dan williams

Tear in inlet boot between carb and cylinder? Sticking throttle cable? Rev3s use a rather short sleeved cable. Contaminant in the throttle bore? A disassemble and inspect is the only way to go.

I just dropped the stiffer fork and shock springs from Steve Saunders into my 2013. Very happy with the feel of the bike now.

Yeah water in the oil. Source can be water ingress from the water pump seal as mentioned or from riding through water and it getting in through the transmission vent or just from condensation. When oil is churned up it creates an emulsion which is why it turns white as the water is suspended in the oil. Eventually the water settles out into the bottom of the gearbox where it gets churned up into the oil again. You have to change the oil several times to get the water out and you can never get all of it as it settles into the nooks of the transmission. Best thing to do is get the oil all churned up before you change it. That way more of the water will be removed as part of the emulsion. With a couple of oil changes you can get most of the oil out but it takes a few.

Basics first, how does it run when it's running? If it runs properly you can ignore the next batch of questions. Are you using it as a trials bike or playing enduro racer? Is the choke properly off. I've seen bent choke rods holding the choke open a bit. Is the ignition timing set properly. OK the laundry list; Wrong plug heat range. A lot of people think the plug heat range affects engine temperature. They're wrong. Plug heat range is to make sure the plug tip stays hot enough to burn off contaminants while staying cool enough to not cause spontaneous combustion. Common. Plug fouls, bike stops, runs fine with new plug. Wrong fuel/oil mixture. People new to trials bikes often mix extremely rich mixtures for a trials bike that merely clog up the works. Typical mixtures in a modern water-cooled "electrofusion" bore engine run 70-1 to 100-1. Very common. Exhaust will be smoky. Again plug fouls, bike stops, runs fine with new plug Incorrect jetting. Standard Mikuni on that bike is probably a 30 Pilot 145 Main. Needle in the middle groove. Possible someone richened it up to play motocrosser or to try and compensate for bad gas. Wear of the needle and seat are also possible as well as damaged jets if someone ran a wire through them to clean them. Float level can also be way off due to bad adjustment or a damaged float filling with fuel and sinking. Somewhat common Plugged exhaust. If the mid muffler and/or final silencer are full of goo it affects the engines ability to breath. Weak running and fouled plugs can result. Somewhat common. Often will have a very smoky exhaust after a prolonged high speed run. Can ignite fire in exhaust system that will burn after bike is off. Ignition timing off. Either set incorrectly or due to a sheared flywheel key. Uncommon but can happen. Engine will run soft off the bottom. Oil leak. If transmission oil is finding a way into the area of the crankshaft through a case defect, bad primary side seal or leaking center gasket it can foul the plug. Uncommon but possible. More likely with an older engine. Usually smoky exhaust Choke stuck on. I once saw a bike that had the bent choke rod holding the valve just slightly open. Bike was hard starting and ran rich off the bottom. How the rider bent it I don't know. Weirdest thing I've seen. Very rare. These are the first places to hunt.

The '08 uses the Keihin carb and it is finicky around water. If you've got any water in the fuel or you've been out in wet conditions it is possible to get a water bubble in the pilot circuit that will sit in the air passage that comes out just behind the throttle slide on the bottom side of the carb body. This water bubble won't evaporate as the passage is small and surface tension holds the bubble together. I chased one of these for quite some time before I figured it out. The best thing to do is pull the carb out, start by sliding the back air boot as far as possible back onto the airbox, and disassemble and clean all the carb circuits. The main jet tower requires a security torx bit. (star bit with a hole drilled into the center) if you really want to take it all apart. Important to blow out all the air passages with compressed air.

You guys sound like Trekkies. Picard was better! No Kirk was better! It's Top Gear. Just a bit of fun.

The best way I've found to deal with the ping is 110 Octane VP C-12 race gas. Just the nature of the beast with a high compression engine. You could try a thicker base gasket but you'll lose some pop out of the throttle.

Yeah that pic shows the most it should travel when the valve is open. At fuel valve closed it should be level. Should have explained better. If you can find Billy's article on setting up the Mikuni all the better. It was what opened my eyes to how the thing should be tuned.

Yeah that's upside down. The bottom of the travel should be level and the top of the travel for the tangs should only point at the right angle formed by the top of the pilot jet housing and the main jet tower. The little tang on the side is what sets the travel.

I did the same gearing change on my '05 and '08 Rev3s. I just found them a bit to abrupt with the stock gearing and I'm a plonker anyway. Speed through the section has never been my thing. With stock gearing I just found 1st to be too slow and second just a bit too fast on the 270 and it seems the same for me on the 300. I ride most things in second now but 1st is still there when I need a crawler gear and there doesn't seem to be that much of a difference from stock and third is useable in more situations. I also haven't noticed any appreciable difference in chain wear.

I've never had a Beta kick back like that. Maico yes but not a Beta. Sounds like you might have broken your foot. I've also never seen a fixed stator. Might be the new norm as the CDI units are all microcontroller based so timing can be set by programming the delay between the trigger signal and firing the SCR that dumps the capacitor to the ignition coil.

Excellent. The point above about making sure the hose clamps are straight is important too. Especially since the Beta clamps are made of butter and won't take a lot of torque. The Mikuni is pretty tolerant of settings but 1 1/2 turns out for the air screw is normal. You may find the bike runs crisper with the 27.5 pilot jet and if you want it to grunt like a tractor I recommend Moto Tassinari VForce3 carbon reeds For the vent hoses don't be too picky. Any hole that is above the float bowl is good enough to stop the tubes from acting as siphons. I just nip a hole with small wire cutters.

