TurboBanshee420 Posted July 22, 2009 Report Share Posted July 22, 2009 building my 421 cub...just thought I'd ask you guys for some pics ideas...yada yada heres some pics of mine as i got it and what i've gotten done so far...only about 2hrs of cutting so far on the one side. BEFORE AFTER, but not nearly done The outside...shiney! Quote Link to comment Share on other sites More sharing options...
No Limit Powersports Posted July 22, 2009 Report Share Posted July 22, 2009 Did you only do intake work? If so you prolly will see little to no improvement over stock. Quote Link to comment Share on other sites More sharing options...
TurboBanshee420 Posted July 22, 2009 Author Report Share Posted July 22, 2009 i highly doubt that it would be no improvment ...however, I've only had about 2hrs to do anything and I was planning to cover all my bases. For such a "badass" cylinder, it sure needs some help... What is the average output from a 421 without work? Quote Link to comment Share on other sites More sharing options...
locogato11283 Posted July 22, 2009 Report Share Posted July 22, 2009 are you planning to do something with the exhaust or what? Quote Link to comment Share on other sites More sharing options...
blowit Posted July 22, 2009 Report Share Posted July 22, 2009 Cleaning up the ports certainly will not hurt anything but you need to be careful not to damage your bore coating when working the windows. The intake really works pretty good out of the box after some clean up. The transfers and exhaust need more help. Dyno numbers area all over the map on the 421 due to setup differences. I have seen as low as 70HP out of them and as high as 110HP. The key is to determine what you want from the bike first. If all you want is to go fast in a straight line, that will take a bit more. B Quote Link to comment Share on other sites More sharing options...
TurboBanshee420 Posted July 22, 2009 Author Report Share Posted July 22, 2009 Yes I'm opening the exhsut port by 15% by volume, also raising it by 1mm across the window curve. Tranfers are pretty good as far as volume for me, but I want to open the windows on all sides by 1mm or so. And blend the sharp edges into the cylinder. I alwasy start with the intake to give me an idea of what kind of airflow I'm working with. besides, the hardest part is gettin gthe air through the reedbox. Once your in, then the engine will do the work from there as long as it isn't getting back pressure reverberations while pumping it up to the top. Killing all the knife edges with strips of emery when I'm done....round nose cuts air better. If you don't think so then youtube some airflow tests. knife edges will make a pressure "wake" and cause fuel to collect in the wave and de-atomize. read this....This guy made 30+hp off his porting and other small thingsMaize583 Quote Link to comment Share on other sites More sharing options...
blowit Posted July 22, 2009 Report Share Posted July 22, 2009 Yes I'm opening the exhsut port by 15% by volume, also raising it by 1mm across the window curve. Tranfers are pretty good as far as volume for me, but I want to open the windows on all sides by 1mm or so. And blend the sharp edges into the cylinder. I alwasy start with the intake to give me an idea of what kind of airflow I'm working with. besides, the hardest part is gettin gthe air through the reedbox. Once your in, then the engine will do the work from there as long as it isn't getting back pressure reverberations while pumping it up to the top. Killing all the knife edges with strips of emery when I'm done....round nose cuts air better. If you don't think so then youtube some airflow tests. knife edges will make a pressure "wake" and cause fuel to collect in the wave and de-atomize. read this....This guy made 30+hp off his porting and other small thingsMaize583 What kind of timing changes are you getting from the 1mm raise on the exhaust? You are correct regarding radii on leading edges in an air stream. However, you are not "cutting air" at all. All the air in the engine is subsonic until it is sent out the exhaust. The "wake" you refer too is an eddy current from in increase in turbulence. Why people still insist on knife edging things, I will never know but after designing aircraft wings, I think I got the gist of how air works. Again, what are you trying to do with the engine? Raising the exhaust will drop power off the bottom. There are many things you can do before going towards timing changes. B Quote Link to comment Share on other sites More sharing options...
TurboBanshee420 Posted July 23, 2009 Author Report Share Posted July 23, 2009 bottom end on a banshee is worthless anyways. I can get back what I lost with higher compression. i just want to get a nice wide band....running a 2-1 dynoport. 34pj's for now. I would like to get a set of rocket pipes eventually. I ride lots of very fast wide long straight trails. mostly railbeds...hard surface. Exhaust changes will give me about 3* more duration. Only to stretch the power a bit higher....I love to hear it scream. The 2-1 pipe does a better job of scavenging the opposing pulse form the other cylinder. They looked ok from rdz, but they needed lots of clean up. I did all the same things to my stocker and got 55.6hp at the wheels. Not too shabby I guess...that was with shearers and 34pjs. Should be much better with a more aggresive cylinder design Quote Link to comment Share on other sites More sharing options...
