Ducman Posted September 19, 2004 Report Share Posted September 19, 2004 I've got no big carb or 4mm stroker experience and need a ball park starting point for the jetting. Well I have my 4mm stroker, tripple exhaust port (aggressive dune port empahsis on top end, not quite a drag port through) installed and ready to go and no carbs to fire the bitch up. Shorty's racing didn't send my stock carbs back bored to 28mm with my motor when they sent it back. Got a hold of them and they said they would send them out ASAP but I still haven't got them almost 2 weeks later and they are a PITA to contact. The whole story will be in the product review I plan on doing when I finally get shee running and some seat time. I wanted a set of bigger carbs anyway so now I have a set of 34mm Mikuni flatsides in the mail. Shorties said that the recommended main size on the bored carbs was a 320 which seems fairly small to me although 4mm strokers are a whole different animal in which I have no experience. But most of Shortys experience is with CPI's and from what I've gathered and experienced Rockets like a bigger main than just about any other pipe and CPI's run a somewhat leaner main. I was running slightly rich on 320's with the stock carbs/motor. I bought a set of 34mm Mikuni flat slide carbs from Moto Carrera. They said the carbs come standard with a #50 pilot and a #280 main and I forget what needle. They said that with a bigger carb the main size needed will be smaller than say the stock carb size but weren't much help at all with giving me a ball park starting point. I'd say about 2 degrees more intellegent than the average stealership. They are sending a #40 and #45 pilots with the carbs, I can get #30 or 35s locally. They said they would try anywhere from a #260 to a #320 main ( I have all those sizes). Mods effecting jetting - stock air box/foam filter lid off, Boisen duel stage reeds/stock cage (V-force coming soon), 34mm mikuni flatsides, BOSS 34mm intake, 4mm stroker tripple exhaust port (aggressive dune port), timing advance 6 degrees, Rocket inframes. Sea Level to 500' Temp approx. 70 deg Thanks in advance for the tips. Quote Link to comment Share on other sites More sharing options...
Oilsmoke Posted September 19, 2004 Report Share Posted September 19, 2004 i am running 270 on my stroker, 34mm round slides at 5000 feet. others run cpi's and ported motors are 270 to 290 with tm 34mm carbs try a 300's and plug chop. Quote Link to comment Share on other sites More sharing options...
Ducman Posted September 19, 2004 Author Report Share Posted September 19, 2004 Thanks Oilsmoke, exactly what I was looking for. What pilots are you running? Quote Link to comment Share on other sites More sharing options...
Oilsmoke Posted September 19, 2004 Report Share Posted September 19, 2004 (edited) the pilots in my son shee which are 34mm flat slide and his friend with ported K&T cylinders, I ported my son shee Both run CPI's, Inframe on the friends and outside drag's on my son. Stock polits but we are at 4300 to 5000 feet. I'm runnng 35's polits in my 34mm roundslides. but remeber my shee is not spot on,It runs very good but i still feel there is more horsepower to find in the jetting. But my Stroker runs great until it gets hot over 180 degrees this is at 1/8 throttle criuse only. It's don't pull 6 th hard like i think it should, 70 Mph with 14/44 gear on sand lake bed at St Anthony egin lake. I will try 260 next summer in the heat. I hope it starts to run killer as it get colder than I know i am still little rich. My plug chops are looking pretty close, But I am Chicken to drop jetting to Fast Passion strokers Cost Money and would hate to burn it down. also this is with 21x12x8 9paddle so this can help you baseline it. I also have a complete set of jet too. 270 to 430. I tryied jetting my Polits down but I never made a mental note on the 32.5 but the 30 and 27 where worse in my 1/8. Tip Index the throttle, Works great on a twist. you did a 3 port Exhaust? Tell me more. I love this engine stuff? Edited September 19, 2004 by Oilsmoke Quote Link to comment Share on other sites More sharing options...
