dan williams

Check out http://www.betamotor.com/system/attachment...evisione_03.pdf page 5 POS 23 part number 29-07314-8 scroll down to footnote at bottom of list. If you look at the 00-06 parts manuals you'll see the extra weight is on the 270 Yes I can see it through the sight glass on my 05 270. No I can't see it through the sight glass on my 08 270 No I couldn't see it through the sight glass on my buddy's 05 250. Not the first trials engine I've seen with an additional weight on the primary side of the crank. My old Bultacos also had an additional weight on the primary side of the crank.

Heh heh I'm up to my ass in MSEEs from MIT here. One of the best things about the two-stroke tuner's handbook is that it taught me the concept of wave propagation at a young age. Something that is the basis of transmission line theory which I have to use designing circuit boards to work with data streams in the GHz region. It was also useful in doing pro-audio work as the theory translates directly to accoustics and how sound behaves in speaker enclosures. I owe a lot to Gordon Jennings.

One thing you might want to consider is before '07 the 270s had an additional flywheel weight on the primary drive side of the crankshaft. The 250s didn't have that and as a consequence felt quicker. The '07/'08 bikes are reversed with the additional weight on the 250 and not on the 270. If you feel the need for a little quicker revving then you might want to take a look to see if yours is equipped with the weight. You can see it through the gearbox oil sight glass.

Ya know Jon damn near everything you could need to know is on Wikipedia somewhere. There is one huge tome called the Art of Electronics but it's probably massive overkill. Hey one cool thing I've recently discovered around Boston is a used book place called "Got Books". I wanted a book on PHP programming and typically I'd go into a Barnes and Noble and plunk down $30-$50 but I picked up a slightly used one for $3.50. Might be worth looking around for a used book shop. Maybe pick up something at a local college book store that sells used text books. I'd love to find a cherry copy of the two stroke tuner's handbook. I just remembered something cool. Way off topic but cool anyway. Did you ever wonder why some deep space probes have this long arm sticking way out from the rest of the probe? It's where a fission pile sits generating heat as the radioactive material decays. Unlike a ship where that heat is used to make steam that turns turbines to make power, spacecraft have big arrays of thermocouples that sit near the hot nuclear material generating electricity.

Ooohh can I get pedantic too? The temp switch is indeed a switch. A thermocouple is different. A thermocouple is a sensor made of two dissimilar metals that generates a voltage when there is a temperature difference between two similar junctions. Very commonly used to measure temperature.

Depends on fuel octane, jetting, compression (rings, cylinder condition, carbon buildup), riding style, air temperature... Like any other tuning technique the only way to really know is to try it and measure the results in your specific application. I know that's not the answer you wanted but it's safer then giving an answer that causes you to seize your motor. Try gradually increasing the advance a small amount at a time and note the results. Soon you'll know more about how that engine responds to ignition advance then the guys who designed it.

Er... trials bikes are pretty much tuned about as good as they can be especially when compared to other racing machines. At best you might improve power by a few percent with port matching and such but there isn't a whole lot you can do that won't fundamentally change the nature of the engine. Your avatar says you've got an '08 125. Sherco used to make 200cc bikes and it's possible the cylinder/piston from a 200 would fit your bike. The stroke is the same. Other then that there's not much else you can or should do. It's gonna be expensive though.

Partially blocked pilot jets will do this sometimes as the bike starts fine with choke but has an issue when hot as it is too lean to start. First thing I'd do is strip down the carb and blow out all the holes with compressed air. Also make sure the gas cap vent is clear and that the vent tubing on the carb is open. Also look to make sure the kill switch isn't partally shorting causing a weak or dead spark. After that hard starting can mean it's time for a set of rings. They do wear and if the bike is three or four years old it can be time to throw in a new set. Even though it seems to run strong once the bike fires up you'll be surprised at just how much spunkier it'll run with new rings. I wouldn't bother doing anything to the cylinder just throw the rings in and it's done. Edit: I should note that lean jetting will also cause hard starting and we are getting to the time of year when going up one size on the pilot and main are useful due to the colder, denser air.

