• Required reading for all forum users!!!

    Welcome!
    Register to access the full functionality of the GSResources forum. Until you register and activate your account you will not have full forum access, nor will you be able to post or reply to messages.

    A note to new registrants...
    All new forum registrations must be activated via email before you have full access to the forum.

    A Special Note about Email accounts!
    DO NOT SIGN UP USING hotmail, outlook, gmx, sbcglobal, att, bellsouth or email.com. They delete our forum signup emails.

    A note to old forum members...
    I receive numerous requests from people who can no longer log in because their accounts were deleted. As mentioned in the forum FAQ, user accounts are deleted if you haven't logged in for the past 6 months. If you can't log in, then create a new forum account. If you don't get an error message, then check your email account for an activation message. If you get a message stating that the email address is already in use, then your account still exists so follow the instructions in the forum FAQ for resetting your password.

    Have you forgotten your password or have a new email address? Then read the forum FAQ for details on how to reset it.

    Any email requests for "can't log in anymore" problems or "lost my password" problems will be deleted. Read the forum FAQ and follow the instructions there - that's what we have one for...

  • Returning Visitors

    If you are a returning visitor who never received your confirmation email, then odds are your email provider is blockinig emails from our server. The only thing that can be done to get around this is you will have to try creating another forum account using an email address from another domain.

    If you are a returning visitor to the forum and can't log in using your old forum name and password but used to be able to then chances are your account is deleted. Purges of the databases are done regularly. You will have to create a new forum account and you should be all set.

GS1100E piston to valve contact

  • Thread starter Thread starter outofcontrol
  • Start date Start date
O

outofcontrol

Guest
Does anyone know if valves will hit pistons on this motor if the timing is off?
I know some motors will collide, and some are designed not to.

I might have made a big boo boo last night when I was trying to start my motor.

About a month ago I took a wrench and hand turned my motor while it was sitting on the bench. I wanted to move some oil around because it had been sitting in a damp garage for so long with the side covers off.

Well, I had the cam chain tensioner off too and (I realize now) I totally screwed up the timing.

I had forgotten about that little incident until I was stumped last night when I found out my exhaust was sucking air when I tried to start it.

Dumb, dumb, dumb.

Well, if I have to replace 16 valves and 4 pistons I might as well get that big bore kit I was thinking about.

-KM
 
Did you have the sparkplugs out then you crank it over by hand, cause if you did and they did make contact hopefully you would feel the contact.

Best bet is to check the timing again and the rocker arm clearance. If it's a stuck/bent valve then when you pull the cam cover off you'll see one retainer lower than the others.

You may just want to pull the head just to make sure.

Good Luck
 
Last edited:
Pull the valve cover off, remove the cams and then blow air into each cylinder. If you bent any valves you will hear the air escaping from either the intake or exhaust. If you do it this way, you dont have to hold the crank in a certain position to keep it from turning. You have to pull the cams out anyway to retime the chain.....Billy
 
Thanks.

I'm going to leave work early today. I am so worried I can't get anything done anyway. I am expecting the worst.

-Kevin
 
I'm not sure if our engines are interference motors (meaning the valve train would come into contact with the pistons if the timing were off), but I'd think you'd have heard something nasty if the valves had tapped any pistons. Unfortunately the only way to be sure is to, at the very least, pull the valve cover and check the valves.

Good luck and hopefully it isn't catastrophic!

Brad tt
 
Yes...there is a very nasty loud and ringing sound when a valve hits a piston on startup after a rebuild.
The timing chain would be quite out of whack ie. not adjusted according to the factory manual if one were to hear that sound...
S.
 
If the intake cam is advanced too far or the exhaust retarded too far, then they could hit the pistons. You can tell from the nice little rings on top of the pistons if the motor was running.
 
piston.JPG


There was contact between every exh valve and every piston.

valves.JPG



When I was trying to start the motor (earlier) I didn't hear anything hitting. When I realized the valve timing was off, I shot compressed air in the plug hole with the cams off and I didn't hear anything come out. It even pushed the piston down. Also, none of the valves were stuck open. I then put the cams in (the right way) and started the motor. It started on the first kick (so to say), but it wasn't running great. I re-jetted the carbs, and I think the sync is all out of whack, but it was running. Then I got nervous and decided to take off the head and inspect some more. I took one of the exh valves out to inspect it and it looks normal.

Here's my question: How does the backyard mechanic inspect the valve to see if it's bent? I spun the valve in the seat and it didn't wobble.

Is there a chance that the valves can just barely hit the piston, just enough to knock the black stuff off? Should I buy all new valves?

-Kevin
 
My mechanic told me while I have the head off to pour alcohol or something in the port to see if it would leak/seep/drip through the valve. It held WD40. I am thinking that things hit, but not real hard; at least not hard enough to bend things up; just enough to knock some deposits off.

