Adjusted valves, does this sound right?
 

So I adjusted the valves, they were INCREDIBLY tight to start with, I got them pretty close to 0.05mm on the exhaust and 0.04mm on the intake. However, they seem louder now? Is this normal? Should I be concerned at the amount of noise my valves are making?

Video of the motorcycle running
https://imgur.com/a/Lw9YHDY

The Hawk 250 sticky does not say what valve lash should be adjusted to. This should be in the first post, which Megadan can easily edit.

For the Lifan KPX, the manual gives clearances of .08mm intake and .10mm exhaust. So yours might still be too tight.

I specifically left that out because at one time I did include it. It's not included so I simply don't have to deal with 50 experts all telling me the numbers I included are wrong and theirs were right.

.05mm is fine. >.05 to .08mm is perfectly within range of every CG engine ever made. Zongshen states theirs as .07mm for both valves with a 2500 miles valve check interval.

The .04mm may be a bit tight, but I have also seen Lifan Xpect lash figures states as .03-.06mm as a range for the intake.

I personally stick with no less than .05mm intake and .07mm exhaust.

You probably made the same mistake so many people make when they first do the valves and set the lash to the wrong Top Dead Center.

A 4 stroke has two moments where it is at Top Dead Center. The first is the compression stroke. The second is the exhaust stroke.

You want the compression stroke.

If you set the lash on the exhaust stroke the cam is actually pushing on both valves during the overlap portion of the cam phase where the exhaust is just finishing closing and the intake is just starting to try to open. This will cause your valve lash to be way out of wack and way too wide.

Let the engine cool off again for a few hours, take the valve cover off and the spark plug out. Use the kick start lever to slowly turn the engine over until you see the intake valve (closest to the carb) open and then start to close. Now you know for sure you are on the compression stroke. Now line up the T mark for Top dead center and set your valve lash.

I had a feeling this was the reason you didn't include it in the stickie...too many "experts" and keyboard warriors...I mostly fit into the latter category. hehe


Maybe you can add a blurb like, "This is where I set my valve lash, feel free to set yours wherever you think is best"?


Thanks for that tip about finding TDC. You kick ass, Megadan, and you have a cool first name. :D

Keyboard warriors I can handle. It's all the experts I just don't feel like dealing with. I work in the machine and electrical repair and refurbishment field. I work with enough overinflated senses of expertise on a daily basis, most of them not even technicians or mechanics. Don't feel like dealing with it here.

I may take your advice on that blurb though, that may keep the experts at bay lol.

As for the name, it's actually a nickname given to me by my dad way back when I was in high school. It has multiple meanings/sources. Inspired by the old video game Megaman that I liked to play. I was also a big metal head in high school, including the group Megadeath, and at that time my Dad had kind of an unstable life after he and my mom divorced and was always moving. Since I was 6ft 5 and 240lb athletic kid I usually helped him move when it was needed, so he called me Megadan the Movin' man.

Heavy lifter. I know that feeling. When I bought my 2002 Dodge Dakota, suddenly everyone was hitting me up to help them move. Did you play hoops? Football? Soccer goalie? lol My game is hoops, all the way. This Hawk is gonna get me to the rec center, eventually.


I put 100 miles on the bike and decided I better check my valve lash. They were tight, zero lash. I just got done setting the lash and took her for a spin, she feels good.


When they're tight like that, it means the valves are not closing all the way?

Yup! Well, they have to be pretty tight to prevent them from closing all the way, but yup, that's it. The real problem is that the hot exhaust gas blowing past the valve seat will eventually damage the seats and valve.

Too loose, you get tappet noise but the valves definitely close. They may not open all the way to let the fuel/air in or the exhaust out efficiently. Performance issue for sure. It essentially changes timing of the combustion cycle.

I'm learning, so bear with me. If they're not closing, especially on the intake stroke, wouldn't that create a lean situation? I pulled my spark plug to rotate engine for TDC and it's pretty white after only 100 miles.

The mixture of air/gas should not change. I am pretty sure the white plug can only mean the mixture is too lean.

Running lean can cause a hotter engine too. Your altitude is helping (as you mentioned), but you need to experiment with slightly more rich jetting to eliminate that.

