sicivicdude

$120 for the rechamber regardless of the finished design needed as long as the head is in good shape to begin with. Obviously, requiring welding it would cost more but that head ^^^ was a free donor head and is going out as a favor. I use software for calculating MSV values for correct squish velocity so rest assured that the combustion chamber shape would be as corrected as possible for a given application. The process for doing it is exactly as pictured above, a special counterbalance for turning each combustion chamber separately and then a special jig to properly support the head while the mating surface is being removed. Once the flycutting operation is over, the head is finish lapped to ensure a proper seal. I think considering the work involved, the price is fair. It's also priced well enough that folks who don't want the "bling" of the cool head, it's a serious budget minded modification.

Well, most people have been led to believe that a stock banshee head isn't rechamberable. Most people think that a "domed" head is the only performance option available That's simply untrue. With a stock head, basically any head shape is achievable just short of a full on alky drag head (not enough meat in there for that). For folks who don't want to spend $260 on a cool head (or similar replacement head) rechambering is an option. It's especially valuable for that "sleeper" look.

I thought about o-rings but decided against it just because of how little space there is around the squish area. This head will be sitting on old school Vito's 68mm bore cylinders using their big bore head gasket so it not only corrects the squish thickness, it also will take care of the sealing chore. Maybe one for a stock bore banshee would be better suited with o-rings to seal it.

So here we have the finished product. Another success story, just an unassuming stock banshee head right? Except, not so much!!!! These are 19cc domes cut at 11 degrees for blaster pistons! Full on get it race cut head.

Just for giggles, I tried the fly cutter "as is". Put on your safety glasses boys, we have chips a flying'! Don't think I'm taking it easy just for show, this is a .011" swipe! Without the flash on you can see this thing whizzing on around. Turning about 250rpm, plenty fast for that carbide bit to knock off some aluminum! No worry about back cutting on this one..... it fits completely under the flycutter! No worries about the bit slipping during the cut (at least not at .011" cut depth)

You can see from this pic, I didn't change the size of the combustion chamber, only filled in the damaged area and polished it: Do both sides the same way to finish off both combustion chambers: Now, remember what I said about the squish area? This is the least damaged of the two sides but I took out approximately 1/3 of the total amount I plan to remove. I have to reduce the chamber volume by quite a bit anyway before this head will be "ready" to run so the squish band damage is unimportant to begin with:

A little more wire brushing with a different stainless brush (the newest one does the acetone pre weld brushing to leave the least amount of contamination possible) yields this: And this: Once the proper amount of material goes into the head, the head is actually gently heated with the propane torch moving around slowly gradually reducing heat until the temperature of the aluminum falls down to below what I can "pull away" with the torch. Cast materials (not SO much cast aluminum but somewhat anyway) all have internal stresses from the thermal expansion that takes place during the casting process. Even with an properly even heated mold, the outside of the cast material is cooled faster than the inside during the casting process. This puts a lot of stress on the parts. Preheating evenly prior to the weld and then cooling slowly (40 minutes in the case of this head, 8-12 hours in the case of a cast iron automobile head!) allows the internal stresses to even themselves out as the entire part cools down gently. We don't want any hairline fractures in this head when we're done from thermal shock, do we? Once the head is allowed to air cool to the touch, I put it in the lathe and began to "round it out". The welds are naturally not the same level as the rest of the combustion chamber and I have no intention of leaving them like that either. Onto the mandrel with the counterbalance to be worked very slowly and meticulously until the weld is flush even with the rest of the combustion chamber (Without taking too much material out!). Remember, ignore the squish band area for now... That damage will all be cut out anyway due to the nature of the head shape needed. After the first round of cutting using the lathe tooling, some polishing takes places to yield the final result:

