HS40 Timing and Torque spec questions

[OriginalWhitey]

I'm rebuilding my HS40 and its been a while since I took it apart. I think I set the timing right by lining up the line on the cam with the mark on the crank but at TDC the intake valve is slightly open.

It doesn't look right to me but is this correct? Also does anyone have a list of the torque specs for the connecting rod and the head or don't they really matter?

Thanks.

 

[DreyeIce]

i beleive they are supposed to be closed at TDC, im having the same problem i think, my valve is open and when it fires, it blows out my carb, try advancing or retarding a little each way till they get closed at TDC,,

 

[cncsparky]

No need to adv or retard the timing. Its a 4 cycle engine, the piston will be at TDC two times during that cycle. During the intake stroke, the intake valve will start to open around TDC. Are you turning the engine in the correct direction? Keep rotating, the intake will close, the piston will bottom out and come back up, power stroke. At TDC both valves should be closed.

Another critical check when rebuilding is to check the valve tappet clearance. It should be .004-.008" when the valves are closed. Too tight and the valve will stay open instead of closing all the way. Replace the rear cover and remove the breather cover to check.

Tom.

 

[DreyeIce]

ohh yeah, two strokes and 1 is a power, so is hw on the exaust stroke, of you turn it, the next cycle do they close?

 

[125ccCrazy]

ohh yeah, two strokes and 1 is a power, so is hw on the exaust stroke, of you turn it, the next cycle do they close?

(1)Intake-(2)Compression-(3)Power-(4)Exhaust

 

[DreyeIce]

(1)Intake-(2)Compression-(3)Power-(4)Exhaust

yeah, thats what i meant,:smile::doah:

 

[OriginalWhitey]

The intake valve definitely remains opens as shown @ TDC no matter where at in the cycle. When rebuilding it, I didn't change the valves or take them apart. Interestingly enough, when I was looking through old pictures this is what it looked like @ TDC:

I don't think this motor was ever rebuilt and it looks like the valve is hanging open the same as now. So what's the deal? This definitely doesn't look right to me but it seems like this is the way it came stock.

 

[125ccCrazy]

The intake valve definitely remains opens as shown @ TDC no matter where at in the cycle. When rebuilding it, I didn't change the valves or take them apart. Interestingly enough, when I was looking through old pictures this is what it looked like @ TDC:



I don't think this motor was ever rebuilt and it looks like the valve is hanging open the same as now. So what's the deal? This definitely doesn't look right to me but it seems like this is the way it came stock.

Thats the engine you are having problems with?? does the valve stay open at any point in the cycle or just when the piston is @ tdc??

 

[DreyeIce]

the only way to find out is to try and run it, im having major breakdowns with my HS40, its not looking good, did you paint that orange intake yourself?

 

[cncsparky]

The intake valve is open all the time? If so, the valve is stuck. It can happen if water is allowed in the engine.

 

[125ccCrazy]

the valve should be closed at tdc but just start to open as the piston starts down, sounds like it's stuck or sticking.... When rebuilding an engine the valves should come out to check the guides and to lap the valves back in so you know they have a good seal....Those valves looked pretty bad and definately should have come out and been re-seated...

 

[blownengine]

Is he lining up the cam correctly? In the picture he lined up the big hole in the cam with the mark on the crankshaft. Shouldnt their be a small dot he lines it up with. Not the huge hole? I dont recall lining up my HS50 with the big hole.

 

[125ccCrazy]

Is he lining up the cam correctly? In the picture he lined up the big hole in the cam with the mark on the crankshaft. Shouldnt their be a small dot he lines it up with. Not the huge hole? I dont recall lining up my HS50 with the big hole.

On my hs50 the timing mark is inline with the hole so that should be okay, something I was looking at today is an h30 cam and an hs50 cam look alike and will interchange but the lobe position is different, I wonder if thats the right cam??? both valves should be closed @tdc...

 

[OriginalWhitey]

The intake valve is open all the time? If so, the valve is stuck. It can happen if water is allowed in the engine.

The valve is open all the time with the cam in. The cam doesn't allow the intake valve to fully seat. Here's with the cam out:

Here's the cam I'm using with the followers (short one is installed on the intake lobe)

Pic of the springs in case it helps:

And yes I know the valves should have been replaced but they were on back order and I didn't feel like waiting to get my rebuild kit so that's why I'm still using the old one's.

Is he lining up the cam correctly? In the picture he lined up the big hole in the cam with the mark on the crankshaft. Shouldnt their be a small dot he lines it up with. Not the huge hole? I dont recall lining up my HS50 with the big hole.

There's a dot on the crank and a line on the cam, that's what the timing is set to. Not the big hole.

 

[125ccCrazy]

That cam looks HUGE on the intake side, what is it?? I've never seen a cam where the intake and exhaust lift was that much different with two differnt size lifters....

Now my next question is: Did you set the lash on the valves??? or did you just assemble everything??..

I can't tell in the pic but if the valve stays open even without the cam in it, if so, I'd be looking at whether the valve is bent or not...

 

[OriginalWhitey]

That's the cam that came in the motor. Both valves are closed without the cam in it. I didn't change anything with the valves since I was reusing the original components. I heard the motor was running before I took it apart, so that's why I didn't change anything with the valves. But now I realize that there may be a problem.

 

[cncsparky]

It looks to me like the exhaust valve stem is lower than the intake, if so, then the shorter tappet would go on the exhaust.

 

[OriginalWhitey]

It looks to me like the exhaust valve stem is lower than the intake, if so, then the shorter tappet would go on the exhaust.

If I put the longer tappet on the intake then the problem of the intake staying open would be even worse.

 

[125ccCrazy]

That's the cam that came in the motor. Both valves are closed without the cam in it. I didn't change anything with the valves since I was reusing the original components. I heard the motor was running before I took it apart, so that's why I didn't change anything with the valves. But now I realize that there may be a problem.

You heard IT WAS running or you heard IT RUN???

are the lobes on the cam 2 different heigths?? more lift on the intake??

I wonder if someone welded the lobe and reground it?? unless it's an optical illusion the intake lobe looks wicked tall.... I think you will have to file off more of the tappet and check the lash , keep filing until you get about .006 on the intake and .008 on the exhaust.... The next problem may be the valve hitting the head if that lobe is as tall as it looks in the pic....

 

[cncsparky]

Is this a compression release engine? The cam looks different than a normal cam. In those engines, I believe a valve is held open at cranking speeds to release some compression, then goes normal once the engine fires. Can you post some better pics of the cam?