How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask RSRBOB Your Own Question
RSRBOB
RSRBOB, Technician
Category: Motorcycle
Satisfied Customers: 1078
Experience:  Former Factory Service Rep, Dlr Line Tech, Service Manager, General Manager, Store Owner
10825618
Type Your Motorcycle Question Here...
RSRBOB is online now
A new question is answered every 9 seconds

2012 250 (lifan engine) same as virago. sometimes it will

Customer Question

2012 250 (lifan engine) same as virago. sometimes it will start, but will not idle. If I can get it to start and keep it at high RPM's it will seem to run alright. At idle it is running very rich and I have tried to adjust the mixture screw but to no avail. The carb has been thoroughly cleaned but still no luck
Submitted: 1 year ago.
Category: Motorcycle
Expert:  RSRBOB replied 1 year ago.

Hi and thank you for your question.

My question is, who cleaned the carbs? This sounds like a carb issue. The lack of idle is usually a clogged pilot jet. However, the symptom of running very rich could indicate a float related problem. Either it is not shutting the fuel off soon enough or the needle valve assembly is leaking.

RSRBOB

Customer: replied 1 year ago.
the bike only has 314 miles on it. I pulled the carb, pulled out the pilot jet, pulled the main jet, pulled the float and needle, pulled the diaphragm and needle, soaked it in carb cleaner for 2 days, then blew out all the ports. I used the good old tube adjustment on the float and got it running, but still rich as can be at idle and of course shuts off after a few seconds of idle. New float needle put in just because I was running out of ideas.
Expert:  RSRBOB replied 1 year ago.
Thank you for the additional information.
The only question I have left relative to the carb clean is what brand of carb cleaner did you use?
Setting that aside and getting back to basics, an internal combustion engine needs 3 things to run. Compression, fuel and ignition.
The symptom you described fits best into the fuel, or lack thereof, category. That doesn't mean its the only option, just most probable. That having been said, we can check all three to see which one is missing.
I will leave the order of testing up to you.
One test is to start it and run it and spray starter fluid into the intake as the bike is wanting to die and see if it gains RPM's again. If it does want to continue to run or rev with the starter fluid, it is not getting fuel and that is what is causing the problem.
Another test would be to put an automotive type inductive timing light on to one of the spark plug leads and start the bike, pull the trigger on the timing light and observe the flash. Now, let the bike return to an idle and see if the flash of the timing light goes away. If it does, you are loosing spark. If the bike dies but the flash doesn't stop then we are not loosing spark.
The third test would be compression, or mechanical condition of the engine. This requires a compression tester. Use is pretty self explanatory with 2 small details to be remembered. Ground the spark plug leads away from the spark plug holes while testing (both plugs out during testing) and hold the throttle wide open during cranking for the test.
Let me know what you find and if you need more help.
Thanks
RSRBOB
Customer: replied 1 year ago.
I might be a little off here, but at idle is where it starts to run really rich, smoke and all out the exhaust. I will try the timing light out and see what I come up with. However I am not sure how the engine can quit and the light keep flashing, but I think I know what you mean and just want to make sure we are on the same page. I can also do a compression test again and let you know what the outcome is. I appreciate your help, but these are all things that I have already done other than running the timing light. I am really looking for the off the wall thing to check because I do this sort of thing everyday of my life and I am out of ideas so please look for the strangest thing you can think of.Thank you for your time
Customer: replied 1 year ago.
sorry I forgot the carb cleaner was just gumout but all ports were cleaned with everything from pipe cleaners to pieces of copper wire.
Expert:  RSRBOB replied 1 year ago.

I guess it depends on exactly where the throttle setting is that it starts running rich. An off the wall thing to check would be wear on the jet needle and needle jet. More times than not I find these problems to be because of something that was overlooked as opposed to black magic or demonic possession. The test about the spark when it wants to die is seeing if it looses spark and then dies or not. If spark is not the reason for it wanting to die, as long as the crank is spinning and the ignition is functional, it will spark for the brief time as it winds down. What you are looking for is to see if it looses spark first and causes it to die. It is harder to explain than it is to see but I am confident you can tell which is happening first.

The reason I asked about the brand of carb cleaner is I have seen carb cleaner/cold parts cleaner for sale at auto parts stores and have little faith in those products to clean internals on carbs. I have found products with dual purposes such as that to be degreasers and have no effect on the residue left behind from evaporated gasoline.

