registered user Posted August 22, 2014 Report Share Posted August 22, 2014 im not a fan of a tall narrow window as it doesnt support good power. 70% width or there abouts seems to work well and doesnt require a huge arc on the roof or large corner radius. ya some people will probly brag how they made the window much wider but then you need large roof arc and big corner radius (which isnt good for power either) to keep the piston and rings from eating themself in short order, so youve really gained nothing by doing this. if you want or need to make the exh area bigger than approx 70%, cutting in aux ports should be the next logical step. then you can maintain a nice window shape on your main port that doesnt chew up the piston and youll gain the extra area needed via your auxillaries lowering the exh floor isnt something i do mostly because the exh gas needs to be gone or mostly gone before the transfers are uncovered , so what does enlarging the lower portion of the exh accomplish ? if your exh isnt long gone by the time the piston gets near the bottom of the stroke, youll have some serious problems with it trying to push back into the transfers and crankcase resulting in a poor running engine. lowering the window also creates more volume in the tuenll as well, which may weaken the pressure fluctuation. if you had a bicycle pump and tried airing up a tire, i dont think you would make much progress with a large hose as you would spent quit a bit of time pumping up the hose rather than the tire. i believe this to be a similar situation with a large exh tunell Quote Link to comment Share on other sites More sharing options...
sheerider11 Posted August 22, 2014 Report Share Posted August 22, 2014 What do you think about Yamahas transfer shape? A straight up and turn. [ kind of like that. As opposed to my Kawasaki Kx cylinder ( kind of like that. Has a bunch of material in there to make the transfer bow out Quote Link to comment Share on other sites More sharing options...
Surfrjag Posted August 22, 2014 Report Share Posted August 22, 2014 you can get in trouble a lot faster and junk a set of cylinders with a bad window. I haven't seen anyone junk cylinders with a bad exhaust tunnel. just sayin... sheerider I like the design of the dirtbikes better it seems to be a better shot over the piston however the banshee being a twin cylinder, doesn't have room to do this with another cylinder right next to it. Quote Link to comment Share on other sites More sharing options...
registered user Posted August 23, 2014 Report Share Posted August 23, 2014 straight up and turn is basically what it is and i cant think of a worse way to make a transfer tunel. however this is unavoidable when you have a inline twin or multiple inline cylinders so close together, but theres really not much other choice in that situation. rotating one of the cylinder forward 45* or 90* would get rid of any limitations on cylinder design but im not sure such a engine would be good in a off road chassis, which is what these machines were origianlly intended for in yamahas eyes. calvin has done a good job on his cylinders, considering the engine design he had to work with. i think he put alot of effort into making the most out of a less than ideal situation Quote Link to comment Share on other sites More sharing options...
Atomic Monkey Posted August 23, 2014 Author Report Share Posted August 23, 2014 Yeah, not caring for the tunnel design on the Banshee... but it is what it is. I can see a definate advantage with a monoblock in being able to sculp the transfers better ( hint... next purchase!). But in dealing with things "as is", there's room to improve. Here's some of my ideas: #1: I wouldn't add boost ports or make the intake so large. I might raise and lower the outside edges, tapering the roof and floor biased towards the transfers for down flow. I would widen and taper the boost port at the outside edges, but not bring it any deeper into the intake than the reed tips. I don't want anything deeper than the reed tips. And I want the boost port directed a little behind the curve in the dome. #2: Enlarge the front of the primary tunnels. There's plenty of room to put a nice radius and contour up there from the case, into an arch that will make the flow aim at the boost port. Welding to fill the outside between the primaries and secondaries really helped with where and how much I could grind the divider. About all the secondaries will get is a little more direction towards the back of the cylinder, and having the kicker redirected/filled. The exhaust has been a little tricky to work out because of scavaging. What I did on these cylinders is try to make the return pulses flow directly across the piston to keep things in the chamber mixing/circulating in the same direction as the flow from the primaries. Ultimately I'm envisioning the return pulse is a cylinder "stuffer" while on the "band". Having it's flow help direct circulation, maybe not a bad thing... provided the split second it's open allows it to happen. Cheers, it's Friday! Quote Link to comment Share on other sites More sharing options...
