blowit

I just felt compelled to hang shit I guess. :biggrin: Sorry about that. Try just ohms and that should get you what you need. It is important to test the coil resistance if there is not voltage output. Some voltage regulators can short to ground and ground all power to the chassis. A resistance check will determine what is really going on most of the time. Brandon

We have only seen a few cracked domes in the shop here and curious, to those who have seen them, can you explain either exactly where the cracks are showing up or offer a pic? Motor setup at the time of the failure would be helpful too. Just trying to do some R&D on a combustion process and need to confirm the origins of this failure mode. Thanks Brandon

Without looking at the bike, I am going to lean on trans failure. The Banshee has 1 gear that we have fought on several bikes that likes to fail. I want to say second gear drive but can't remember. Anyway, it welds to the drive shaft and you need to remove the chain to roll it. If you pull the clutch and chain and still cannot spin the axle shafts of the trans, open it. The superseding part for that shaft now has an anti-friction coating on the ID to reduce these problems. We have also seen a shift fork shaft come out and that will give you some headaches. Brandon

Guess I read that differently. Would like to see a pic of this anyway. Just does not explain the high comp and that is what I am wondering about. B

Tru dat. I am interested what is going on. Rippen, I might lean towards piston replacement if he indicated visible damage with the pistons but indicates they look perfect as I read. I would agree though, sometimes piece of mind is a good thing. Don't know how many motors we have done where guys felt it is better safe than sorry and we catch a crack in a skirt that would have lasted another hour before failure. We actually had one pop while the customer was demonstrating it's sickness. I heard it and told him to shut it off and it locked just then. I think we were able to save the crank on that one though. :biggrin:

What are DC Ohms?

207 is more than we would recommend but I do not think I would replace pistons just because the motor has run with that compression. We have several out there at 190psi at 1000ft, +4*, and they are just fine. I will agree though, you get some shit fuel, you could get some detonation. We have a couple small secrets to running higher compression without problems but most is just in proper tuning. Brandon

The first check I would make is dome displacement. We have seen the mis marked before. 154-207 is a huge difference. That would be about a 4-5cc difference in chamber displacement. The reeds can hold back cranking compression numbers (very rare) but they have no way to increase them. You can test the motor with them out. I really doubt I would tear that engine down till I knew what was going on. Make sure both pistons come up to true TDC where the outer top edge (timing edge) of the piston is flush with the top of the cylinder. YOu have something obviously off here. wrong piston, dome, huge amount of carbon, plug in pipe, etc. You are kind of proving my point to others though that a stock stroke banshee CAN hold more cranking compression than most people think. 207 on pump fuel, impressive but not disasterous. brandon

Looks like you are a new user and not trying to beat you up over your question. There is a ton of info on the site though and the search functions work good. I think I have personally touched on this stuff around 100 times by now. We port and build engines. I will say, as I do to most though, it really pays to be informed. Books and more books. Sounds more like you are not trying to be a port master but rather make something run a little better. Do some homework here and you should find what you need or report back with further questions. Brandon

To be honest with you, you may want to poke around the site a bit more for more info regarding measured ports vs what we are really looking at which is port open duration in degrees of rotation. Do plenty of research before you cut. Rod angle has a specific effect on duration that is not linear with relation to port height. Brandon

I agree with most of what you said. Some people think we are nuts for running 190psi in a Banshee with 91oct fuel but if you calculate the CR, it tells a much different story. Other engine configurations are on a totally different playing field too. I could not totally agree with you on the effects of port timing or cams in a thumper. Those components relate directly to CRR and are very valid and realistic numbers that show how a bigger cam can actually cause your engine to run worse. Most 2-stroke tuners that know much will usually recommend a head mod with porting to "get back" compression loss from porting. One consideration with porting is cylinder fill efficiency. A better flowing head or cylinder will "fill" more efficiently and will cause a higher dynamic CR at higher rpm. It seems rather elementary to calculate the "ideal" CRs on paper but getting to real world dynamic CRs get very confusing because it starts to relate back to the variable of time for open/close of valves but where the tendencies and properties of air simply do not change with rpm. Example might be to blow air into of 2L bottle with a .25 hole drilled in the bottom. If air is applied slow, there is no pressure build but if you hit it, you can still explode the bottle, even with a leak in it. I guess where I was going with that was a table that relates CR to octane simply cannot be applied to all applications in a general fashion. Good for an ideal baseline though. Guess I could blab all day about these issues. :biggrin: Brandon

