New Slant Heads for 80cc's: Compression Boost!?

europorsche914

europorsche914

Member
I was on zoombicycles forum today while ordering another motor kit for my new moondog/(shorewood) and i found a thread about the new heads they sell for $12.95.
New Slant Head: Zoombicycles Motor Bicycle Engine Kits 80cc Slant Head Cylinder Cover (A-2B) | 14-Addons | 6-Parts and Accessories | RuiHong Enterprises Ltd..

Thread: zoom 80cc slant head upgrade evaluation - Zoombicycles Motorized Bicycle Engine Kit Forum.

I ended up ordering one of their new engine kits with this head already installed and ordered an extra head for my other motor. Ill let you guys know if it helps -Justin



UPDATE:
Purchase the following for successful installation*****:
(1) Slant Cylinder Head: Zoombicycles Motor Bicycle Gas Engine Kits 80cc Slant Head Cylinder Cover (A-2B) | 14-Addons | 6-Parts and Accessories | RuiHong Enterprises Ltd.
(1* or 2*/****) Head gasket(s): Zoombicycles Motor Bicycle Gas Engine Kits 80cc Head Gasket (A-3) | 10-Gaskets | 6-Parts and Accessories | RuiHong Enterprises Ltd.
OR Sick Bike Parts
(1*/**** or 2*/** or 3*/**/***) Cylinder Base Gasket(s): Zoombicycles Motor Bicycle Gas Engine Kits 80cc Cylinder Bottom End Gasket (A-7) | 10-Gaskets | 6-Parts and Accessories | RuiHong Enterprises Ltd.

*Most 69cc/80cc engines utilize m8 head studs, but the gaskets pictured show m6 diameter holes. The gasket holes may need enlarged for the larger studs...
**The reason for 2 or 3 cylinder base gaskets is some engines need the extra space to prevent the piston from hitting the head... Use only one gasket if you can get away with it! :)
***If you have modded your motor to reach extreme rpm (boost porting & other porting), I noticed my connecting rod is stretching enough to allow the piston to hit the head (power drops and slapping noise...) either add another base gasket (total of 3) or dont rev so high (10,000+rpm when it occurs for me). I didnt have any damage and it has happened a couple times (not intentionally), but i dont recommend it. BUT if concerned add another gasket or head gasket to make up the space...
****Jet silver motors currently sold by zoombicycles have the slant cylinder head preinstalled and they use 2 head gaskets and 1 base gasket to prevent the piston from hitting the head. I think that this raises the chance for a head gasket leak especially with the higher compression but so far i havent had any leaks on my stock jet silver motor so maybe this is another viable solution to the clearance issue, especially since this leaves the port timing unchanged.
*****Try at your own risk!! I cannot guarantee that it will work on absolutely every application (differences in manufacturing & tolerances etc.), I'm merely stating what worked for me and others. Have Fun!!!
 
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Justin
My first thoughts on the head was ya hoo. More compression = more power....But more power = more heat. The fins on that head look almost non existent ! I really wonder if overheating will be an issue ? Let us know how it goes...POPS
 
I thought the exact same thing when i read the thread and saw the picture but then I looked a little closer and although the fins are shorter there are 13 fins on the slant head versus 11 on by BGF. I figure that the extra fins will atleast equal the surface area of the original. I guess ill just have to be the test subject on this one ;) -Justin

(slanthead on left, standard on right)
 

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Hi, already have a bicycle with that head installed from factory is the black engine they sell and report no problem from overheating. I live on a tropical climate that 90 F and more most the time and no problems with overheating. Since is my first engine I can't compare, but can say it pulls very good and have some good hills here to test.
Get us in touch when you swap heads and got results.

brnot
 
New Slant Heads improve performance? Myth or Fact?

Ok... this question has been bothering me for a while... does this slant heads really improve performance? Myth or fact? Anybody? Dyno tests comparison???

(?):-{
 
well i dont have access to a dyno but if i notice any difference ill let you know. Im surprised no one else has compared the old motors to the new slant head ones (80cc). Im curious to find out what happens cause i read somewhere (besides the thread above) about the compression bump in the newer slant head motors and the only place i found the 80cc version of the cyl head is zoombicycles We shall see... -Justin
 
I bought one yesterday. I'll definitely tell you if performance improves. I live at an altitude over 6000 feet and on a steep hill. I can only pull up the hill in 1st gear (34 tooth sprocket) and it lugs in 2nd gear. If there is any power difference, it'll be very apparent for someone in my situation of high altitude power loss and lots of Colorado hills.

Stay tuned :-)
 
Found these reviews on zoombicycles site (one is the same guy that started that thread...):

Customer Reviews:
fenderhole (Sunday, 08 March 2009)
Rating:

freakin awesome! engine now has gobs of torque and gained 7mph on top end... best US $13.00 (Convert) i ever spent!


farmboy72 (Saturday, 31 January 2009)
Rating:

The slant head adds some bottom end torque due to the smaller combustion area which adds compression. the head is not painted so if you dont paint it
it stands out like a sore thumb. Overall the slant head is well worth the 12 dollars.


I hate waiting for the brown truck to show up!! -Justin
 
Come ON! I am at the edge of my seat waiting for the verdict! I guess I should just order one and find out for myself...
 
No package yet. the tracking number says its still in washington state. Maybe they sent it back to china for a final quality control check. Justin
 
It works as advertised. SIGNIFICANT increase in compression as evidenced by needing a lot of effort and force to pull start my HT engine. I can now climb any steep hill in 3-4 gear instead of 1st gear with is a 34 tooth megagear. The stock headgasket on the boy doesn't go fast engine was 3 times thicker than other HT engines Don't know how much of this stole power from me but the thinner replacement head gasket and sland head are a winner for me.
 
Now im real excited for this new head!! Im out of town today and the package is sitting at my house, Ill probably install it tomorrow. Glad it worked out for you donuts!! BTW did your BGF have 6mm head studs? Does the new slant head have larger holes for 8mm studs (80cc PK motors typically have 8mm studs where as BGF have 6mm studs)? How does the surface area of the old head compare to the slant one? I guess i could answer all these questions tomorrow myself when i get home... (I also have a shifter kit with a 34t mega range its great for standing starts ;).)
-Justin .shft.
 
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I think I will buy one of those bad boys!! Need more excitement in my life.
 
My BGF engine had 8mm studs. It was an engine that came equipped with a centrifugal clutch and pull start. The head gasket was about 1/2 mile thick and I have never seen on this thick before. I wonder if BGF is using thicker head gaskets to derate the engines for the centrifugal clutch kits. The clutch cannot handle the torque of the higher compression head with thinner headgasket at lower rpms.
 
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