So I just picked up a used crf 70 with a supposedly brand new lifan 125cc motor. Previous owner just put the motor on the bike and said he never even started it. He couldn't get it started when we came to look at it but I bought it anyways. Turns out it wasn't wired right. Brought it home fixed the wiring and then it fired up. However it runs like crap. It sounds weird and smokes like a 2stroke. I'm not sure which way is choke but if I turn the choke lever one way it revs really high. If I turn it the other way it almost dies but barely runs and the little piece the choke lever pushes vibrates like crazy. I cant get the right amount of slack in the throttle cable either. It seems way too long so I can't really make the bike rev. When I got the bike before I started it I checked the plug and seemed slightly oily on the end like it had been ran for a few minutes but still looked new. Then I ran the bike for maybe a minute and a half and pulled the plug again and it was very oily. So its obviously running very rich. So I assume the jetting is off which is causing the smoking but I'm not quite sure how to fix that. This bike smokes a lot, oh and its blue smoke if it matters. So any ideas on how to fix the smoking and get the throttle adjusted properly?

Ok sounds like you bought someone else's problems.  Asuming that the engine is not wore out and he lied to you claiming it was new/never ran.  You have multiple issues and a few things need to be checked/fixed before you can properly diagnose if the jetting is off. First off drain the oil and fill it up with the correct type of oil and  quantity/amount (usually 850cc but if it has a dipstick use that), sort of sounds like the guy overfilled the oil OR didn't change the shipping oil (contributing to the smoke).  Next is the throttle cable.  I asume he just used the stock CRF70 cable which may or may not work with the carburetor you have, sounds like it doesn't so you might want to source a shorter cable and throttle assembly.  This is asuming there is not enough range on the screw type adjuster.  Next, remove the air filter and you can see the correct position for the choke "on" or "off" the vibration of the choke handle is normal.  With the choke off and the engine up to temperature if the bike will not idle try raising the idle speed by turning the screw that is in the center of the carburetor with the air filter off you can watch the slide move up and down while adjusting this screw.  After correcting all these issues and with a brand new spark plug you can now try and determine if the jetting needs some work.

Understand I am asuming A LOT with your information given.  The guy might have sold you a completely worn out pile of sh*t.

Follow me or ask me a question http://teammgr.weebly.com/  I have lots of info here and constantly update it.

Edited by thejunkman, 12 April 2012 - 01:11 PM.

Well I think you hit the nail on the head with the too much oil theory. They guy told me he never even put oil in it. So when I went to buy the bike I checked to see if it had oil in it just to see if I could kick it over. The bike was on a hill so I didn't realize it had wayy to much oil in it. So my dad was trying to tune the carb today to get it to run good and of course while it was running the clutch cover seal suddenly started to leak oil, a lot. I wasn't there but when I came back I noticed a big oil stain on the floor so it seemed like a lot came out. I checked to see if it had any oil in it and surprisingly it was over the amount that it should be on the dipstick. So it must have had to much oil which caused the seal to fail. Do you think that the excessive amount of oil would be causing it to smoke so much? I'd like to try and start it up now that it has a lot less oil to see if that's the problem but, I am not sure that I should with the bad seal, however it still has enough oil in it to run and it doesn't seem to be leaking now that its just sitting and not running. It seems like a new engine. None of the paint is worn off the cases or anything. Thanks for your help.

Drain the oil and replace it with the correct type and quantity.  Use a decent quality oil.  Clutch cover seal, as in the gasket? or the kickstart seal?  Either way put the correct amount of oil back in before going further.  And yes too much oil will cause smoking because of the design of the horizontal cylinder.  Also make sure the crankcase vent is open and clear, inadequate venting can cause blown or leaky seals because of the pressure that builds up from the crankshaft and piston moving inside the engine.

Its leaking from the clutch cover seal. Any idea how much oil it takes or do I just use the dipstick?

Read my other posts. If it is the gasket around the clutch cover that is leaking try tightening the bolts just a little bit more, but not too much you can either strip the threads or break the bolts.  IMO an brand new engine should not leak oil around that gasket unless the cover has been removed for some reason in the past.