You could put a new plug in there now that you have adjusted the valves while you wait for jets. If it turns white then you have confirmation ;)

Oh, and running a little on the rich side too will not hurt anything. Too rich can cause carbon build up in the long run, but running too lean can cause premature heat damage. Better to be on the rich side, and it will start without choke in warm weather!

if the valves are over tight and not closing you'd have compression loss and combustion leaking past the intake...Also the valves need to make enough contact with the valve seats to transfer heat into the head...if the valves cant transfer heat they can burn up.

A white plug suggests an overly lean air/fuel ratio. So you might want to look at re jetting the carburetor...unless its EFI...which is beyond my tinkering capability.

Ok, sense is being made and I'm trying to keep up. I said "intake stroke" above and meant "compression", but I have no idea what I'm talking about. lol


I'm scouring this site to find answers on my stock carb. This guy:


https://www.chinariders.net/showthre...ock+carburetor


says a CV/CVK fuel screw from Kawasaki will work on these carbs. If I replace my stock screw (non-adjustable) with this screw, will I be able to richen the air/fuel mixture? Or should I look at re-jetting? Or, both?

There are a few things to do.

Get into the carb by cutting a flathead slot in the heads of the break-off screws underneath the bowl. You can replace these with good allen bolts (probably M4-0.7 threads) when you put it back together.
The main jet is on the end of the center larger post. It dips into the fuel when upright, in place to draw fuel to the venturi. You might go one step larger on that main jet, say 110 to 115, or 115 to 120. I had a 120 in there OEM, and upped it to 125.

The pilot jet is probably also too lean. It is the other jet poking down into the fuel. Make one step there too, say38 to 40. Mine had a 40 in there. 45 was too much, and I backed off to a 42, which was perfect for me.

These sizes depend on what's in there. I posted complete info on which jets to order for the Templar (Templar resource sticky in the dual sport category), but I don't know what type of jets go in the Hawk. The same process applies, so you might look into that.
https://www.chinariders.net/showpost...09&postcount=7

That THIRD brass stem with no jet on it is for the air screw, which you should have on your carb too. You probably need to drill out the cap to access the adjustment screw. This is the fine tune pilot circuit adjustment. It usually is set ~1.5 to 2 turns out. Some of theses make it more rich, others make it more lean when you open them.

Last thing in the carb is shimming the needle. This needle is in the slide tower. Unscrew the cap and the slice/needle come out with it, and the throttle cable is attached.

Look at post 5 here for a procedure that applies to the Templar carb. Yous will be identical or very similar. I went with one single tiny washer (maybe 1mm).
https://www.chinariders.net/showthread.php?t=32177

You're 100% right, I completely forgot to do it at top dead center... I will follow your advice and redo the valves.

Thank you so much!!

I played football, though not particularly well. I mainly just did weight training and was in ROTC, so I had to meet certain physical standards.

When the valves have no lash the risk comes when the engine gets hot, particularly the valves, which are the hottest individual parts of the engine during operation. They can only shed heat as long as they are in contact with the head, and that contact is the narrow band the seat and valve face contact area, and the extremely minimal contact with the stem and guide.

As they get hot, they expand, and that little gap is there to provided room for the valve to expand so that they don't get pushed ever so slightly open. Even a fraction of a millimeter of a gap at the valve seat causes a loss of compression and greatly reduces the valves ability to shed heat, which then accelerates the problem.

The potential damage and other issues of this were covered already by others, so I won't bother going into that.

One less talked about detail with the CG engine design, and why it can operate with very small valve lash specs when compared to other small singles is actually down to the aluminum pushrods. The cam being located in the lower case half, the cam followers being located in the cylinder, and the valves themselves at the top of the head with all of the engine being made of aluminum means that as the engine also expands and grows from heat the followers move away from the cam and the valves move away from the followers. The pushrods, being the same metal as the engine, expand at the same rate as the engine, so most of the lash put into the valves is to compensate for the expansion of the cylinder that pushes the rockers away from the followers. As the valves get hot they actually help take up some of that slack when they grow themselves. That is why the CG engine runs fine with so little valve lash compared to other engines.

When I played around with the chromoly steel puhrods I discovered that even when set with zero lash, the cylinder expansion was so much greater than the pushrods that the valve noise became fairly loud.