-Kevin
 
If you have the head off and the valves look like they all seat, check for leak down like said, then clean up the pistons and heads, on any other motor I would lap the valves, here it seems to be a no-no. The first time you turned it over did it actually run? If it didn't I don't know if there is enough force to bend the valve, also it would depend on how far off the cams were as to the amount of contact. :-s
 
If you have the motor running, there is no need to pull the head to check for bent valves - just run a compression test. I'm afraid (while there is nothing wrong with it) you are taking the hard way on this one.

As for lapping the valves, if they are surfaced properly (fresh valve job), there is no need. If you need a valve job, get one, save the lapping for when you have no access to a professional valve job.
 
Last edited:
You could remove the keepers and retainers and springs. Then rotate the exhaust valve while watching the bottom of the valve rotate in the chamber. Does it stay center or does it rotate to one side???

Also push the valve open, rotate it 1/8 of a turn at a time, then pull it shut, do you see any daylight between the mating surface. A flashlight in the port helps.

Also check the valve guide. If the valve makes hard contact with the piston it can cause the valve stem to flex and the tip of the guide that protudes into the port can crack off and may find it way into the cylinder. Don't asked how I know that one.
 
If the valves held WD-40, I don't see how you could have a problem. I'd say you got lucky by about .001 or .002
 
RacingJake said:
You could remove the keepers and retainers and springs. Then rotate the exhaust valve while watching the bottom of the valve rotate in the chamber. Does it stay center or does it rotate to one side???

Also push the valve open, rotate it 1/8 of a turn at a time, then pull it shut, do you see any daylight between the mating surface. A flashlight in the port helps.

Also check the valve guide. If the valve makes hard contact with the piston it can cause the valve stem to flex and the tip of the guide that protudes into the port can crack off and may find it way into the cylinder. Don't asked how I know that one.
Click to expand...

Jake,
I did exactly what you describe here. No wobble when I spun 3 of the valves in the seats. After 3 of them I sprayed WD40 in the ports and let it sit for a couple hours, and it still didn't leak through. I rode the bike tonight, and I think I got lucky; by a thou or two.

it sure does need a tune up though. I'm going to sync and tune the carbs tomorrow.

-Kevin
 
Kevin, the other thing you can do is spray machinist's bluing around the valve seat, and while it's still wet, stick a valve in, and pull it out. If you have a full circle of bluing on the mating valve face, you are all set. I worked many moons ago in a automotive machine shop, and this was a crude, but effective method to check for bent valves. The best way is to place the valves on "V" blocks, and check them with an indicator. If you want, mail me your valves, and I will dial check them no charge.
Rich
 
Sounds like you got lucky indeed. If you were running stock cams that help too.

Get that thing dialed in and open her up.
 
Spring height ok?

Spring height ok?

You might want to check your springs to see if they are within spec. If they are too short this could explain the contact.
 
My friends '82 GS850L bent valves and damaged pistons!

My friends '82 GS850L bent valves and damaged pistons!

My friend Pete who is on this board was riding his '82 GS850L when the valaves hit the piston and made a mess of the motor! GS motors ARE interferance I guess.
 
retrex said:
You might want to check your springs to see if they are within spec. If they are too short this could explain the contact.
Click to expand...

Oh I know why they hit, I just don't know how hard they hit. The timing was so far off that the exhaust was sucking air when I tried to start it. It was basically timed to my random spinning of the motor with out the tensioner on. I knew something was weird when the motor spun so freely when I hit the button. it also wouldn't open the petcock (no vacuum) to let fuel in.

I guess they hit, but not very hard, and pretty slowly. the motor was not even close to starting. It probably would have been worse if the timing was just a 2-3 teeth off instead of totally wrong. I got lucky like a roulette gambler gets lucky – slim chances.

Thanks for the offer Clam, but I'm going to keep them in.

-Kevin
 
One way to check the valve sealing is to clean each valve using a steel wire brush (on a bench grinder is quick) and clean each of the seats using a brass wire brush (on a drill motor works well). Then apply a small amount of lapping compound to the sealing surface of the valve and reinstall it in its original hole without the spring or related keepers and retainers. Slide a piece of fuel line over the stem that grips it and spin it to lap the valve on its seat. Once lapped, wipe both seat and valve clean of all compound and visually inspect both for a complete contact circle of constant width. If present, it is sealing fine. If not, it may require more lapping, valve seat repair or replacement valve. I've had very good luck with this "tune-up" and replacement of valve seals.

Another check is to take the assembled cylinder head and position it so the port is vertical. Fill it with kerosene or gasoline (no smoking, duh!) enough to cover the valve seats and inspect the combustion chamber area for signs of leaking. No leakage is best, a small amount of seepage can be tolerated if no opportunity exists to correct it, a leak is not acceptable.

Obviously a racing motor would be built to tighter tolerances, but this would suffice for many a street ridden unit. Works well on my dragsters as well. Good luck.
 
You must log in or register to reply here.
Back
Top