I am not trying to be insulting to your intelligence nor your competence, but to be able to help you, I need you to answer the questions I would be wanting answered in my own mind if I were looking at it myself. So far,you have been very accommodating on providing those answers.

RSRBOB

Customer: replied 1 year ago.
LOL yeah I haven't found anything yet that I can blame on demonic possession however this one might make me change my mind. Bike at idle is running at 1300 RPMs a little on the high side just so I can keep it running. Timing light stays blinking until the engine dies, and I have checked the jet needle and installed new jets just for arguments sake. I agree with you on asking the questions you would run through your own mind and that is why I am here because I ran out of ideas to ask myself and figure some sort of outside ideas might cover something I missed. Once again thank you for your time and patience.
Expert:  RSRBOB replied 1 year ago.

Thank you for the additional information.

When you inspected the needle, what were you looking for? Also, understand that the jet needle and needle jet function together. I have never seen any carb rebuild kit that included the needle jet. Needle jet A.K.A. emulsion tube, what the main jet screws in to.

Did you try using the starter fluid spray as the engine was wanting to die? We want to do this because if it has no effect on the engine running, it means we are not facing a fuel supply issue. It still sounds to me like it is a fuel supply issue, for reasons yet to be determined.

You also have not mentioned what you used for carb cleaner, and the reason that is important to me is not all products work as well as we would like.

I don't think I asked you where you have your float level set at either. Have you set it, measured it or checked it?

BTW, does this engine use a Mikuni carb? If not, what brand carb is it?

Thanks

RSRBOB

Customer: replied 1 year ago.
Carb cleaner is just gumout, starter fluid as the bike dies doesn't do much good because by this time plugs are pretty much fowled. I only installed a new main jet (120) as I said just for argument sake and yes this a Mikuni carb. I used the clear tube way of measuring floats and I am sitting about 3/4 up the side of the carb. These have not been tampered with yet. I am having a hard time thinking it is lacking fuel only because of the rich mixture at idle, but I am still open to all ideas.
Expert:  RSRBOB replied 1 year ago.

Thank you.

Did you take a look at the enrichener plunger? I have seen the rubber seal on the inner end of that crack and cause leaks. Did you have to use a wire or anything on the pilot jet to get it cleaned out? Also, you mentioned 1300 RPMs. Are you measuring this with a tachometer? I imagine a Lifan does not come with a tach, but do you have an inductive tach? A 250 V Twin is not going to idle at 600 rpms like some harleys do. I would say idle speed on a Virago 250 is right around 1000 rpms.

On the mixture screw, are you turning it in to try to lean out the mixture? In is lean, out is rich because it is a fuel screw and not an air screw.

The next question would be what does the air filter look like? Have you tried seeing if it will idle without the air filter? I do not expect it to be able to rev up without an air filter but it should idle. We need to think of overly rich as too much fuel for the air, whether it is excess gas or insufficient air.

RSRBOB

Customer: replied 1 year ago.
Rubber seal is like new. I don't see any cracks or anything that would cause problems. As far as cleaning jets there was really nothing plugged up I just ran some wire and pipe cleaners through for my own mind set. I started the mixture screw all the way in with just a light pressure and the backed out one turn and worked from there. The air filter is a K&N foam filter and idles a little bit better off and actually revs and runs better without it. Yes I have a tach and dwell that I hook to it.
Customer: replied 1 year ago.
Would changing the pilot jet to a lower number maybe help my situation? Right now it has 2.0 in it, could a 1.75 maybe do me any good?
Expert:  RSRBOB replied 1 year ago.

Thank you for the additional information.

If you ran a wire through the jet, and this thing runs better without the air filter than with it, I would suggest starting with a stock size pilot jet. Being a brass jet, it is really soft and very easy to enlarge, causing the bike to run rich. Stock pilot jet on a 2006 Virago 250 is a 17.5. I therefore agree it would be a worthy test to put a new 17.5 PJ in and see if it runs better. If your fuel level is only about 3/4 of the way up on the side of the float bowl, it is too low. On the Virago carb there should be a line cast into the float bowl that is used for setting the fuel level. I don't know if aftermarket carbs include that or not, but I suggest taking a look at the float bowl to see if it is there.

RSRBOB

Customer: replied 1 year ago.
I am going to try out a 175 in the morning and let you know what happens. As far as the float goes, if it is too low all I have to worry about is maybe running out of fuel on WOT with a load on it right or am I missing something? I know floats have a place they should be set at, but I always thought that set wrong you either run out of fuel or fuel runs out of the carb.
Expert:  RSRBOB replied 1 year ago.

