High compression pistons, where to get?

turbowrenchhead

turbowrenchhead

Member
Jul 13, 2011
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After taking it on the trails this weekend it would bog in 6th in sand. I would like to add just a bit more power so it doesn't do this anymore. I was thinking a bigger piston higher compression would be the way to go. However where do you get one? I don't want to go aftermarket exhaust and have it to loud for the trails. They have a strict 96 db limit.
 
you don't buy high comp pistons for 2-strokes. instead you get your cylinder head machined for better squish and higher compression.

contact any of the builders on here and they will gladly help you.

Ken O'Connor Racing, FLOTEK, CHutzell, and i dont think hes on here but Wildcard
 
You generally don't raise the compression on a blaster by getting a taller piston. Generally that's only done on 4 jokes where valve lash or timing chain length is an issue. 2 strokes generally have the head lowered towards the piston to raise compression instead of the piston rasied.

There are several choices for 96 dB compliant aftermarket exhaust systems. That really just means you can't have a gut pipe or drag pipe.

Porting your cylinder would also help but really getting air in and out is more than JUST porting, a good pipe and some airbox modifications are needed.
 
no high comp pistons here. I i would suggest exhaust, some aftermarket would be in spec but not sure which ones. If not, remove airbox lid, add uni airfilter, get the head redesigned and cut for higher compression, and get the jug ported. Without a pipe, these mods will be choked down, but would still alot a good power gain.
 
How much can you machine down the head to still use 93 octane fuel? I'm a mechanic and I have porting tools and have done much porting in the past on auto. If I know how much to port the cylinder I can do it myself. I will have to farm the head out to a local shop. I was also looking on ebay and they do sell hi comp pistons. I also seen that there is a 72mm bore piston. Does one have to get a larger cylinder for that?
 
if yoy have the machinery, i would start by decking ur head .10 at a time and find the sweet spot, too much compression on a 2 stroke will make the powerband un-usable and cause pre-detonation and all kinds of headaches
 
Don't have the machinery. I have to take it somewhere. If you do start to get detonation just run a mix of 110 octane with your pump gas.
 
turbowrenchhead said:
How much can you machine down the head to still use 93 octane fuel? I'm a mechanic and I have porting tools and have done much porting in the past on auto. If I know how much to port the cylinder I can do it myself. I will have to farm the head out to a local shop. I was also looking on ebay and they do sell hi comp pistons. I also seen that there is a 72mm bore piston. Does one have to get a larger cylinder for that?
Click to expand...

Link to the piston you are talking about. Blaster pistons are pretty universal as far as wrist pin to deck height and ring land thickness so the words "high compression" may just be a sales gimmick in that particular case.

There is no set number for milling a head down and still being able to use a set octane. That all depends on external influences and the particular engine setup... and engine setup is something engine builders generally don't talk about too much as it is their livelihood.

You can look at Ken O'Connors youtube video's about doing a port cleanup for the blaster. That's a start in the right direction. He doesn't cover intake window or the upper half of the transfers for good reason. You have to really know what you're doing to modify them and you have to have special tools (more special than a simple dremel generally)

Head design is another sensitive information topic with engine builders. There are calculations for squish clearance and bowl size to compression ratio to bowl diameter percentage.

If you'd REALLY like to get involved, there are several books to read about the various subjects. Some are aging but still quite relevant. "2 stroke performance tuning" by AG Bell is a good palce to start. He's very straight forward and easy to understand on a basic level but also covers some fairly in depth topics too. Beware it's a long read with a LOT of information covered.
 
I would go with a full kit. Just the sleeve installed wont net you that much in hp gains. Plus a machine shop has to install it. The L.A. sleeve kit comes with upgraded intake, and port mapping over the stock setup and also come with an mx port job already done. Great for what you need, just bolt and go. Highly recommend a pipe and bigger carb to go with this though.

http://www.lasleeve.cc/index.cfm?event=product.display&product_ID=2020
 
that would be great except it would need a new big bore sleeve, might as well sleeve your own. If you wanted the sleeve your current cylinder, I would send the cylinder to ken oconner racing and have him do the sleeve and port job all at once.
 
looks like that high compression piston your seeing says....."high compression kit"
i'd say they're using a very thin base or head gasket to increase compression
i wouldnt run that, use only factory yamaha base gaskets, the green "kindergarden"
paper ones like to leak
i also see no wrist pin bearing in that
 
This guy on ebay states there is a dome on the piston. You have to read starting from the bottom to understand the conversion.

This is the piston I inquired about.

Namura Piston Top End Kit Blaster 200 Hi-Comp. Std - eBay (item 390275864355 end time Sep-24-11 20:39:52 PDT)

Dear turbowrenchhead,

Hello, you can use this item on a bone stock machine, or with any mods. For best performance you should run a aftermarket exhaust, and intake. Thanks again.

- dirtparts

Dear dirtparts,

What size jets and carb are you using in conjunction with this piston? Are you running aftermarket exhaust as well? What would you recommend to do along with this piston?

- turbowrenchhead

Hello, you would still be able to run 93 octane with this item. Thanks

- dirtparts

Dear dirtparts,

One last question. Since stock compression requires to use 93 octane. If you use this piston does it recommend a higher octane level?

- turbowrenchhead

Dear turbowrenchhead,

Hello, that sounds correct. Sorry they don't give us a exact number, just going off what we have installed in our shop. Thanks

- dirtparts


Dear dirtparts,

So that would raise the compression ratio 3/4 of a point then? Stock is 6.6:1. Are you looking at 7.3:1 roughly?

- turbowrenchhead


Dear turbowrenchhead,

Hello, it is by the dome on the piston. Thanks

- dirtparts


Dear dirtparts,

Does it increase it by using a dome on the piston or by using a thinner head gasket?

- turbowrenchhead



Dear turbowrenchhead,

Hello, this item will increase your compression by about 10 lbs. Thanks again.

- dirtparts



Dear dirtparts,

What is the compression ratio of this piston kit?
 
Last edited by a moderator:
new pistion and topend gasket set 94$
wouldnt run it without a bore and hone eather around like 80$
that comes out to about 174$......
redisgned head head about 60$
redisgned head is more power then that pistion bet my life on it.......
now read that take it in and think witch do you think is better and less money
 
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