Found out why my motor died this time...

[arthurdent510]

Had a valve go through the front piston :P  The head is done, I'll have to replace it.  The con rod looks ok, and the sleeve looks ok as well.  There's some small scratches in it from when I pulled the piston out, going to take the hone to it and see if they'll buff out.  Time to take a trip to the local bike junk yard and see how much he wants for a new head and piston :P  At least the piston will make a neat desk ornament!

[QBS]

How did you manage to do this?

[Lucky]

spring/keeper/valve failure from either over heating (unlikely since the head is wet) or over reving..

My guess is Arthur fully enjoys putting his bike thru her paces! :D

[Re-Vision]

Can probably find what you need if you don't mind paying the postage from Texas. Engine had a busted timing chain which damaged one piston, other parts appear okay. Yours if you want them.    BDC

[arthurdent510]

Not too sure what caused it...  wasn't over-reving it, was only at 5k or so, unless the tach was lying to me.  It's possible that the timing chain slipped, but the tensioner looked good.  Couldn't spin the motor, so I wasn't able to verify the timing marks.  All the valve keepers are in place still as well, even the one for the valve that broke off.  I've just had bad luck with this bike :p

[QBS]

It would seem that if the cam timing was off (due to cam chain irregularities, or whatever), that the other intake valve would also have been open at the wrong time and thus, also be damaged.  5k rpm is very low rpm.  Certainly one would be able to discern the difference between 5k and 13k rpm.

Strange that the keeper assembly on the loose valve was still intact.

[arthurdent510]

Yea, I last set the timing in early spring, it's run a bit since then with no problems.  So I don't think I had it set wrong.  It's possible though :-p  I'll have to pull the timing chain and measure it, see if it's stretched out or not.

[Kenny]

 I'm putting money on the "Valve" adjustment being out of spec. Was this an intake or ex. valve.? I know we have had several discussions on the valve settings never needing adjustments however after over 100,000 kms on these engines you can expect the Ex valves to tighten up.After this happens (gradually) the neck of the valve stretches, and in the end breaks away & heads for the piston.
    This also happens if the valve is not corretly adjusted.
                    Cheeers Ken S. ;)           
 

[Rikugun]

Sorry for your misfortune, that is a bummer for sure.

Just looking at the pics I would have guessed over revved. If it happened at only 5k, then I'm fairly intrigued by all this. Unless, someone else rode the bike and had the valves floating but it didn't grenade until you rode it later?

Do you know the history of the engine and how often the valve lash was checked? How many miles on the engine when it failed?  You mentioned last setting the timing in early spring - that sounds like the top end was apart for some reason. Did the tensioners and other bits go back together correctly? Or maybe something left loose?

Kenny, How does the neck stretch? If the valve is tight (as in zero clearance or held open), it won't hit the seat, right? Burnt valve yes, but stretched?

[Kenny]

 The valve seat to valve head can get a build up of combustion material & it can stretch at this point, deterioration of the valve & seat can start at this point. My 84 R100 gobled up an Exh valve this way each time you adjusted the valves the Exh had no clearance.
       My 83 Vision always is on the tight side as far as Exh valve clearances.
                                        Cheers Ken S.  :D         

[Raj1988]

Hope you geter fixed and ride again...

[arthurdent510]

Just an update... pulled the motor apart yesterday, I'm surprised at how much metal was in the bottom of the motor.  I didn't think the piston had that much material on it!  Pulled the transmission apart and got everything cleaned up as well, there were bits of aluminium everywhere...  kinda wish the piston was steel so I could just use a magnet to pick up all the pieces :-p  Everything is cleaned up though finally, just have to get the mess back together now...

On a side note, I got the bits to fix the fuel pump on my Triumph today so at least I'll have 1 running bike again!  Not having a bike to ride sucks  >:(

[akvision]

Art,
What part of the country are you in?

I have a  motor and could ship it to Seattle for $50 then truck it to you.  I will give you the motor.  It is stuck from sitting and internal rust.. but it is complete for your needs.. maybe.  It was the former BluV that I did not want to try to recover and I used it for parts.

If interested check the trucking cost from Seattle.  My flat twin is coming by barge in the next two weeks so I will have a good shipping container.  3/4 plywood

Akvision..

[arthurdent510]

Thanks for the offer!  Re-vision actually had the parts I needed, so I think I'm set.  I just need a couple head gaskets now, and then to reassemble everything.  I'm hoping to have a majority of the motor back together by the end of the weekend.  Maybe even get the motor mounted part of the way, so I would just have to drop the heads in and be off and running.  It's getting there!

[Walt_M.]

You've probably already done this but that kind of failure could have damaged your con rod and bearings so don't forget to check 'em.

[fret not]

Walt is right, check out the rod and crank bearings while it is still apart, rather than putting it all together and finding the oil pressure disappearing.

[Re-Vision]

How do you check them? I would like to know if the ones I have are any good.    BDC

[Walt_M.]

A good check for the con rod is a magneflux which most machine shops should be able to do. As for the bearings, I would recommend just replacing the small end and wrist pin. Check the big end for clearance and any scuffing.

[Rikugun]

A magnaflux will check for cracks but I'd also check to see if it's bent. You may also want to measure the holes at 2 axis to see if they are deformed. Was there any obvious damage to the top of the rod once you got the piston off?

As far as bearings are concerned, I wasn't aware the small end had a bearing. Is it a caged needle bearing like on a 2 stroke? I didn't see one listed on the exploded view so maybe I just missed it....

[fret not]

To check the rod bearings you have to take them off the crank for inspection, then check the clearance with Plastigage.  For reference and comparison there are some good pics of different types of wear/damage to plane bearings on the Clevite bearings site.

I'm not sure how you would check the main bearings except with inside and outside micrometers.