dan williams

Yeah classic port configuration. Basically you shouldn't feel much or any difference at low RPM. At high RPM the column of mixture in the intake tract never goes to zero velocity so the reeds never close and closing the intake tract with the piston restricts the flow. That's why they use intake extenders, to add a longer column of air to act as a forced induction system. If I remember correctly back in the 70's this was Suzuki's big deal at the time on the RM's with a case/reed induction system where the intake fed the crankcase directly through a reed valve with no other valving. At the time most engines used no reeds and had a piston port intake. So yeah it'll run out of revs sooner then the cutout piston. Not important and probably safer if you're not an expert.

Looking at the exploded diagram it's the intake so it is a modification to add top end power.

Typically that would be to delay the port closing to add more rev. Is it on the transfer port or the intake?

There is a method to that madness. A 125 will take time to build revs to get into the powerband, the 250 had quicker response then the 260 because it had less flywheel weight on the crank and the 260 will hold revs longer because of the additional flywheel.

Title pretty much covers it all. newenglandtrials.org hosting company is having server issues. The NETA novice/beginner school is full so if you're not on the list don't show up.

Have him grab a wonking big handful of throttle. If it waits a second then loops out it's a 125. If it loops out immediately it's a 240. If it loops out and keeps cartwheeling it's a 260. Sorry couldn't resist. You should be able to tell just by riding. If it can pull third gear off idle it isn't a 125. The 125s need some throttle before they get going. They'll go up big stuff but they require a liberal use of twist grip.

Watching flames shoot out what looked like 10 feet to either side of the bike while you're holding the bars gets your attention very quickly. So does the smell of all the hair on your arms burning off in a flash. I've carried a fire extinguisher ever since.

So no posts since August. Has the brand just dried up and blown away?

Paul is dead on. The swearing helps but under your breath if there are young'uns about. They'll learn soon enough. When the bike is tipped over the float valve opens and the fuel just dribbles into the carb throat and down into the engine. That means you've got a great source of fuel already sitting in the bottom of your crankcase when you pick the bike up. That does two things, makes the mixture extremely rich which is why you kick it over with the throttle wide open and the fuel tap off to try and purge some of the fuel out of the crankcase. The other problem is the spark plug has now probably seen more fuel then is wise and has fouled. After a little while a hot engine will cause the fuel to evaporate off the plug but until it does you can kick like a gorilla and there will be no fire in the hole. In cases where it just won't fire pull the plug and drop in a fresh one and most times it'll start right up. MotionPRO makes a flat racheting (sp?) spark plug wrench that's easy to carry and can get into the tiny space Beta allows for such things. Do NOT remove the plug and kick it over to get the fuel out of the crankcase unless you are wearing a NOMEX suit and have a big fire extinguisher nearby. Trust me on this. I hold the world record for the flaming Bultaco throw. Damn lucky I didn't burn my sister's house down. I was younger and stupider then.... Well I was younger.

The carb is not all that well sealed. Don't get all in a bother. Usually the worse the problem seems the more obvious the fix. Take the carb off and do the cleaning/setup routine again paying careful attention to detail. You will have to do it several times a year with the Keihin so you might as well get good at it. The Keihin is a finicky beast especially in the presence of water. The pilot hole in back of the slide on the Keihin is tiny. Seriously it's tough to see even under a microscope. That's why it's important to clean the carb with a good source of dry compressed air. Anything that can carry moisture like drug store grade isopropel alcohol which is a significant percentage of water is a no no. My guess is when you take if off this time you'll find some simple mistake like the needle sitting in the slide wrong or a hose clamp not installed properly. just be careful and precise and remember cleanliness IS godliness when working on a carb.

Come to think of it this reminds me of a local who used to ride and was picking up a new bike. After a "few" beers to celebrate and with the new bike strapped to the front of his car he left. Bike fell off and he ran it over. oops.

Heh heh the new Beta Racing has new clutch plates with "larger guide" surface. Sounds like the message got through.

What you have done is joined us. Welcome. May you have as many years of addictive trials fun as I have.

Water pump corrosion is probably the biggie. Only way to really check is to drop the side cover. You could slyly ask if it's OK to use tap water as a coolant. If the reaction is "Sure" then be wary. If the owner tells you to only use premixed propylene glycol like Engine Ice or Silkoline Pro-Cool then it's probably good. Unless the owner reads this Carb problems and clutch problems all have fixes pinned to top of this forum.

I don't think it's a setup. The condition of the car vs the bike says that was his pride and joy. Probably wanted his buddy to film his brilliant way of transporting his bike. I'm sure there were many cream filled dessert cakes excreted (twinkies pooped)when it hit the pavement.

If you notice at the end the gas container without a cap on the nozzle just has Darwin award written all over it. Considering the condition of the car's body he could have just run some eye bolts through it and been fine.

If the stroke is the same I withdraw my conclusion. I thought it might be because the parts lists I looked at have different numbers for the crank.

There is only one overflow tube and it comes out of the bottom of the carb. The two tubes that come out of the sides of the carb are pressure vents for the float bowl and are not supposed to leak fuel even if the float valve is stuck on. The reason they do leak is the tubes are so long they end below the fuel level in the float bowl so if gas gets splashed up into the vent circuits and starts flowing down the tube it acts like a siphon and keeps flowing until the flow is interrupted. There are two common fixes, one is to change where the vent circuit is exposed in the float bowl which involves drilling of the carb body. The other fix is to just nip a hole in the vent tubes about halfway up the carb body. Nipping the hole in the tubes is something I've done to many Betas and it works very well for no money. OK there is one other fix and that is to route the vent tubes up over the carb but that can lead to the bike running rich if fuel gets into the tubes and returns to the float bowl.

It actually looks pretty good.

Even if it is you'd have to have the cylinder re-plated and properly size rings and piston. My guess is since they have different crankshafts the stroke is different the ports don't match. So now you'd be replacing the crankshaft as well. In the long run you could easily spend more money trying to make a 200 into a 250 then just buying a 250. Summary: No don't even try unless you own a machine shop and have a lot of time and money to spend.

What's that big leather looking thing behind the gas tank?

My other observation was going to be how many pilots ride trials. The dual mag/plug thing makes sense. Two flame fronts will raise the pressure in the cylinder faster so if the engine is designed to expect two flame fronts there will be a small percentage of unburned mixture or at least not burned at the optimal time to make power.

Was it already all the way in?

Engine knock under load is usually a low grade fuel problem. Beta's like octane since they have rather high compression ratios. If the bike has seen over four years on a set of rings a new set will liven it up but will raise the compression making the the knock worse if it's fuel. Get you hands on some race gas if you can and see how it runs on the good stuff first. Don't trust the octane numbers on the fuel pump at the local station as they are often far from the truth.

Heh heh There are no rules and you break them at your peril.