my 01 banshee has a bearing going bad, i thought maybe tranny so i changed the oil cuz the anti freeze was leaking into it, put a new o ring on the connector hose, filled it up and got it warm. i was guna do comp test but it was late and i was ready to go home so im guna try to do it today. but now im pretty sure its one of the crank bearings going bad, when i put it together i put my 05 crank in it, which has o ring style bearings in the center, the 01 has pinned, are the o rings just to keep it from spinning and if they are stretched what can i do? and i bought a head from one of the mechanics at the dealer that his friend shaved, he doesnt remember how much was taken off, he thinks 2mm and said the comp would be around 200? and told me to advance the timing +5, is that going to be too high for the stock crank? or cause any problems? its always been reliable and i want it to stay that way. he also has a extra flywheel theyre guna cut down, he said they could take about half a pound off of it.
banshee question
- Thread starter Reaper26
- Start date
I believe all the model cranks are the same. they should all have pins to keep the outer race from rotating. if you run a lot of compression on a banshee stock crank, you can run the chance of twisting it. running high compression and advancing the timing that much will cause detonation even if you run high octane fuel. I would keep the timing stock and adjust accordingly. also, if you are running the stock head chamber with cut down cylinders, your squish band will be way out of whack and run the possibility of piston to cylinder contact.
i havent put the head on yet, im waiting to get the flywheel back, and its prob guna go on my 05 anyway. its the stock head, cylinders will be bored, im putting the tomey kit and my V-force reeds back on it, and my pro circuit pipes on the 01, ive got to have a crank for the 05 and was guna buy a welded one.
I would never bolt on a head that you don't know anything about. If you want to up the compression buy a pro design cool head with 21cc domes. Sounds like you need to check out the crank. I just ordered a hot rods crank for my shee because I am bumping up the compression. Stock unwelded cranks are a ticking time bomb especially when you bump up compression.
For stock cylinders, +5 timing is a bit too much. ATV guys TEND to have a misconception about ignition. Rich1 can tell you that advancing the ignition is going to allow for more top end power on a static ignition adjustment system (like the banshee).
If you have a head decked 2mm, that's going to be a drastic jump. The stock heads are around 23cc, so if you deck them 2mm, you'd get {stock cc - (bore x bore x amount decked x .0007854)} = 23 - 6.43 = 16.57cc. That's race gas territory all day long. You'd really be sitting close to 200 static IIRC. Problem is, if you drop the cc, you pack all the trapped gasses into a smaller area and require less ignition advance because the burn time requirement is reduced. In the end, you could actually keep the timing stock or retard it a tad and still have gobs of power down low and retain the stock top end.
I wouldn't run any lower than 118 octane. And definitely have that crank trued and welded. TBH, a decked head isn't going to perform that well once you go beyond 1mm shaved.
Best option: A Pro Design head with 21cc domes is a great option and you'll be sitting at around 150psi on good cylinders. Personally, I'd go with chariot performance because they look better, use Pro Design domes, are cheaper, and you can use the factory studs. Use that with about +2 timing and you'll be doing great.
For 50/50 race/pump, go with 19cc domes and +4 timing with a welded crank.
If you have a head decked 2mm, that's going to be a drastic jump. The stock heads are around 23cc, so if you deck them 2mm, you'd get {stock cc - (bore x bore x amount decked x .0007854)} = 23 - 6.43 = 16.57cc. That's race gas territory all day long. You'd really be sitting close to 200 static IIRC. Problem is, if you drop the cc, you pack all the trapped gasses into a smaller area and require less ignition advance because the burn time requirement is reduced. In the end, you could actually keep the timing stock or retard it a tad and still have gobs of power down low and retain the stock top end.
I wouldn't run any lower than 118 octane. And definitely have that crank trued and welded. TBH, a decked head isn't going to perform that well once you go beyond 1mm shaved.
Best option: A Pro Design head with 21cc domes is a great option and you'll be sitting at around 150psi on good cylinders. Personally, I'd go with chariot performance because they look better, use Pro Design domes, are cheaper, and you can use the factory studs. Use that with about +2 timing and you'll be doing great.
For 50/50 race/pump, go with 19cc domes and +4 timing with a welded crank.
I am in the process of doing the same thing. I will be installing a new welded hot rods stock stroke crank. I am undecided on dome size so I am going to order 20cc and 21cc domes. I will be playing around with timing too.
