Ready For performance!

Nooflyer · Oct 18, 2013

Hey guys i've following this thread for awhile now and bought my motorized bicycle a couple months ago and i love it.
Now i'm ready for some performance mods. The engine is all broke in (300-350miles) already and i'm trying to figure out if i buy an expansion chamber or a Fred head?
If you guys think i should buy the fred head first then which cc (5cc, 6cc, or 7.2cc) should i get?
Or if i should just get the expansion chamber should i buy the SBP, banana expansion from ebay, or the speed demon expansion from Bike Berry?

Here's how she sits so far!

maniac57 · Oct 18, 2013

Nooflyer said:
Hey guys i've following this thread for awhile now and bought my motorized bicycle a couple months ago and i love it.
Now i'm ready for some performance mods. The engine is all broke in (300-350miles) already and i'm trying to figure out if i buy an expansion chamber or a Fred head?
If you guys think i should buy the fred head first then which cc (5cc, 6cc, or 7.2cc) should i get?
Or if i should just get the expansion chamber should i buy the SBP, banana expansion from ebay, or the speed demon expansion from Bike Berry?

Here's how she sits so far!

Buy the pipe first. Once it's installed and the engine is properly jetted for it, then think about other mods. I've heard good stuff about the fred head but it's far to expensive for my taste. Pretty though!
CR Machine also makes some nice billet stuff.
Arrow has reed kits, heads and ported cylinders if you have serious cash to play.
Me? I'd just ride the wheels off it with a pipe and a 36 tooth sprocket.
If I ever spend for a hot rod bike, it will be a KTM or Morini.

Nooflyer · Oct 18, 2013

Ok thanks.
What's your top speed and acceleration with the pipe?
And which pipe do you have?

xseler · Oct 19, 2013

Pablo has the SBP Expansion chamber on sale..........got one on my Cranbrook!! I've got a 44 tooth sprocket, acceleration is better than I expected, and top speed so far is 33.5mph.

Another performance part that you should consider is a front brake. I feel much safer with the one I added.

Huffydavidson · Oct 19, 2013

The speed-demon & the Bannana are P.O.S.
SBP is the way to roll. Or Jakes gota nice one.
On the head , well the depends on what motor you've got , and what mods you have the skills to do.
And then last but not least, how much $$$$$$$$ can you and will come up with .
And I won't tell you my top speed cause that'll just start another argument around here.
But I'll say this, I'm in 45 mph zone and I'm not getting run over.

Nooflyer · Oct 19, 2013

LOl yes front brake is in the mail!

And i have a 68.5cc engine from boygofast. I'm pretty sure my skill level is sufficient enough to assemble an aftermarket head. I also already have a new head gasket ready as soon as i decide which route to go.

My engine arrived with 2 head gaskets for some reason ( maybe it had over 100psi of compression) but i want to minimize one for higher compression. That's why i was thinking having an aftermarket head to cool things down. I could just drill a couple holes in the exhaust tip for a performance boost.
Sounds about right?

Kevo48 · Oct 19, 2013

I bought the banana from bikeberry and got clocked at 41mph flat land and I weigh 240.....the pipe came apart at the welds though...they want to inspect the pipe before they send me another one...

Intrepid Wheelwoman · Oct 19, 2013

Kevo48 said:
I bought the banana from bikeberry and got clocked at 41mph flat land and I weigh 240.....the pipe came apart at the welds though...they want to inspect the pipe before they send me another one...

Nice bike, I like the long low lines.

Nooflyer · Oct 19, 2013

@Kevo48
is that the bent springer forks off ebay? And how difficult it is with assembly?
I'm thinking about adding the straight springer forks to my collection also!

Kevo48 · Oct 19, 2013

Thanks @Intrepid Wheelwoman

@Nooflyer yeah the installation was easy. The kit didnt come with a head nut so I had to grab one from the local bike shop.

rogergendron1 · Oct 20, 2013

i decked my stock head down to 6cc..
its easy with glass and a lot of sand paper and a good 4 hrs of time lol...
first measure the heads cc by bolting a piece of plexy glass over the chamber and filling it with water from a needle note how mutch water it took to fill that is the stock cc

then sand it way down and remueshure... not where you want it ? keep sanding and remeasure ! keep this up till you get 6cc in the chamber then polish the chamber pretty good and focus on grinding the trnsition from chamber to plug chamber smoother so its more like a single dome and nice and polished ... you should now have a 6cc to 6.5 cc combustion chamber

now get some 220 grit and finnish the gasket surface on the glass to make a good seal !!

at 6cc with a stndard grubee gt5 66cc motor you should have around 11:1 comp 66cc +6cc = 72cc 72cc divided by 6cc = 12 so its 12:1 but you have to take in acount the jug deck hight and piston crown exe... its closer to 11:1 with the standard jug and piston

you can also do piston ramps on the tranfer ports and exhaust to moddify your timing some and creat better flow!!!!

