dan williams

Cold air is denser so the effective cylinder pressure is higher. Basically like running a higher compression head. Bet it ran stronger then usual.

Love the bark of a healthy 270! Couple things you can do to tone it down. Go down one tooth on the counter shaft sprocket. Did that to my '05 and '08. Made a world of difference for me. Get carbon fiber reeds. Smooths out the bottom and adds wonderful grunt to the low end. Check your pilot jet. Stock Mikuni jetting is a bit on the rich side. Usual first mod around here is to replace the stock 30 pilot with a 27.5. On the 07-08 models the 250 got the primary side flywheel that the 270s had in previous years and the 270 lost the flywheel. This makes the 07-08 270 jerky and more prone to stalling at low RPM but makes for exciting acceleration when you whack the loud handle. Understand that the 270 has higher compression so each beat of its noble heart is a little stronger then the 250. You can drop the compression a bit with an extra base gasket. But why would you?

Ah the basic disassembly is a piece of cake. Unlike most things on a trials bike. Parts book is here http://www.betamotor.com/system/attachment...t_05_motore.pdf The cleaner the bike the better. You don't want to be dropping dirt into the open engine. 1. Lay bike on side. (so oil doesnt leak out when you open the case) 2. Remove shift lever. (1 bolt on base of lever) 3. Remove four bolts on clutch housing cover and lift off cover being careful not to damage gasket which is a thin o-ring that sits in groove in case. 4. Remove 6 bolts and washers that hold springs. Remove springs. Put them in a baggie so you don't lose them. DON'T TOUCH THE CLUTCH LEVER! Duct tape it open, stuff it with cheese, hire an armed guard. Whatever it takes. If you pull the lever with the pressure plate loose best case you'll have to push everything back in place. Worst case you'll pop the slave piston out of it's cylinder, unseal the hydraulic system, push the thrust bearing out into the sand, lose the little ball bearing and leave a path of death and destruction whereever you go! OK maybe a little dramatic but I have the tendency of grabbing levers by habit and with a hydraulic system in pieces the result is never good. 5. Remove pressure plate. This exposes the thrust bearing that pushes the pressure plate. I usually just leave this on if it looks OK. Here's where it gets tricky 6. Remove clutch pack. Because you didn't pull off the whole side cover you can't just grab the whole pack from the sides.This is where I have a few special tools namely small bent screwdrivers and dental picks. By carefully reaching around the side of the clutch basket two tools at a time you can gently extract the fiber plates one at a time. The steel plates will come out with the fiber plates. The last one is tough. 7. Put the cover back on, taking care not to damage the O-ring. This keeps gremlins from gettting into the cases and lets you stand the bike back upright. The more invasive procedure is to take the whole sidecover off but that means taking the kick starter off and the coolant feed for the water pump and is generally more of a pain then necessary.

Hi Shercoman. cooling systems are designed to run under some pressure. This keeps the coolant from boiling even above the temperature it would boil at in open air. That's why the temp guage in your car can show 230 degrees and the water's not spewing out everywhere. It's also why a pinhole screws up the whole system. The cap acts to regulate that pressure. Too much and the cap is supposed to vent if the system pressure gets too high. That's why the cap has a tube on it. Just like your car it's intended to dump into a reservoir but on trials bike they don't bother with the reservoir. It could be your cap is venting at too low a pressure but the cap could be fine and something else in the system is causing the pressure to spike. Check your cold fluid level and make sure you are using the proper coolant. I now use propylene glycol based like Engine Ice or Silkolene Pro-Cool. That way I don't feel bad for destroying the planet when I screw up working on the bike and pour half the cooling system on my shoes. Actually the real reason is it's premixed with distilled water which is critical on the newer bikes with magnesium cases. Tap water and bottled water will do only if necessary but they contain ionic contaminants which act as electrolytes turning your cooling system into one big electroplate tank. Unfortunately the magnesium cases become the sacrificial electrode. If you use tap water flush that stuff out ASAP. Ron Commo Sr. who is the big dog in the US on all things Beta used to tell me to not completely fill the cooling system and I was always having to put more fluid in. One day I decided to challenge the conventional wisdom and just fill it to the top. I haven't lost coolant yet. That alone defies logic as the expansion of hot fluid alone should displace some. Does your bike only do this under certain conditions like really hot weather (weakness in cooling system like a blocked radiator) or really cold weather (lean mixture because of denser air) or after a long slow climb (heats up all bikes)? Is your radiator clean? Gotta have air flow or the fan's just a party noise maker. Is your ignition advanced to give a little extra "snap". Are you running good fuel? Low octane fuel that causes minor pre-ignition will spike engine temperature. All in all it doesn't sound like too big of an issue.

