350skabarat Posted August 22, 2012 Report Share Posted August 22, 2012 Ok I've found out why my projection method didn't work. You need to take crank stroke and conrod length into consideration. I did this and it worked out, my exhaust opens at 89 and closes at 89 before tdc. The reason why I think its not 90 is because I only put two barrel bolts on and never torqued it down properly. If I had I think my deck height at tdc wouldve been less than 0.8mm. Anyways what I did was widen my port from 43 to a little over 45mm. Widened it 1.1 ±0.2mm on each side. Its sitting at 67.5 percent of my 66.25 bore. So its not on the limit but its my first real port job so I'm taking things slow. What I did was take masking tape and paste it in and measure and move it till it was right as you can see. And here is the end result I then calculated if I raise my exhaust by O.3mm I'd add just about a degree on opening and closing so the duration should be on 182 now. I don't wana go more cause I want all the bottom end I can get! I'm also running pc's and I've read they good for a low mid port. I used a dremel extension with a thick carbide tip tip for the sides of the exhaust and then I use a hand swiss number 4 file for the roof. It took me two days like morning till night to do just this! It wasn't that bad to widen the port but to blend it in so its strait!!!! Oh my sac!! Lots and lots of work! Next thing I did was cleanup some casting floors deep inside the transfers, don't have a pick of it. I also sharpened the intakes of the transfers. Next think on the list was the casting of the bottom of the cylinder. If you put your barrels on and flip the case and look by the transfer intakes you can see that this is a restriction no doubt about it! So what I did was put my piston in the barrel and put it at bdc. Checked where the piston is at bdc and marked it. Then I fliped the cylinder and checked if the piston comes past this casting. If it did I wasn't going to grind it but lucky lucky it doesn't come past it. So I measured 2mm and scribed a line. I couldve gone more but baby steps hey baby steps. Lol. Here are the pics I'm sure you can see what a restriction this piece of the cylinder has. By just looking at it. The pic above is after I grinded 2mm off and matched the cases to the barrels. Now I still wana do my transfers as I want a nice wide powerband with more bottom power, I just need a 90 degree piece for my dremel then I'm set. I'd also like some input on this aswell? I have some figures in mind but I'd like to hear what you guys think first? Also what's your comments on stagered transfers with 1degree differences?Oh I almost forgot, best pic of all Lol I know I messed the zero up abit but its not bad Quote Link to comment Share on other sites More sharing options...
350skabarat Posted August 22, 2012 Author Report Share Posted August 22, 2012 Sorry I just copied this thread from our south african 2stroke forum so the projection method I was talking about was a method of calculating port timing but I kept getting wrong figures cause I was not taking crank stroke and conrod length into consideration. Quote Link to comment Share on other sites More sharing options...
ATVridinMaNiAc Posted August 22, 2012 Report Share Posted August 22, 2012 Nice work, curious to see how it runs. Quote Link to comment Share on other sites More sharing options...
mike0chek Posted August 22, 2012 Report Share Posted August 22, 2012 Nice work, curious to see how it runs. ya me too, be sure to let us know. Quote Link to comment Share on other sites More sharing options...
350skabarat Posted August 22, 2012 Author Report Share Posted August 22, 2012 Nice work, curious to see how it runs. I will definitely give a full review when I'm done. Need a new crank, pistons and rebore so its gana be a while from now so ya. Quote Link to comment Share on other sites More sharing options...
registered user Posted August 24, 2012 Report Share Posted August 24, 2012 get a degree whel then you dont have to screw around measuring shit Quote Link to comment Share on other sites More sharing options...
350skabarat Posted August 24, 2012 Author Report Share Posted August 24, 2012 get a degree whel then you dont have to screw around measuring shit I have a degree wheel and yes they do work nicely, but remember you basically judge when you think the port cracks open? So IMHO I think measuring port roof height to the top of cylinder minus your deck height is much more accurate. But a degree wheel is just as acurate if done correctly. What I ended up doing was using both methods and then got a mean between the two.... Does any1 no what a good blowdown value for bottom end power? I reworked my ports abit and this is where I'm at: Exhaust: 184.2 Transfers: 120.1 Boost: 105.5 Blowdown: 32 What do you guys think? I must also add that I increased my exhaust ports "time area" not only by making it a tad higher but also by widening it by 1.2mm on each side. So I need some help here guys? I wana go for good low end power so I'm not sure if I should make my transfers duration longer to lower my blowdown or increase my transfers "time area" by making them abit wider but not higher. I also wana ask, what's best for a broad powerband; boost opening before transfers or transfers opening before boost. Stock cylinders the boost opens after the transfers. So ya any help would be much appreciated. Thanx Quote Link to comment Share on other sites More sharing options...
