AZ Erik Posted September 18, 2006 Report Share Posted September 18, 2006 (edited) OK so I got this Banshee right? Most of us do. Ofcorse I buy the thing as said by the person selling it. It has a nearly new top end....4 mill, 80 hp... yada ya. Well After sitting in my garage and never getting the chance to ride it last year I finally got around to putting the compression tester on it to figure out if I can run pump gas or not. 107psi, 109psi... teriffic. Off comes the top end. It has Blaster p1 pistons (Weisco) stock 66 mm bore. Hot Rods 4 mil crank. Dune porting on the jugs and a cool head with 22 cc domes milled. Now the milling looks pretty serious to me, Like a 1/4 inch and possibly a crappy squish, this I'm not sure about. I was told that this motor runs at 165 psi. I'm located at 3800 ft above sea level. The bike came from PHX and that's where it was supposedly running 165psi. It also supposedly pulled off 80+ on a dyno. There was some pretty hard wear on the piston walls and some in the jugs but nothing that really stood out to me as what would drop the compression 60 psi. So I ordered a set of .010 over WSM pistons and will drop the jugs off for a .010 over and cleaning before putting it back together. My worry is that with the 22 CC domes I could only be sitting at about 112 psi and will have spent money for no reason other than a fresher top end. If this is the case the top end was ok? What do most people with 4 mills run for domes? Do most have 22 cc's cut? (If not what size did you get cut) Am I right in thinking that a 22 cc dome, cut will still be a 22 cc dome even with a stoker or does piston height change the dome cc? I can see where the burn is on the domes and it's about 1/2 way into the cut so I would guess that the piston height is correct. All of my riding is done in Glamis or Gordon Wells so that's where I'll be needing to plan for my pressures. I'm not all that happy right now as I've had all ov about 15 minutes of seat time on this one and dropped $300 unplanned change today, I'm just trying to find out if I need to add domes to that list as well. Edited September 18, 2006 by AZ Erik Quote Link to comment Share on other sites More sharing options...
Bansh-eman Posted September 18, 2006 Report Share Posted September 18, 2006 I finally got around to putting the compression tester on it to figure out if I can run pump gas or not. 107psi, 109psi... teriffic. well 107 and 109 sound way low... my 4mil with 22cc domes is getting 145 and 141..... It has Blaster p1 pistons (Weisco) stock 66 mm bore. 66mm isnt stoke, stock bore is 64mm What do most people with 4 mills run for domes?Do most have 22 cc's cut? (If not what size did you get cut) Am I right in thinking that a 22 cc dome, cut will still be a 22 cc dome even with a stoker or does piston height change the dome cc? i have 4mil and run 22 domes... runs fine, what type of riding you do? if your not racig alot then id stick with the 22's if you go higher then your going to have to run higher octane. you should be able to get away with 104 octane maybe a little lower ... now that assuming you get your compressio backup like it should be. Quote Link to comment Share on other sites More sharing options...
AZ Erik Posted September 18, 2006 Author Report Share Posted September 18, 2006 The pistons I bought are: New WSM .010 over, 66.25 mm piston kit for Yamaha YFS 200 Blaster, 1988-2004 models. I did mic. out the cyl before buying them. I dune ride only and I'm big (like 300 #'s big) so I need the grunt. I kind of figured I'd be sitting around 145 to 150 for the psi. I'm just hoping that the top end was way older than he said (I was told it had like 3 hours on it) and that's all it is. I don't know what the stroke is on this motor but it's got the h129 crank, not sure about the rods, is there a number on the back side of them? I thought 155+ PSI was the cut off for having to use a 50/50 mix of race gas? Quote Link to comment Share on other sites More sharing options...
AZ Erik Posted October 3, 2006 Author Report Share Posted October 3, 2006 Well the rebuild was a waste of time and money. After the rebuild I ended up with a whole 100 psi (after 3 minutes of run time on the motor) I've sent Noss a PM. What's the chances that if the squish is cut wrong or too deep that would yeild my 105 psi on 22 cc domes? I have no problem putting different domes on it but I need them cut for the stroke and the bore. 4 mill plus the blaster pistons. I;ve got to find out what's wrong with this thing as my old 'stock 2001' with port work and the same pipe and carb set up kills this bike currently. I wouldn't think any one would spec out a motor at 105 or so psi unless that's the trick to getting sick amounts of top end, I don't know, can someone who does chime in? Quote Link to comment Share on other sites More sharing options...
trex banshee Posted October 3, 2006 Report Share Posted October 3, 2006 (edited) the H129 crank i believe is the 4 mill stroker with 5mm long rods. If i were you check your squish clearence. To do this just get a soft peice of solder and put it in the cylinder so when you turn the engine over by hand it will smash the solder, then mic the smashed part of the solder. I was told that they run best between .032 and .048 thousandths. Lots of builders have their own preference though. Just check this so we can get a good ballpark number. Edited October 3, 2006 by trex banshee Quote Link to comment Share on other sites More sharing options...