Yup, that's what I refer to as "cold stick"

Yay! Andy pinned my post. That's the internet equivalent of Mom sticking your schoolwork up on the refridgerator. Jezza> Er what's next? Working on an ignition system that even I have to admit, after swapping everything else, now looks to need a stator rebuild. I de-potted the CDI I thought was bad and am trying to build a simulation model. chewy> No it's not a new discovery. As Frank Zappa said, "There are only so many notes. It's all been played, unless you go micro-tonal." I miss Frank. You have a milling machine? Now I'm wicked jealous. (NOTE: use of the term "wicked" to amplify the following adjective. This particular affectation is indigenous to the city of Boston and its surrounding environs. For further study see, Matt Damon). I would be very interested in the softer springs as there can be a little chatter with four springs that may be due to uneven pressure on the pressure plate. HAM2> My fat little fingers. One problem with doing this by hand is you get bored and stop paying attention. That is until you punch a hole in your hand with the file. Stings a bit.

Yup, brass hexnut looking thingy with two wires coming out of it. On your bike I think it will be on the bottom right corner of the radiator. Most people will just stick a screwdriver across the two terminals. Fan should come on. Be careful though because it's not the most robust piece of gear and if you put pressure on the terminals they'll snap. As for actually testing the switch you can do what most people do and just run the bike until the fan comes on or go whole hog and throw an Ohm meter on it while dipping it in boiling water. Usually I find it just worth it to test it on the bike, and have a spare in the toolbox. Little beggars are pricey though.

OK folks, being off work for a week (mandatory holiday shutdown) I had time to complete the fiber plate modification document. This makes the clutch progressive, eliminates drag, cold stick, slip and reduces lever pull (if you leave two springs out). And the best part... It's free (if you already have the files and Dremel polishing wheel) Yes it will cost you some time but hey you're working on your bike. That's still quality time compared to working on the car. The PDF came out over 10Meg so if you don't have a high speed connection it may take a bit. Sorry but the pictures are necessary. Enjoy Andy Edit: File optimised and size reduced to 1.8MB Clutch_Fix.pdf (Also going to pin this topic so it stays up top)

You need several thing for the system to function. A working water pump. A well sealed system to maintain adequate pressure to keep the water from boiling. A working fan and switch/electrical system. Enough fluid in the system to circulate effectively. Two possible scenarios, 1 Failure of the cooling system. 2 Over heating of the engine from something other then the cooling system. If the engine ran properly at the time of the failure, no pinging or loss of power it's unlikely to be #2. Just because the fan was coming on all day doesn't mean the fan or switch didn't just fail at the end of the day. I think this is the most likely explaination. I've never had a switch failure right at the start of the day. Always in the middle of an event when all of a sudden I'm getting steamed like broccoli. You know the test, just start it up and short out the switch to see if the fan runs. If it does then wait for the engine to heat up and see if the switch switches. If it does then you got a real mystery. I would hope it was just low coolant. Something I found in my truck last week. Engine was fine but heater was sporadic. Weird but cheap to fix. You can try running the engine briefly with a coolant hose disconnected to make sure the pump is working. Betas with magnesium cases have a reputation for corroding the water pump housing but it's much less common with aluminum cases like your '05. Might be worth pulling the side cover off for a peek. Don't get stressed over it. It's fairly common to have this happen at some point in your trials career and it's usually the switch gone bad.

I think you're reading in a bit too much into the date as it pertains to the Montesa. My guess is the plant is shut down until April 1 2010 and will reopen at that date. That may or may not include restarting Montesa production. All we can conclude from the press release is that they are not ruling Montesa production at the facility finished for good.

The only Canadian girls I know who ride trials seem worthy of worship.

There is no substitute for a real trials helmet for a couple of reasons. The main one being the weight of the helmet. Bouncing around for a few hours with an old MX helmet really does a number on your neck. The other critical thing I find with a good trials helmet is they don't roll down over your eyes on drop offs. Usually a benefit unless you're too scared to look. Ventilation is also better on a trials helmet, especially the newer ones. Unfortunately they are rare and it's hard to find a place to try on the different brands to get a proper fit. I've had NZI carbons, OFFXON carbon and currently have a Shiro commander. The NZI was my favorite for fit and lightness but spooked me when I put it on and both straps ripped off in my hands. The hardware NZI uses corrodes rather badly. The OFFXON never felt right and would roll over my eyes but did its job during a backwards head smack into a log that made a very loud sound. (at least inside the helmet it seemed loud) The Shiro is heavier but cheaper and seems to stay in place better but the shell has unstuck from the styrofoam liner being held on with just a daub of hot melt glue.

I've heard they were heavy and sluggish but damn they were pretty.

