I just finished installing it. when i rev the throttle the engine revs, but the bike does not move. I tried with the choke on and the bike moves just a little bit but there is almost no power. I pulled the throttle all the way but it just sounded like it was damaging the engine and barely moved at all. did i put too much oil in the crankcase maybe? any thoughts?
no power in newly installed 4 stroke
- Thread starter jerry campo
- Start date
What is your gearing like? Is the engine stock? How much vibration is there when you pull the throttle?
what do you mean exactly by gearing? for the engine or the bike itself? i bought the 4 stroke engine kit off of ebay.com, it came with the engine and everything else needed for the conversion. there is moderate vibration unless i pull the throttle all the way and max out, then i really feel it vibrating a lot! i hear it nmaking clanking and rattling sounds. also it seems to want to die out on its own so i give it more gas via the throttle. i think its also possible my carb got clogged up or something
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Your carb is lean or your idle adjust screw is too far out, and your bike's gearing is too high. The vibrations are caused by the clutch trying to engage, and the dying is caused by low idle or a small or blocked jet.
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i see. ill try adjusting the idle screw first before i try cleaning the carb. how do i fix the gear problem?. do i take the clutch cover off?
EDIT: I just took off the clutch cover to expose the clutch. it smelt of burnt rubber and there was a lot of black powder that was shaved off the clutch from all the friction. it looks like it has been failing to engage as you said. what do i do now?
EDIT: I just took off the clutch cover to expose the clutch. it smelt of burnt rubber and there was a lot of black powder that was shaved off the clutch from all the friction. it looks like it has been failing to engage as you said. what do i do now?
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First, what is your engine size? I don't know much about the 49cc clutches, so I won't be able to help with that one.
If it isn't a 49er, what is your clutch type? If it's a cvt, then you need to replace your belt and increase the tooth count on the wheel sprocket. If it's a centrifugal clutch, you need to just replace the unit, and increase the tooth count. If it is a 79cc, are you running the transmission plate? If not, do so. That could be the primary reason it isn't grabbing. The 79cc engine needs that gear reduction to be able to function properly.
its 49cc 
. the clutch has 3 engaging sites with springs at each one it looks like. its exactly like the one is this video
. the clutch has 3 engaging sites with springs at each one it looks like. its exactly like the one is this video
Ok, so you need to get yourself a caliper and measure that shaft. You will also need to get a clutch puller just in case it's tapered. If it isn't, at least you were prepared. When it comes to tools, there is never wasted money unless the tool is ridiculously expensive, like a certain spoke threading tool sold on Amazon....$400, what are they runnin, a highway robbery ring? Anyways, you will also need a torque wrench, some shop rags, and a soft bristled brush to sweep away all that clutch pad material.its 49cc
Ok, once you have all your tools, you can go about pullin off that burnt up clutch. To do that, just follow the video's instructions at the beginning and end. Skip all the case stuff unless you want to do some internal upgrades, like replacing the apparently plastic cam gear...plastic? Like, what is PLASTIC doing in such a critical area?
Once you have your clutch replaced, its time to do some preventative care. Check your gear ratio. To do this, count the teeth inside the gearbox, dividing the large one by the small one, and then do the same for the output sprocket and wheel sprocket. If it doesn't reach at least 14.0, your gearing is too high and your clutch isn't engaging. If you've got the stock 44t, up it to a 52. In this case, it's better to go too low in gearing than burn up another clutch. It is also a good point to be able to ride the thing while also diagnosing fuel delivery. Poorly running, your engine should be able to do about 18mph with a 52t, 20mph when running right. At that point, you can start experimenting with gearing.
One other thing, and this is important: make sure there is no oil leaking around the shaft! Any present oil will make the clutch slip under power, generating a lot of heat that will anneal the springs and lock the clutch. This is what is known as heatlock, and is pretty well known around the 4 stroke community.
If anyone else knows any better about these little things, now would be a good time to pitch in.
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Jerry make sure all three shoes spring outward, use a screw driver to move them. Look for any points that may be preventing one from making contact with the drum, you may be able to see the lack of wear on one shoe. You are pedaling up to speed before giving it gas right?
hey Greg, one of the shoes has significantly less wear than the other ones. all 3 shoes spring out, but I dont see anything that would prevent that one from springing out all the way and engaging. do I look for anything specific? what if I just put a spacer behind the clutch bell so that it is closer to the clutch, would that work? if not, would getting a new clutch really help? im afraid of getting a new one and having the same problem still. thanks for your responses guys.
Try moving the spring to another shoe and see if the problem moves with the spring, also look for a spot on the plate the shoe can hang on.
i will try and switch the spring around in the morning. what exactly do you mean by finding a spot the shoe can hang on? and just to clarify, the clutch isnt engaging because that last shoe isnt touching the bell right? or at least that is what is suspected to be the issue?
The back plate that the shoe rests on may have a rough spot causing the shoe to stop spring out, look at it closely and see if there's something different about it.
You can sand the shoes and the drum to give it more grip, slipping causes hot spots that will chatter.
i just broke the clutch trying to check the shoe movement. i managed to get the whole clutch off without the pulley tool pretty easily, i ordered a new clutch right now. the clutch i just broke has the keyslot and i dont think the new one does. does it matter? anyhow, i found oil leaking into the clutch area after i removed the clutch, must be from when i over filled the crank case, and this might be the cause of this all
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