Valve Adjustment Fail: Lifan Xpect

[70fstbck]

OK. I’m starting a new thread here because 1) I’m really frustrated with myself. 2) I’m not finding all the answers anywhere else and 3) it seems there’s some misinformation going around and I really want to get this straight.

Last September I got a Lifan Expect through Powersports Max. Overall. A good purchase experience. Before even starting, I changed the oil to a high zinc blend for break in. I rode the bike 200 mi without going over 50. I changed the oil at 200 mi and proceeded with normal operation. From start up to 709 mi, it ran great if only a bit slow as I never got over 60 on flat road.

At 709 mi, I changed the oil again and it continued to run well. At this point, I decided to adjust the valves to see if I could get a bit more power. This is where things went bad.

I turned the engine to TDC and removed the valve cover. I did this w/o pulling the gas tank. The valves were very tight and really didn’t move at all. I adjusted the intake valve to .03 mm and the exhaust to .05 mm (as in the owners manual) and cranked the engine over with the spark plug disconnected to make sure there were no problems. It seemed to be good, so I reassembled and started the bike to let it run. Now I can hear the valves tick, it lost power and started to smoke. I shut it off and wrote this post. Obviously, I did something wrong.

Has anyone else had this happen? Everywhere I looked, this seemed to be a straight forward job, yet I’m left very frustrated as I took my bike from running fine to a real problem. Maybe someone else has had this experience. Looking forward to some conversation. Maybe the light will come on and I’ll get it straightened out. Thanks in advance for relaying your valve adjustment experience.

[Michigan Sportsman]

I ratcheted the engine around an few revolutions, aligned the “Tl”, and and adjusted the valve lash. I ratcheted the engine around an few revolutions, aligned the “Tl”, and rechecked the valve lash to find them both tight. So I readjusted the valve lash, ratcheted the engine around an few revolutions, aligned the “Tl”, and rechecked the valve lash to find the exhaust perfect and the intake very loose. I say to myself… “Self, this can’t be.” With the “Tl” aligned the valve lash should be consistent. So I ratcheted the engine around an few revolutions, this time observed the action of the valves in relation to the “TI” alignment and discovered there were two different valve positions when the “TI” is aligned. I adjusted/rechecked them on the CORRECT INTAKE CYCLE.

Hope this helps.

[Megadan]

Misinformation is a huge issue. It's something I have been fighting against for a while, but it is an endless battle. Ask anybody about valve lash and you get as many different answers as you do people answering.

I am surprised to see the manual state .03mm for the intake. They may have changed it, but IIRC the last time I saw the Xpect's valve adjustment numbers they stated a range of .04-.06mm for both valves. I personally run .05mm intake and .06mm exhaust on my bike.

What Michigan Sportsman stated in his story is also very very important. Adjusting the valve lash at the correct TDC is something that many people tend to get wrong. It needs to be adjusted at TDC on the compression stroke. The easiest way to tell this position is to rotate the engine in the direction it runs in, and if you are unsure, remove the spark plug and turn the engine over with the kick start lever and observe. While turning the engine over, observe the intake valve (closest to carburetor/throttle body). Once you see the intake valve rocker push down and open the valve and then close again, pay close attention to the marks on the flywheel. When the T mark comes back around, this is TDC on the compression stroke.

If you adjust the valve lash on the exhaust stroke TDC the cam profile is actually slightly engaging both valves due to valve overlap, so your .03mm intake value is now .3mm when it's on TDC of the compression stroke (not an acurate number, just to make a point). This results in very wide valve lash that makes a lot of noise due to the violent impact of a rocker being accelerated very quickly across a large gap to slam into the valve tips, and reduces the effective duration of the camshaft resulting in a loss of power.

Now, to clarify one other point because I think it is easy to confuse, there is "tapping" (think tick tick tick) and there is "clacking" (aka very loud prominent tapping noises). These engines will always make a light tap/ticking noise when they run with the valves adjusted. Just the nature of the beast with a solid valvetrain. No nice hydraulics here to take up the gap and cushion the violence. So even adjusted correctly, don't worry if you hear said noises.

Lastly, it is very possible to over tighten the lash adjuster jam nuts and actually increase the valve lash value. Check it after tightening the jam nut and make sure you didn't open up the gap. Don't bear down on them when you go to tighten them, just a simple snug up is all it should ever need.

[Boatguy]

Very much looking forward to a confirmation of the numbers also.

It’s time for the 4000 mile maintenance on mine and it also runs like the OP’s did. Perfectly. There is no tick from the valves. The only thing it ever does and has always done is pop a bit on deceleration using engine braking. It’s always done this. What is this a sign of in terms of the valve adjustment?

