Hawk Valve Clearance

[Republic]

Ok, something is amiss. When I adjust the valves spot on at TDC as indicated with the T mark, it sounds like I'm shooting a gatling bb gun into a bucket and I get this big of a gap on the 'alternate' stroke:




Could my T mark be on the wrong stroke?

On my previous bikes I adjusted valve clearances when the alternate valve was at full valve lift, could I do the Hawk the same?

[Mudflap]

You need to turn the crankshaft 360 degrees from where you adjusted, it's on the wrong stroke.

[pcspecialist]

if that is 360 from the stroke you adjusted them on, you adjusted them on the wrong stroke and are currently on the stroke you should have adjusted them on.

[Republic]

Ok I've got it finally. I'm an absolute idiot. Its good that I've got a relatively simple bike to learn these things on.

[BlackBike]

Originally Posted by Republic

Ok I've got it finally. I'm an absolute idiot. Its good that I've got a relatively simple bike to learn these things on.

No harm no foul, We're All in This Together.

[Ariel Red Hunter]

Originally Posted by Republic

Ok, something is amiss. When I adjust the valves spot on at TDC as indicated with the T mark, it sounds like I'm shooting a gatling bb gun into a bucket and I get this big of a gap on the 'alternate' stroke:




Could my T mark be on the wrong stroke?

On my previous bikes I adjusted valve clearances when the alternate valve was at full valve lift, could I do the Hawk the same?

No the T mark is in the right place ; marking Top Dead Center. What you have forgotten is that since this engine is a four stroke, the "T" mark comes up twice for every firing stroke. Only one of those strokes is the compression/ignition stroke. Where both valves are closed. Yes, you can adjust them the same way you used to on the other bike. Just test them to be sure.

[rtugwell]

hate to dig this back up but every where the net says the tolerance closes after warm, but i hear it more after its hot, you say this is common?

[Mudflap]

Seems to be common wisdom that valve lash decreases as the engine heats up but that is not the case with many engines. I've measured the Lifan CG engine valve lash when cold and hot and verified the lash increases as the engine heats up. It's highly likely that all CG engines are like that but not absolutely guaranteed. Not too difficult to verify.

[chinatoys]

When hot, valve lash increases the most on push rod type motors. That's because the motor "grows" when hot increasing the distance between the cam and the rockers. Combine that with hot thinner oil and you can get quite a racket.

That's partly why most other push rod motors have hydraulic lifters.

[Musictrek]

While getting the bike ready for the new cluster. I went for the valve check. Without the tank peace of cake. As common, the exhaust side was slightly gapped larger than the exhaust. But still, not even a .003 feeler gauge would fit on the exhaust side. Intake forget about it. Interesting though, that valve train wear actually makes the gaps tighter. Anyway, I went with the .003 inch gap on both sides.

[Musictrek]

Originally Posted by Musictrek

While getting the bike ready for the new cluster. I went for the valve check. Without the tank peace of cake. As common, the exhaust side was slightly gapped larger than the exhaust. But still, not even a .003 feeler gauge would fit on the exhaust side. Intake forget about it. Interesting though, that valve train wear actually makes the gaps tighter. Anyway, I went with the .003 inch gap on both sides.

Top dead center for valve adj

[Kingraider]

Yea it's all trial and error boys on these bikes I have the tt250 and the first time I did the valve check mine was ticking loud then I realized how to keep the adjustment nut still and just adjust the little screw on top to .07 I did both valves at that and now it's good with very little ticking sound . I did mine at 460 miles and I've changed the oil twice now. Ready to put some Miles on her

[pete]

Originally Posted by chinatoys

When hot, valve lash increases the most on push rod type motors. That's because the motor "grows" when hot increasing the distance between the cam and the rockers. Combine that with hot thinner oil and you can get quite a racket.

That's partly why most other push rod motors have hydraulic lifters.

so in this case you could set the valve clearance at zero on a cold motor if the valve lash
increases when the motor gets hot ?...

I don't think so...........................

The valve clearance is there because it reduces when the motor gets hot...
as the motor gets hot... valves / push rods etc increase in length closeing up
the valve clearance...


..

[Mudflap]

Originally Posted by pete

so in this case you could set the valve clearance at zero on a cold motor if the valve lash
increases when the motor gets hot ?...

I don't think so...........................

The valve clearance is there because it reduces when the motor gets hot...
as the motor gets hot... valves / push rods etc increase in length closeing up
the valve clearance...


..

Remember, the cylinder and head also expand when hot. On the Lifan, Zongshen, and Taotao CG engines I've checked the lash increased as the engine heated up. May not be the same on all CG engines.

[ChrisWNY]

What I found when I adjusted when the engine was cold was that the rocker arm and other parts don't move as smoothly/freely as they do compared to when the engine is warm. My valve gaps ended up being way too wide after doing a cold adjustment (the tapping was noticeably loud as well). When I readjusted the valves after I had warmed up the engine, the loud tapping noises were reduced dramatically and valve clearance was perfect after rechecking them at TDC after a few miles of riding.