Depends a bunch on what you are trying to achieve. Brandon

One of the things to check is how you are calculating the value. We will use nothing but corrected compression ratio here or CCR. This is also how pretty much al metric OEMs calculate because it is much more relative to actual engine conditions. This will only assume the "trapped" volume and ignores total stroke for the calculation. For a base line, our OEM calculations are a 30mm exhaust port from zero deck, Piston comes to full TDC, 22cc head, and .8CC for the head gasket. That brings us to 6.35:1. This is pretty much why we can get away with a pretty small head chamber from stock and still run pump fuels. Detonation is NOT entirely based on CR. Other factors, especially in two strokes, are squish zone, squish velocity, clearance, dome lofted surface contour, etc. Many other factors will play in which is why engine testing is generally used for final determination of fuel requirements. I agree with above comments. Something in the calculation is high. I recommend just using the good old calculator and the mentioned burette to learn actual volume data. You did not say, but I assume you are using a billet head? Brandon

Technically, yes but delta between the two will be very minimal. Because you are changing effective rod angles, it will change the port timing some what but not really enough to notice. This has zero bearing on what the measured timing height is at TDC realizing that by adding 795 pistons and a +4.92mm rod comes out the same at TDC. Brandon

That setup is considered a "long rod" crank. A very common setup but usually coupled with a +4mm stroke as well. The long rod decreases rod angle for increased rpm ability and reliability but when combined with the +4mm stroke, puts you back to near stock specs. We have little doubt if Yamaha ever once ran the YFZ350 engine through R&D after it's debut in 1987, they would have added a similar setup. The LR, +4mm strokers run very nice. Brandon

Um, I am actually trying to think of an ATV I have "not" rode I think after working 15yrs in the industry, I am pretty well informed on suspension. I stated the obvious because it is, well, obvious that the banshee geometries are not right. Camber, bump steer, king pin angle, CG, all come to mind. I do not think you will find a pro racer that will tell a story of how the banshee geometry is "perfect". Keep in mind, ride quality and performance handling rarely go hand in hand. You may also be confusing suspension with that cushy stock seat the banshee has. :biggrin: I think by the time you put in all the hours to do a motor swap, you will be money ahead to get a different bike. If you are super stuck on the banshee, I would get nothing but a snow motor for that app. Twin 2-stroke Rotax auto trans. Anything else would be a waste of effort IMO.

I noticed a thread about Craigslist and got me thinking about how I have never found a way to search "all" of Craigslist for certain items. IS there a way to do this?

D, I guess we are in the opposite side of the court. We prefer electronics over mechanics because of the tunability. I really feel it is a toss up in using an override trans or our manual shift interupter. However, as mentioned, once you apply a powered shifter, the electronic side would have an advantage. Our site only shows a kit for the Banshee but we have built kits for several other bikes where overrides are not being cut so there is no option B on that side. The cons we see with our kit are that it does have to cut engine power for shifting and this could show up in a crag race but there are generally other, larger factors that would affect an ET. The cons we have seen on the override are just wear and tear as you "are" reducing the power handling of the trans but cutting it. We also have a few racers that refuse to run an override simple because of parts availability. Guess you can always have another trans sitting around too though. This is kind of why we feel our kit and an override are a near toss up but ours costs less and takes less effort to install. :biggrin: Regarding hard shifts. One thing people commonly miss in hard shifting transmissions is the ""clutch"". No unload, No shifty!! One trick we have done in the past is slightly bend the drive plates so they actually help disengage the clutch a bit once the pressure plate is off the plates. Clutch plates that stick together can cause enough drag on the trans to make the trans hard to shift. You also would need to take a HARD look at the inner and outer clutch hubs. Nearly every single hard shifting bike we have looked at, had grooves worn into the hubs. The banshee trans is deficient in many way from better designs. One of which is the lack of roller bearings on the shift drum, another is the shift detent mechanism (shift star), another is in the throw or travel from gear to gear. We started doing a mod on the shift drums about 3 yrs ago to add bearings to the shift cam and it helps a TON but we have not had much demand for it. We have fought hard shifting bikes for years so our shift box is what we saw as the simplest fix as well as a good performance add on. I think any Banshee over 75HP should be looking at ways to ensure the trans is going to work right. Nothing more irritating that having over 100HP and getting beat down by a 350 bike because you cannot shift.... Brandon