I’ve been hesitant to try this valve adjustment because the manual says exactly what the OP is saying, yet I read different numbers all over the place here.

Anyone know the correct numbers?

I don’t want to mess mine up with a valve adjustment either.

[TominMO]

Originally Posted by Megadan

What Michigan Sportsman stated in his story is also very very important. Adjusting the valve lash at the correct TDC is something that many people tend to get wrong. It needs to be adjusted at TDC on the compression stroke. The easiest way to tell this position is to rotate the engine in the direction it runs in, and if you are unsure, remove the spark plug and turn the engine over with the kick start lever and observe. While turning the engine over, observe the intake valve (closest to carburetor/throttle body). Once you see the intake valve rocker push down and open the valve and then close again, pay close attention to the marks on the flywheel. When the T mark comes back around, this is TDC on the compression stroke.

Lastly, it is very possible to over tighten the lash adjuster jam nuts and actually increase the valve lash value. Check it after tightening the jam nut and make sure you didn't open up the gap. Don't bear down on them when you go to tighten them, just a simple snug up is all it should ever need.

Great info above, bears repeating. I always rotate the engine with the plug out, when doing it by hand. You can put it in gear (2nd or higher is better) and rotate the rear wheel, or (in neutral) use a socket on the bolt to find TDC. To avoid loosening that bolt, since you are rotating it CCW, I want to make sure there is no compression, so out comes the plug.

As a general rule, exhaust valve clearance should always be a bit looser than intake. The intake valve gets cooled by fuel entering the combustion chamber, but the exhaust valve does not have this benefit.

Some people have reported that the valve lash tends to tighten over time. Not sure why this would be, but all the more reason to err on the loose side.

Here is what I use, FWIW. These all work fine for me.
intake:......0.005"......0.127mm
exhaust:...0.007"......0.178mm
plug:.........0.035"......0.89mm; NGK DR8EA

[KSSK]

Originally Posted by TominMO

Some people have reported that the valve lash tends to tighten over time. Not sure why this would be, but all the more reason to err on the loose side.

I think it's because as things wear and break in, like the valve and the seat in the head, that causes the valve to raise a tiny bit higher when it's fully closed by the spring. That effectively eats up whatever valve clearance you had set before the wear occurred.


Often the specs for intake/exhaust will be different, but on these engines, a tiny bit looser is better than too tight. My guess is for simplicity they just decided .06mm for both.

[TominMO]

Originally Posted by KSSK

I think it's because as things wear and break in, like the valve and the seat in the head, that causes the valve to raise a tiny bit higher when it's fully closed by the spring. That effectively eats up whatever valve clearance you had set before the wear occurred.


Often the specs for intake/exhaust will be different, but on these engines, a tiny bit looser is better than too tight. My guess is for simplicity they just decided .06mm for both.

Good points.

So now Lifan says 0.06mm for both. I can live with that. I doubt that the differences of .01mm that I used will matter. Recommend not overthinking this, just go with .06mm.

[KSSK]

Originally Posted by TominMO

Good points.

So now Lifan says 0.06mm for both. I can live with that. I doubt that the differences of .01mm that I used will matter. Recommend not overthinking this, just go with .06mm.

Yeah, I'm sure you're fine. The fact that these engines are incredibly simple means they aren't very refined, but the good side is that these little details often don't matter much.

[Megadan]

Originally Posted by TominMO

Some people have reported that the valve lash tends to tighten over time. Not sure why this would be, but all the more reason to err on the loose side.

Because as a general rule of thumb, they do tighten over time. As KSSK stated, the valve face and seat are constantly being slammed together, and over time the valve face and/or seat tend to wear, which causes a decrease in valve gap. The valve stem itself also ever so slightly stretches out.

This happens quickly during the break in period, which is why so many Hawk owners come crawling to the forum asking why their bike doesn't run right with only 400-600 miles on it. They didn't set the valve lash when they got the bike, and in that short time the valves have seated and stretched so much they aren't sealing when the bike gets up to temp.

I have a feeling Lifan widened the gap to .06mm simply to increase the service intervals. The .03mm/.05mm spec is likely the minimum spec for each valve, and I say that with some confidence because most valve lash specs are given in a range. IE - the intake valve would be .03mm-.06mm. If you set the valve lash at the minimum, it will need to be checked more frequently. Set it at the maximum, and it can go a much longer time between valve checks for the cost of maybe the slightest bit of extra tickyness. I would rather do a valve check every 3000 miles instead of every few hundred myself.

It also bears keeping in mind that these manuals are translated form Chinese to English, and while Lifan's manual is way better than most, some information may have been lost in the translation.

It also doesn't help that every company tends to state a slightly different spec as well. CSC tells their owners to set both valves to .07mm during break in.

