No compression after rebuild

[XEGREAPER]

I have a sdg 125cc manual 4 stroke pit bike. I bought it after getting It home I realized the spark plug hole was stripped the bike still started it lasted for a bit then it popped one day shooting the spark plug out and destroyed the threads. I just got a new head for it put that on after a few days of ridding the cam sprocket popped off shooting the cam cover off and sending the cam chain down and braking a tooth off the oil pump gear. The bike started smoking from the cam chain hole. I realized after taking a closer look I caused this hole mess in the first place. I forgot the dowel pin that goes in the center of the cam sprocket. so I had my work cut out for me after taking the hole engine apart and replacing the oil pump sprocket and putting everything back toghter I got no compression I dont have a tester to tell how much compression there is  if there is any at all but I can tell the difference from before to now so the bike just wont start I've messed with the timming on the bike checked the piston rings and cylinder. I'm stuck and NEED HELP!!! anyways my guess would be a few different things.

1st the timing I've lined up the t mark and the notch in the head with the sprocket got nothing maybe I'm doing that wroung 

2nd I've taken the head off to make sure the piston and cylinder was ok everything looks good I aslo checked to see of the rings were placed right all good there 

3rd My only other guess would be the clutch is stuck from sitting to long idk if this is possible or not but I know of the clutch is Engaged the bike wont let you kick it is this a possibility?

Any help/responses would be gravely appreciated I've been playing with this thing for about 2 weeks now and I'm just stuck. 

Thanks again austin 

[Hndyman55]

Maybe you adjusted the valves too tight not letting them seat and make a good seal

[XEGREAPER]

1 minute ago, Hndyman55 said:

Maybe you adjusted the valves too tight not letting them seat and make a good seal

Thanks for the response I set the valve clearance at .003 for intake and exsaust do you have a different suggestion? I forgot to put that in the post also just clarifying I should adjust the valves at top dead center right?

[Hndyman55]

Yes you adjust them at top dead center on the compression stroke. Just after the intake closes but before the exhaust opens

[XEGREAPER]

1 minute ago, Hndyman55 said:

Yes you adjust them at top dead center on the compression stroke. Just after the intake closes but before the exhaust opens

I'm pretty sure I did that correctly I'll dubble check again in the morning do you have any other ideas on what might be causing my problem 

[Hndyman55]

When you had the head off did you visually inspect the valves to make sure they weren’t bent from hitting the piston? Or flip the head upside down on a bench and fill the combustion chamber with some sort of fluid to make sure they make a good seal and not leak out

[XEGREAPER]

2 minutes ago, Hndyman55 said:

When you had the head off did you visually inspect the valves to make sure they weren’t bent from hitting the piston? Or flip the head upside down on a bench and fill the combustion chamber with some sort of fluid to make sure they make a good seal and not leak out

Let me first  applagize I'm still a little new to all this and thanks again for the ideas when I had the head off I shined a light up the exsaust hole and I could see a bit of light coming through the valves I thought maybe the exsaust valve was opened a bit would the valves be closed if I had the head off? Also I'll give the hole fluid things a try do you suggest putting oil to see if it leaks out?

[Hndyman55]

With the head off the valves should be closed tight. I use water. Some use brake fluid. Main thing you want to find out is if any liquid runs out the combustion chamber

[mlatour]

24 minutes ago, XEGREAPER said:

when I had the head off I shined a light up the exsaust hole and I could see a bit of light coming through the valves

By the description of the failure, that valve is likely bent.

You were perhaps able to set the proper lash but the valve isn't seating evenly around in it's seat.

 

If you remember if it was the intake or exhaust valve, remove either the headpipe or intake boot

and you will feel/hear compression escape while kicking over the engine.

Edited December 17, 2018 by mlatour

[XEGREAPER]

7 minutes ago, Hndyman55 said:

With the head off the valves should be closed tight. I use water. Some use brake fluid. Main thing you want to find out is if any liquid runs out the combustion chamber

I think that might be my problem let me check tomamrow and get back to you thanks for the help 

[XEGREAPER]

1 minute ago, mlatour said:

By the description of the failure, that valve is likely bent.

You were perhaps able to set the proper lash but the valve isn't seating firmly in it's seat.

