Increasing the compression of your Motorized bicycle engine (49/66/80cc)
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- Опубліковано 17 бер 2013
- Increasing the compression of your motorized bicycle engine can help increase fuel economy and power, BUT it doesn't necessarily mean that it will always do so. In this JuiceMotoParts tutorial we will show you guys several ways on how you could increase the compression of your engine. Feel free to comment or shoot us a message if you have any questions or need any trouble-shooting advice. Check us out at Juicemotoparts.com for more information on how to tune your motorized bicycle engine as well as our line of line of high performance products. Thanks for watching and as always, GET JUICED!
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These engines surprisingly tend to not pre-detonate. I messed with a few heads and ended up shaving the head until the piston kissed the head and wouldn't run. I added a slightly thicker head gasket and the squish was 0.04" and it ran really well. One night during a one mile wide-open run, I looked down and the spark plug was glowing! I bought a colder plug the next day.
Oh- I wanted to add that if you bump up the compression a bunch, you can raise the exhaust port ceiling and not lose any low end power while gaining power on the mid and top end.
I've done a similar process and the best effect it had was to make the mating surfaces flat and even giving a better gasket seal for less blow by,
Still a good idea to go through these engines and clean and chamfer.
Remember, this is a cheap mass produced product, good learning tool
Another technique is to build a support block to hold the cylinder and head with a beater piston to center the head and lapping compound to head and cylinder mating surfaces and use lapping process to match surfaces, ive done mine this way and don't run gasket
With very minimal blowby and more power
Is there any way to build up any more compression with a one-piece head/jug?
That technique is how Aluminum heads are repaired for doing a blown headgasket job, that's how I fixed my Honda accord's blown HG. Glass with sandpaper and sand the head to properly align it fo warped heads
take the head to aa machine shope and have theem shave 0.025' or there abouts. you could even have them cut an oring groove for no more head gaskets
Just put a couple oz of stp along with your 2 cycle oil ?
thanks
There is a small ridge there I believe it's a seal remove that won't it cause a leak?
How about if grind off a millimeter would that work?
What is the stock compression before sanding the head
yes in most cases but the ignition on these may need upgrade more compression more rpm - draft air/fuel etc...
im looking at doing a motor bicycle as a hobby for myself. still trying to find reasonably priced bicycle kits that are motor ready.
but in the mean time im going through hotrodding these engines. i came across your video and wanted to ask if you decide to go excessively high on compression wouldnt using high grade 91 octane fuel negate the preignition? it does that for cars and i do want to bump compression up enough to keep the bicycle under the limits that make it a motorcycle but at the same time powerful enough to run 30 - 40 mph.
U can bumb it up so high as long as you have high enough octane fuel. But at some point the power and comp. Ratio difference just become so tiny, that it doesn't make a difference anymore, rather port and buy a tuning carburador
Hi,
I have installed a new Copper head gasket that is 1/10th of a millimeter thick. The stock ones are around half a millimeter thick. I have an angled head to improve compression and the stock motor uses 9:1 compression. It is a A95cc (66cc) motor. Is the 4/10 of a millimeter difference allowing too high a compression? Will it cause any knocking? Thanks for your help.
does this work on most slant head motorized bicycle engines...I am about to order one,,,and im already planning on upgrading it,,,,is this a route I should take to try to get more power,?
Can you spare an old cylinder and 49cc piston to an old man in West Virginia please
Thank you?
or simply drill out the head and tap it for a larger spark plug yeah good idea put the crank on a drill press and drill out some excess weight as well please
How long do you have to sand the head, to get around 180psi of compression? (That sould make a compression ratio of 12.24 which schould be decent)
deecnt to break your engine
The head should be moved in a figure of 8 when you are attemping to lap it in so that you dont get high spots and if you are attempting to remove material to raise the compression ratio put it in a 4 jaw chuck in a lathe or similar lapping it is only ment for removing very minor inperfections.
Thanks
correct!
one question if i were running a 14.0:1 fuel and air ratio and using 94 octane what is the safest max compression before knocking occurs.
