Hey, ive used the search tool but couldnt find any info specific enough, maybe i missed something. But I wanted to know... I got a Polini series 2 case, a BZM silver race crank, and a BZM 6 port head w/c, but ive never messed with polini or BZM. I have built other small two stroke engines in the past, and currently work as a machinist, so im familiar with a wrench and precision measuring tools. I wanted to know if there is a specific "squish" setting I need, or single gasket I should use? Or maybe someone could just recommend a good all around setting. I can give you more information if you need, but if theres any input you could give me, thatd be great! Thanks!
Also I bought a set of Blackwidow reeds, and now im reading that theyre no bueno... is this true?
.5mm is what we are after, if you choose to lower the whole cylinder by changing base gaskets you will also change the port timing of the motor, this matters most for the "replica" motors because they come with a 1mm+ squish all the time and need to be lowered so much that the cylinder moves enough to mess with timing, what we do with the replica's is to mill/lathe down the top of the cylinder, this way we get a lower squish and keep the port timing where it's at. I doubt you need to do anything other than change the head insert or gasket to get that .5mm, I'd also bet you're probably really close to .5mm anyhow, because you are using QUALITY parts.
black widow reeds are fine, they are not much if any better than normal Carbon fiber or fiberglass, but I wouldn't call them crap.
Quote:
Originally Posted by donkeypunch85
Hey, ive used the search tool but couldnt find any info specific enough, maybe i missed something. But I wanted to know... I got a Polini series 2 case, a BZM silver race crank, and a BZM 6 port head w/c, but ive never messed with polini or BZM. I have built other small two stroke engines in the past, and currently work as a machinist, so im familiar with a wrench and precision measuring tools. I wanted to know if there is a specific "squish" setting I need, or single gasket I should use? Or maybe someone could just recommend a good all around setting. I can give you more information if you need, but if theres any input you could give me, thatd be great! Thanks!
Also I bought a set of Blackwidow reeds, and now im reading that theyre no bueno... is this true?
hey thanks for the advice! So if i just buy the full gasket set from say, Midsouthminimoto for $16, all i have to worry about is the little head insert basically?
One last thing. As i was looking on midsouth yesterday for gaskets, i came across a Bi Zeta Silver Race Crank, and it said it was for the 40cc, but the guy i bought all this stuff from told me it was 50cc. And I know him and his son race pro in Canada, and they know their stuff (as far as i can tell). Is there a silver 50cc crank out there? or should i get the red race crank and sell the silver? I want a 50cc when its all said and done.
You wont have to worry about the insert. You will just want to use the thinnest base gasket that comes in that set of gaskets. That is if your looking at the gasket kit that has 3 or 4 base gasket in it. But than again if you got that motor from someone who races pro I would think that motor would already be setup. Have you checked the squish yourself? I would think that it would be set somewhere from .47 to .43 or even all the way down to .3mm. No there isn't a 50cc crank it would use the same crank no matter if it is 40cc or 50cc as they have the same stroke. Although you can get a crank that has a little longer stroke. Which you would raise the cylinder up to set the squish. I believe the BZM 6-port is a 50cc cylinder. I would check the squish before ordering anything and if the squish is set already I would run it as it is.
Check the squish by taking off the head run the piston to the top while holding the cylinder so it doesn't raise up. Take a piece of 1mm solder and cut it almost as long as the bore but short enough so it doesn't touch the cylinder wall. Lay the solder across the wrist pin and take a small piece of tape and tape it in the center to keep it in place. Drop the piston to the bottom and replace the head. Put a socket on the flywheel bolt and turn the motor so it hits the solder a couple times. Than pull it apart and measure the smashed ends of the solder.
Last edited by StrayDawg63 : 04-02-2009 at 10:56 AM.
why not just bend a piece of solder and stick it through the spark plug hole and squish it. Much easier
For a 2-piece kit you get a much more accurate measurement of the squish. There is a .4 to .6 difference in measuring with the L-shaped piece of solder and running a piece all the way across the piston. Theres just to much play in the wrist pin bearing to get a good accurate measurement.