You know it's bad when you have to break out like every different process you have available in order to do one job This head is pretty well beat to death. Luckily, not completely to death Basically, ignore the squish area damage. Because of the head design needed, all of the squish area is going to be gone anyway. If we ignore the obvious damage in the squish area, that leaves us with two main problems to start with: Two rather large "dings" down inside the combustion chambers. The one in the left cylinder is a doozie. You could lose a pencil lead tip down inside of it. Nothing a little "mad scientist-ing" by SCD can't handle... We start ALL aluminum welding projects (and ESPECIALLY ones on cast aluminum) with thorough cleaning. Oil, grease, dirt and aluminum oxide all work together to form a huge mess if you just tried to go after it with the tig welder without cleaning first.. All of the "crud" has to come off in order for filler material (good aluminum) to go back in... Those two combined leaves it looking a little better: A little "pre heating" before we even strike the first arc ensures a nice stable arc start with minimal wander and even less contamination. Propane torch laid directly onto the first damaged area. Check the temp with an infrared non-contact thermometer. Once the entire head is upto temp, we strike the arc. When the welding's finished here's what we're left with IMMEDIATELY after closing down the welding arc:

@Blastard: Or Sicivicdude could come talk to him I got your PM over on BF but figured I'd go ahead and answer your question where anyone might be able to benefit from it. Knowledge is only powerful if everyone knows it, otherwise it's only dangerous! The radii of the a-arms is set. With any unequal a-arm setup where the upper is shorter and the wheel is at 0 camber at sag point (with rider weight static) the camber will always be negative as it moves past that point (into the compression region). The upper arm will ALWAYS keep a shorter arc than the lower arm if they're are unequal length with the upper shorter. What this means is two things. If you run "flat bottom" tires like MX tires, you're going to be chewing up the inside lip of the tire when the entire front suspension travels (like coming off a big jump or hitting a large whoop). This is the disaavantage of the unequal length suspension, there is however, an advantage and the advantage outweighs the disadvantage. While running on the "edge" of the tire isn't a real detriment on dirt suspension isn't only design to travel in 2D (wheels straight ahead while both a-arms experience the same travel and forces) it's designed to operate in 3D. The unequal length a-arm setup helps during frame roll to keep the contact patch larger on the outside front tire during a turn. This means that the weight tranfer goes onto the "solid" tire and you grip easier. To the question of what's the "proper" camber setting actually is determined by frame rigidity, rear tire ply rating, and compression control setting. A heavy side wall rear tire on a super stiff frame with strong shocks requires little to no negative camber at sag. Frame roll will be limited by the rear tires and frame and any bouncing (that would disturb the contact patch) will be limited by the strongly valved shocks. If you have a stock ungussetted frame with balloon rear tires, you may want 0-3° of static camber so that as the frame rolls in a turn, your outside tire will but more, not less. 99% of the quads out there do not have variable caster (the upper and lower a-arm pivot planes aren't parallel). In fact, I can't think of a single one that does off the top of my head. Most designers design in "static" caster (including the venerable TRX250R) in order to simplify the operation of the suspension. When you're talking about caster (versus camber) a little bit IS A LOT. Most automobiles have ~2° caster built in for "centered" steering while most atv's have less than 4° (more demanding turning but also more predicatable) The notalble exception being the TRX250R, which has a bit more. There are two ways to adjust caster, you can either "tilt" the a-arms so that their travel moves backwards as it moves upwards or you can stagger the outer pivot points so that the lower is "in front" of the upper. One means that the spindle moves in relation to the steering stem (which affects your ackerman angles) and the other means that the a-arms don't do any correcting themselves, only the spindles do. Most suspension designers go for both actually. The blaster (and banshee) both have a tiny bit of "cant" to the frame which points the pivot plane upwards towards the sky. (the TRX250R is an extreme example of this) while the upper ball joint is ALSO located about 1/2" behind the lower ball joint (to roll the pivot plane of the spindle "back") to increase caster. You COULD design a suspension with a "violent" swing in caster by changing the angle between the upper pivot plane and lower pivot plane. I'm not sure what you'd want however. Seems to me that you'd want approximately the same amount of caster (between 2-5°) throughout the entire travel but if you were going to make it change, you'd want more caster towards the upper end of the travel to make the suspension want to self center during large jumps with full suspension bottom.