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Need to increase my cpmpression 4mm stroker


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Ive put together what i hoped would be a mean dune quad but somethings missing from the picture.

 

What i have...

04 Banshee

4mm hotrod crank and rod

Wisco Blaster (573m0665) 66.5mm pistons

Cool head with 22cc banshee domes

2mm bore spacer

Kiene 34mm PWK carbs with pod filters, jetted with 185's

FMF fatty pipes

Carbon fibre reed valves

PTR port job

Standard ignition timing

 

I checked the compression and it only showed 83 and 87psi, then i checked the squish, i had 2.5mm.

I removed the base spacer and set up a squish using thicker gaskets to achieve a 1mm squish, this has now given me 100 and 103 psi.

The bike is alot more responsive down low since i corrected the port timing by lowering the bores back down.

 

 

I still need to get the compression up alot higher to make thins thing do what its meant to.

I intend to run 98octane at sea level.

 

I think my only option left is to change the CC's in the cool head.

 

Can anyone help with a CC selection to achieve a higher compression, suited to my set up and fuel?

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Im running the 573 pistons with domes that are cut for the 2mm extra on a four mil. Take out the spacer plate and get some domes cut.I run 17cc with 165 in each side.I run the wiseco gasket kit and don't have any problems. Call noss machine dave will hook you up and a site sponser.

http://www.nossmachine.com/

Another thing try a different tester some time thats whats wrong.

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Im running the 573 pistons with domes that are cut for the 2mm extra on a four mil. Take out the spacer plate and get some domes cut.I run 17cc with 165 in each side.I run the wiseco gasket kit and don't have any problems. Call noss machine dave will hook you up and a site sponser.

http://www.nossmachine.com/

Another thing try a different tester some time thats whats wrong.

 

 

Ive removed the spacer plate and made a slighty thicker gasket to give me a 1mm squish, which should be the same as the Wiseco gasket.

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=280468196200&fromMakeTrack=true

Is this the kind of dome i should be running?

Im in Australia so its a little harder to get things sorted out for it as not many people over here go out side of the square to modifie these motors to this extent.

I have thought about the calabration of the compression tester, i will be testing it on a stock banshee today to comfirm is operation.

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Ive removed the spacer plate and made a slighty thicker gasket to give me a 1mm squish, which should be the same as the Wiseco gasket.

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=280468196200&fromMakeTrack=true

Is this the kind of dome i should be running?

Im in Australia so its a little harder to get things sorted out for it as not many people over here go out side of the square to modifie these motors to this extent.

I have thought about the calabration of the compression tester, i will be testing it on a stock banshee today to comfirm is operation.

 

 

Bump

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Ive removed the spacer plate and made a slighty thicker gasket to give me a 1mm squish, which should be the same as the Wiseco gasket.

http://cgi.ebay.com/...mMakeTrack=true

Is this the kind of dome i should be running?

Im in Australia so its a little harder to get things sorted out for it as not many people over here go out side of the square to modifie these motors to this extent.

I have thought about the calabration of the compression tester, i will be testing it on a stock banshee today to comfirm is operation.

 

I don't believe those domes are for a stroker...

you can PM dlnoss, he is a member and a site sponsor (dlnoss)...

 

I am also concerned about the spacer that was originally installed. With a spacer, you don't need stroker domes. If you then pull the spacer, your pistons will hit the head.

 

These are stock cylinders?

Is your crank long or short rod?

 

I am beginning ti think that you may a mismatched pile of parts. Pull the head and park a piston at TDC and post a pic, please.

 

Rick

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you should have domes cut for a 4mil with blaster pistons... get ahold of NOSS tell him your setup and he'll cut you a set of domes.

 

 

Can you explain what is done when cutting domes for a 4mm with blaster pistons?

The items on ebay are suited for blaster piston in a banshee.

What other difference is needed to the domes for the 4mm.

As stated above, im in Australia, Its not easy for me to deal with companys over there.

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I don't believe those domes are for a stroker...

you can PM dlnoss, he is a member and a site sponsor (dlnoss)...

