I had no experience in mechanics at all and i thought, "hey might as well build a motorized bike", I installed a grubee skyhawk "80"cc on a cruiser and it turned out pretty well. Ive been looking at threads on this site for a couple days and just registered. while I have learned a lot, i still have a few questions if anyone could help me out. I live in an area full of up and down hills, I have a 44t sprocket and while i can tackle the hills the engine really strains and i have to give it some leg power and Im a lazy person.a shift kit is not an option for me and i was wondering if an expansion chamber would help me out on the hills. My max on a straightaway is about 20. The the engine bogs out at full throttle but i think it is just a cable problem. could my speed be a carb problem because it is at factory settings. Im really just shooting in the dark here and have no idea what im talking about so sorry if i sound like a total moron right now. Thanks for taking the time to read this and responding to a total noob's questions.
New and Inexperienced :D
- Thread starter Ryanp
- Start date
Welcome to the forum. You've come to the right place for help and advice.
If you live in an area of steep hills and are not looking for high top speed, you might consider going to a little larger rear sprocket. A 48 or even a 50 tooth sprocket will give you a lower gearing and better hill climbing ability.
As for you current top speed these little engines will run and perform better after a few gallons of fuel. The break in time is when we recommend a fuel mix of 24:1 then after a couple of gallons moving down to a 32:1 mix. Do not use the 16:1 often recommended in the installation instructions. That's just too much oil.
To determine where you are as far as your fuel to air mix you'll need to determine this by reading spark plug color. You want it to be a nice chocolate brown color. Not black and not too light in color. Too dark will indicate a rich mix and that can be fixed by raising the clip on the carburetor needle a notch or two. If the plug shows light grey to white it means the mix is too lean. Lower the clip a bit. I'd wait until you have some miles on the engine before trying too many changes however. A well broken in engine will tell you what it needs better than one that is new. Good luck, ride safe.
Tom
If you live in an area of steep hills and are not looking for high top speed, you might consider going to a little larger rear sprocket. A 48 or even a 50 tooth sprocket will give you a lower gearing and better hill climbing ability.
As for you current top speed these little engines will run and perform better after a few gallons of fuel. The break in time is when we recommend a fuel mix of 24:1 then after a couple of gallons moving down to a 32:1 mix. Do not use the 16:1 often recommended in the installation instructions. That's just too much oil.
To determine where you are as far as your fuel to air mix you'll need to determine this by reading spark plug color. You want it to be a nice chocolate brown color. Not black and not too light in color. Too dark will indicate a rich mix and that can be fixed by raising the clip on the carburetor needle a notch or two. If the plug shows light grey to white it means the mix is too lean. Lower the clip a bit. I'd wait until you have some miles on the engine before trying too many changes however. A well broken in engine will tell you what it needs better than one that is new. Good luck, ride safe.
Tom
Thank you very much 2door. Im running on the 16:1 ratio right now and im glad to have someone actually give me their knowledge instead of reading the straight outta China instructions. Ill probably drain that stuff out and give it a leaner mixture. also thanks for the adjustment tips, ill definitely pull that plug out after a few more miles. I didnt imagine such a quick and helpful response so thanks again. Oh and hello dan thanks for the greeting 
Make sure you mount the engine nicely to reduce as much vibrations as possible; also look through the forums for tips on reduction vibrations.
I found too much vibrating will shake up the fuel line and you'll start seeing gaps between the fuel in the line and this bogs down the engine because not enough fuel is running into it.
Forcing you to idle a bit for the fuel to collect in again, but also riding slower for less vibrations.
Someone suggested enlarging the fuel needle value thing or something (I have to find that thread again to double check) to allow more fuel in at a time, which helps.
I found too much vibrating will shake up the fuel line and you'll start seeing gaps between the fuel in the line and this bogs down the engine because not enough fuel is running into it.
Forcing you to idle a bit for the fuel to collect in again, but also riding slower for less vibrations.
Someone suggested enlarging the fuel needle value thing or something (I have to find that thread again to double check) to allow more fuel in at a time, which helps.
if it bogs out at wide open throttle chances are your carb needs to be adjusted, there is 2 screws on most carbs try playing with those a bit until you get it performing better.
for the fuel/oil mix i use 32:1 break in and running it. i have had no issues mine is a 66/80 cc grubee as well. definitely sounds like a carb issue for the bogging down, check the spark plug color to see if its lean or fouled . if its too lean it will be white or a really light color, if its brown without gunk all over it its about right, if its black with a bunch of gunk you are running to rich. Fuel air mix can be changed by the needle clip setting.
Well i think its been a week. i took my bike out for a ride a few times during the week and for some reason it let me go full throttle and i felt a serious power increase from the last time i rode it. I did nothing to it. Maybe the engine is breaking in? But i still think you guys are right about my carb. im going to check the plug soon. for some reason, my engine is very inconsistent. for instance if im on a flat surface riding at a constant pace. ill feel a satisfying vroom followed by a few bogging sputters, then back to the vroom, this repeats throughout the whole ride.
The intake manifold gasket from the factory is a joke . Changing it will improve starting , idle , and high speed running , if you address this next . I put it off for awhile only because I was a casual rider . But it was one of the first adjustments I should have done .
Hey Ryan, I think that sputtering may be what is referred to as 4 stroking. Sounds like your engine is running a little rich. I would leave it that way for break in for now. It may be just right after break-in.
It is safer to run a little rich during break-in because rich mixture=cooler running. Also means less power and economy.
After a few tanks of gas, If it's still sputtering(4-stroking) a lot at high speed, you can work on leaning it out some.
I usually always try to keep the mixtire adjusted to where I get just a little 4 stroking at high speed,so I know that it's not too lean to cause damage when I run the sheet out it LOL or hafta climb a long hill.
To get an accurate plug reading you need to do a plug chop.
Run it hard at high rpm for about a munite, then immediatly and simontaneously chop the throttle,pull the clutch and press the kill switch, and coast to a stop.
DON'T try to remove the plug,or mess with any fasteners on an aluminum engine while it's hot! Good idea to use anti sieze lubeon the plug threads too. But beware that with thread lube,,versus dry threads, that you need to use less torque when tightening things to avoid stripping threads.
I normaly run walmart 2-stroke oil at 50-1 in all my 2-strokes, ultralight planes included, but any oil rated TCW-3 is good. Some of them are 20 yrs on this mix. Never had any problems with wear or carbon buildup.
When I open up a recently run engine ran on 50-1, there is always a rather thick coating of oil everywhere inside, so I don't see any reason to use more than 50-1 oil in my mix,except for break-in. I use 32-1 for that.
This is just my experience, YMMV