The boy's come a long way from when he used to crash his mini-cycle into my truck in Ossipee NH. I'm proud of him. Why did the organizers have a problem with a headset? It seems like all the other sports allow them and in a closed course obstacle race it would be more effective then flagmen as a safety system. I'm curious on what basis they made them stop using the system as I've found nothing in the rules to prohibit communication devices.

Yes

Make sure you blow out all the carb orifices with compressed air. Just taking the jets out and making sure they are clear may not get the water out of the carb.

Water is heavier then oil and will separate out and sit in the bottom nooks and crannies of the transmission. So even if you drain the oil you probably still have some water in there. Once the transmission is spinning again it will just emulsify back into the oil. Two things to try are to run the bike for a while to get the oil/water emulsified and drain it while it's still mixed. It won't get all of it but it will help. The other I've found is a good synthetic oil will tend not to emusify so easily. Because of the vents in the transmission and our habit of riding in rain and mud holes there's always going to be some water in the gearbox even if it doesn't come from the water pump. As long as a bike isn't left sitting for weeks at a time I don't think it does any damage.

As for me I don't use a ramp to put my bike in the truck. I pick it up. But at the end of a 4 hour trial with the stock clutch I was having problems holding in the clutch and dropping points as a result of the lever slipping out of my finger and I won't ride with two fingers on the clutch. I had that hand slip off the bars once and it was ugly. Maybe you farm lads who are pitching hay all day or the guys who can practice 5 days a week have better hand strength but many weekend warriors spend the day in front of a keyboard and just don't have the "Kung Fu" grip. Any trials bike clutch feels fine for quick ride around the yard.

Amen brother.

Very nice exercise but I've had to deal with a similar situation so I know where the hammer has to fall. One of our clubs a few years back made the event too hard. Long hard loop, long hard sections and a hundred rider turnout. Halfway through the event they stuck a sign up changing the end time lengthening it by an hour. They were then told to take it down as the time cannot be changed after the event starts. Here's the problem. Rider sees sign, assumes he has more time and takes his time on loop and in sections. To his surprise and horror receives late points or times out. Rider doesn't see sign but is told by fellow riders or club official and does same. Rider doesn't see sign and assumes he is late so hustles through loop and sections dropping more points than usual to finish without time points or time out. Rider doesn't see signs and blasts last loop taking voluntary fives on harder or longer sections to not time out. There is only one way to reconcile this mess. Unfortunately in this case the difference for one of the top riders was a 1st or 3rd place finish. Result MAYHEM. Rider filed a protest (NETA doesn't charge for protests, just seems wrong to us). My ruling based on the rules was that if the rider wished to continue with his protest the only solution was to disqualify the event from year end points. no telling what other classes it may have affected in some subtle way. This was made clear to all the riders and the event promoter. The option was given to the protesting rider to withdraw his protest which he did much to the relief of the other riders and club but it was made known to the rest of the riders that this guy was essentially getting screwed for their benefit and that they owed him. That's one of the key points to something like this is you shouldn't rush in to fix it unless there is a protest. Riders don't like to be mothered. But if there is a protest you must act and it must be defensible within the rules. When somebody inevitably whines about the rules you invite them to the annual meeting where the rules are made. There they can defend their ideas just like the rest of us have to. (NETA annual meeting is open to all members) The only exception in NETA is safety. The NETA officers are empowered to make or alter rules during the season if it directly affects the safety of riders, spectators or officials but that rarely happens. Curiously enough at the next event this club had I intercepted the trials master on his way to put up another sign changing the time halfway through the event again. How thick can you be?