That is generally correct on extremes in the float height.

Currently, since it sounds like your float level is low, I don't suspect that is what is causing the rich condition.

Altering the float height in 1mm increments can make fine adjustments to mixture, but, as I said I don't believe we are that close yet.

We need to get this overly rich condition straightened out then see if it runs out of gas at high RPMs. Running out of gas at idle is not a symptom of float adjustment.

Let me know how the 17.5 PJ works out for you.

RSRBOB

Customer: replied 1 year ago.
Well I changed out to the 175 pilot and it runs at idle a little bit longer, but still loads up after a few minutes. New thing since changing the pilot jet is the plugs are actually melting on the ground side. Put in new plugs and for the first few minutes it sounded and ran great then started to die down. I tried to adjust the mixture screw a little at a time but like my initial problem it seems to make no change. Should I maybe try a smaller pilot jet? Also there is a marking on the float bowl and I was off about a 1/16 so I don't think that is too far off, but I set the float to match it by the tube method.
Expert:  RSRBOB replied 1 year ago.

Thank you for the additional information.

I would not suggest going any smaller on the PJ.

It is scary that the plugs are melting. Exactly what spark plug are you running?

RSRBOB

Customer: replied 1 year ago.
NGK CR6HSA
Expert:  RSRBOB replied 1 year ago.

Thank you again.

If your float level is low, you need to adjust it.

The plug is an optional plug, but close. The melting symptom is very concerning to me. Melting is from extreme heat, heat that is generally associated with leaness.

This seriously sounds like your engine has 2 different problems going on at the same time.

The melting plug sounds lean, which could very well be. I also think your fuel screw should be out at least 2 1/2 turns as a starting point. Small adjustments at first on your fuel screw are not going to make a monumental difference. I suggest if you want to see if adjusting ti will help, start out turning it one half turn at a time. If it improves running, back it out another 1/2 turn. Keep doing that until it starts getting worse, then come back in 1/4 turn at a time until you achieve max idle.

Another possibility on the lean condition is an air leak. Have you sprayed the intake manifold from the carb towards the cylinder heads with contact cleaner to see if it affects the RPM? If you have an air leak, it will either cause it to rev up or loose RPM. Any change in RPM while spraying the contact cleaner is bad. It means it is sucking air from somewhere and you need to investigate that.

When you pulled the plug out, even though it was melted, was it dripping in gas? What color was the tip?

If it truly is flooding out, either the needle valve isn't seating or the O ring around the outside of the needle seat is leaking and letting fuel flow past it. This is all very confusing symptoms because you said it is flooding out, yet the fuel level is close to being correct. Normally those two conditions do not co-exist.

Let me know about the color of the plug and the results of the air leak test and we can go from there.

Thanks,
RSRBOB

Customer: replied 1 year ago.
Not getting anything as far as air leaks. Plugs are soaked and black as can be. I can turn the mixture screw almost all the way in or take it almost all the way out and it has no effect on the running of the engine.
Thanks again
Expert:  RSRBOB replied 1 year ago.

This is making no sense whatsoever. I am totally missing something here.

Plugs that come out black and dripping do not melt. Excess fuel, whether it is overly rich or flooding out, which it sounds like at any given time either situation applies to your engine, cools the combustion process. Leaness causes excessive heat that could melt spark plugs.

Have you run this with the air box off so you can see if raw gas is pouring into the intake? If it is, it shouldn't be. The other huge contradiction we have going on is you say you can check the fuel level and it is about where it is supposed to be, but the plugs are dripping, and I am assuming they are dripping gas. Is it gas or is it oil?

I need to back way up here. I realize the bike has 314 miles on it.

1.) are you the originial owner?

2.) has it ever run correctly for you?

3.) If it did run correctly at one time, what has happened to it since it did? Been sitting?

4.) Any recent service work Tune up, routine maintenance or repairs done recently?

5.) Have you done a compression test in the last couple of weeks? If not, would you please do that?

6.) Any possibility the exhaust is clogged/plugged up? Feel for exhaust pressure at the ends of the mufflers just to see if it has reasonable exhaust flow.

I am torn between bailing out because we can't make any headway and nothing makes any sense. Everything contradicts conventional wisdom and sticking it out because I am so fricking curious as to what it is.

If you want me to opt out I will so another expert can try his luck at helping you.

