dan williams

I can't see any picture.

Hunting at idle usually indicates a slightly lean condition. Disassemble and blow out the carb passages with compressed air. Also if there was a large change in conditions then the jetting can be slightly off. Usually this just an issue when the temperature changes dramatically like between winter and summer. While you've got the carb apart make sure your floats aren't binding on the bowl gasket and are set at the correct height.

Er, the plug heat range doesn't change the engine temperature unless the plug is so hot that it causes pre-ignition. The heat range is just the amount of heat that is conducted away from the tip of the plug. It has to be hot enough to burn off contaminants that can short out the electrodes and cold enough to not ignite the mixture before the spark. Your engine must have been well into a sustained pre-ignition condition for a considerable amount of time to hole a valve. I'll bet you were going like a bat outta hell when it failed. Lucky it didn't stick a piston. For the record I NEVER let the parts guy tell me what the equivalent plug is. I always look it up myself and if I have to change to a different plug I always take it out and read it after 10-15 minutes while keeping a very close ear on my engine.

Not necessarily equivalent. The plug that comes with the 08 is an NGK BR7ES not (BPR7ES). This is a non-projected tip plug. The Champion N7YCC of the earlier bike is a projected tip plug. Not sure if the change was due to a different head design but it is a worth a mention.

Think about it. A larger carb is only going to make a difference at wide throttle openings. The difference between a properly tuned Mikuni and a properly tuned Keihin isn't as big as the other changes in the engine. There are a lot of differences in my '08 270 compared to my '05. Stock throttle tube on the '08 is a fast throttle white tube, the intermediate muffler is different on the '08. The '08 270 has no primary side flywheel weight and the crankcase volume is reduced. I believe the '08 also has a different head with slightly higher compression. So if you want more snap off the bottom end you should be focussed on the things that have been done for the factory bikes for years. A high compression head, advancing the timing, shorter head pipe, matching transfer ports and basically anything that makes the engine a more efficient air pump. Just remember that even though these mods will make a bike hit harder most will also make it run less predictable at low RPM. Jordi, Dougie and Albert won a lot of world championships with that same Mikuni. Despite some of the earlier posts on here the Mikuni is not the root of all evil. To be blunt it's a lot more tolerant of conditions then the Keihin and easier to tune as well.

Check the easy stuff first. Freeplay in the throttle cable, i.e. it snaps back when released and you can hear the stop in the carb. Make sure the kill switch isn't partially shorted. Beta kill switches are notorious. Make sure you have good fuel. One of the problems with pump gas is the ethanol in the fuel picks up water. Since it has a higher affinity for water then pre-mix oil, fuel which has absorbed water in humid weather can precipitate the ethanol out to sit in the bottom of the tank. That creates a whole host of issues with carburation. If you can see a spark that's usually a good indication that the CDI/Coil are working. The spark that comes out of a bike isn't that easy to see unless it's pretty dark. I find that often when a bike has sat and won't start the carb needs to be pulled off, disassembled and every oriface hit with a blast of compressed air to clean it out. That usually gets my bikes going again. A lot of guys will tell you to run wire through the passages but I've always believed that to be a bad idea. Especially after getting a look under the microscope on the Keihin. The bypass passages on that carb are tiny. I've had issues with a bubble of water sitting in one of the pilot vent holes making the bike run less then stellar. Even in 100F heat the surface tension of the water kept it from evaporating. I wouldn't jump for the CDI until you have eliminated the other, cheaper possibiities.

Honest reply? Find the local Beta dealer and pay him to have a look at it.

The NETA scorecards have a 25 point misconduct block. We also have a number plate rule that not only lets the checker know what line you should ride but who you are. It's important to make sure the checkers know they have the authority to give such penalties. It's very important for trials masters back up their observers decisions unless there is a clear misunderstanding of the rules on the part of the checker. There's nothing more deflating then to come out of the woods and see that the rider who protested a call you were clear on whined to a clerk and got a gimme.

Could be. Found these materials property charts for seal materials. Viton has much higher temp rating. http://www.pspglobal.com/low-temperature-seals.html http://www.ahpseals.com/tech/materials.php

On my 270 it smooths out the bottom end and adds significant torque. I can pull a gear higher on climbs or stay down in first and crawl up serpentine off cambers. I would imagine the effect would be even more pronounced on the 125 as there is less airflow to open the reeds so the lower mass of the VForce should broaden the low RPM power. Should make the bike easier to ride.

