blowit

I think your dyno is broke Jeff.. Did you get a chance to inspect the port layout and timings? I cannot imagine them stepping too far off the already proven path but who knows. I might suspect tire slip with those dyno numbers but usually torque will go up somewhere. I would be straight pissed with those numbers on a 421... Hell, our 421 stock cylinder stuff will spank that hard! huh.

Can you post a pic of your piston? I also did not see your list of mods. If you are running stock porting, 300 certainly should not be melting pistons. twice on the left as well leads me to some other ideas. You need to do some careful testing when it runs again to ensure things are right. plug color, ignition, jetting etc. Also need to make very sure the brass washer is under your main jets. That will cause things to go lean. You many also have a severe carb balance issue that is leaning that cylinder out at WFO. Mull Engineering

We were discussing making some small changes to our water pump gears to work with the larger PTO gears without having to cut them up. Problem is there is a few different ratios being used and we will have to watch our gear structure so we do not have any adverse affects. I doubt it will be an issue but we should probably do some FEA of a new design and see how it looks structurally. Going to have to get some gear diameters so I can determine how much we can trim. Brandon

Just curious. I do not have plans to make any but wondering how many actually run the larger primary straight cuts? Not just the replacement straights. Thanks

The "up" is stamped into the gasket, not printed. It does not exactly jump out at you. However, they can be flopped without any major concern. I would not pull one just to flip it.

Vitos does not roll their own. They have Some wiseco and some other lines. Check the bottom of the wrist pin boss for a "W" or post a pic and I can likely help.

You better stop there and test fit the pistons. I have seen this myself where the shop does not take the time to test fit. I got one back with .005" taper!! Without rings, the pistons should just fall through the hole. If they do not, do NOT run them. Also, as mentioned above, make sure your rings are in their home about the locate pin in the ring lands. IMO, if the ring end gap is way off, there is something wrong with the bore, not the rings. Wiseco has been pretty accurate on rings for some time. Mull Engineering

http://mullengineering.com/rt/support.htm I recommend you read a tech article we did a while back on comp testing. In short, do NOT put all your trust in a comp test. I have seen them literally ready to grenade, all while showing perfect compression. If you beat on it for a year, spend a few bucks on gaskets at the least and open it to see how it is wearing. If nothing else, it will give a gauge as to how long the motor will last. You really need to mic the cylinders and pistons as well as inspect the rings for proper wear. Piece of mind is a great thing! Mull Engineering

10Mil stock cylinder setups are not ideal because of major port timing issues. I highly recommend a new cylinder setup if you want to go to 10mil. You will have to raise the barrels and the ports will already be wrong before lifting them. 10mil stockers were the craze 10 years ago before aftermarket cylinders took over. I would not recommend any more than 7mil on a stock cylinder. Mull Engineering

I would say if you only lost a couple threads, you may be just fine to use as is. Run your studs in and bolt a head up and torque it and see where you are. If they pull out, there is an issue. Usually, there is 25-25 threads in there which is more than enough to handle the axial forces in question. OTOH, I have done plenty of Helis. Making parts right now that require 1200 of them! I would recommend a DIY project. Nice to have on hand in a pinch and know how to use them.

Head, carbs, fuel lines, timing. Those are your main areas of concentration. I am not sure where you are in your state of tune but as of lately, I have been discouraging people of switching to alky unless they have plenty of tuning skills. Alky can be finicky, bitchy, and a real PITA for some users. Most that use it are either running on the strip and their bike is drained down at the end of the day, or those who have plenty of experience with it. Personally,all my bikes run it but it can really suck dune riding when you have to be concerned with getting to fuel before you run out. E85 - I have yet the see a setup that I am truly happy with. Too much variance at the pump to keep the bike dialed in. Brandon

I think you are on the right track. check grounds and "certainly" test for continuity from the engine to the frame. That is a common issue. The coil is very rigid and rare to fail. However, the termination points on the coil that plug into the wires commonly have issues. I recommend unclipping the wires from the coil, cutting a small length off the wires, and reterminating. Also, check those plug caps. They go bad and cost people all sorts of coin in new electronics they do not need. Brandon Mull Engineering