Capone Posted October 4, 2006 Report Share Posted October 4, 2006 (edited) Well the rebuild was a waste of time and money. After the rebuild I ended up with a whole 100 psi (after 3 minutes of run time on the motor) I've sent Noss a PM. What's the chances that if the squish is cut wrong or too deep that would yeild my 105 psi on 22 cc domes? I have no problem putting different domes on it but I need them cut for the stroke and the bore. 4 mill plus the blaster pistons. I;ve got to find out what's wrong with this thing as my old 'stock 2001' with port work and the same pipe and carb set up kills this bike currently. I wouldn't think any one would spec out a motor at 105 or so psi unless that's the trick to getting sick amounts of top end, I don't know, can someone who does chime in? Well since no one has addressed this yet, you said you're @ almost 4000' elevation, thats perfect on for your compression. Since you're located so high above sea level, don't be scared to take your domes smaller. It isn't the dome size that makes you have to run race fuel, its the compression. And even at an 18cc dome your only at ~165lbs of compression at your elevation. 165 was always my mark for using a higher octane fuel. Throw a smaller dome in your head, 18 or 19cc. What they're talking about with the solder is the stuff that comes on a roll, use the thicker material, and unroll it about 6-7 inches but leave attached to the roll... stick this down in your spark plug hole and kick the bike over, pull the solder out and measure its thickness on smallest smashed area. This is your squish. Since you're saying you need your domes cut, I take it you're not running a spacer plate? Why don't you give dave a call and actually talk to him, alot of the builders on this site are pretty busy to check their messages and emails daily. As for me... I'd suggest smaller(19cc) domes, and advance your timing +4 with an ajustable timing plate, use either full or a mix of race fuel afterwards. I definately think you'll like the turnout. Hope this helped a little. Edited October 4, 2006 by Capone Quote Link to comment Share on other sites More sharing options...
badassbanshee479 Posted October 4, 2006 Report Share Posted October 4, 2006 3800 ft and 22cc domes equals low compression, I would drop down to 19 or 20 cc domes and try that if your compression still is not up where you like it I would be checking for air leaks and or leaking head gaskets. my 421 cub only has 170psi at 900ft above see level with 18cc domes. Quote Link to comment Share on other sites More sharing options...
AZ Erik Posted October 4, 2006 Author Report Share Posted October 4, 2006 When I got the bike it was running straight vp. With the timing advanced 8 degrees. It had instant grunt but fell on it's ass in the mid to upper RPM (this is on the street) I was banging gears as fast as possible and it just kept going but it never did wrap out. It has a timing plate (+/_ 10) I backed it down to 5 degrees when I put the lightened flywheel on, before this build. I rode it with that wheel on it and it didn't feel much different. It was lacking, that's for sure. I have a feeling this squish is really deep. I have a picture of the dome out of the bike, I'll post that up tonight. I need to get the solder to check it. I seriously doubt it's anywhere near the .032 to .048 as there is a defining line in the dome of where it's 'burnt' from combustion and it's half the squish depth. It looks to me more like the thickness of a penny Kd's is saying a 19 or 18 cc off the shelf dome would be fine, Noss wants to cut one, RDZ isn't answering, I can't really think of other builders besides Trinity and calling Steve Abbott Quote Link to comment Share on other sites More sharing options...
Ducman Posted October 4, 2006 Report Share Posted October 4, 2006 I didn't read all of the above posts, but a couple things I can say for sure. Check your squish, you can loose a lot of compression if the squish is too much. .030" to .040" is typically ideal. Also off the shelf domes that are cut for banshee pistons are going to give up compression when used with blaster pistons because blaster pistons have less of a dome, flatter dome, and need a flatter squish angle. When you measure the squish the solder will only be smashed at the very edge of the cylinder and will get thicker quickly as you go towards the middle of the cyliinder. Also if you have a motor capable of 80hp then the exhaust port is going to be pretty high and that will also give you low static compression. My best advice is measure the squish and send the domes to Noss. He will then be able to cut some new domes that will have a perfect squish angle and clearance and dome size to maximise the type of fuel you want to run. I have had to do this on two different motors and both times Noss cut some custom domes for me that came out perfect. Also check to make sure the air gap on the flywheel timing pick up is at .020", your description of poor performance sounds similar to when I had the timing pick up air gap too large. Quote Link to comment Share on other sites More sharing options...
