Clutch/bottom end Problem?

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stroker

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So I have this used bike that I've been troubleshooting that I started a thread about a while ago here:

http://motorbicycling.com/showthread.php?t=38092

But the thread is 3 pages long and a bit hijacked so I'll start fresh here.

I think I've got it narrowed down to the clutch/bottom end. The reason that I say this is because I can get the motor to run and sound like a 2-stroke should at high RPMs. But this is only with the clutch disengaged (handle pulled). With the clutch engaged the bike sounds kinda like it does in the video when you hear me twisting the throttle towards the end of the video. It barely has any power, and sounds bogged down, almost like a 4 stroke. With the clutch disengaged I can get it revved up to that high 2-stroke whin-whin-whin. But the bike also does not want to idle with the clutch in (idle screw on the carb. also all the way in).

Another reason I think it is the clutch is that the previous owner really monkeyed with the cable to the point where the end was completely frayed and unusable so I took it off and have no cable/ clutch handle. What I've been doing to test the bike is push the clutch arm in (the clutch bar over the motor drive sprocket, (it stays pushed in, is that bad?)) and then flick it out to engage the clutch/start the motor.

I also noticed when I pulled off the clutch cover there was quite a bit of strong smelling dirty oil/grease (maybe gas mixture?) on the inside of the cover.

I tried spinning the flower nut out a bit, but so far that did not help, would doing that more help? Is there such a thing as too much clutch engagement that causes the motor to bog down?

Thanks for helping out a rookie! :-||
 
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Al.Fisherman

Al.Fisherman

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stroker said:
So I have this used bike that I've been troubleshooting that I started a thread about a while ago here:

http://motorbicycling.com/showthread.php?t=38092

But the thread is 3 pages long and a bit hijacked so I'll start fresh here.

I think I've got it narrowed down to the clutch/bottom end. The reason that I say this is because I can get the motor to run and sound like a 2-stroke should at high RPMs. But this is only with the clutch disengaged (handle pulled). With the clutch engaged the bike sounds kinda like it does in the video when you hear me twisting the throttle towards the end of the video. It barely has any power, and sounds bogged down, almost like a 4 stroke. With the clutch disengaged I can get it revved up to that high 2-stroke whin-whin-whin. But the bike also does not want to idle with the clutch in (idle screw on the carb. also all the way in).

Another reason I think it is the clutch is that the previous owner really monkeyed with the cable to the point where the end was completely frayed and unusable so I took it off and have no cable/ clutch handle. What I've been doing to test the bike is push the clutch arm in (the clutch bar over the motor drive sprocket, (it stays pushed in, is that bad?)) and then flick it out to engage the clutch/start the motor.

I also noticed when I pulled off the clutch cover there was quite a bit of strong smelling dirty oil/grease (maybe gas mixture?) on the inside of the cover.

I tried spinning the flower nut out a bit, but so far that did not help, would doing that more help? Is there such a thing as too much clutch engagement that causes the motor to bog down?

Thanks for helping out a rookie! :-||
Click to expand...
A few things come to mind.... Vacuum leak, either through the intake manifold or at the carburetor. Seal leak, on either or both ends of the crankshaft. Could have a leak in the gasket between the crankcase and clutch case. Carburetor float or needle adjustment. The clutch wouldn't cause this problem, as long as the engine can run with the clutch handle pulled (clutch disengaged), and the engine pulling the bike without slipping (clutch engaged) I really don't see a clutch problem, unless I missed something.

 
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S

stroker

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Well I don't think it's the carb, I've tried 2 different ones and different needle settings. I don't have an O ring between the manifold, so I guess I could try that.

I did forget to mention there is a bit of the smelly oil (gas?) leaking out onto the frame, but I think it's just coming from behind the clutch cover.

I just figured it was something to do with the clutch since the motor behaves completely different with the clutch engaged? The motor barely pulls me and bogs down with it engaged. But I really don't know much about the bottom end and the crankcase and how all the seals and gaskets work. And I don't really understand your picture, motor with the jug pulled off?

Sounds like a complete motor tear down for a fix, which might be a bit beyond me at this point. Probably buy another whole kit since its just a bit more than just the motor. Then rip this sucker apart and learn about it when I have time?

Thanks for the help Al.
 