Probably arround 12.5:1 to maximum 14.5:1 compression ratio it might take more but i wouldn't try that😂
12,24 compression ratio should be 180psi of cranking pressure, so go between 180psi and maximum 210psi (after that your engine would probably knock the shit out of itself😂)
Ive done this to my bike. However the bike wont run properly because it cuts out... do i need to adjust my fuel:air jetting or fuel:oil ratio?
fuel oil only lubricates the cylinder, i would adjust the jetting
If it causes knocking,you simply have to switch to a higher octane gas
OK so I've already done this and my bikes pushing 150psi is that ok , and should I be running a higher octane fuel
Good question! I wish someone would reply, my head cap was slightly warped so I was thinking of doing this to the jug and head cap so they mate up tight again, I am getting oil leaking from the head when I run my engine. If I do this will a octane higher than 89 be better for running? I heard lower octane is better for these engines.
hi i had to put my whole engine together even had to put piston on but the engine started smoking a lot like it cant breath i , its got plenty of gas flow and the engine head is tight , but acts like its not getting air , any suggestions i would really appropriate it , oh and i even took the breather off and dint help , could it be my gaskets i cut them to size my self?? thanks
its your gaskets you never cut are install the engine without gaskets I been building motorized bikes for 2 year now I know what I'm talking about
yeah i got my 80 cc chopper running after i put new gaskets in the engine and also i put sealer around them , i riding scooters for three years but only been riding these bikes for year now , thanks for getting back with me
Jacob jhonson it's your spelling that's the problem
mark kasper Dint tell me you haven't appropriated the odd suggestion in your time :-)
Just a noobie question, whats the difference between high comp and low comp, and will there be a bad effect or good on the engine?
This may be 4 years too late but with higher compression it heats up the air fuel ratio more witch makes a bigger combustion to push the piston down faster
the piston is closer to the explosion at higher compression and not as much energy is lost to head and walls, meaning more power and vetter efficency at the cost of higher octane ratings, cause its more likely for your fuel to explode early (knocking) due to it being compressed (since due to that the fuel heats up and so could start burning) killing your engine. Lower compressions mean the exact opposite, so lower is often used for forced induction or shit engines
Unless you plan on mounting a turbo on your motor ,,, 150-180 psi is optimal for naturally aspirated !!!
I sanded down my head gasket instead and it does difference aswell. Oh and by the way it was burnt lol!
Will not using a gasket work with smoothing the top/head?
It will mostlikely leak and knock the shit out of your engine😂
thogh there is a chance to do so, you would need to smooth it like insanely flat and accurate on both sites to work
And you might need some cooper paste to seal it realy, but i duno
do a compression test and/or run the engine and check the spark plugs. Let me know!
How much compression is the engine supposed to have when running factory specs while your doing a compression test ?
i have 120cc 2 stroke engine.. my bike lost power when i change the pipe.. Why??
backpressure
you can make a head gasket with a coke can, its thin and works great! watch my video on my bike with only thin head gasket, ported motor, and pipe. Rest is stock and it screams
Hi, i drop a woodruff key from the magneto part and i don't know where to stick back the woodruff key to..help please?
untidy87 key on rod line magnet up push on then bolt
I am for india
my bike is ported but not not power I restored the engine 2 time but compresser is not improved what I can do
What are you on about mate
hi im tring ro install a pull starter on my motorized bike it wont start could u possibly know why it wont i have it in the way i saw on a UA-cam video.I think i have too much compression? what do i need to do?Help please!
+Lena Clark The soft silk rope pull starts work better than the kind made with metallic pull cable... The metallic cables bind up and shoot the spring to hell or rip the handle off and skins knuckles..
you can live without a pull start. if your bike needs a pull start to run after a few seconds of pedaling then it might mean you need to do some adjustments.
you can live without a pull start. if your bike needs a pull start to run after a few seconds of pedaling then it might mean you need to do some adjustments.
also to add is that pull starts can be problematic. the cable always breaks
Some of the NEW style PK-80 engines have just that a great amount of compression. FRED AT CR MACHINE MAKES A HEAD WITH A COMPRESSION RELEASE MECH. CHECK IT OUT AT CR MACHINE
Ive been looking around quite a bit for some answers without asking.. ive had my 66(80)cc ZB80 kit in use since March 2014, and this isnt the first time ive had this issue, it bogs out when i try and open the throttle, (sometimes) other times, it rips down the road50+ km/h i have to play witht the trottle to top out and lean back to put some weight on it
when im riding close to top speed i hit a small bump and lose power like the clutch is slipping? from the impact mabye?
I have a few problems with it at the moment because of lack of time or patience troubleshooting with my Father(30+ year machanic) recently retired from work because of an accident.
standard setting just dont work on it anymore
Upgrade your carburetor to a Dellorto sha 14.12 carb
+Jake Softley DC is right the SHA carbs a nice touch. They have a handicap of not being able to deliver enough fuel to modified engines so getting a jetting kit is another step. The NT carbs and others the floats eventually begin to bind or get holes in em and also the once the port for the needle seat get dirt it's not repairable...