Usually that setup will dial in with a 290-300 with your elevation and temp. I think we have a different prospective on "falling flat". Rich conditions tend to smoke and blubber and lean conditions sound like they are getting there but your butt says otherwise... Let those plugs talk to you... I think you will be happy in the 290 range. I certainly do not think you need to go richer. I usually dial in T5s here on a 280 main and about 300 with pods and 310 with our intake kit.. Brandon

Usually is a symptom of lean jetting, tall gearing, or timing too far advanced. Brandon

Keep in mind too that the cases will wear before the shaft will (on the shaft OD). The cases are Al and the shaft is hardened steel. Other areas of wear are the moving components (claw) on the shift shaft. Mull Engineering

I would be more than pissed with a deal like that. That is just an out right "don't give a shit". B

Are you using a gasket on the pump cover? Even if, there are some wide mfg tolerances in that area from Yamaha so some do rub a bit but excessive rubbing can be an issue. You can help it by grinding off a bit of the tip on the drive shaft that goes into the center case. That typically bottoms out and pushes the impeller outward.

Are you using a gasket on the pump cover? Even if, there are some wide mfg tolerances in that area from Yamaha so some do rub a bit but excessive rubbing can be an issue. You can help it by grinding off a bit of the tip on the drive shaft that goes into the center case. That typically bottoms out and pushes the impeller outward.

Secondary must be tested lead to lead. Remember to add the wire resistance if you test with them in the circuit. I will bet your coil is fine. They rarely actually fail but the lead terminations do need fixed up every now and again... If your engine runs, your secondary sure is not O/L Did you put your leads together and deduct that resistance to your measurement? Mull Engineering

Because there is not other drain for them other than the drain bolt in the side of each cyl. Most people just remove them and flip them over to drain the jackets.

As I said, I am thinking skirt failure from cause of port chamfer or bore size but that is merely a guess not even looking at the engine right now.. With that much Al flying around, you may very well have hurt the crank. Just have to take it apart and go from there. Building without measuring is a recipe for disaster. Important to know what you have...

There is a laundry list of reasons why a piston can fail but it sure looks like yours was due to improper port chamfer or hole clearance. If the skirts are all busted up, which I suspect, you need to carefully mic the bores and have a pro inspect the chamfers. BIG cause of unknown engine failures. All that piston crown damage is from foreign objects bouncing around in the combustion chamber, Something let go to get the big chunks up there. Mull Engineering

Unless there is a stamp on the stator that says "X" number of winds and with what, it is a best guess as to what you have. The best you can do is put one into an over drive condition and measure the output. The voltage will taper off and from that you can estimate the "rated" output. The generator in the Banshee is a permanent magnet type and the output will be determined by the number of turns in each coil pole and the magnetic flux or field created. Because of the permanent magnet system, the stronger the magnets in the flywheel, the more excitation you will have from the fielding coils. Resistance tests can lie to you because for instance a larger diameter coil wire can be used along with more turns to test out at the same resistance yet have much more output once in operation. I would recommend just doing some testing. I used to do this when I was 15yo. Add 50w, 100w, 150w, etc to determine how much the system can handle. I found the old 250Rs had a powerhouse from the OEM. I think around 120watts. You cannot overdrive a system like this.. Mull Engineering

I am in total agreement with above but not sure if the difference in bore sizing would be causing such a drop in comp. I wonder if the holes are egged. Round rings in an oval hole never works out too good. However, the old rings would have worn to this egg shape. I would certainly want to look closely at the squish clearance. Probably a good idea to pull the topend and get a more thorough QA inspection. As mentioned above, skirts don't just break for no reason. Also keep in mind that that gauge is NOT a bible but merely a tool. Tools can fail. Mull Engineering

You really need to not only inspect your clutch plates, but the basket and inner hub. Grooving of the basket and hub can cause the plates to stick and not move correctly thus does not unload the transmission correctly. If you do not unload the trans, it does not want to shift. Signs of clutch problems commonly show up creeping forward when the bike is running, in gear, and the clutch pulled or if engagement is rough or "all or nothing". Warped drive plates can also cause excessive drag. They can be inspected on a known flat plate and feeler gage for warping. As Jeff mentioned, shifting problems are often caused by the clutch. Mull Engineering