trickedcarbine Posted August 23, 2014 Report Share Posted August 23, 2014 You tig weld.....? I mean you're in the mood to experiment right? Quote Link to comment Share on other sites More sharing options...
registered user Posted August 23, 2014 Report Share Posted August 23, 2014 i hear ya on the tunells. it is what it is. something you may consider on these cylinders or future ones if you do another set, is keeping a fairly high upwards angle as they enter the cylinder. this will decrease the angle in the upper portion of the tunell where it turns and heads to the cylinder. trying to go into the cylinder flat with a straight up tunel design puts a sharp turn in your tunell. pointing the transfers up will lessen the angle of the turn. i forget the intended purpose of your engine ? or maybe you never mentioned it. anyways on the stuff i do i dont normally get concearned with the intake being to large. really you want to put in as much mixture mass as possible. if you increase mass transport 15% and lose 14% velocity your still gaining. some people over look the reed block as well. on some engines the reed block can be modified quit a bit to work better. on the engines ive dealt with the stock reed block windows seem to be too small and the petals are restricted in how high they lift. ive modified a couple different oem blocks and they work well. you may not be using oem reed blocks but i thought i would mention it anyways since alot of people think oem stuff is junk and throw it in the trash. alot of times it is junk but often times it can be modified to work pretty well Quote Link to comment Share on other sites More sharing options...
Atomic Monkey Posted August 23, 2014 Author Report Share Posted August 23, 2014 I have VF4 reeds coming from cleaned stock cages with Boyesen 2 stage. In mock-up, the intake did appear need some work to actually "use" VF4s. The problem I have with what I've done is how low the intake was dropped... it looks like a weak spot in the sleeve. That's the whole reason I'm looking into different cylinders. The intended purposes of my engine is the be a trail machine. For that reason I didn't worry about making the exhaust port as wide as I could've. DB.... what U got in mind? Quote Link to comment Share on other sites More sharing options...
registered user Posted August 23, 2014 Report Share Posted August 23, 2014 some times its a compromise between not grinding a area as large as you think it needs to be in order to preserve the structual intergity. whether the sleeve will crack and cause problems is hard to say as your the only one with a birds eye view Quote Link to comment Share on other sites More sharing options...
Atomic Monkey Posted August 23, 2014 Author Report Share Posted August 23, 2014 Thought I'd post up a pic of the sleeve side of the exhaust. Maybe there"s room to improve??? Quote Link to comment Share on other sites More sharing options...
trickedcarbine Posted August 23, 2014 Report Share Posted August 23, 2014 Looks good. The temptation to make the exhaust wide is usually a hard one to fight off, but the banshee cylinder puts the exhaust right on the transfers. Makes it difficult to pull it off. You seem to have a nice compromise there. Quote Link to comment Share on other sites More sharing options...
Atomic Monkey Posted August 30, 2014 Author Report Share Posted August 30, 2014 Had the case welded today on the stator side to beef up the outside of the transfers in order to gasket match, and eliminate any worries of popping through. Quote Link to comment Share on other sites More sharing options...
trickedcarbine Posted August 30, 2014 Report Share Posted August 30, 2014 Not many folks doin' that. Worth a shot if you are DIY'n it. Quote Link to comment Share on other sites More sharing options...
Atomic Monkey Posted September 1, 2014 Author Report Share Posted September 1, 2014 Maybe its just the case I have, but to gasket match (I'm using a cub gasket) put the line for removing material on the outside wall, and wouldn't allow for the radius I wanted. Quote Link to comment Share on other sites More sharing options...
Pasi S. Posted September 1, 2014 Report Share Posted September 1, 2014 Just my honest opinion. You are doing good work! Looks good, and you are taking this seriously. Should make good power. Quote Link to comment Share on other sites More sharing options...
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