wall 4 valve timing.

[whitehouse260]

i have a wall 4 50cc that is not running, does anybody have a timing diagram for the camshaft? like when cylinder 1 is supposed to intake? i have a set of plans in article form that i got on ebay, but i appear to be missing a few pages.
thanks,
matt

 

[gbritnell]

I just rebuilt a Wall 4 for a fellow but I'm not sure which 4 it is. The one that I have the intake opens basically at TDC. There is only 4 degrees difference between the flats on the intake and exhaust lobes.
The cam centerline spacing is 115 degrees. The lift is .281. The base diameter is .375. The nose of the exhaust lobe is .094 wide and the intake is .047 wide. The firing order is 1-3-4-2.
gbritnell

 

[whitehouse260]

Was it the flaT head? Or the ohv(30cc)?
Thanks,
Matt

 

[whitehouse260]

ok new question, do you want to rebuild another one? do you know of anyone who would? i think the camshaft is made wrong on cylinders 1 and 4, the exahst valves suck air in when turned one direction and the other direction they push air out cylinders 2-3 seem to be fine.
thanks,
matt

 

[stevehuckss396]

Might get some help if we knew what part of what country you are in. If you are anywhere near Michigan I would be happy to take a look at it.

 

[whitehouse260]

That would help wouldn't it... I'm just outside of Louisville, Kentucky. I've tried off and on for 6 years to get it to run most it would ever do is pop

 

[gbritnell]

The one I rebuilt is a flathead. Here's a couple of pictures. I had to make a new cam for this engine. The original builder didn't leave enough metal on the oil pump lobe and it wouldn't pump oil.
gbritnell

 

[bluejets]

Sounds like the valves are leaking.
Cam is more than likely ok.

 

[whitehouse260]

They could be but I seem to have compression on those cylinders if I turn it the other way

 

[bluejets]

But you said in an earlier quote (#4) they were sucking and blowing air depending on which way you turned the engine.
Now you say this is not the case??

 

[whitehouse260]

No, if I turn it one way and put a finger over the exhaust of cylinder 1 and 4 it will suck air/finger in if I turn it the other way doing the same thing it pushes air/finger out which is probably ok, except that the other 2 cylinders are the opposite. I probably didn't word it very well the first time.

 

[bluejets]

If the crank is in the same position for all your observations, that would be correct as the pistons are at opposite points and cycles of the 4 strokes.

I assumed you had the crank in the correct cycle position for testing other cylinders.

This is where a picture is worth a thousand words as it appears your description is only leading to confusion.

 

[whitehouse260]

it shouldnt matter where it is in rotation, because it is being rotated with a starter/drill. i could be wrong but i dont think have the exhaust valve taking air in is correct.

 

[bluejets]

That's why I said the valves are more than likely not sealing correctly.
Back to where we started.

 

[whitehouse260]

Maybe but it appears the cam shaft is also made wrong on cylinder 4 the intake valve opens before the exhaust...

 

[bluejets]

Again, that depends on your observation and interpretation of events.
It's a simple enough proceedure to attach a degree wheel to the crankshaft and decode the valve timing by watching the valves open and close.
Intake always open before the exhaust, it just depends where as to whether or not it is correct.
Reverse rotation will also give incorrect results.
You have the advantage that you have the engine in front of you, we cannot see. All we can do is offer suggestions.
Is it possible a cam has been built backwards? Sure, I done it once but everything was a-about, not just one or two lobes.
I qoute leaky valves as in 99.9 percent of instances this is the area that catches people out and they refuse for some reason to accept it as a defect and why the engine won't run.
Above test with the degree wheel will confirm one way or the other.
Watch for approx 110 degree overlap at tdc on exhaust stroke.

 

[whitehouse260]

I have been messaging back and forth with Steve hucks he agreed with me after a little trouble shooting that it is the can shaft. When I go the engine apart and the cam shaft out the cams for cylinder 4 were way way off like more than 100deg off. I'm lucky that the cams were just loc tited on and ot machined as a whole!
My guess is the builder assembled it and it shifted while it was curing and he didn't realize.

 

[bluejets]

More than likely moved when trying to run it.
I use independant cam pairs as well , reason being the use of heat treated drill rod. Long cams tend to bend when heat treated. Tried many suggested methods without success, basically waste of time and effort.
Method I use here is to assemble cam pair blanks on 3/16 steel rod, then drill and pin each with 1/16 roll pin. Lock shed doors,mark and grind all the cams in correct sequence, disassemble and heat treat cam pairs, polish and refit with roll pins.
You could of course use a metal type like 4140 that does not require heat treatment, except here in Aus 40mm dia is about the smallest anyone stocks.
Would not trust the loctite method ever.

 

[mohavegun]

A complete firing cycle for one cylinder is two revolutions of the crank, The crank throws are 180 degrees apart, 1 & 4 at 0 degrees and 2 & 3 at 180 degrees. This engine fires one cylinder every 180 degrees of crank rotation. Each pair of cams is timed in the same respect as the firing order. The best way to understand this is that the camshaft runs at 1/2 the speed of the crank/ SO>>> when you check the camshaft timing you need to rotate it in a couple of VEE blocks and run a dial indicator on the cams, a timing disk mounted on the end of the cam will tell you when (in rotation) the individual cams are at open. There is a store on ebay that has plans for both of the Wall 4 cylinder engines. The two engines are based on the same block geometry and the cams are nearly identical and the timing is given at top of lobe in degrees so a timing disc would be easy to make for this engine. You really need one or the other of the two drawings which is on ebay. The flathead is a 50CC and the overhead valve is a 35CC. I have been toying with the idea of building a 50CC OHV engine from the designs.

 

[mohavegun]

You could put a degree wheel on the crankshaft and watch the valve lifters or the valves themselves and very quickly determine if crank / cam timing is correct...

Just a thought