So I drained out the oil. There was around 1250cc's of oil in it. I assumed that both of the large bolts on the bottom were drain plugs.  One of them had some type of oil strainer come out of it and I'm not if I just shove it back in or it goes in a certain way because it had holes for the oil to flow through. Here's what it looks like along with the bolt that holds it in.



It came out of the hole on the right side of the picture which is on the left side of the bike.

Well apparently that is the cam chain tensioner, right? Can I just shove it back in and put the bolt on?

Yes, the piston goes in first, (black plastic tip end first), then the spring (small tight coiled end in first), and then the cap.

Note to self: No need to remove the cam chain tensioner assembly for an oil change.  

Yea haha, I had noo idea that was the cam chain tensioner, I thought it was just another drain plug.

I drained it out and it had about 1400cc's of oil in it. So after refilling it with 800-900cc's of oil it still smokes. Less than before but it still does. Is there a fuel mixture screw on the carb for this bike? Oh, and any idea what size throttle cable to order?

Post up a few pics of the carb you have, from a few different angles, and we can all see what you have to work with.

Here's the backside
and heres the front

It looks like a Keihin carb from an XR/CRF70. In your pic above, you have the choke up in the ON position, the air screw should be a small brass screw that goes into the carb body at an angle just behind the choke lever. The stock carb used a throttle cable with the carb cap attached to it. Your best bet would be to unbolt the carb at the manifold and undo the carb cap from the carb body, to see if the cap is attached. If so, you can just order a replacement cable with the cap.

Tutorial on setting the idle mixture screw if you need it.

http://teammgr.weebl...adjustment.html

So I finally got some time to work on it. I think I got the throttle adjusted right, it actually works now. It wasn't in the cap in the carb very well. However I still cant get it to run right. The fuel screw is in one of the hardest positions to adjust, I cant get a screw driver on it so I have to adjust it very slightly with pliers which is very difficult to do with it running because I keep burning my hand cause this bike gets so darn hot. Before I had the throttle working it would run very oddly. Sometimes idling quite high and then it would all of a sudden rev wide open. Now that the I got the throttle on there and did some minor adjustments with the fuel screw it idles slightly high when I start it and keeps getting higher and higher very quickly until its wide open after about 4 seconds. So now its very had to adjust the fuel screw when its running. I can keep it from going wide open if i hold the brass colored knob the choke lever pushes on slightly still. If I hold it completely still  it shuts the bike off and that's my only way to kill it since it has no kill switch. So how do I stop it from immediately revving so high? Is it possible that there's not enough free play in throttle cable?

So today I loosed up the throttle free play as much as possible. I started it and it was just idling high and the rpms were no longer rapidly climbing. Let it run for about 2 minutes while I was getting my tools to adjust the carb and it started to get very hot quick and then it started to smoke out of the part where the exhaust connects to the engine and it sounded like something was loose inside the engine and was rattling around so I shut it off right away. This bike seems to run completely different every time I start it. Sometimes bogging sometimes idling very high and sometimes lots of smoke out of the exhaust.

Here's is some more pictures of the carb.


I assume this is the fuel screw right?


What does this screw do?

and just to clarify which way is choke?



And here's where its leaking oil from

Edited by DMS 56, 04 May 2012 - 01:30 PM.

Pic1. Yes, that is the fuel screw, you turn it OUT to richen the mixture, and IN to lean it.

Pic2. That is the idle adjustment screw, to raise or lower the RPMs at idle.

Pic3. That should be choke is ON position. The small groove and slot on the choke handle is where you would attach a choke cable, and, pulling on the choke cable knob or lever would lift the arm up to put the choke ON. You can verify it by removing the airbox and looking at the butterfly plate in the carb.

Pic4. Should be the choke OFF position.

Pic5. There should be a big round gasket behind that clutch adjuster plate, or you could use a thin layer of YamaBond or ThreeBond 1194 to seal it and stop the oil leak.

Have you checked for air/vacuum leaks between the carb and the cylinder head?