I'm running a 48 pilot, second groove from the bottom on the needle and I think a 108 for the main. Basically the stock jetting works fine with the VForce. There is a slight difference in the diameter of the exit of the carb and the VForce intake manifold but it's so small that it's not a big concern. Especially since most of the time the carb is barely open anyway.

27.5

Having worked with British engineers for many years I get this but I wonder how many lads on this side of the pond are going, "The dog's WHAT?"

Recommend you smooth the fiber plate fingers. It's what makes the clutch slip.

On the '05 270 there is an extra flywheel weight on the primary side of the crankshaft. It is visible through the gearbox sight glass. Curiously on the '07 and '08 the additional weight is on the 250 and not on the 270.

Sound like a bigger problem is little Johnnie needs to learn life isn't going to go his way all the time. You sound like you're in panic mode to fix it because of the tantrum. Reward that behavior now and by the time he's a teen with access to cars, drugs, alcohol, sex and weapons you will have lost the opportunity to get his head straight. Riding as a reward for good behavior will payoff much better in the long run though it's tougher in the short run.

Have bought from the web site. Yum.

I guess I should have been more clear about removing the clutch pack. I meant remove it only as a diagnostic tool to separate the crank from the gearbox. I believe you are still in for a case split no matter what.

Only thing I can think of is the shifter mechanism has broken. Sounds like one of the gears has broken loose and is being chased into engagement at the same time as another gear in one direction and spread apart in the other. Remove the clutch pack and see if the crank spins freely. Then I think you're in for an engine split. Even if this frees up you should probably split the cases and check it out or you may do much more damage. Sorry but this sounds like major surgery.

If my buddy hasn't put the special spring on his new bike yet I'll see if he can run it through the stroke to see if it does the same thing. If it does you probably don't have a problem.

Whether four stroke or two stroke the octane required depends mainly on compression ratio. A higher temperature in the combustion chamber is what causes detonation so anything that raises the mixture temperature too high before the proper ignition time will cause detonation. That includes advanced ignition timing/poor cooling (yes mud in the radiator) /lean mixture/ flogging the engine under heavy load. Different fuels will spontaneously ignite at different temperatures. The trick in an engine is to maintain the mixture temperature and pressure just under the point where the fuel ignites without the spark. The common misconception about race gas is that it makes more power. That has a grain of truth to it but the main feature of higher octane fuel is that it has a higher flash point so it self ignites at a higher temperature then lower octane fuel. This allows more aggressive ignition timing and higher compression ratios to be used. It also allows for a leaner mixture since there is less need for the cooling effect of fuel vaporization.

I hate to say it but you need to throw a timing light on it to make sure the spark is in the right spot and also check that the ignition is advancing properly at the higher revs. That way you'll be able to eliminate any doubt you have on the ignition. I learned that from a Can-Am with the Hiro motor. Fought with it for years changing parts and tuning to no avail. I even checked it with a timing light and it looked good until I revved the engine and the spark retarded instead of advancing. Turned out the trigger and charge wires to the CDI were reversed. Flipped the wires and the bike ran perfectly. Also be careful what you remove. Years ago it was chic to remove the regulator from Betas to save weight. It seemed like a good idea since it was only a one wire device and didn't seem to do anything. Problem was it was a shunt regulator that dumped excess current above a certain voltage and without it you fry the cooling fan.

Agreed, higher octane gas. Even though the throttle setting is the same in the higher gears you are putting a heavier load on the engine and that can cause detonation to be much more prevalent. Also realize pump gas is notoriously inconsistent. Even premium fuels like Sunoco Ultra which I used to run until I got a few bad batches. A car is so mildly tuned it'll just suck it up and run lousy but a trials bike tuned to within a gnats *** will let you know immediately when you've got a bad batch. See if you can get your hands on some race gas. It won't make any more power but it will dramatically reduce the occurrence of detonation and it's consistent batch to batch.

If it's pump gas it could be due to moisture absorbed by the ethanol.

Er not to put too fine a point on it but is there a problem with damping while the suspension is working? It may be that the shock is actually working properly. If you haven't found fluid leaking out you may be looking for a problem where one doesn't exist. In the past when I've had new shocks that had pressurized internal volume when I ran them through the stroke I would notice the same effect. There seemed to be a dead zone of no damping at the start of the stroke and then heavy damping. If I went faster though the damping occurred throughout the stroke. My theory was that there was probably some dead zone until the internal volume taken up by air was filled with oil/air emulsion. As for the bottoming you may need a few turns of the spring preload there bubba. Of course if you do have a loss of damping the cranked up spring can make for an exciting ride.