug. Always a difficult decision.