TurboBanshee420 Posted July 23, 2009 Author Report Share Posted July 23, 2009 i did the same thing maize did to his on my 670....took alot of money this past year from guys with 800's and this and that...they were mad! Quote Link to comment Share on other sites More sharing options...
blowit Posted July 23, 2009 Report Share Posted July 23, 2009 i did the same thing maize did to his on my 670....took alot of money this past year from guys with 800's and this and that...they were mad! Numbers I have would bring you up 4-4.5* total duration and I am not sure I would do that with the dynoport pipe. Much more than stock durations really leans towards drag pipe tuned lengths. B Quote Link to comment Share on other sites More sharing options...
trickedcarbine Posted July 23, 2009 Report Share Posted July 23, 2009 was that you building that turbo shee on hmt with the you tube vids, what ever happened to that thing Quote Link to comment Share on other sites More sharing options...
FireHead Posted July 23, 2009 Report Share Posted July 23, 2009 Dyno numbers area all over the map on the 421 due to setup differences. I have seen as low as 70HP out of them and as high as 110HP. The key is to determine what you want from the bike first. If all you want is to go fast in a straight line, that will take a bit more. B I see you are leaving my red hot rod out of that hp range. :biggrin: You're 100% correct though................... Quote Link to comment Share on other sites More sharing options...
dajogejr Posted July 23, 2009 Report Share Posted July 23, 2009 Did you only do intake work? If so you prolly will see little to no improvement over stock. Exactly right. Dyno the bike BEFORE you port it so there's no questions. i highly doubt that it would be no improvment ...however, I've only had about 2hrs to do anything and I was planning to cover all my bases. For such a "badass" cylinder, it sure needs some help... What is the average output from a 421 without work? With the casting flaws cleaned up, it is the best cylinder on the market bolt on. Period. There is no disputing that. If you find a "better bolt on cylinder" let me know. Let me give you another hint. Porting the cub, you'll find 80% of your power in the exhaust, the rest in the transfers and very little in the intake. Dyno proven, hundreds of runs on these cylinders, not guessing here. Have you degreed that cylinder in yet...to know what and where to remove the material? The rest of the work is in shaping the ports as well. On a well known and trusted dyno in are area, my 4 mil cub made 85 HP with stock carbs and T5s, cleaned up by Jeff @ FAST, LOTS of timing and compression on 110. I never did dyno it after I put Shearer inframes and 35PWKs on it...but prolly low to mid 90s after that. Quote Link to comment Share on other sites More sharing options...
dajogejr Posted July 23, 2009 Report Share Posted July 23, 2009 Wait...I just read your other post. You're putting 34PJs and a 2 into one exhaust on it? Never mind my post. Just clean up the casting flaws and run it. Unless you're putting a turbo on the bike with that two into 1....you just neutered a world class pit bull and made it a chihuahua. By raising the exhaust ports you're removing any little bottom to mid it had, you're not going to get that back by compression, timing and a 2 into 1 exhaust...sorry. Quote Link to comment Share on other sites More sharing options...
TurboBanshee420 Posted July 23, 2009 Author Report Share Posted July 23, 2009 Like I said, I'm running the dynport until I can afford some rockets......I like shearer, but they are too short a band for me. Maybe the larger volume rockets will get me what I want.....wide power, not so peaky. I've run the dynoport on lots of different set-ups through the years on this thing and it always has held its own pretty good. plus the sound is sweet. I don't think worrying about "peak" numbers really matters much. So far I haven't touched the windows except for the intake which doesn't matter much really as far as timing goes. If raising the exhaust is a bad idea, then tell me now, before I go and do something I shouldn't.....you guys are the cub pro's....not me by any means. turbo project...yes...that was me. Yes I finished the build, with no luck getting help tuning. I ran into a wall there trying to ride with a laptop sitting on my lap (go figure) so I could get some recordings of what was going on. I got as far as getting it to run and idle, but was WAAAYYY to rich to do much more with. I'm not familiar with how far each adjustment gave me. It's all in a nice sealed tupperware container and waiting for a rainy day. Not so worried about it now. I'm restoring my scarab and have no time to go there...along with tons of other shit. When it catches back up to me I'm sure i'll get pissed it never got "done" and throw it back on. The whole turbo thing has been a god damn thorn in my side for 5 years. Started in 03 when my brother talked me into trying it with carbs....after i failed to get enough fuel in there with carbs I gave up...in 06 I started planning it out again with efi...worked out well so far. Learned more doing that project then I ever did in school! Anyone have a port map I can use? daj...What do you suggest i do with the exhaust? open the small boosters? open the main port? raise lower??? fill me in big guy...You apperiently know tons about the cubs. And what about the transfers? c'mon now, don't tease me lol As far as I'm concerned...making holes bigger isn't where the power is. Timing and shape is where 2 strokes like the work done. I learned that on all the 670's I've done so far. Man what a difference alittle rounding and removal of sharp edges make. Air is pretty flexable from a pressure stand-point...Inside a pump it will do what it's told... to a point The pics don't really do much justice, but all the things I have done so far is only to help push the charge down toward the crank/transfers. I just wanted to get rid of the huge lip on the bottom/side on the intake windows. I feel it shouldn't be channeled more tightly...it should open like a bell going in. (if you know what I mean) look closely at the pics and you'll see what I mean. The first few are before shots (duh). There will be a small pressure drop going in through there, but not enough to reak havoc...The charge will be under vacuum anyhow sooo... Quote Link to comment Share on other sites More sharing options...
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