billet head- very nice!

bluenosegoat

bluenosegoat

New Member
So I've been waiting and watching Pirates web site now for months waiting for the billet heads to be available and finally earlier this past week they were! I received 2 of them yesterday. Pirate cycles is excellent with thier shipping, just cant believe how fast I got them. Well got the head installed on my mtn bike with a cns carb, billet intake, sbp pipe and shift kit. Very nice fit and really looks good. Performance? I cant say I really notice any increase in power but the engine sure does run smoother and I seem to be reaching higher rpms. I was a little disapointed because I really expected a power increase but I am still happy. I think I have the carb dialed in once again and using the recomended high octane fuel (well 91 at the pump) as I always do. The other head I will be installing on my sons bike with a stock carb and a pocket bike expansion chamber and see what it does for that set up. Overall I'm happy with the head but not what I was really hoping for. I suppose that i really dont need to go any faster, bike already hits low 40's and thats plenty fast enough for a bicycle! ( see the 35mph dent in the tank- that hurt, alot) Thanks Pirate and Manic, very nice product.
 

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what engine did you put it on? I've got a Dax engine and a BGF engine and was wondering if it would fit these bikes. Are you comparing the billet head over a flat head or slant head HT enigine? There is a noticeable differende betweent he flat and slant head HT engines.
 
The engines I am putting the heads are from BGF. They are the XB if I recall and claimed 68.5cc with slant heads. I was told by bgf and on this forum they are the same engine as the pk 80. The billet heads were designed for the "pk 80" and the gt5 so I dont know how they might work with other engines. The heads fit absolutely perfectly so I believe my engines are in fact PK 80's. I could not find an actual "PK 80" so thats why I bought these engines with all intentions of getting these heads. I've waited a real long time for them! I have only rode around the block a few times and got the carb set so I havent gotten it out on the road yet but will this afternoon.
 
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Didnt get the chance yesterday to ride but just got back from a quick 5 mile trip. Engine fired up fine but wanted the throttle bumped a little to stay running for the first minute or two. (it was still 90 outside at 6 pm so dont think it shoulda needed choke). Idle is perfect. Exhaust note is a little different. Doesn't have the ping ping as much anymore- strange. I cant tell about the torque increase from a dead stop but when shifting in higher gears it does seem to pull harder. No more "flat" spots in the power band and the engine is reaching higher rpms. I cant wait for the weekend to put some miles on the bike and really see the benefits of the cylinder head. For now I feel it was 50 bucks well spent, so much cheaper than building rock crawlers and still so fun!!!!!!
 
Put a few more miles on the bike and checked the plug. It was running a little lean so I moved the needle up (e clip down) to get some more fuel. A little tinkering with idle and mix screws and she is running great! Still not the performance increase I was really hoping for but the engine runs better all the way around. Goin to put the other head on my sons bike today if I get my stretch cruiser welded up and have time.
 
so it sounds like i just wasted my money ordering the same head maybe with a expansion chmber youll see better results but of course you would have to test the expansion chamber with both heads to see the different but it also makes sense that with higher compression you would have to tune the expansion chamber differently or maybe i am wrong
 
I have the sbp pipe on now and I have never really messed with tuning the pipe. I did try a shorter head pipe (1/2 in shorter) a long time ago but didnt like the results so just went back to the original uncut head pipe piece. I dont know that the compression is really that much greater. I thought I would feel the compression increase while starting. With the shift kit I would've thought I would be able to tell any difference- having to "kick it over" but I cant tell any difference.
 
hmmm heres a thought maybe your piston doesnt have a curve on it pirate cycles sells them

is your piston flat or curved up
 
I will have to check that! When i installed the head it was at the break of day so lighting was bad- had my head lamp on! I almost hope it is a flat top piston! I'm sure a domed one would kick up the compression considerably. I still havent gotten to my sons bike yet but I will be spending alot more time on my bikes in the next few weeks- just got laid off so back to side work and bike building. 2 engine kits on the way.
 
