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QUOTE (twostroke @ May 1 2009, 05:29 PM) index.php?act=findpost&pid=40771Can some one tell me if you can run a stock head on a big bore. I need more compression.


Yes you can but you will need to send it out to get it CC'd for what compression you want and also have it cut for the bore. I believe a stock head you can only run up to 67mm pistons but don't quote me on that
 

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Discussion Starter · #3 ·
QUOTE (1996dragshee @ May 1 2009, 05:02 PM) index.php?act=findpost&pid=40781Yes you can but you will need to send it out to get it CC'd for what compression you want and also have it cut for the bore. I believe a stock head you can only run up to 67mm pistons but don't quote me on that
thanks for the info. do you know what cc's it should be. The cylinder bore is 68mm. The last machinist that done the cylinders and cut the head may have messed it up. We only have 100# of compression.
 

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Discussion Starter · #8 ·
can somebody tell me what domes are used in a cool head? What brand do most use ? I am new to the banshee's and trying to get my motor to have more compression. I understand what the squish of the chamber is but do not know what the #'s mean. Can anybody helpme? The motor is a 68mm stock stroke long rod on 92 octane gas.
 

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Do you already have a coolhead? Most coolheads use the same dome (Prodesign, NOSS are the most popular). But a few others have their own design. What exactly are you confused/questioning about?
 

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He might mean the numbers like 22cc, 20cc, 19cc+2 etc. The lower the number the more compression it has. for example i have 19+2. The +2 is for my stroker set up. Im still on pump gas(149.5psi) due to my port job though but i am on the limit. If i was go to go 18cc or lower id have to mix some race gas or go strait race gas. As for squish, i dont understand that. I never did a squish test.
 

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Discussion Starter · #11 ·
QUOTE (RagunCajun @ May 3 2009, 08:19 AM) index.php?act=findpost&pid=40895He might mean the numbers like 22cc, 20cc, 19cc+2 etc. The lower the number the more compression it has. for example i have 19+2. The +2 is for my stroker set up. Im still on pump gas(149.5psi) due to my port job though but i am on the limit. If i was go to go 18cc or lower id have to mix some race gas or go strait race gas. As for squish, i dont understand that. I never did a squish test.
The bike shop that we used cut a stock head for a 68mm big bore and have always had low compreession. I would like to get it back up to where it should be at around 130 or so. I think he may have cut to much out of the chamber. I have not cc'd it yet but will do so tommorrow night. I will also check the squish and see if that is the problem. Thanks for your help. May also try to get a cool head and see if that raises the comp.
 

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A machine shop worth their salt should be able to get that chamber cut properly and get your compression up as well.
When you hear cc's, that means volume of the head.

In other words, if you were to put a spark plug in, fill the head with liquid to the very top without spilling over, it would hold that many cc's of liquid. As said, the less cc, the more cranking and static compression.

My advice is get a Chariot or Noss head and have domes cut for your application. They'll need to know what stroke the crank is, bore size (as said, 68mm) and the type of piston you are using (banshee and blaster are the most common types, but the dome angles are different)

PM backcountry on here. I get all my domes from him and have had great success with his work.
 

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ok since noone caught this. the long rod blaster set up sometimes ends up a lil low on the deck height you need to have a GOOD builder go over the WHOLE motor and figure out whats going on. there can be a few things going wrong here a quick squish check can enlighten us pretty quickly if the "shop" that did the head didnt ask for the deck height when you told him that set up you MIGHT ask them again. 100psi is CRAP a decked, cc'd head SHOULD be around at LEAST 150-165ish OR more depending on what type of fuel you are wanting to run the shop did ask that right??
 

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Discussion Starter · #15 ·
QUOTE (camatv @ May 4 2009, 06:36 PM) index.php?act=findpost&pid=41218ok since noone caught this. the long rod blaster set up sometimes ends up a lil low on the deck height you need to have a GOOD builder go over the WHOLE motor and figure out whats going on. there can be a few things going wrong here a quick squish check can enlighten us pretty quickly if the "shop" that did the head didnt ask for the deck height when you told him that set up you MIGHT ask them again. 100psi is CRAP a decked, cc'd head SHOULD be around at LEAST 150-165ish OR more depending on what type of fuel you are wanting to run the shop did ask that right??
thanks for the info. you are right about the pistons being a little bit low. They do not reach all the way to the top. Do you have any suggetions as how to correct the problem?
 

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You have to measure deck height, in your case, negative deck height.
Bring the piston to TDC, measure at the very, very edge of the bore how far down in the cylinder the piston is from the edge of the deck.
Any builder should be able to cut you some domes based on that number, unless it's WAY out of whack, then you might have to work towards decking the cylinders, different base gaskets, etc, assuming the pistons are the correct ones for your setup.
 

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the banshee stroker pistons are taller than the blaster pistons.. i wouldnt chop up the cylinders you can also use a thinner base gasket. or seal the cylinders to the top case with NO base gasket. you may change your mind later and use different crank piston set up and then you will be mad that your cylinders are all decked down and your pistons are sticking out the top..

i did a couple of 370 long rods back in the days for mx racing.. i dont think the long rod really helps at all. BUT it lets you run the larger bore pistons that wen't available back then..
 
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