Topic: valves

[snowcap]

Hi I am new to all of this and learning along the way. With the help of my brother-in-law I set the cam timing on my 1971 cb500 and all went well with that. We then began to replace the cylinder head cover and had trouble getting it to seat so we put the bolts in and began to secure them in a manner that it would be going together evenly. After the cover was on we tried to rotate the crank using the nut on the points plate and when we did we herd a noise like a ping coming from different valve openings.We messed around with the valve springs by pushing down on them with a screw driver and were able to get the cam to rotate with out any noise. Later, like idiots we realized the tappets were not lined up with the top of the valve and that  we were supposed to back off the tappets.My question to anyone is, has anyone done this and not damaged their valves or have I ruined my bike. I have not been able to start the bike because the points don't work. Please don't beat me up I have done that enough to myself. Thanks.    

[camelman]

It sounds like you bent your valves when you installed your valve cover.  It is very easy to do on those models.  Use the search feature, and you'll learn all about it. Sorry for the bad news. 

Camelman

[TwoTired]

Yes, almost certainly bent a few valves.  Start shopping for a used head, a top end gasket set, and a Honda Shop Manual.

[snowcap]

Should I try to start the bike and hope for the best or assume I bent stuff and take it all back apart?

[TwoTired]

If the valves are snapping when you rotate the engine, those valves are bent and can't seat.  Depending on how badly bent they are, there is a possibility that the pistons can smack the valves.

Bent valves don't allow compression.  No compression means the cylinder can't fire.  Even if you got it to run, it wouldn't run on all four.

What's the point of running it?  If you can do a compression check and it comes up healthy across the four, then proceed.  Otherwise, shop for parts and/or do the tear down.

[CBGhia]

If it makes you feel any better, I did the same thing.  I only bent one valve, but I bought a good used head and the other one is on the workbench for an eventual rebuild and maybe a mild port.

[sangyo soichiro]

So why is getting a new head preferred?  Are the guides messed up?  Or something else?  I take it that more than just the valves are messed up?

By the way snowcap, you have my sympathies.  Tough luck.   

[CBGhia]

I got a new head because it was easier.   The guide could be damaged, and more so if you try running it.  Used heads can usually be had pretty cheap for these bikes. 

[gnarlycharlie4u]

whoops

well I suppose you know better next time.

what's up with the poll?

[Gordon]

what's up with the poll?

Some people accidentally hit "New Poll" instead of "New Topic" when posting a question.

[TwoTired]

So why is getting a new head preferred? 

Only because of money.  It usually removes uncertainty about other valves that aren't bent enough to stick but enough to wear out guides/seals fast(er).  Otherwise, you are really looking at a complete head overhaul to properly inspect the extent of the damage.
And I actually said "used head", not new (egads, THAT would be expensive!)
I think the valves are like $50 each.

Cheers,

[sangyo soichiro]

So why is getting a new head preferred? 

Only because of money.  It usually removes uncertainty about other valves that aren't bent enough to stick but enough to wear out guides/seals fast(er).  Otherwise, you are really looking at a complete head overhaul to properly inspect the extent of the damage.
And I actually said "used head", not new (egads, THAT would be expensive!)
I think the valves are like $50 each.

Cheers,

Thanks TT.   

[MRieck]

 I have seen broken guides too. It depends...the head can be "better than new" BUT it will cost some dollars.

[snowcap]

Thanks to all who have replied , and sorry for  doing "new poll" , I'll know better next time. I think I am getting the feeling most of you guys would not try to start it and just take it apart , assess the damage' put it back together with the knowledge that everything is right. One last thing , how many p.s.i. is acceptable for a completely cold motor , we got 60 p.s.i. after we put it all together , is this another sign things are bad or is this ok? 

[camelman]

Like TT said, your cylinder pressure is going to be a mess with those bad valves.  I wouldn't trust anything you read until you have a better cylinder head on there.

Check your cylinder walls as well as your ring gaps when you have the head off.  You can tell if you have a problem pretty easily that way.

Camelman

[TwoTired]

60 psi on all four?
That's not encouraging.
But then, did you have the choke and throttle open?
Were the valves adjusted correctly?
And did your tester add low volume?  See the engine FAQ about comp. testers.

[dave500]

if the valves still go through the full travel they aint bent,you MIGHT be lucky here,did you get the cover screwed down fully or back it off when you sused it werent right?lucky you didnt snap of a lug on the cover more than bend a valve!

[faux fiddy]

I put a head back on, had trouble turning the wheel in gear, but did not force anything too much I hope).

Might have been a freak out, loosened everything, checked the horizontal marks on the cam gear, torqued it back down, spun it okay. It should all be okay, just a freakout on not wanting to spin the thing too hard I hope.

Haven't checkd compression, but when I spin the wheel I do like the sound comming out of the spark plug holes. Like whipporwills in the spring.