I have experimented with different valve gaps on my Hawks. From the .08mm intake and .10 exhaust (.003in/.004in) that was a very common spec in the Hawk community for a long time, to running them quite literally at finger tight and then tightening the lash adjuster (call it .01mm for the heck of it.) I have settled on my .05mm intake and .06mm exhaust as the best balance between service intervals and valve noise. The .08mm/.10mm spec does work, but is also quite noisy.

In my opinion the valve lash range to check for and adjust to is as follows.
Intake: .04mm - .06mm.
Exhaust .05mm-.07mm.

I simply set mine in the middle of those ranges. Is that based on anything? No. Just a compilation of manufacturer recommended specs and my own experience. Makes a nice consistent sewing machine like ticking noise as it should without the "HEY! I AM TICKING NOW! levels of the wider .08/.10. and you can go a couple thousand miles between checking them. I have put 2k miles on my bike since setting the valves to those specs and I just checked them 2 days ago. Still within spec.

[KSSK]

There are threads on the Lifan X-pect lash here on this forum. The manual says .03/.05mm, but Lifan has told people that the spec has been updated to .06mm for both.

I adjusted mine to .06mm and it's running fine. Mine were way too tight from the factory and had basically no lash.

Here's the thread in question:
https://www.chinariders.net/showthre...Yc8x_0osuDQc9Y

Originally Posted by oincman

Reread the email and he said 0.06mm (I read it wrong), which would be .002, but he said both intake and exhaust were to be 0.06mm.

It's been pretty chilly here so I haven't ridden it since. Maybe later today or Saturday I'll get a chance to take it back out.

[Boatguy]

This is where I’m really not cool with this. Three different people, three different valve measurements.

And the manual agrees with the original poster.

And here’s yet another post. A 4th person for 4 diff values. This is quoted from the thread KSSK linked to above.

“ They must have listened and adapted. I just checked my new XPect and they were at .06+mm intake and .08+mm on exhaust. I left them alone and will check again at 600 miles or so.”

So, does it really not matter what they are set to at all? Everybody has a different number and everybody says it’s running great.

Mine is already running great. Should I even bother looking at it? Or is it something you look at once it starts running poorly?

[KSSK]

Originally Posted by Boatguy

This is where I’m really not cool with this. Three different people, three different valve measurements.

And the manual agrees with the original poster.

It's not really three different numbers.

The manual says .03/.05.

Lifan now says it should be .06mm on both.

The other numbers are ones people are choosing to use for whatever reason or citing from memory, but aren't numbers from Lifan.


Attached is a photo of the numbers in the manual, which Lifan has now told people have been updated to .06mm.

If you're concerned, you could contact Lifan yourself. I've found them to be pretty responsive to emails.

[70fstbck]

Thanks so much for the responses. I turned the engine over several times to where the T lines up, but the valves remained tight. I’m going to try again. This time I’ll remove the spark plug too. There’s some little thing I did wrong, so I’ll just go back and try again. Sorta like the definition of insanity.

[Megadan]

Originally Posted by 70fstbck

This time I’ll remove the spark plug too. There’s some little thing I did wrong, so I’ll just go back and try again. Sorta like the definition of insanity.

Somewhat like the definition of insanity, but do yourself a favor and don't go out there thinking you are doing the same thing again. You want to keep a fresh mind and literally go through the steps. We often make the most mistakes when we lose focus on the task at hand and start skipping steps or become inattentive.

It's most critical to ensure that you are on the compression stroke when you find TDC.

Also make sure to use a Go/No Go method to double check your lash.

This means that, without forcing the feelers through, if you set the lash .06mm, use a .07mm feeler and try to get it to pass between the adjuster and valve tip. If it manages to slide through, re-adjust and try again. The next size up should not be able to pass, aka No go.

[severely]

Originally Posted by Megadan

Somewhat like the definition of insanity, but do yourself a favor and don't go out there thinking you are doing the same thing again. You want to keep a fresh mind and literally go through the steps. We often make the most mistakes when we lose focus on the task at hand and start skipping steps or become inattentive.

It's most critical to ensure that you are on the compression stroke when you find TDC.

Also make sure to use a Go/No Go method to double check your lash.

This means that, without forcing the feelers through, if you set the lash .06mm, use a .07mm feeler and try to get it to pass between the adjuster and valve tip. If it manages to slide through, re-adjust and try again. The next size up should not be able to pass, aka No go.

Great advice as usual. I remove the spark plug AND valve cover and use a plastic straw in the spark plug to ensure TDC and proper compression stroke. With the spark plug removed and valve cover removed you can rotate the engine freely to watch the valves open/close and know with certainty correct TDC after the intake valve closes.