I will not knock your CDI as I am sure it works well but keep in mind our kit "includes" all custom designed brackets and switching so there is no R&D work. You may need to better define fine tuning with that CDI though. You will easily wrap 50 dollars in comparable switching to ours in the US. Production costs are another story. While I can vouch for quality in our shop, I cannot in others. We have to maintain certain minimums here and hard sometimes to compete with other parts of the world. We see more and more jobs going to other countries every day so I am sure it is just a matter of time before we have no choice but to have our components built elsewhere just to make a sale.

The 450s do not have that top gear as the Banshees do so your top speed will be pretty hot. In order to allow the engine to survive long pulls like that, you need to jet a bit fat, and run twice the amount of premix oil you do now. I would recommend 20:1 yamaR. Remember that as you add more oil, your fuel viscosity will increase and demand bigger jetting without starving the engine. Also, if your timing is way advanced, you might back that off a degree or two for good top end pull. Should not be much of a race!

many of these types of ignitions require use of a contact switch for operation of an ignition interrupt. To use a contactless sensor, the designer would have to designate a certain switch or type of switching to tune accordingly. MSD has had these for pro bikes for years. They work well for street aps but we were unable to get any reliability with a contact type switching. Keep in mind, the switch must repeat to the millisecond to work well for this application. The really nice thing with our contacless sensor is the ability to tune the shift point without messing with the switch itself. Basically adjusting the sensitivity of the switch and the trip circuit. Those guys do have some nice logic circuits though and do great work with PV controlling.

Just read most of the thread guys and thought I would offer some info on our shift kit. We designed the circuit to use a contactless sensor with full digital timing and switching. Contact type switching will inevitably fail due to wear and/or debris. We use unique concepts in the circuit to increase the accuracy and repeatability. We have designed in overload circuits to protect the kit as well as advanced timing pots on the box to allow fine tuning of shift points and timing with a small screw driver. We have also designed in an air or electric shift circuits but have not come up with a design we are happy with just yet for those options. We have about 100 of these kits in the market around the world but most are in dedicated race situations or on sponsored bikes. We have some in desert racing that are used solely for reduction of rider fatigue for long duration events. We do not currently have these kits on the market because we are still working to improve the installation simplicity for the general user. We also feel we may have over engineered the kit for the current market and pricing seems out of line for some. We refuse to send our production parts to china at this time to save a few bucks so we still have some things to work on. As far as function, this offers the same benefits as an override trans but without the cost and effort of install. There are some pros and cons to both but we prefer electrical options over mechanical ones due to tunability. Hope this helps answer a few questions.

Tires slipping on wheels. Put a mark on both and go ride it. If mark misaligns, there is your problem. Brandon

If you hit it with a hammer hard enough, it will split.... Get the cylinders off and discover the extent of your damage.

U wanna go to a banshee frame for "better" suspension???? The banshee honestly has about one of the worse suspension setups from the OEM. Might look at something lighter and better handling. Just a thought. You could also lose the trans all together in the banshee and put a CVT from Comet on it. Of course with the torque band of a banshee, it would be about all or nothing. B