AZ Erik Posted October 4, 2006 Author Report Share Posted October 4, 2006 (edited) RDZ called back. I'll be checking the squish tonight or friday. The air gap on the pick up sounds like it could be a cause as I had moved the timing plate and also changed the fylwheel. It looks to be pretty big to me. I'll be ripping this poor thing appart again shortly. I thank all of you for your help. Any idea about where I should have my compression to keep my ride good for shooting bowls? Edited October 4, 2006 by AZ Erik Quote Link to comment Share on other sites More sharing options...
dajogejr Posted October 5, 2006 Report Share Posted October 5, 2006 Any idea about where I should have my compression to keep my ride good? Depends...do you want to run race gas or not? I'd run 18cc or 19cc domes...and you could probably still get away with pump/race mixed. You can either run less compression and more timing, or vice versa. As told to me by my friend...less compression is easier on the bottom end... I'd check with Dave Noss directly to see what he recommends the squish be set at....and as said, all builders have preferences. Quoting a friend again, smaller bore pistons, such as you have, don't need as tight of a squish, when you start getting into bigger bores, say....72mm or bigger, you need the tighter squish. Quote Link to comment Share on other sites More sharing options...
ohiobanshee Posted October 5, 2006 Report Share Posted October 5, 2006 A blaster piston on a 5mm longrod crank will be .040 or 1mm down in the bore a tdc. If you dont have a spacer plate it might be a longrod crank not a 4mm stroker. A piston .040 down will have real low cranking compresson. Quote Link to comment Share on other sites More sharing options...
AZ Erik Posted October 5, 2006 Author Report Share Posted October 5, 2006 Measuring from the edge of the piston? Because I know the very top of these pistions are way above the deck height. I can get a measurment when I ccrack it open tomorrow night. These pistons come way up out of the bore in the middle, not sure around the squish. I'll be having Noss or RDZ cut the domes so either way I'll be sending my domes out to them. I have been dragging ass thinking I had a month before Halloween weekend, crap it's 10-5 already and we're going out the weekend before halloween, I need to get moving :beer: Quote Link to comment Share on other sites More sharing options...
RILS Posted October 6, 2006 Report Share Posted October 6, 2006 Measuring from the edge of the piston? Because I know the very top of these pistions are way above the deck height. I can get a measurment when I ccrack it open tomorrow night. These pistons come way up out of the bore in the middle, not sure around the squish. I'll be having Noss or RDZ cut the domes so either way I'll be sending my domes out to them. I have been dragging ass thinking I had a month before Halloween weekend, crap it's 10-5 already and we're going out the weekend before halloween, I need to get moving :beer: Why are you even messing with blaster pistons.If your running a 4 mill with 115rods then you can run a 80 over 795 series piston or if your running 110 rods then just run standard pistons. Either way your going to have to have the domes cut and david noss can do it or many others but i agree with your elevation is the problem you said in a earlier post you were running vp so why dont you just slap some 18s or 19s in there hell at 4000ft maybe 17s and get some lowend. In my experince i like to run about 180psi im at 900ft and run 18s at 180 on my 4mill cub and it will snatch your arms off at the twitch of a thumb, but ive ran this 175-190 range on everthing from stk stroke stk port to drag ported stk cylinder with very good luck. Quote Link to comment Share on other sites More sharing options...
AZ Erik Posted October 7, 2006 Author Report Share Posted October 7, 2006 (edited) Because whoever built the motor used blaster pistons. I simply used them again incase they had to be used and I had 1 week to get pistons and assemble it for a dune trip (I cut it within 12 hours of us leaving. But tonight I finally got my squish measurements, kinda. If' I'm doing this right it's completely forked. About .130 for the squish. This was done via 4 pieces of .063 solder twisted so it's not really even close to an accurate reading. But it's the only way I was able to get a measurement. Check the pics: Piece of .063 solder Cyl at tdc The ring groove you can barely make out How I finally got some of the solder to be smashed, but just barely I cc'd the domes at 24.5cc's but I'm sending them to Noss to double check. He'll be cutting me some domes next week. Then I'll do the clutch and check that ign pick up as well. Edited October 7, 2006 by AZ Erik Quote Link to comment Share on other sites More sharing options...
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