 

I am also concerned about the spacer that was originally installed. With a spacer, you don't need stroker domes. If you then pull the spacer, your pistons will hit the head.

 

These are stock cylinders?

Is your crank long or short rod?

 

I am beginning ti think that you may a mismatched pile of parts. Pull the head and park a piston at TDC and post a pic, please.

 

Rick

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I don't believe those domes are for a stroker...

you can PM dlnoss, he is a member and a site sponsor (dlnoss)...

 

I am also concerned about the spacer that was originally installed. With a spacer, you don't need stroker domes. If you then pull the spacer, your pistons will hit the head.

 

These are stock cylinders?

Is your crank long or short rod?

 

I am beginning ti think that you may a mismatched pile of parts. Pull the head and park a piston at TDC and post a pic, please.

 

Rick

 

I understand what your saying.

If id simply removed the spacer, then yes the pistons would hit the head but ive made a base gasket thick enough to give me a 1mm squish with my cool head running banshee domes.

The pistons dont go above the deck or they wouold be hitting the head.

Its been a while since i put the motor together but i think its a long rod.

All that i can work out now after having a 1mm squish is that the blaster pistons have a different angle on the dome of the piston and the cool head domes would work better if they were cut at the same angle.

What gets done to the domes when running a 4mm stroker? and is it relevant since i have a 1mm squish

I cant pull the head off as the bike is 700km away while im at work.

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I understand what your saying.

If id simply removed the spacer, then yes the pistons would hit the head but ive made a base gasket thick enough to give me a 1mm squish with my cool head running banshee domes.

The pistons dont go above the deck or they wouold be hitting the head.

Its been a while since i put the motor together but i think its a long rod.

All that i can work out now after having a 1mm squish is that the blaster pistons have a different angle on the dome of the piston and the cool head domes would work better if they were cut at the same angle.

What gets done to the domes when running a 4mm stroker? and is it relevant since i have a 1mm squish

I cant pull the head off as the bike is 700km away while im at work.

 

If your pistons do not go above the deck then you are correct that you would not need stroker domes. And the domes in your link above should work.

A stroker dome is cut 2mm to allow for piston clearance if it goes above the deck.

 

If/when you get the proper domes, you may need the spacer...

 

Rick

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If your pistons do not go above the deck then you are correct that you would not need stroker domes. And the domes in your link above should work.

A stroker dome is cut 2mm to allow for piston clearance if it goes above the deck.

 

If/when you get the proper domes, you may need the spacer...

 

Rick

 

Thanks rick, that helps to clear things up a bit.

This was my first ever 2 stoke build and im learning along the way.

The main problem i found was that the Blaster pistons have a higher pin, meaning the piston crown was sitting to low in the bore at TDC and also sending my porting out of tune.

After lowering my bores 1.5mm by taking out the 2mm spacer and making a gasket to give 1mm squish, i found that ive corrected the port timing and positioned the piston higher up in the bore, where it should be sitting correctly.

Im running the Blaster piston because my stock bores were at the end of their life and i needed to take them out to 66.5mm. The place that i bought the 4mm kit from said the blaster piston would fit but was unsure on the workings, looks like i got sucked in but not a bad things as im learning.

One thing im still concerned with, regarding the domes i linked above. If the blaster pistons normaly sat lower in the bore on a standard crank in a banshee engine, then maybe those domes might sit inside the bore slightly, meaning il have to raise my bores again with the 2mm spacer and end up screwing the tune on the ports.

I doubt that would happen as they are listed to work on 68.55mm bores and i asked if they will be suiting to 66.5mm bores, which makes me think no part of the domes go below the deck.

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Lots of information here:

 

Forgive me if I repeat what has been said so far.

 

If you are using Banshee piston domes with Blaster pistons, the dome size will be deceptive because of the difference in crown volume. The trapped compression will be lower because the squish angle is steeper than it should be with the flatter Blaster piston. Besides the compression being lowered, the bottom end performance would suffer a lot.

 

In your situation, a custom dome is probably a good idea instead of a 'shelf' or Ebay dome.

 

I sent you a PM with some additional information.

 

-David

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