fall_down_stand_up
New Member
This is very informative....I think im going to buy a slant head....
John-John
John-John
Do slant heads really make a difference in power?
- Thread starter fall_down_stand_up
- Start date
turtle tedd
Member
K.i.p Tag on my motor is exactly the same as yours..purchased from Pirate Cycles.....invoice says..66/80cc Jet Black Limited black-limited edition bicycle engine kit...$144.00....have not taken head off..put it back in box....Del mar with the Grubee is running strong..still tweekin and riding it............so is ours the domed piston or flat??
That paper label is on all the motors I got from Zoom... even the 50cc. Why they would put a 80cc label on 50cc bike is beyond me. The other way around is much better.
last year they were riveting 67cc metal tags to all the bikes. It was a pain to drill them out and fill the holes. I guess the paper ones are an improvement over that.
I'd really like to get a handle on this dome vs flat piston issue. Is it random or is there any way to guarantee one type. Maybe email Zoom.
I also wonder if you can see the 2 or the 5 or make out the shape through the plug hole. Taking engines completely apart loses it's appeal after the first 5 or 10.
last year they were riveting 67cc metal tags to all the bikes. It was a pain to drill them out and fill the holes. I guess the paper ones are an improvement over that.
I'd really like to get a handle on this dome vs flat piston issue. Is it random or is there any way to guarantee one type. Maybe email Zoom.
I also wonder if you can see the 2 or the 5 or make out the shape through the plug hole. Taking engines completely apart loses it's appeal after the first 5 or 10.
Riding Rich
New Member
You could check for the Dome shape through the exhaust port.
Crank the motor to expose the top of the piston in the exhaust port.
This is an interesting thing.
I wonder myself now how you could determine what piston you will get with a motor.
My EPA tag is the Same as Well.
I will say one thing.
The PK i got has soo much power i can't believe it.
It snowed here about 6 in.
Rode it to work 5 miles.
Spun back tire the whole time and i got a 36T on there right now.
Crank the motor to expose the top of the piston in the exhaust port.
This is an interesting thing.
I wonder myself now how you could determine what piston you will get with a motor.
My EPA tag is the Same as Well.
I will say one thing.
The PK i got has soo much power i can't believe it.
It snowed here about 6 in.
Rode it to work 5 miles.
Spun back tire the whole time and i got a 36T on there right now.
I was hoping to avoid removing the exhaust. Specially in sub-zero weather. Half the time there's a leak when I put it back on and I don't like buying or making gaskets.
Tell me about it. That spinning wheel in the snow is much worse with the slant. I can't even start the engine unless bare asphalt. And the salt ain't doing the bike or engine any good at all. I'm thinking of putting the knobbies back on.
Riding Rich
New Member
.
I have a solution to the spinning back tire deal.
King size 50T sprocket. Hot off the laser.
Unfortunately I think you have it backwards, There is absolutely no doubt that my 54t is MUCH harder to start and skids a lot more in snow than my 32t. Same engine.
Riding Rich
New Member
Really? i have allways ran a 36T.
I would think the bigger sprocket would make it easier.
So as far as the sprocket goes you think it's better not to change it.
I would think with the slant and a 50T i wouldn't need to peddle to takeoff.
What kinda experience you got out there?.
I would think the bigger sprocket would make it easier.
So as far as the sprocket goes you think it's better not to change it.
I would think with the slant and a 50T i wouldn't need to peddle to takeoff.
What kinda experience you got out there?.
Riding Rich
New Member
BTW
I e-mailed Justin and he says all the motors him and Taco have torn into had the dome piston.
Also figures the engine makeup is dependant upon MFG. Date.
Justin has replacement Dome Shape pistons.
So if you got a flat top it might be possible to put the Dome piston on there.
As long as the wristpin location in the piston is the same.
And i would think it is.
I e-mailed Justin and he says all the motors him and Taco have torn into had the dome piston.
Also figures the engine makeup is dependant upon MFG. Date.
Justin has replacement Dome Shape pistons.
So if you got a flat top it might be possible to put the Dome piston on there.
As long as the wristpin location in the piston is the same.
And i would think it is.
Just the opposite. Think about it. Big sprocket on back easy for engine to turn wheel. Hard for wheel to turn engine. Ratios work in reverse when wheel is turning engine.
That's theory but it was driven home last week when clutch on my 32t (travel bike) started slipping and I switched to the 54t (tow bike). Again obvious when I fixed and went back to using the 32t.
Also note that super low gear in motorcycles and cars causes loss of control on ice. Wheels break loose easy when locked to engine. Best of all is clutch disengaged.
Riding Rich
New Member
Well i guess i should let the sprocket alone and work on some studded tires.
I have to do something.
I have to ride.
Otherwise it's the bus and longer time in the cold.
There all asking me what color flowers i want for my funeral.
