blowit

I would want to know your exhaust port duration and your method of checking the comp. I am thinking your tester is lying to you. some testers can be off by over 3ccs by not having a schrader valve in the end of the tester and not threading in all the way. Brandon

The first things to look at are carb sync and TORS if you have those still. You indicate that one slide is open more than another so that is the first indicator that a cable is toast or out of adjustment. Get the slides to work in unison and that should help. After that is solved, then I would proceed to a carb clean. B

Unplug all electronics but CDI is safe to leave on chassis for welding. Brandon

The guy that qouted you was me. Please keep in mind that a simple facing of the deck is what you are looking for and we step a mountain and beyond that with our mods. Many companies get over 100 bucks for a lesser service. We completely recut the chamber, improve atomization and squish characteristics through our specific flow pattern. I am sure there are plenty of guys with a Bridgeport that can help you out but our services are not near the same. It's important to know what you are paying for. Our head mod is result of many hours of engineering and dyno testing. You will not that from Jo Blo next door with a Bridgeport though. Sorry we could not be of service. Brandon http://mullengineering.com/

I guess I was assuming Keihin carbs here since the 165 would be a valid Keihin size. I did not comp for the porting since emery clothing the ports should not affect them enough for jetting changes. Brandon

175 main jet and fine to use pump fuel with the 20cc dome at 500ft and above sea level. Brandon

Sounds like you might want the check your impeller. The OEM piece is plastic and failures are common. Antifreeze offers no benefit in cooling capacity but rather increases boil over and freeze protection. There are additives that have more exothermic value like water wetter that can help in cooling but sounds like you have a mechanical problem. Also note that if you topped of the overflow bottle and suddenly it vents on the pipe, this is completely normal. As long as the bottle maintains some fluid in it, you are fine. We always route that hose under the bike so it does not make a mess on the pipes. Brandon

I think what you are asking is the math involved to achieve 50:1?? You just need to know that it refers to 50 parts of "something" to 1 part of "something else". This can be applied to any unit a measurement. probably the easiest is fluid ounces in the US. Just remember that there are 128 ounces in 1 gal of fuel. The 50:1 would just mean for every 50 ounces of fuel, you need to add one ounce of oil. I am sure someone here has a trick table for you if that is what you are asking. If not, sorry to insert the elementary math lesson. Brandon

I'd agree with that. .090 and .100 over is pushing it simply because as the sleeve heats, it warps and wears the piston pretty fast. The thinner they are, the worse they warp. That being said, that is better than running it until it blows. I am curious if you need a bore?? Are you sure your bore is out of whack?? New pistons will generally get you back in tolerance as long as the bore is still good. If you have no one to measure the bore for out of round and taper, we always offer that service free. Brandon

I am kinda wondering if there is porting on these cylinders and the boost port is too high. We see this a bunch in strokers with incorrect porting. Or should I say stock ported cylinders with a stroker crank. If you cannot find the cause, I would try new pedals and role on. Brandon

Sounds like your CDI is taking a nose dive. Check the resistance on the stator and if it checks ok, borrow a buddies CDI and test. Brandon

Sounds like a raised exhaust port to me!! Verify the squish but yes, a raised port can drop you 20lbs. Brandon

Increase of what?? you tell me. What is my problem?? Brandon

huh, last time we had a motor that made a holy piston on the dyno, it was lean and "detonating". We decipher the difference with piezoelectric sensor data overlaid on the ignition pulses. Brandon

200 mains on a stock carb is damn lean!! Stock bikes come with either 200 or 210 stock. If you have any mods at all, you need more fuel. Check those pilots. stock was 22.5 or 25 and you will need more with any mods. You need to have extra plugs on hand when checking jetting because once they color, they can lie to you. Grey is NOT tan. You might shoot a pic but grey is generally Al stuck to the plug and not good at all. Tan is fine. Lets call it light brown. You might also note the ambient temp and humidity. You may be lean and when it is hot or humid, it runs fine because it is a bit richer. Brandon

Run it till it blows. Then you'll know for sure!! Brandon

Were you, by any chance, WFO in 6th for a distance before this happened?? What generally happens is detonation. Your see thru hole is a tell tale sign of that. Most of the time, a lean banshee will be fine until you run it out for long distances. This will cause a gradual EGT rise until well in the red and since an expansion chamber motor will recirculate exhaust to the top end, this causes rapid heating and uncontrolled flame front propagation thus detonating. may need to jet for long hauls on the open roads. Brandon

A 9 hear range is a colder plug and possible used in hotter months to detour detonation. I would suggest checking compression before doing too much. Yes, 8 is the stock heat range but 9 is not uncommon in the dessert. Brandon

It would seem your numbers are pretty close. The only thing I am baffled about is that 33mm exhaust. And you can really see why the plate is not a good option unless for drag racing. Those transfer numbers are too aggressive for a smooth, linear response. We wrote our own porting programs just because we need to "know" how these numbers are derived. We used one and did the numbers on it and found several degrees error because of rod angle issues. We just found it easier to know what we have. That is not saying all software if crap though, it would just be nice to see the equations. Brandon

If you are looking at a plate motor, the deck height reference should be zero. You might check your software and see if pos or neg deck refers to the piston above the deck. We always refer to neg deck as having the piston above the deck but that is not really an industry standard. Brandon

Ah, you have me wondering now if you are just using the new piston TDC as your deck for reference instead of a negative deck. That might explain that. So many ways to looks at these things I guess....

I have never seen a stock cylinder with a 33mm exhaust. Your 179 sounds like you might be referencing a zero deck and not a -2mm deck which is what you would have in a non-plate 4mm motor.

A comp ratio is the delta of two volumes and independent of atmospheric pressures. Pumping or static numbers are theoretical on the books based on 100% cylinder fill which is rarely the case. We have seen many calcs are are close but the ratio will generally be the best way for tuning. The OEM listed the Banshee years ago as a 6.5:1 motor. Most of our measurements hold the banshee around 6.0:1 in stock form. This of course can vary depending on several tolerances. Oh, comp ratios can be calculated as either uncorrected, or corrected. The corrected measurement is a much better way to compare ratios.

Well I would sure do a leak down test on that motor before I opened it all the way. No leak= a waste of teardown time. You may find a leak but unless you have smacked the cases, I have never seen one stress crack. The magnafluxing shouls be a last resort. There plenty of other ways of finding the problem. Once you identify leaking, you need to find the actual leak. That is crucial so you know you have beat the problem with a proverbial sledge hammer. Brandon

Maybe I just do not understand what you are saying but moving the cylinder up or down will not have a linear change in duration. I thought you were referring to a stroker in which you would just adjust the ports up 2mm to "match" the -2mm deck. That would not yield the same durations as a stock motor. That is about all I was saying. Brandon