Buying a bike that's beat will be trouble no matter what brand it is. I've seen good reliability from Shercos except for the rear shock. If you buy another used bike check it out before plunking down the money. You will usually get what you pay for as trials riders are pretty savvy as to the value of their machine. If you buy used buy a senior rider's bike. Usually much lower wear and tear and they have the money and experience to maintain the bike.

I currently use Spectro "Golden Gear" but just about any good oil will be sufficient. I've also used mobil1 10W30 motor oil in the Beta but Betas shift kinda notchy (sp?) anyway so it's tough to see much difference and since I smoothed the tabs on my fiber plates the clutch really doesn't seem to care what I put in as long as it's not ATF. I tried ATF years ago and I couldn't ride the bike at all. Most bikes transmissions will work fine with any good oil with the possible exception of GasGas because of the radical clutch design. One thing I did notice when I used Mobil1 is that it didn't emulsify like other oils when a little water got in the gearbox. Always found that interesting. Perhaps because it was a pure synthetic.

As always Jon, YOU DA MAN! Hadn't thought this through to this detail but it makes perfect sense now.

Glad to be of service. Good thing I'm a better mechanic then rider. Got my butt handed to me this weekend in Sr B. I'm looking into a set of shims that one of the other guys on here has made for his bike. It would allow the use of all six of the stock springs and I think reduce the plate chatter I get with the four springs. More even pressure on the pressure plate.

Max is right. The Keihin is a tricky little beast to set the float on. I think I could do a Mikuni in my sleep at this point but the Keihin took me three tries. It's also really tricky to get the float bowl back on as you probably discovered. I found that the usual way of doing it holding the carb upside-down is not as easy as holding it rightside-up and putting the bowl on with the floats at the bottom of their travel. Only took me three weeks to figure that one out. I hate that angled overflow tube. You didn't damage that tube by any chance did you?

Yeah if the floats are too high the engine will cut out on downhills. Lower the floats and all should be good. I also find a little higher idle on the '08 helps a bit too.

OK, couple of questions, Do your friends have 270s? There is an additional flywheel weight on the '08 250 that's not on the 270. When you take the carb off do you blow out all the passages with compressed air? I have noticed the Keihin is a lot more prone to getting blockages in the pilot jet circuit because the holes are a lot smaller then the Mikuni. Yeah I know they look about the same but if you put it under a microscope you'll see that a few mm down the hole the diameter gets much smaller. Even a bubble of water can plug it up and make your bike run soft off the bottom so it's worth the exercise of pulling all the jets and screws out and blowing the passages out. Even though your '08 is one of the first the carb on it has been in production for many years so it's unlikely you got a bad one. One thing that I'm not thrilled with on the Keihin is there doesn't appear to be a removeable needle valve seat so if you have even the smallest scratch in the float valve seat your only option is to relap the valve seat. Next time you take the carb off make sure the vent hoses aren't kinked. It's easy to pinch them when stuffing it back into the bike. I can't think of much else that will cause it to rev slower that doesn't involve a timing or compression issue. Maybe blocked exhaust. OK I'll stop rambling.

How much you want for a set?

The NETA rules are clearly stated that a rider cannot protest another rider's score. Also an observer can only score on direct observation. Yes somebody is gonna get away with a point or two but that's part of the game. I don't know if there are analogues in the ACU rules but there needs to be. As far as calls from rider A, why in grid's name are you accepting them? He has NO say in the matter and letting him think he does is asking for trouble. Sometimes you have to be the daddy. The kids aren't going to like it but it's for their own good. Any decision other then eliminating the section is going to be worse in the long run. You're only starting to see the problems that are coming down the pike if you waffle on this.

Yeah you'll notice the top guys use the least throttle on the stuff we duffers are really hammering. The big difference is confidence. They trust their bike (and reactions) much more then we do. So we tend to hit it harder then necessary with less then outstanding results. I like your attitude though. It's all about having fun and you will get more confidence as you get more time on the bike. Of course the beauty of it is as you get better there's always bigger stuff to try.