TRY GOING UP ONE SIZE ON THE MAIN JET
ok how about Silicone Instant Gasket high temperature
Having smoke come from my 48cc 2stroke head cant find it what could it be
What's your fuel mix ratio? Too much to 2 stroke oil in your mixture. Also use a synthetic oil don't use semi synthetic. I did. Was alot of sludge. I was using Castrol .. bit I keep my bike in the house so I now use Rock Strawberry 2 stroke oil.. I can recommend that. Also mix your fuel in a can and pour it in never mix in the tank .. will cause ya all kinds of issues. Mine now has alot if mileage on it.66 / 80cc .. running like a dream. I didn't see much difference between a slant head and a "high compression cylinder head,' but either way use a copper head gasket for best results and never over torque the head bolts try and get the perfect 'squish gap' ...
most likely its the gasket under cylinder
umm that's questionable. I think that the slant head does give you some more power but others may disagree. What you can do is get a thinner head gasket or shave the head a bit.
Well.. vibrations usually mean that either a you have not mounted the engine properly OR that some kind of bearing is going bad in your engine. How long have you had it for/miles have you put on it? and if your engine is loosing power on full throttle, your carburater is probally flooding the engine with to much fuel. I suggest going down on your jet size! message me and we can deal with the problem together! Thanks!
JuiceMotoParts what seems to be the problem when my RPM is at 5-7 RPM running at high speed and goes down to 2 RPM and will then race to 1 RPM and die when i hold the clutch on my motor bike running at high speeds?
why go through all that hassle? when you can simply fit a thinner head gasket..
Same results but only takes like 10mins to do..
did you even watch the video?? that what he said at one point..sheesssssh!!!
lol that is what i though and i am a complete noob
@ make one out of a soda can
lighten the counter weights please
so if more compression, will it run on diesel?
+Riebulka Ryzis please dont, just dont
okay ill try on kerosene with racing fuel
Theoretically yes. I built one of these engines to run on methanol. It ran for about ten minutes and then the entire top end shot off because the threads for the studs in the block let go. I ended up having to helicoil to 5/16-18 and replace the jug and head .
It won't be able to shut off, since it self ignites
cut the airflow ant it will
Static vrs dynamic compression..there is a difference that isn't realized nor discussed in this video
try removed all the gasket of your motorcycle cylinder head, the top and the bottom gasket..
Air leak
Hey OK 😂😁😁😁😁
a belt sander can sand it down quicker. some ppl who are anal about true flatness of the head would hand sand it on a peice of glass with the sandpaper glued down.
a belt sander? wow....
I do it with vibration sanding machine
Sry for the late response but shoot us an email @ juicemotoparts@gmail.com and we would be glad to help!
Increase compression to 190 psi forged rod milled piston 40% bigger jet 20° timing advance and running on methanol 👍
you sound like Marilyn Manson
check out my motorised bike.. 70mph+
predenseanation ? what? dude its predetination as in the fuel detinates before the piston reaches TDC (top dead centre) which causes knocking or pinking which is the sound of the piston tapping against the cylinder walls as it is forced down before it has reached the top of its stroke causing it to twist slightly and knock.
Every one of these bike engine videos, regardless of whether it's engine rebuilding, compression working, port and polish...literally anything, offers NO measurements or torque values. No torque for head replacement, no measurements for compression increases....there is NOTHING out there!! That's why a lot of this stuff FAILS! Can anyone help with this? Surely the engine designers had specs in mind. What are they???
Doug Polk engine specs vary so widely but Frederic Chelminski on UA-cam- channel is his name -has alot of spec info and in-depth technical info about these kit engines.
Good way to ruin your squish.
totally moronic. if u want to increase the compression remove the head block bottom gasket alltogether and use reinz gasket glue to mate the head to the lower block.
thing is u totally make the bottom and upper rod bearings suffer , and these are the only ones than can go and destroy yr engine in less time than keeping it stock
Laz N and dont you think that would change the port timing?
Laz N that would fuck up ur port timing
This is not to raise the compression this is to find out if the head is warped! you would be there all day to remove enough by this method. Also there is more than just removing material to modifying a cylinder head. you really need to stop you need to learn a lot more before you try making these videos.
if you sand in a figure 8 motion and the sandpaper only removes material in some areas it shows your head is warped that's all this is ment for.