mixmastermike09 Posted May 6, 2014 Report Share Posted May 6, 2014 Hey guys, New here on HQ and looking some suggestions or to see if any of you have ever seen this issue. Background... Fresh build - 4 Mil Cub - New Cub Cylinder/Piston/Rings - New 4 Mil Crank - New 39 PWK's from FAST - New Cool Head DMC Alien Pipes - Stock Stator - Stock CDI - Stock Coil - VForce 3 Reeds Bike runs strong up to about 5,300 rpm and then it just levels off, won't turn any harder... Looking for any suggestions on what to look for. Ex: Stator ? Coil? All and any help appreciated. Michael Quote Link to comment Share on other sites More sharing options...
tfaith08 Posted May 6, 2014 Report Share Posted May 6, 2014 What size domes are you running? What's your jetting? Have you done a plug chop (I'd hope not, but if you have, let's see it)? Have you done a leakdown test? What is your timing set at? Does this occur in all gears, to include neutral? Is one or both of your pistons in backwards? Does it miss at 5300rpm or just level off? How do you know it stops at 5300? Generally, that problem persists with engines that have too hgih compression, terrible jetting, extremely clogged exhaust (which yours doesn't per your post), or something rubbing/grinding/catching really, really bad. Even then, you typically don't see a loss of revs more than 1000-1.5k rpm or so. Also, aren't DMC Aliens for bottom end power? If so, why the 39mm carbs? Quote Link to comment Share on other sites More sharing options...
mixmastermike09 Posted May 6, 2014 Author Report Share Posted May 6, 2014 Domes are 22CC - Right off the top of my head I can't remember the jetting, I purchased the carbs new from the guys at FAST and they sent me the jetting for my mods and altitude. No plug chop thus far. Have not done a leakdown, but I will when I get in from work this afternoon. Timing is at 0 It occurs in every gear including neutral - both pistons are installed correctly. Basically when it gets to around the 5300 range it just levels off, if anything there may be a little spit back through the carbs, it comes close to sounding like a car with a rev limitier... I have a MyChron Digital Tach and Temp Gauge hooked up and set correctly to monitor rpm & head & coolant temp. As for your question on the Pipes, yes they are to my understanding for bottem end power, but they were with the bike when I purchased it, so I'm just using them for time being. Quote Link to comment Share on other sites More sharing options...
Larry's Shee Posted May 6, 2014 Report Share Posted May 6, 2014 JMO, but trail pipes on drag clys just won't work Quote Link to comment Share on other sites More sharing options...
sstaton1983 Posted May 6, 2014 Report Share Posted May 6, 2014 trail pipe with drag porting ftmfw Quote Link to comment Share on other sites More sharing options...
mixmastermike09 Posted May 6, 2014 Author Report Share Posted May 6, 2014 Hey guys, I know that the pipes with the setup arn't the best/proper for drag, but It's what I have right now, until the drag pipes come in... At any rate, even with stock pipes it should turn in the 8K range... Quote Link to comment Share on other sites More sharing options...
Deadbeat Posted May 6, 2014 Report Share Posted May 6, 2014 maybe your tacho is fucked Quote Link to comment Share on other sites More sharing options...
mixmastermike09 Posted May 6, 2014 Author Report Share Posted May 6, 2014 Nah, I have 2 MyChron's and 2 Digitron's that I run on serveral other things and they all check the exact same. And yes I have them set for 2 Sparks per rev... I've been building 4 stroke Kart Racing engines for 15yrs and several V8 Drag motors... I'm not a rookie engine builder, but I am a little new to the banshee engines. Just looking to see if anyone has ever ran across this issue before. Thanks for all the feedback tho guys.... Quote Link to comment Share on other sites More sharing options...
RadarRacing Posted May 6, 2014 Report Share Posted May 6, 2014 Dont worry about the pipes for now you obviously have a plan. Things to check in the order I would check. Plug color , if it were way rich it will not rev out Motor,coil ground , motor grounded to frame Stator pickup to flywheel gap Quote Link to comment Share on other sites More sharing options...
mixmastermike09 Posted May 6, 2014 Author Report Share Posted May 6, 2014 Thanks Man, This is exactly the kind of info I was looking for, a good place to start checking... I will go through it this afternoon and report back my findings. Quote Link to comment Share on other sites More sharing options...
RadarRacing Posted May 6, 2014 Report Share Posted May 6, 2014 (edited) Before you get it completely tuned or think its perfect now definately get a set of shearers for it. You will have huge gains everywhere with them. They will be at least 5-10hp stronger even down low and the top will be ridiculous compared to what you have now. They will be stronger even at 4,000 and up. I forgot to add you should make sure it passes a leakdown test. I had a motor years ago that wouldnt rev and it was leaking bad under the back of the cyl at the base gasket. It wouldnt have ran long like that as it was very lean. New gasket and sealed up and all was good. Edited May 6, 2014 by RadarRacing 1 Quote Link to comment Share on other sites More sharing options...
mixmastermike09 Posted May 7, 2014 Author Report Share Posted May 7, 2014 Well guys, I think I have found the problem... Ran a leakdown on it tonight and discovered the left cylinder was leaking quite a bit. Pulled the head to find some guad marks in the cylinder wall... Went ahead and pulled the Jug and piston on that side and discoverd a cracked sqirt on the piston... Fortunatly the cylinder cleaned right up with a couple passes on the hone, got a new piston and rings / gasets and such on the way. On another note - Wondering if anyone can give me a ballpark on jetting with this setup - so I will have a ballpark jetting when I get it back together this weekend. 421 Cub (Stock Porting) - 39mm PWK Carbs w/ 8" K&N's - VForce 3 Reeds w/ billet spacers - Shearer oof SB Drag Pipes I'm on the east coast NC 135ft elevation (Sea Level) Temps in the 75-85 range currently Not looking for dead on, just a good starting point so I will know what I need to get ordered. Thanks again guys! Quote Link to comment Share on other sites More sharing options...
sleeper06 Posted May 7, 2014 Report Share Posted May 7, 2014 Did u use a diamond hone, if not u might have messed up nik second I would start 52 pilot 175 main needle 4th clip Quote Link to comment Share on other sites More sharing options...
mixmastermike09 Posted May 7, 2014 Author Report Share Posted May 7, 2014 I did use a diamond hone on it, it wasn't bad just took a couple passes to clean it up good. Thanks for the jetting info... Quote Link to comment Share on other sites More sharing options...
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