or just buy a puch 70cc hi hi for 30$ lol !!!!! and save 4hr of work

here is how to measure comp !! a verry good read !!!
http://www.sacoriver.net/~red/uccr.html

rogergendron1 · Oct 20, 2013

the stock measurement for boar and stroke pluss the chamber is 80cc
the boar and stroke is 66cc
that means the chamber stock is 14cc !!!! well pluss the space in between the piston crown and so forth so stock comp is66cc boar and stroke pluss 14cc chamber space equals 80cc tottal div by 14cc chamber is 5.75:1 lol..... stock is a little less than 6:1 comp !!!

you can take the stock head down a lot !!!! i had to take mine almost down to the cooling finns to get to 6cc ... i also had to reshape it a little to make the dome a large single chamber for quick burn, my final chamber size is 6cc

i am dead poor and can not afford a supper duper billit head lol so for me this was the way to go, it cost me nothing but time, i did it during comercials watching tv !!!! in one night !!! and it was the single most power boosting mod i have done ! going from 6:1 to 11:1 was a large boost in power ! that along with a pipe and some moderate porting and piston ramping will give you what you are looking for with no cost what so ever if you own a dremal tool !

Nooflyer · Oct 23, 2013

Thanks. I'm waiting for my front brakes and my springer forks to come in the mail.
I may just try taking the head down a bit. Just afraid of overheating even though i'm running a little rich.
As far as port matching, I think that might be my last performance mod as i'm afraid of messing up the timing and what not.
So does the milling the head down 6cc help in bottom/top end or all around performance?

maniac57 · Oct 23, 2013

Increased compression helps power EVERYWHERE in the rpm band.
How it's delivered is more dependant on pipe, porting etc.

Nooflyer · Oct 24, 2013

Ok did you guys happen to have a picture of before and after decking the head?
I just want a visual picture of how far you guys actually went!

dodge dude94 · Oct 25, 2013

Could an individual use a dremel at slow speed to grind the edges down and what not? I had smoothed my head and combustion chamber down with 400-1000gr paper but I want more, more quickly. lol

maniac57 · Oct 25, 2013

How you remove material does not matter as long as it ends up perfectly FLAT for good sealing.
I'd be VERY careful trying to use a dremel to deck a head. You will still have to lap it on glass to remove all the dremel marks anyway.
Why not just use coarser grit sandpaper in the early stages and switch to fine at the end?

dodge dude94 · Oct 25, 2013

Hmm.. true. I'm pretty good with a dremel, but I think even I would FUBAR the gasket mating surface. I was thinking about using it to level out the squish band or whatever.

What if I dry sanded with 200-300 paper? Wet sanding was great, but it still loaded the 400 up. lol

rogergendron1 · Oct 26, 2013

Nooflyer said:
Ok did you guys happen to have a picture of before and after decking the head?
I just want a visual picture of how far you guys actually went!

look at my thread on the puch 70 hi hi ...
it has detailed pics of how far down you can take it and plug clearance pics allong with side by side pics of stock and decked rechambered ....

i ground it waaaaaay down with 80 grit !!!! then test fit it and resurfaced the gasket mating aria with 220 grittill it was silky smooth the reshaped the chamber to eliminate the squish and give it a single hemi dome to aid in faster more complete combustion, it worked great for top end speed and midrange ! i did about as much as you can do to a stock head !
it has been take down so far the outer edge of the cooling fins got sanded and the diamiter of the chamber is only 43mm as aposed to the stock 47 ! and the chamber is a single dome as aposed to the stock double dome with outer squish.
pm me if you want my old stock decked rechambered head its 6cc and will net around 11:1 comp run 92 or better octaine !

plz read !!!

http://motorbicycling.com/showthread.php?t=51203

you will find info on the head here

rogergendron1 · Oct 26, 2013

ok here is my old head ... high comp .... you can see how much is left of the gasket surface, just a hair thicker than a fingernail ! and also you can see where some of the second dome where the plug seats has been smoothed out to make it one large dome and also you can see that the chamber is about 5mm smaller in diamiter than stock. ( the more you take it down the smaller it gets). also notice the squish band is gone ? it was decked right out ! it was so small it was useless on this motor anyway. a good squish needs to take up at least 30% of the chamber or its ineffective. and its imposabe to do that to this head, unless you welded to add material to the chamber only to mill it of again at the right angle lol then your left with a chamber thats too small and still improperly shaped !

therightmost pic is of a head from BGF the one left of it is of 2 stock heads, the one on the left is typicaly what you get and if your real lucky you get the one to the rght of it bolth are the same comp bt the one on the right has better castings and what they call a squish band highlighted in red lol

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