RSRBOB

Customer: replied 1 year ago.
Please realize that I have appreciated everything you have thrown at me because I am lost myself and like I said I do this every day of my life and that is why I made the joke about blaming it on demonic possession or however you stated it. I can't make sense of it. To break things down No I am not the original owner, this is a customers bike (trike) that he built. Bought a brand new lifan engine (turn key) to put on it. He says that the bike has always ran well, but would never idle right and that is why he brought it to me. I have not looked to see what compression is suppose to be on it, but figured sense the thing runs great at high RPM's there shouldn't be a problem especially since it has so few miles on it. The one thing that does bother me and I have tried to(in a redneck sort of way) to adjust is exhaust. He has straight pipes running off of this and I know cv carbs like a little back pressure but this has still not helped me in the least. Please understand that I am glad you have been putting up with this, but the only reason I am here is because I ran out of things to try and you have given me a few ideas that I did not try, however that is why I asked for your most off the wall thing to look for. I do not hold anything against you because you have been great. I am going to order another carb and see if it makes any difference. If it does than I am going to say that it is a freak of nature and something was wrong beyond normal repair of the carb. If it doesn't work I am going to tell the customer to send the whole back and tell them that something just isn't right. If you have something else to try please let me know because this is probably driving me more nuts than it is you (of course I don't know that for sure....lol)
Expert:  RSRBOB replied 1 year ago.

The one thing that I have held back is double checking the cam timing and see it if is maybe off just 1 tooth. The other thing would be make sure it is in phase. The rear cylinder should be the #1 cylinder because it is to the left as you sit on the bike. It should come up to TDCC first. Then, something like 270 or 300 degrees later the front cylinder should come up on TDCC. If it comes up on TDCC before that, the engine is out of phase. You might also check the valve clearance as well. Does this thing have the YICS box on it?

RSRBOB

Customer: replied 1 year ago.
Does not have YICS, not sure if this is because with one carb it really isn't needed or was just not added. Intake is at .004 and exhaust is .006. Has 2 marks on the cam gear and just visually they seem to be good.
Expert:  RSRBOB replied 1 year ago.

Since we are dealing with what appears to be an obscure problem, is it too much to ask to go through the complete procedure for checking cam timing? I have seen cams being off 1 tooth and producing some inexplicable symptoms. If it were me, I would certainly be looking.

RSRBOB

Customer: replied 1 year ago.
I will do it just so we can knock something off of the checklist, however it will be probably at least a day before I get back to you depending on how things work out tomorrow.
Customer: replied 1 year ago.
Well both lines line up at TDC with the cam gear on both cylinders. Will be at least Wed. or Thurs before new carb comes in.
Customer: replied 1 year ago.
One other thing and not sure if this means anything or not. On first start the bike will idle alright for probably about 5 mins, once it gets warm that's when it loads up. Just thought I would throw that out there just incase it triggers something.
Expert:  RSRBOB replied 1 year ago.

When you say they both line up, do you mean at the same time? Did you check the 270 degree or so revolution to be sure it is in phase?

As a bike warms up, it tends to run richer. I just cannot think of a single scenario where the plugs come out so wet and black and melted.

Whenever you have new info, just post it. I get notifications whenever something new is added. If I come up with anything else, I will post it for you.

One parting shot tonight, have you checked the oil level and made sure it isn't over filled?

Well, maybe 2 parting shots. Are you running this with the A/F on or off?

RSRBOB

Customer: replied 1 year ago.
no just when the cylinder individually is at TDC. Oil in the glass has a small bubble which is pretty much like any other bike or quad and running without the air filter
Expert:  RSRBOB replied 1 year ago.

I feel like we are wasting a lot of time here because the answers you give me are not fully complete. I know they make sense to you but in this forum, I need to be positive in my mind I know what you are seeing and doing.

For example. Running without the air filter, do you mean no air filter in the air box or just an open carb? If the air box is off, what I would like to know is do you see raw gas running in the throat of the carb?

The fuel level check and adjustment you did is next. Was that test done while the bike was running? If not, that is the correct way to perform that test.

I want you to explain exactly what you did to check the cam timing. What cylinder did you start with and are you watching the intake valve of each cylinder to know it is coming up on compression or are you just watching the timing marks?

RSRBOB

Customer: replied 1 year ago.
open carb and yes I can see fuel going into the carb coming out of the needle jet. Float level is bike not running. Cam timing is plugs out turn by hand making sure on compression stroke starting with rear cylinder. Just to add something the gas is basically splashing out the top of the carb