Ah clips from some of Dale Malasek's videos. I loved those videos especially the voice over. Dale's an airline pilot and that dry voice that comes out of the cockpit during a flight is what you get with these tapes with just a twist of dry humor. The other thing I miss about the commentary is it is highly informed. I've lost track of most of my tapes over the years as I loaned them out and even sent some to the Leno show to get them interested in a appearance by Jordi Tarres at the time of the last Donner world round. Even though I had a producer interested it just never worked out. Pity, it would have been amazing.

That will work for a short time but it isn't the solution. I did that before but it never lasts. The treatment of the fiber plates I do only needs to be done once to last the life of the clutch pack. I shot the pictures of the mod and will try to have them and the description up this weekend.

Puts him in a competitive space with Paul Clipper's "Trail Rider Magazine", at least as far as east coast events, Trail Rider had a nice article about the Vermont National in it this month.

OK, It's tough to tell who's joking and who's really got a bee in their helmet on technical issues/opinions. I agree at low speed rake/trail would seem insignificant for the stabilizing effect on the front wheel in a straight line. Trials suspension is a different animal as a few degrees of rake can significantly change the effort required to turn the front end back to neutral on an incline. On steps there is significant energy stored in the suspension and how that energy gets loaded and released will be affected by rake/trail/offset of the forks. On of the things that I found fascinating watching the super slow motion video of Albert Cabestany on YouTube was the reaction of his forks during various maneuvers. At the super slow motion speed you can see the fork tubes flex just from bouncing on the rear wheel. With the increased rake will it be necessary to hit the front wheel lower on an obstacle to get the same lift? Will the front end tuck faster on drop offs? Does deflection of the center of balance change because there is less offset from the axle. All will be answered when the bike becomes available. All I know is I want to try one.

You're going to have to be a little more specific than "all that" and "it".

I rather liked the USD forks on my Betas. Of more interest is the forks have no offset. That alone can explain the USD approach. It'll be interesting to see how the front end reacts on steps since on almost all modern trials bikes the fork/steering pivot are parallel or at least near parallel. On this bike there has to be increased fork angle to compensate for the loss of trail in the steering geometry. Also interesting to see how it affects stability on drop offs. There's more here then just cosmetics.

Are those the new "aggressive" IRC trials tires? Funny thing is trials bikes are pretty robust, when used as trials bikes. Once you take them out to flog like an MX bike their lifespan is remarkably short.

Didn't notice you are on a 125. I gotta agree with ShercoRider. The 125 needs a whole different attitude then us lazy big bore riders have. I still like the reeds for helping low down chug but that's limited on a 125. Clutch and throttle are your best friends for hard acceleration.

Since I'm doing a set now I suppose it's time for me to drag out the camera and document the procedure. Will post in a few days. Really.

Sorry I didn't get to this earlier. Busy at work and then flu. The heavy springs are there to compensate for the friction of the rough fiber plate tabs. If you just pull two springs without doing the whole procedure you will end up with a worse performing clutch, with a light pull. It works on the EVO. I'm currently giving the treatment to a set of plates for one of the top New England riders. He's ordered his 2010. I worked on the plates for his '09 EVO and after the last event this year he handed me a spare set of plates to put in the 2010. He was amazed at how good the clutch was especially when he saw his competitors fighting with their grabby, dragging clutches. He doesn't talk about the modded clutch though. I don't think he wants to give up any advantage. Oh yeah. Finding neutral on a Beta even with the modded clutch...good luck. Not really on topic but why do trials bikes shift so clunky compared to Japanese trail bikes of the '70s? I've head lots of explanations but the one that makes the most sense to me is that they use two shafts in the transmission instead of three to save weight and space and that makes it much less mechanically simple to shift gears.

Once the center nut is off the puller should pop it off. If it's been stuck on there a long time there may be some cold welding (can't remember the proper name) that sticks it on tight. Not trying to be a smartass but you may have to be less of a girly man with the wrench on the puller.

I love the VForce reeds on my Rev3. The same cage and reeds will fit the Sherco. My '08 also has the Keihin which runs great when clean but is more sensitive to temp and humidity and tends to get dirt and moisture in the pilot circuit more then the Mikunis I've always used. Try the reeds first with your old carb before springing for the Keihin. You may find it's enough of an improvement. Worth mentioning the difference I see with carbon the reeds is much more low end torque. The bike pulls hard off idle allowing me to feather throttle in places I couldn't before. It helps finding traction but more importantly gets me out of trouble when I do something over my head (often). The Keihin on the other hand wakes the bike up on the top end. Whack the throttle to full and it jumps like a scalded cat. I think you'll be really pleased with the ridability of your bike with the Boyesen or VForce reeds. Keihin's kind of an aquired taste.