Bikeguy Joe

Bikeguy Joe

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How does the bike ride with the engine off and the clutch pulled in? I mean does it ride O.K., or is something dragging causing the engine to be over taxed?

How old is the gas in it?

What color is the plug?
 
S

stroker

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The bike rides fine with everything disengaged. Other than being heavy cause it has a useless motor on it ;-)

Gas is good. Come on, give a little credit.

Plug looks new, tried a different known working plug as well.
 
Bikeguy Joe

Bikeguy Joe

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Alrighty then....what I meant was "what color is the plug?" "Looks like new" tells me it's shiny. It should have some carbon, or a brown or grey color to it, unless you haven't run it more than a few seconds.

I would love to "give credit" but when folks are doing long distance diagnostics for folks that can't get a bike to run, we have to ask the obvious and esoteric.

Sometimes people have "good gas" that is months old, or mixed at 16:1.

See what I am saying?

From what I saw in the video (heard) it does at least fire up. You said it runs with the clutch pulled in, but that's not in the video.

I think you also said in the other thread that it is leaking gas (unburned raw gas/oil mix) from behind the clutch cover? That ain't right.

Did I get any of this right?
 
Bikeguy Joe

Bikeguy Joe

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I know this sounds like a stupid question, but how fast are you pedaling when you let the clutch out? If the engine is very new, it's possible you could just be going too slow when it starts and it won't pull the weight.
 
S

stroker

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Ya the ceramic? is white still on the plug. At least the last time I had it out before I got it to run @ high RPMs with the clutch disengaged. I guess I should check it again.

Think the gas is somewhere around 32:1 with good oil, not more than a month old.

Ya that video is from a while ago, before I got the motor running for more than a few seconds. I guess I could take a new one, might be hard to juggle the phone though.

There is stuff behind the clutch cover and looks like its leaking out a bit between the cover also. Not sure what it is, but its dark colored and like thin oil, not grease, also has a strong smell, not sure if its gas or some kind of lube from the crank case. I did have some gas spill from carb work I was doing, and that it right below the carb.

Thanks.
 
S

stroker

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I go down a hill pretty good when the clutch is out, pop the arm and that is how I get the engine running. Then I disengage the clutch and I can get the engine sounding good, like my other bike that runs good.
 
Bikeguy Joe

Bikeguy Joe

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Sounds like gas from the carb leaking....but I can be wrong. You may want to take the clutch cover off and see how much is in there though. We are talking the bigger rearmost cover on the right (sitting on the bike) right? Still if it's from there probably from the carb leak.

Try running it at "high(er)" rpms unloaded for a few minutes, then after it cools off a little remove the plug and have a look.

A month old can be pushing it for some gas, depending how/where it was stored, how old it was when you got it ect. still it should run if it's within reason.

You said you tried a couple of different carbs, but where is the needle adjusted? NT or CNS carb? I don't know jack about the latter...
 
Bikeguy Joe

Bikeguy Joe

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If you had a cable on there, I would say get it running then pick up the rear of the bike and let the clutch out and run it and see what you get.

Also, probably been asked, but did you check for an air leak yet?
 
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S

stroker

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2 different NT carbs, one is older white style air filter cover, and one is new with the black style filter cover.
Needle setting in the 2nd one from the top and all the way to the top. My other bike runs good in the 2nd notch down.

Not sure on the air leaks, don't know how to check really, listen for hissing? I should probably go get a few O rings for the carb/manifold. Do any O rings work or do I need a special gas resistant kind?

And ya the clutch cover the one with the 2 gears and the flower nut, yes there is oil/grease/gas mix whatever in there.

If I picked up the rear end, the wheel would spin with the clutch out, because it does pull me on flat ground just barely- it just bogs down and I can't get the motor to rev up at all even at full throttle. Now with the clutch arm in I can get that bad boy to redline!

The gas is fine in my other bike.
 
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Al.Fisherman

Al.Fisherman

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Please explain..
stroker said:
If I picked up the rear end, the wheel would spin (engine running?) with the clutch out, because it does pull me on flat ground just barely- it just bogs down and I can't get the motor to rev up at all even at full throttle. Now with the clutch arm in I can get that bad boy to redline!
Click to expand...
What you are describing sounds like...
1) incorrect timing..check the key in the magnet it might be stripped,


2)compression leak. Check compression, it should be higher then 120 psi.
 
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