That was a very informative post tfaith
That was a very informative post tfaith
Thank you, good sir.
Ah, time for an engine theory write up, I guess. Starting with ignition...
With engine building, your ultimate goal should be to minimize pressure BTDC and maximize pressure for the maximum amount of time ATDC. No sh*t, huh?
It may seem elementary, but your air/fuel mixture (afm) takes time to reach maximum pressure after ignition. Your burn time requirement is determined by atomization, head shape and volume, fuel type, temperature, spark plug gap, and a few other things.
If you can gain a lot more pressure time (my term as far as I know) ATDC while only marginally increasing pressure BTDC, go for it. However, if you advance ignition too much, your increase in pressure BTDC will start to climb in proportion to the amount of increase seen ATDC with an equal amount of timing.
Let's say that your combustion pressure during burn peaks at (this number is hypothetical) 1000psi. If you can increase the time that your piston sees that pressure while only marginally increasing pressure BTDC, again, you'll see gains. Now if you never reach that pressure because your timing is too retarded, advancing is the key. Keep in mind that your piston is moving and that as your piston travels downward, you'll lose the potential for maximum pressure time.
This is why your advance exists. You want to have maximum pressure time on the piston. If you reach maximum pressure 10 degrees ATDC, and it takes (at the given, unidentified rpm) 20 degrees to complete combustion, your ignition is at 10d BTDC. If you advance the ignition so that your pressure time BTDC increases just below what is seen with the increase in pressure time ATDC, you'll gain power. Now if you increase the advance so much that you build peak pressure at TDC, you're going to be bad off. You can sacrifice some after so that you can lose pressure before (good), but only to a certain extent.
Take engines with a standalone Engine Management System (sEMS). 9/10, tuners start with 0 advance and increase it until they see a drop in performance. They may increase it 5 degrees across the board and see gains everywhere, so they increase it another 5. They may see a drop in power everywhere below 5k rpm, so they back it off by 2 below 5k, and add 2 above 5k. They repeat the process, advancing and retarding the ignition tables (most have 16 rpm areas that each have adjustable parameters for every aspect of fuel and ignition) until maximum power is realized across the board. 999/1000, the lower rpm ranges will require MUCH less advance than the upper rpm ranges because f burn time. Now if you switch to ethanol with a slower burn rate, the timing requirements increase proportionally.
In short, you don't want to advance too much. Even if you have the octane to support it, too much may not be good for power. If you add 5 degrees and see 2 more hp at peak and over rev, I bet you're going to be dropping power everywhere in the lower rpm ranges.
Now as for heads, you have to maintain your squish. Back years ago, increasing compression usually came with a reduction in squish, meaning that higher compression meant more power, always (or at least it did in everyone's minds back then). Though increasing compression does help, I dare someone to set up a banshee with higher compression and factory squish clearances; they'd be a little bit regretful. Sure, power will be had, but the ability of packing the gasses into a smaller area and getting better atomization is 90% of what's going on. Reducing the squish clearance is going to pay off quite a bit because you're reducing the amount of end gasses. This fights detonation and aids combustion a bit more.
Tapping on both ignition and head shape, when you advance the ignition too much, you increase the volume that is occupied by your afm when the plug fires. This increases burn time requirements because the flame has to travel further, allowing your end gasses to heat up, increasing your chances of detonation. Again, making too much ignition bad.
*side note here, that last "detonation" auto corrected to "sensation". Wouldn't the have been great?*
Now if your squish is too small, you can bang your piston on the head at high rpm. This is because rods stretch, pistons stretch, they swell with heat, bearings aren't perfect, etcetera. That's why you may have .030" of clearance, but have marks on your piston and dome when you tear them apart. Some builders build 4 strokes whose piston just taps the head at max rpm. Popular hot rodding did a write up on it some time back.
In the end, you want to maintain squish and have just the right amount of advance.
Again, 2mm off the head is too much if you ask me. Dome shape is compromised. 21cc domes and +2 timing would do great. 20cc domes and -1 timing would do great as well if you want more bottom end power and want to stay on pump gas. However, you don't want too much compression as you will lose over rev.
If that math is correct, 16.5cc is alky teritory. From what I have seen .030" is safe max on stock head.
A stock head can be re-chambered for more comp and better burn by Mull Engineering, $80-90.
A stock head can be re-chambered for more comp and better burn by Mull Engineering, $80-90.
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