Hey StrayDawg, What do you think about something shaped like this?
the squish section would be closer to straight while being inserted, and then bend back into shape once through the spark plug hole, the top bend would be like a handle.
just a thought I had while trying to be different..
Sure if you can get it through the sparkplug hole and keep it over the wrist pin.
Just so you know when I tested both ways it was using a Polini 50cc motor not a rep motor.
The silver insert cranks are designed so the engine does not exceed 40cc............class regs. The gold cranks bump cc upto a full 50cc and increase power slightly........you can run either crank in either 40 or 50cc but if you use the gold crank with a 40cc barrel the engine capacity exceeds 40cc.
You must measure the squish clearance and then add or remove gaskets to achieve what you require. No less than .4mm!
You wont have to worry about the insert. You will just want to use the thinnest base gasket that comes in that set of gaskets. That is if your looking at the gasket kit that has 3 or 4 base gasket in it. But than again if you got that motor from someone who races pro I would think that motor would already be setup. Have you checked the squish yourself? I would think that it would be set somewhere from .47 to .43 or even all the way down to .3mm. No there isn't a 50cc crank it would use the same crank no matter if it is 40cc or 50cc as they have the same stroke. Although you can get a crank that has a little longer stroke. Which you would raise the cylinder up to set the squish. I believe the BZM 6-port is a 50cc cylinder. I would check the squish before ordering anything and if the squish is set already I would run it as it is.
Check the squish by taking off the head run the piston to the top while holding the cylinder so it doesn't raise up. Take a piece of 1mm solder and cut it almost as long as the bore but short enough so it doesn't touch the cylinder wall. Lay the solder across the wrist pin and take a small piece of tape and tape it in the center to keep it in place. Drop the piston to the bottom and replace the head. Put a socket on the flywheel bolt and turn the motor so it hits the solder a couple times. Than pull it apart and measure the smashed ends of the solder.
Hey thanks for the reply, sorry im slacking on getting back to you. I bought this engine in pieces, so it did not come with any set squish. The guy i bought it from sent me four gaskets for the base of the head, ranging from .003" up to .040" I believe that was the biggest one. I finally got around to toying with everything yesterday. I used the thinnest gasket when i put it together, but as i got to the end, i realised he didnt send me any gaskets (or does it use O Rings?) for the head insert. So as expected the piston was actually touching at TDC. I guess the next thing to do is order seals for that.
I dont have the internet at home. so as i laid out the parts yesterday i realized i didnt know which side the tapered end of the crank went on. I "guessed" the tapered end was for the clutch, since ive seen a lot of my goped engines use that end for the clutch, am i wrong?
The silver insert cranks are designed so the engine does not exceed 40cc............class regs. The gold cranks bump cc upto a full 50cc and increase power slightly........you can run either crank in either 40 or 50cc but if you use the gold crank with a 40cc barrel the engine capacity exceeds 40cc.
You must measure the squish clearance and then add or remove gaskets to achieve what you require. No less than .4mm!
So what youre saying is if im looking for 50cc, im going to have to buy a different crank huh? What would you recommend? Im looking for something I could run everyday if I like, just for fun, or take to the races and still keep up with the rest. Did i mention this engine is being retrofitted to a GoPed GoQuad?
If you're on a 50cc barrel then the gold 39.8mm crank is the best performance option...........there isnt that much in it though so unless you're a serious racer the silver 39.2mm crank might be the cheaper option. If you use the gold crank in the 40cc engine the cc = 40.3cc (thereabouts)............not legal in some 40cc classes.
If you're on a 50cc barrel then the gold 39.8mm crank is the best performance option...........there isnt that much in it though so unless you're a serious racer the silver 39.2mm crank might be the cheaper option. If you use the gold crank in the 40cc engine the cc = 40.3cc (thereabouts)............not legal in some 40cc classes.
everyone keeps mentioning the "barrel". are you talking about the piston sleeve, intake, what? Sorry if thats a dumb question. Not worried about classes or anything. Theyre letting 60cc zenoahs in the race so the more cc's i can get the better. Thats why i want the 50cc setup. All the cranks are the same price. So thats not really an issue. What will pull the most power out of this i guess is my goal?