I think most people are more afraid for me than i am.
I'm lovin it.
I have to do something.
I have to ride.
Otherwise it's the bus and longer time in the cold.
There all asking me what color flowers i want for my funeral.
I think most people are more afraid for me than i am.
I'm lovin it.
Took me twice as long to get there and back.
K.i.p
New Member
I was upset because the people I bought them for were very specific about wanting 50cc due to legal issues. It was a relief to see they were not 80cc.
It's easy to judge this by outside cylinder size. I can now tell the difference at a glance.
george_n_texas
Member
Mine and kidcrash's 48cc kits were labeled the same way.
turtle tedd
Member
The Chinese assembly guys have parts..stickers and rivited plates included..they just keep putting them whatever stuff going out the door Shwinn Del-Mar rear wheels..started out with Falcon Hubs , ran out ,Crainbrook Hubs next , then found a box of missilanious hubs use them too...if it looks like rice it must be rice...
george_n_texas
Member
Be interesting to know the turnover rate in them factories as well as the literacy rate. Personally I think they do a fine job for the price I paid especially since more than half of the money for the kit probably went stateside.
bairdco
a guy who makes cool bikes
this is from Graham Bell's Two Stroke Performance Tuning... (http://www.kreidler.nl/artikelen/performance-tuning-graham-bell/performance-tuning-graham-bell.pdf) looks like he's down with the center fire head...
...Researchers have found that it is the gases at the very outer limits of the
combustion chamber, called the 'end gases', that self-ignite to cause detonation. These
end gases are heated by the surrounding metal of the piston crown and combustion
chamber, and also by the heat radiating from the advancing spark-ignited flame. If the
spark flame reaches the outer edges of the combustion chamber quickly enough, these
end gases will not have time to heat up sufficiently to self-ignite and precipitate
detonation. Herein lies the key to prevent detonation — keep the end gases cool and
reduce the time required for the combustion flame to reach the end gases.
The most obvious step that would satisfy the second requirement is to make the
combustion chamber as small as possible, and then place the spark plug in the centre of
the chamber. Naturally the combustion flame will reach the end gases in a small
combustion space more quickly than if the chamber were twice as wide. Additionally, a
central spark plug reduces flame travel to a minimum...
...Researchers have found that it is the gases at the very outer limits of the
combustion chamber, called the 'end gases', that self-ignite to cause detonation. These
end gases are heated by the surrounding metal of the piston crown and combustion
chamber, and also by the heat radiating from the advancing spark-ignited flame. If the
spark flame reaches the outer edges of the combustion chamber quickly enough, these
end gases will not have time to heat up sufficiently to self-ignite and precipitate
detonation. Herein lies the key to prevent detonation — keep the end gases cool and
reduce the time required for the combustion flame to reach the end gases.
The most obvious step that would satisfy the second requirement is to make the
combustion chamber as small as possible, and then place the spark plug in the centre of
the chamber. Naturally the combustion flame will reach the end gases in a small
combustion space more quickly than if the chamber were twice as wide. Additionally, a
central spark plug reduces flame travel to a minimum...
Riding Rich
New Member
Yes that is correct.
This mostly helps with detonation and if you don't have squish band like the HT center fire it don't help.
The slant has the advantage of having a squish band, Way higher compression "50% more over std. centerfire", much smaller combustion chamber "5cc vs 8cc and also flipping the head with the plug angle toward the intake directs heat out the exhaust + gives more uniform heating of the cylinder meaning less bore distortion.
I believe you can find all that in Grham's book too. Look how close the plug is to the piston top "close" vs the center fire "below the deck" , So which one has a shorter flame front distance. I ran that PK yesterday and it sounds and feels like a REAL ENGINE.
Anyway my Grubee was fun till i found the PK.
This mostly helps with detonation and if you don't have squish band like the HT center fire it don't help.
The slant has the advantage of having a squish band, Way higher compression "50% more over std. centerfire", much smaller combustion chamber "5cc vs 8cc and also flipping the head with the plug angle toward the intake directs heat out the exhaust + gives more uniform heating of the cylinder meaning less bore distortion.
I believe you can find all that in Grham's book too. Look how close the plug is to the piston top "close" vs the center fire "below the deck" , So which one has a shorter flame front distance. I ran that PK yesterday and it sounds and feels like a REAL ENGINE.
Anyway my Grubee was fun till i found the PK.
truckd
Well-Known Member
O.K Guy's toiling over the Grubee Skyhawk/GT5 80/66cc and the pk80/68.5cc wich is really the better engine???
I'm currently having a BTR fabed for me(by someone we all respect on this forum) and I really don't want to stick a piece opf crap motor in it, so give me some positive feed back on this matter
I'm currently having a BTR fabed for me(by someone we all respect on this forum) and I really don't want to stick a piece opf crap motor in it, so give me some positive feed back on this matter