Ducman Posted September 19, 2004 Author Report Share Posted September 19, 2004 The tripple port exhaust has a small boost port machined on either side of the exhaust port just like PassionRe's boost ports on either side of the intake ports. I discussed this with Shorty's and they said that they thought it was more important for the top end to make the exhaust port as big as possible. Make it too big and the rings will hang up on the port. The small side ports make the total exhaust port bigger than the main port can be made. They said the boost ports on the intake side would make a good torque motor but didn't think that it could get all the exhaust out on the top end, like too much intake and not enough exhaust. Now I know PassionRE makes a bad ass motor that pulls to the sky so I'n not buying it hook line and sinker. However, the supercharging effect of the exhaust is what makes the 2 stroke power band happen so I can see that the exhaust side boost ports probably achieve a higher top end cylender pressure and exhaust flow. Now all that said, the main reason I got the Shorty's 4mm stroker engine build was price. The Passion kit was like $1250 for the porting and all the parts needed and you put it together yourself. Shorty's gave me a price of $1465 for the following: wiseco 4mm long rod crank ($450), stroker domes, prodesign ignition advance plate, lighten flywheel, bore the stock carbs to 28mm, tear down and rebuild the motor, and return shipping all included. That was with my %10 discount for first time purchase from shorty's. Passion probaly builds a better motor and I'm finding out that Shorty's customer service kinda sucks so you kinda get the quality and customer service vs price trade off. To be fair, around Laborday weekend is one of the most buisy times of the year for Oregon dune customers. The other factor is that portland OR is within driving disance of Northern CA, Passion in OK is not. I figured if something got screwed up and I needed to wring someones neck, I could make a trip to Shorty's. He he he. Although I'm sure that Passion gets enough business from the HQ and he has established a solid rep for customer service with people on the HQ. Back to the 34mm carbs, (Oilsmoke) Thanks bro, I guess I will probably try the #40 pilots first since you said that #35's worked for you and #30's and 27.5's were too small. If the #40's are too big then I'll get some #35's and try them. I'll try the #300 mains to start with and do a plug chop when shee's broke in. How about the needle, Middle clip? Hopefully the standard needles don't have too steep of a taper. Quote Link to comment Share on other sites More sharing options...
Oilsmoke Posted September 19, 2004 Report Share Posted September 19, 2004 (edited) 6DP17 this is the needle I am currently using and it Edited September 19, 2004 by Oilsmoke Quote Link to comment Share on other sites More sharing options...
Ducman Posted September 19, 2004 Author Report Share Posted September 19, 2004 Believe me, I thought about it! Shorty's said that they thought it might be starting to make the cylinder too swiss cheasy. Too many gaps the ring is passing over putting a lot of stress on it possibly making it unrelaible. I think it would work. It would be a good question to ask PassionRE why he doesn't do this. I'm sure he could. There must be a reason why he doesn't. 14 port banshee stroker motor yielding 4 stroke death and destruction! Quote Link to comment Share on other sites More sharing options...
PassionRE Posted September 19, 2004 Report Share Posted September 19, 2004 Believe me, I thought about it! Shorty's said that they thought it might be starting to make the cylinder too swiss cheasy. Too many gaps the ring is passing over putting a lot of stress on it possibly making it unrelaible. I think it would work. It would be a good question to ask PassionRE why he doesn't do this. I'm sure he could. There must be a reason why he doesn't. 14 port banshee stroker motor yielding 4 stroke death and destruction! The triple exhaust ports are not based on the same princaple as my 12 ported intakes. They serve two entirely different needs or wants. Triple exhausts are for increased Time/Area calculations with lower exhaust ports. 12 ports are strictly intake enhancement where atomization is concerned. They dont replace each other. The reason I dont do triple exhausts is because it simply isn't neccessary, and its a difficult operation to do properly and safely. With the correctly shaped exhaust ports I can manipulate T/A and blowdown T/A specs wherever I want and still not need the triples. Even with the huge transfers on my stroker motors, I can build the exhaust port to ratio out correctly and save me time, and my customers money....Jim Quote Link to comment Share on other sites More sharing options...
Oilsmoke Posted September 20, 2004 Report Share Posted September 20, 2004 Hi Jim I would like to tell you I am Very happy with my motor, And the Power it has, I smoked a Great running Cr500 Up chokecherry and the Lake bed. It lauches hard and after that not many can catch it. I love that i can get off and than back on it up a steep dune and not loose the power like the 350 Ported motors do. Quote Link to comment Share on other sites More sharing options...
PassionRE Posted September 20, 2004 Report Share Posted September 20, 2004 Glad you like the engine Steve....it is a really good blend of torque and speed. Saw the pics of your bike on your other thread and have to hand it to you, the bike looks awesome...good job my friend....Jim Quote Link to comment Share on other sites More sharing options...
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