turbowrenchhead Posted August 24, 2012 Report Share Posted August 24, 2012 Here is a pic of my DIY intake port job. This is the rough cut, still have to go in and polish Quote Link to comment Share on other sites More sharing options...
350skabarat Posted August 24, 2012 Author Report Share Posted August 24, 2012 Here is a pic of my DIY intake port job. This is the rough cut, still have to go in and polish Looks like you on limits hey? What you going for? Aggressive drag? What's you exhaust and transfers at? Looks good! Quote Link to comment Share on other sites More sharing options...
ClayAiken Posted August 24, 2012 Report Share Posted August 24, 2012 Getta vid up of this running when its done. Hopefully it turns out well for you. Quote Link to comment Share on other sites More sharing options...
turbowrenchhead Posted August 24, 2012 Report Share Posted August 24, 2012 Looks like you on limits hey? What you going for? Aggressive drag? What's you exhaust and transfers at? Looks good! I'm shooting for 65-70 HP. I don't know how to measure my degrees. I did this from copying other port jobs out there and did much reading up. I still have to assembly my bottom end so I can see how close my ring lands get to the port. Hopefully they are not to close. If they are then I'll chalk them up as practice. Quote Link to comment Share on other sites More sharing options...
registered user Posted August 24, 2012 Report Share Posted August 24, 2012 I have a degree wheel and yes they do work nicely, but remember you basically judge when you think the port cracks open? So IMHO I think measuring port roof height to the top of cylinder minus your deck height is much more accurate. But a degree wheel is just as acurate if done correctly. What I ended up doing was using both methods and then got a mean between the two.... Does any1 no what a good blowdown value for bottom end power? I reworked my ports abit and this is where I'm at: Exhaust: 184.2 Transfers: 120.1 Boost: 105.5 Blowdown: 32 What do you guys think? I must also add that I increased my exhaust ports "time area" not only by making it a tad higher but also by widening it by 1.2mm on each side. So I need some help here guys? I wana go for good low end power so I'm not sure if I should make my transfers duration longer to lower my blowdown or increase my transfers "time area" by making them abit wider but not higher. I also wana ask, what's best for a broad powerband; boost opening before transfers or transfers opening before boost. Stock cylinders the boost opens after the transfers. So ya any help would be much appreciated. Thanx i was gonna try and help but looks as you got it all under control . 184.2 ? WTF is that. 2 tenths of a degree. hahaha good luck dude Quote Link to comment Share on other sites More sharing options...
350skabarat Posted August 25, 2012 Author Report Share Posted August 25, 2012 i was gonna try and help but looks as you got it all under control . 184.2 ? WTF is that. 2 tenths of a degree. hahaha good luck dude That my friend is accuracy. Accuracy is a must! I don't just grind away. That's just plain stupid. Take your snobby comments else ware. Quote Link to comment Share on other sites More sharing options...
350skabarat Posted August 25, 2012 Author Report Share Posted August 25, 2012 i was gonna try and help but looks as you got it all under control . 184.2 ? WTF is that. 2 tenths of a degree. hahaha good luck dude That my friend is accuracy. Accuracy is a must! I don't just grind away. That's just plain stupid. Take your snobby comments else where. Quote Link to comment Share on other sites More sharing options...
Pasi S. Posted August 26, 2012 Report Share Posted August 26, 2012 That my friend is accuracy. Accuracy is a must! I don't just grind away. That's just plain stupid. Take your snobby comments else where. I have done some home made porting, because I live in Finland and just like you, far away from Professional builders. I need to ask you, how you can measure " .2 " degree? I have had some serious problems even read my exhaust durations, like is it 198 or 199 or even 200. ..just asking, and I want to learn more. Quote Link to comment Share on other sites More sharing options...
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