 

If you remember if it was the intake or exhaust valve, remove either the headpipe or intake boot

and you will feel/hear compression escape while kicking over the engine.

Now that you mention that I did notice hearing air coming from the exsaust port when turning the engine over 

[XEGREAPER]

One more question do you think I will need to use a grinding compound after replacing the valves since the head is so new If so what works best. Also I know I need a valve compressor roll is there any specific one I should get?

[mlatour]

Other members will have to chime in as can't help you with cylinder head tooling of procedures,

myself sent my CRF cylinder head away to be fully serviced rather than buy the tooling.

[Hndyman55]

One more question do you think I will need to use a grinding compound after replacing the valves since the head is so new If so what works best. Also I know I need a valve compressor roll is there any specific one I should get?

Yes you should use grinding compound to lap the new valves in the head. I don’t know of any specific brand of spring compressor I’m sure most will work. If you’re handy you can make one yourself. I used a big C-clamp and an old deep socket which I cut a big notch out of to access the locks/keepers. To remove the locks get a socket a little smaller diameter than the retainer and pop it with a hammer to compress the spring. The locks will fall right out.

[XEGREAPER]

5 hours ago, Hndyman55 said:

Yes you should use grinding compound to lap the new valves in the head. I don’t know of any specific brand of spring compressor I’m sure most will work. If you’re handy you can make one yourself. I used a big C-clamp and an old deep socket which I cut a big notch out of to access the locks/keepers. To remove the locks get a socket a little smaller diameter than the retainer and pop it with a hammer to compress the spring. The locks will fall right out.

alright so i just finished talking the head off and tested the valves like you said i have a leak in the exhaust so im assuming that my problem anyway i had a spear 110cc head laying around i checked the valves before i put it on and there no leak but to my supersize after getting the 110 head on i still didn't have compression i was wondering if maybe it would be something else other then the valves  or would a 110 not work it bolted on i had to change the timing chain to a shorter one and everything lined up with the timing would the dot on the 125cc cam sprocket be different from the one for the 110  

[dirtbkr188]

As long as both cam sprockets are the same number of teeth, the 110 head "should" work on the 125 lower end. 

Your comment 

...I had to change the timing chain to a shorter one...

leads me to believe the sprockets do not have the same number of teeth.

[Mr.mudman112]

Most likely bent a valve. You may have had the correct clearance, but I’m thinking maybe it was never seating right. As for adjusting, your going to adjust valves at tdc on compression stroke. As for timing, I usually do a fraction before T, possible to get a bit more power out of it.

Next step I’d say is to pop the head off and check your valves. There’s a poor mans compression tester, stick your hand on the intake boot, and/or the other hand on the exhaust manifold, a suck or push means you’ve got compression! Keep us updated

[XEGREAPER]

On 12/25/2018 at 12:30 AM, Mr.mudman112 said:

Most likely bent a valve. You may have had the correct clearance, but I’m thinking maybe it was never seating right. As for adjusting, your going to adjust valves at tdc on compression stroke. As for timing, I usually do a fraction before T, possible to get a bit more power out of it.

Next step I’d say is to pop the head off and check your valves. There’s a poor mans compression tester, stick your hand on the intake boot, and/or the other hand on the exhaust manifold, a suck or push means you’ve got compression! Keep us updated

Sorry for the long wait on the response with the holidays it's been hard to get to the garage anyways I didnt get a chance to check the compression how you suggest thanks for the idea I'll do that tommarow. I did make some progress I did have a bend exsaust valve I found put by useing a recent suggestion about taking the head off and putting some water over the valves to see of I got a leake like i said the exsaust valve was bent I switched that out put the head back on and then I came across my next problem idk what it is about this bike but I cant figure anything out with it anyways after getting everything back toghter I can only get it started with starter fluid I know for a fact I'm getting fule I thought maybe my valve lash wasent set right checked that everything was good there so I dubble checked timming everything seemed good there when I was spinning the fly wheel tho I can hear a sucking sound comeing from the intake hole is that normal. I thought maybe my intake valve was bent to but after putting the new exhaust valve on I put some more water in it and I didnt have a leak. Any suggestions would be grate once again sorry for the late update