bummer man getting laid is good but laid off is bad at leastyouve got time for bike maybe sell them in thise econiomic time a cheap form of transportation is desired many are going back to pedal bikes and many more would love to put a motor on that epcept for they die hards who beleive if you wanta motor on a bike buy a motor cycle but dont realize how much cheap er lighter and more fun these hts are
 
WildAlaskan said:
bummer man getting laid is good but laid off is bad at leastyouve got time for bike maybe sell them in thise econiomic time a cheap form of transportation is desired many are going back to pedal bikes and many more would love to put a motor on that epcept for they die hards who beleive if you wanta motor on a bike buy a motor cycle but dont realize how much cheap er lighter and more fun these hts are
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I was building and selling bikes before the job (wal mart remodels) and will do so until the next job comes about! I really enjoy it and was fairly successful with it. I picked up another bike today and hope to post for sale by wed. I live near the light rail and bus hub station so just might take some of my bikes down there and see what happens! I know I prefer to come and go when I choose and here in Az you can ride year round with ease! well maybe some sweat but beats pedaling in 115 degree weather. I will be pulling the head off to check on the piston shape sometime today. You made it sound like you have one of these billet heads on the way, please let me know how it works out for you.
 
You guys are getting warmer...

There are, that I know of, three different piston top shapes...flat, crowned, and crowned more.

This is the reason why I made a point of specifying which engine/s the current billet head should be used on.

I had both the PK80 and the Grubee GT5, (compliments of Pirate Cycles), at the shop for the benefit of taking the measurements on the granite.

These engines have the lesser radius piston crown...i.e. taller dome.

If this cylinder head is used with a lesser dome piston...you will likely NOT see any benefit.

If used with a flat top piston...you will likely realize a power loss!

The shape of the combustion chamber MUST be matched to the deck height and the piston top geometry.

This holds true for any 2-cycle engine...not just the Chinese bicycle kit engines.

You guys are certainly welcome to experiment...as far as I'm concerned a sale is a sale, and it's not up to me to question the logic or the application.

The current offering has been proven to greatly increase the bottom end torque when used on the PK80, or the Grubee GT5.

Note: If you can fit a GT5 piston to your "other brand" engine...and you are able to achieve a near zero deck height...the billet head will give the expected power increase.

Jim
 
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yuppers i ordered one on friday i dont know when its gonna make it here but the motor im gonna put tit on is in the same shipment and the build is a winter build so i really dont see this decked out bike hitting the streets till april winters last long up here and start earlier

i was thinking of trying it on my zoom cycles 66 but with just a poo poo pipe it may run hotter and i dont want to put the expansion chamber on it cause the pipe is clamped on and a pain to get a proper seal on acount of a heli coil for a exaust stud
 
Creative Engineering said:
You guys are getting warmer...

There are, that I know of, three different piston top shapes...flat, crowned, and crowned more.

This is the reason why I made a point of specifying which engine/s the current billet head should be used on.

I had both the PK80 and the Grubee GT5, (compliments of Pirate Cycles), at the shop for the benefit of taking the measurements on the granite.

These engines have the lesser radius piston crown...i.e. taller dome.

If this cylinder head is used with a lesser dome piston...you will likely NOT see any benefit.

If used with a flat top piston...you will likely realize a power loss!

The shape of the combustion chamber MUST be matched to the deck height and the piston top geometry.

This holds true for any 2-cycle engine...not just the Chinese bicycle kit engines.

You guys are certainly welcome to experiment...as far as I'm concerned a sale is a sale, and it's not up to me to question the logic or the application.

The current offering has been proven to greatly increase the bottom end torque when used on the PK80, or the Grubee GT5.

Note: If you can fit a GT5 piston to your "other brand" engine...and you are able to achieve a near zero deck height...the billet head will give the expected power increase.

