New Engine running - no power

Predator303

Predator303

New Member
hello again :)

i just finished installing a new complete engine (SkyHawk) and was able to turn it on after couple seconds. i have a couple questions. before i already went to the gas station i moved the bike trying to see how the engine turns without the clutched pulled and i realized that it actually turns (with spark plug in).

means, low compression or something isnt right and there is a leak. here is the first question:

- does for you guys the engine turn even if you are not sitting on the bike without your weight?

because my old engine would never turn without my full weight and a minimum of speed. it had a really good compression and was loud as h*ll. the new one sounds like those typical motorized bikes without any power that cruise around with 15-20mph - my old engine holy **** - it had much more power and sounded almost like a 1 cylinder harley.

i also noticed that something didnt seem to work well with the carb, because it wouldnt rev up even with the clutch pulled, basically like with choke. its stuck around 3.000rpm i would guess and to get there it takes forever.

now i have two explanations.

- either there is something wrong with the compression and i dont have full compression for some reason (i can only compare to my old engine

or

- this is how the regular engines come and my old engine was taken of a big piece from the head cover to increase the compression. i also find it weird that the engine does not really rev up, only like a turtle even though the carb was set up very good before.

- the other question or favor i have is, please somebody show me a good quality image of the bottom (combustion chamber) of a regular head (not SkyHawk). that would help a lot to answer my question, because my old head doesnt have that ring standing out as the SkyHawk. on the other side the chamber seem to be bigger at my old head.

thank you guys for any input. its already 1am in the morning and i worked all day on the bike and i wont turn it on anymore but it will be interesting to see the answers.
 
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lowrider, there is usally more than one possible solution to a problem. even when the engine turns over, the clutch can still be loose. if the engine is moving with the clutch released, that is the first thing i would check. I would also check to make sure that your headbolts are properly torqued, and that the head gasket is making a proper seal. The head bolts need to be tightened in a 'Z' or 'X' pattern. also check to make sure the spark plug is properly seated and tightened. There could also be oil behind the clutch pads from the factory, so check that as well. To adjust the clutch, pull the clutch lever in and back the flower nut off a quarter turn at a time and check the bike each time until the wheels dont move freely. if they rock back and forth a bit, that is ok. also check to make sure your clutch cable isnt too tight or too loose. if you check all that stuff and still dont figure it out, its probably an air leak.
 
also play with your idle screw a bit. Even if your carb was tuned good on your other engine, it may not work the same on the new engine. You have to realize that every single one of these engines is a bit different, and what works on one engine may not work the same on another engine.
 
bigbutterbean said:
lowrider, there is usally more than one possible solution to a problem. even when the engine turns over, the clutch can still be loose. if the engine is moving with the clutch released, that is the first thing i would check. I would also check to make sure that your headbolts are properly torqued, and that the head gasket is making a proper seal. The head bolts need to be tightened in a 'Z' or 'X' pattern. also check to make sure the spark plug is properly seated and tightened. There could also be oil behind the clutch pads from the factory, so check that as well. To adjust the clutch, pull the clutch lever in and back the flower nut off a quarter turn at a time and check the bike each time until the wheels dont move freely. if they rock back and forth a bit, that is ok. also check to make sure your clutch cable isnt too tight or too loose. if you check all that stuff and still dont figure it out, its probably an air leak.
Click to expand...

yes everything was correct and i checked all that already. i took off the head again and it doesnt looks like its sealed by reading the oil film but i just sanded my old head again, cleaned it and installed it and it have a little more compression now but still turns without me sitting on the bike but sounds like more compression now without turning it on.

i just double checked the clutch and opened the cable (screw) so its fully opened but it still is the same.

BUT i have to say that the clutch makes shuffling sounds and it was hard to push the bike (but that could also be because my disk brake is aligned new and might be too tight).
 
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if you turned it in, you loosened it. if you turned it out too far, that would loosen it a bit as well. turn it in a quarter turn and see what happens.
 
I tighten it a little more because the flower nut seemed to be stuck out too much but it didnt actually made any difference but its very hard to pull the clutch, i need all the power of my arm to turn the arm. still for me the way the engine turns too easy and especially how it sounds, its a compression thing. or does it take a while until the piston rings seal completely with those china engines?
 
Um, yeah, they take awhile to break in, at least a gallon of fuel. it still sounds to me like its a clutch adjustment issue. if its really hard to pull the clutch, its too tight. the clutch being too tight can make it act almost the same as if its too loose. pull the clutch in, lock the lever, and turn the flower nut out a quarter turn at a time until the wheels dont spin freely anymore and the engine kicks over smoothly.
 
interesting way to do it. i will try that first thing in the morning. i just checked your local time and its also 3am over there right?
 
The flower nut has nothing to do with the engine not revving up. It also has nothing to do with how "tight" the clutch is. It adjusts range of engagement.
 
You adjust clutch tension by turning the internal collar. If the bike has low compression, it will lack power.

Double check the inside of the clutch cover to see if it is rubbing while you have it off.
Then STOP TURNING THE FLOWER NUT!!!!!
 
I have had power issues caused by loose clutch in the past. also had revving issues due to over-greasing my gears, probably cause the excess got in behind the clutch pads, causing slippage. engine would rev, but bike wouldnt move like it should. also overtightened my clutch cable a tad once, and the clutch grabbed really hard. so yes, a slightly out-of-adjustment clutch CAN cause power issues. He also sprayed wd40 in his cylinder before starting the engine.
 
when you push the bike does it just roll with a little resistance ot does the engine turn over with the bike if it just rolls along its a clutch issue if the engine turnes with it its that your rings arent good and the engine is spinning with little compression from whats working.
 
@ butterbean yes but thats a different thing. it doesnt slip, it just 1. doesnt rev up from the carburator and 2. when i do get some speed and it rev up slow, i also feel that there is no good compression. i have to try now if its better with my old head that i installed last night or not, because if not it can only be the piston rings.
 
JonnyR said:
when you push the bike does it just roll with a little resistance ot does the engine turn over with the bike if it just rolls along its a clutch issue if the engine turnes with it its that your rings arent good and the engine is spinning with little compression from whats working.
Click to expand...

from my experience its a compression problem and the clutch might be too tight but that have nothing to do with the main problem of the compression or low power. i dont even think it have enough power right now to get it to roll from dead stop.
 
it could have been that head that you had not sealing right i hope its that and not that you have bad rings or a over sized bore with the rings floating in it or something stupid like that while you have the head off try lubing the cylinder wall with 2 stroke oil and see if it helps.
 
I will try the old head now and drive it a little to see if the compression is better or gets better and if not I take the head off and see if liquid run down the piston if I fill it up with some.
 
A picture is worth a 1,000 words ;-}

You have a new Skyhawk (48 or 66cc?) motor or whole kit?

If it's just the motor what carb and intake?
If it's a kit is it the CNS 1 carb with Z intake?

And the original head is on oriented which way? Plug pointed back, straight up, or forward? Or do you have the 'other' head on it?

No, you should not to be able to turn a new Skyhawk motor easy, it is not even 'easy' with the plug out. As they break in they loosen up in time not get tighter.

In short you may have 2 problems so help narrow it down ;-}
 
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