If the pilot jet is 50 something's odd. Stock was a 30 and most people around New England near sea level changed to a 27.5. I believe the stock main is a 140. Before you go after the crank seals check the intake manifold for splits and make sure there are no casting defects in the inlet tract. Check the reeds while you have it apart. Reed petals don't need to be sitting absolutely flat as air pressure will close them but they shouldn't be frayed or cracked/broken. When you shut the idle screw all the way down the engine should just die on zero throttle. The other screw is an air intake for the pilot circuit in the carb. It's fed from one of the holes in the intake bell. When you clean the carb remember to run compressed air through the carb body after all the screws, jets, fiddly bits are out. I find it best to just disassemble on a paper towel so I don't lose any pieces. Don't run wire or anything harder than monofilament fishing line through a jet as you can scratch it and change the jet size. The tubes on the side that get melted are vents for the float bowl and are the cause of the famous Beta peeing gas syndrome. Nipper a small hole in the tube about halfway up the carb body to stop the carb from leaking.

Beta dealers should have them. I got a couple of spares from Ron Commo. He might still have some if you're in the US. I should note that I'm not sure they fit the 2013. I bought the spares for my '08.

Thought the same of my '13. Went one leaner on the pilot and didn't like it at all. Went back to stock and dropped the needle 1 groove. Helped immensely. I know it shouldn't off idle but it did. Also put in VForce reeds. (luv 'em) and went down one size on the countershaft to make 2nd my main gear.

Doesn't it depend on the length of the bolt as well since what you're measuring is the stretch of the bolt. The head bolts are mighty short and if he's stretched the others and snapped one and the earlier info is a significantly lower torque then I'd be suspicious of the 21-22Nm number. Here's the numbers from the original post. I did check on the flywheel nut and it is correct. Call a dealer or your importer. Tightening torque Rev3: Shock absorber-Swingarm 45Nm Shock absorber-Frame 45Nm Connecting frame rod-frame 23 Nm Cylinder-Crankcase 20-23 Nm Primary drive gear 120 Nm Handlebar 25 Nm Engine-frame 50 Nm Swingarm bolt 90 Nm Front wheel axle 65 Nm Rear wheel axle 65 Nm Steering stern bracket 25 Nm Rear fender bracket 10-15 Nm Front brake pad 20-23 Nm Rear brake pad 20-23 Nm Engine Head-Cylinder nuts 15-16 Nm Front axle fixing nuts 10 Nm Flywheel 140 Nm

Won't fit. Fork spacing is different. I tried. Had to buy an EVO to fit the new fender.

Try writing datasheets for integrated circuits. Bike stuff is cake by comparison.

Nice summary Billy.

Just trying to get him thinking and providing more information. Pre-ignition is when the mixture ignites before the spark due to a hot spot in the cylinder, fleck of carbon, hot plug electrode, pocket of free radicals in a poorly designed engine. This causes combustion chamber pressure to peak before the piston reaches top dead center instead of slightly after it where the pressure increase in the combustion chamber generates power. This means inertial energy stored in the flywheels/crank is wasted compressing a higher pressure gas. That energy manifests as heat raising the engine operating temperature often leading to detonation. Detonation is an uncontrolled burn that occurs due to extreme pressure/heat condition causing significant portions of the mixture to reach their auto-ignition point, and depending on the shape of the combustion chamber, starting multiple flame fronts which cause a rapid rise in combustion chamber pressure. Far more rapid than the pre-ignition scenario. This rapid pressure rise is akin to hitting the top of the piston with a hammer and is mechanically devastating to an engine.

OK the key here is why has its behavior changed. I assume you had it for at least 6 months when it didn't kickback? What may have changed? Did you start using a different fuel? Have you changed the wiring at all? Maybe disturbed a connector that changed how the CDI box is reacting to the firing signal from the trigger coil. First thing is when a mechanic tells you can't change the timing on a competition bike RUN! He WILL screw it up badly. Tell us more detail. Does this happen when the engine is cold? Does it occur with the choke on? Does it only happen when the engine is already warm? Was there any event that preceded this happening like a crash that revved the engine? Have you checked the condition of your reeds? Once the bike starts does it run normally? These are high compression engines and even something as simple as low octane fuel will detonate without much provocation. Help us to help you. If you got Billy T's attention you have access to one of the smartest Beta guys on the planet.

Perhaps the best modification I did to my '95 was to bolt a Mikuni on it. But there are circumstances to explain. The Dellorto is not a bad carb. Lot's of bikes use them with great results. The problem on the '95 Beta is that the particular model of Dellorto used was a new type with a two piece pilot jet and when they were introduced on the Betas there were no parts available to tune the carb. Typically Beta jets their bikes rich off the bottom end and the standard setup in the US or at least here in the northeast for a Mikuni was to drop the pilot from a 30 to a 27.5 and sometimes drop the main to a 135 (I think). With the '95 there were no pilot jets available so the bike tended to bog off the bottom and suddenly get real interested in the proceedings once the transition to the needle jet started to become dominant. Unfortunately this made it tricky to time hits or use fine control in turns making the bike seem too powerful. I spent many months looking for jets for that Dellorto before finally giving up and just buying a Mikuni. The bike was transformed from a crashing machine into a bike that pulled smooth and strong with a predictable response that made it a joy to ride. If you can now find jets for the Dellorto I'm sure you can properly set it up to be a great carb. If not though the Mikuni is a world of better.

Reminds me of the US national where we where instructed to be lenient and not too strict on the rules. One of the "experienced" local guys who was observing asked, "So what rules do you want us to ignore?" Making rules and then not enforcing them opens the door to all kinds of abuse.

I'll usually run Spectro or Bel-Ray gear oil. I'm not fond of ATF as I think it makes for an abrupt engagement. Experts tend to like that better. I think any good gear oil is fine once the mod is done.