Jim
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Thanks Jim. Yep I have been told that my engine is the "new version" of the pk80 from the guys at BGF and couple members here on the forum. Now wether that is true or not I cant tell. I know the heads were designed for those engines specifacally- the pk80and the gt5. thats why I searched all over to find one but only came up with these engines from bgf. I think they were called "XB" 68.5cc. I still havent taken the head back off to check the piston shape or deck hieght but I am real happy with the way it runs now!
Dont mess with it if aint broke!
The engine idles so much nicer now and seems to just run smoother everywhere and the engine is definately reaching higher rpm's, I'm sure I'll mess with it but I have other bikes to build now.
Thanks jim for the very nice looking and very functional head!
 
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bluenosegoat said:
Thanks Jim. Yep I have been told that my engine is the "new version" of the pk80 from the guys at BGF and couple members here on the forum. Now wether that is true or not I cant tell. I know the heads were designed for those engines specifacally- the pk80and the gt5. thats why I searched all over to find one but only came up with these engines from bgf. I think they were called "XB" 68.5cc. I still havent taken the head back off to check the piston shape or deck hieght but I am real happy with the way it runs now!
Dont mess with it if aint broke!
The engine idles so much nicer now and seems to just run smoother everywhere and the engine is definately reaching higher rpm's, I'm sure I'll mess with it but I have other bikes to build now.
Thanks jim for the very nice looking and very functional head!
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bluenosegoat,

This morning I went through and measured a bunch of pistons that I have here at the shop.

I have engines from all of the major distributors as of about 6 months ago.

The photos below show the difference in piston crown height. Some of the newer engines from BGF, DAX,...etc. may have the .160" crown. The only ones here that have the .160" crown are the PK-80 & GT-5.

I figured I would put this out there for those who can get a measurement. This is the guaranteed way of knowing whether or not the billet head will be a match for other engines.

The extra .060" piston crown makes a BIG difference!

I made a special tool for the lathe that uses a cam guide for creating the squish band and combustion chamber geometry. It would be a simple matter to make a new cam that would allow the tool to correctly chamber the head for the .100" dome piston.

If enough people text or email Pirate Cycles, Justin will order them from me.

I'm glad you're happy with your new billet head...but...If you can get an accurate measurement of the crown on your piston, and you determine that it is closer to .100" than .160"...let me know.

I'll ship you the first billet head for the .100" piston to try out...then you'll see what all the fuss is about. ;)

Jim
 

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Thanks Jim,
I did remove the head today, I just had to see the piston shape. It is domed but not as much as your picture shows! I have a pretty good eye ( with my glasses on) bein a finish carpenter/ cabinet maker for years and I'm 99.9% certain I have the .100 dome piston in my engine. The engine is also at least 9 months old- thats how long I've been waiting to get my hands on one of these heads! When I'm done here I'll be placing an order with pirate for the pk80 piston amongst other things. Thank you so much for the pictures!
 
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i am greatly releived my kit that should be arriving thursday is a gt5 so it is gonna be great when i get it up and running
 
WildAlaskan said:
i am greatly releived my kit that should be arriving thursday is a gt5 so it is gonna be great when i get it up and running
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What kind of bike are you building just out of curiosity? You being up in Alaska I'm real curious!
I got my first bike ready for sale tonight, its a cheapo roadmaster mtn bike but it really looks sharp! I feel much better about this roadmaster than the one I first built for my son. It at least has linear pull v brakes and all the welds look sound. Getting hard to find a good used bike for a decent price around here so resorted to wally.
 
well im going to use this frame cause its so lagre and easy to work in i might transfer it all over to a smaller frame later but not likely i usualy sit that high anyway http://motorbicycling.com/f42/so-heres-bike-im-gonna-use-24346.html

and heres a plan for my lighting system as well a a few lights im going to build one for mycurrent bike and see how it goes if all is well i plan on either copying it or simply changing it over to my new bike

http://motorbicycling.com/f50/simple-lighting-system-24596.html
 
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