J-Madd

If your crank is not welded, you probably should get some bigger domes. Most people say the the crank probably needs to be welded even on stock compression.

Requiring bigger jets is not always an indicator that one motor needs or likes more fuel than the other. I run 0.116" mains in 16 mil Cheetah and 0.124" in the 4 mil Cub. The 610 cc Cheetah no doubt requires more fuel than the 421 cc Cub.

Yep. THE fastest twin cylinder (as far as I know) in the world (from Puerto Rico) runs all stock ignition.

Looks like you got if figured out.

There's not a ton of Mikuni advice out there. I have a set and still couldn't tell you crap about them. If you want to run some Keihn PWK 35 mm or some PJ 34 mm I'm sure you could get lots of help on this site.

As long as your pistons aren't worn too bad you're probably fine re using them. Check the wristpin journal (our whatever its called) for excessive wear, and look for cracks or any damage to the skirts. Best of luck beating that 450. They are effortless to ride compared to a Banshee, imo.

I always liked 15/41 or 15/42 for that motor.

What kind of track do you plan on racing him on? Man a bone stock YFZ will put a stompin' on ya unless your racing in a straight line; or you have tons of suspension work...and maybe even still them. They come out of corners HARD because of the instant torque they produce.

My freakishly fast bolt on Banshee has never been beat by a YFZ with pipe, filter, cam, HC piston (or any other bolt on modded banshee for that matter.) Most piped YFZs are easy to beat for me. I think the Yamaha factory just made my cylinders in perfect specifications So, you might as well try with the bolt ons first. Mill the head 0.020", drill you your stock stator plate as far as you can (puts the timing at about +5 probably), reed cages (if in your budget - hell mine just has stock), and you should be good to go.

You won't find a lot of info about where to start jetting stock carbs on a cub. There was a long thread a few years ago about how a guy had to go with relatively small jets due to the fact the that the Cub creates more intake velocity than stock cylinders and draws more fuel through the jets. Good luck. And yeah, as mentioned, check your plugs to see where your jetting is at.

I have only seen one Banshee running the newer Vito's cylinders (Cub copies more or less) and it ran very well. I'm sure he had some additional porting done to them though. Those are gonna be drag race style cylinders, just like the Cubs. The older 400 cc (or whatever) monoblock would be more trail friendly. I have also seen only one of those run, and it was not much faster than stock, but that could be in the tuning.

The tree hugging EPA fags just shut down St. Joe State Park here in MO due to lead content from the old mines that used to be there. Good luck, I hope ya'll can keep the dunes open.

Turn the atv/motor up on its side stator side down. Install the vito's pressure plate in place of the stock pressure plate. Put 1 or 2 balls in each groove. Install the springs and steel outer plate making sure you install an aluminum spacer around each bolt as it goes into the spring. I think that's about it.

I got the chart from a Planet Sand member (Matt Haynes [Macanic])who said that was the stock timing curve for a Banshee CDI. I have no proof of that being true, I just always believed him.

I jumped on the pvl bandwagon a year or so ago and put it on 3 of mine. They are all back to stock ignition now. Gotta box full of flywheels, stators, coils laying in the shop. Make sure the spade connectors on the coils are on good and make sure you have good ground from stator to engine. You can run a ground wire from the stator to a head stud to rule out a bad ground. Good luck.

What cylinders are they made for?

I'm sorry, I thought you were being sarcastic. I know the dynojet kit sucks for the YFZ, which has a Keihn FCR carb. I thought the Zuki would be similar. Also, it's difficult to get help with the dyno jet because the numbers don't cross reference to the oem jets (I don't think.)

I'd call and ask him. Probably just a mistake. On gas, you'll always need to run the "8" series plugs. On alky you run "9" and sometimes "10."

Did you verify that it has no spark, or are you just going by the sound of it when you kick it over? Sounds like its out of time to me.

Usually going to a better chassis will get you faster times than upgrading your motor on a stock chassis. I know of a 397 Cub that has run 3.72, but his complete setup only weighs around 220 lbs. Weight (and weight transfer) is everything. That being said, I ran 4.08 on my 4 mil Cub in a 315 lb stock chassis, and took me a 100 passes just to get in the 4.08s in a 250 lb strutted dune chassis.

Your gonna need to drain the oil (obviously) and water, or you'll just have a big mess when you take the cover off.

Compare this curve to the Dyna "stock" curve posted above. You'll see what I'm referring to.

Well,it isn't exactly stock per se. THe timing doesn't retard as much at the higher rpms like the stock cdi. But it is definitely closest to stock (and labeled "stock" by Dyna.)

I always replace both unless they are fresh pistons and I manage to grenade just one of them. It sounds like there are more than a few hours of run time on this engine. If and when you need to replace a piston, go ahead and replace both.

Torque the head back down and do a compression test. If that shows low (< ~105 or so psi, depending on elevation)you can just hone it and install new pistons and rings. I wouldn't bore it unless the is damage to the cylinder.