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A A A A Author Topic: Erratic revs  (Read 1378 times)

CX PHREAK

Re: Erratic revs
« Reply #50 on: 23-Jun-21, 13:22 »
My best guess as to the bending of the valves would be a valve strike on the piston at some point.

This may have been caused by a worn out camchain allied to an over rev.

Due to the placement of the tensioner the cam timing on these motors retards as the chain wears. Bad cam timing can cause valve strike.

While this is a full set it's likely your most cost effective option for guide replacement. A machine shop can do the job and it is best to have the seats recut at the same time and the new valves ground in.

https://www.ebay.com.au/itm/303547277819?hash=item46acd3e1fb:g:pocAAOSw0vJcHXQa

Or you could source another head which may or may not have its own issues.

gm

Re: Erratic revs
« Reply #51 on: 23-Jun-21, 14:15 »
thanks again
CXPHREAK
I'll let you know how it goes

RAM

Re: Erratic revs
« Reply #52 on: 28-Jun-21, 16:00 »
Has there been sticking of the valves in the guides caused by burning oil/worn rings?
Do you use a top end lubricant in place of leaded fuel?
How did the bore look at BDC?

gm

Re: Erratic revs
« Reply #53 on: 21-Jul-21, 17:51 »
Hello Gurus
I hope you are all well and coping with the current COVID restrictions.

In response to RAM
I’m not sure if the valves were sticking but some shafts had discolouration that might indicate overheating.  I had been using a lead replacement additive in the fuel but I think I may have been a bit remiss in recent times (bad on me).  The bore looks clean and smooth. 

One item that might not be right is that the rocker has a sticking point for both the right- and left-hand sides.  I am not sure if this is normal or if it is likely to affect the operation.  I couldn’t figure out how to remove the rocker shaft.

On reflection of the situation, I had some doubts as to how to proceed. I removed the Right-Hand Side (RHS) head and although it was not as bad as the Left Hand Side (LHS) it wasn’t a pretty sight. I also double checked the LHS stats.
Briefly the stats for both sides are:
•   springs range from 48.9 to 50.55mm mostly around the 49area,
•   shaft diameters range from 6.52 to 6.58mm mostly around the 6.55,
•   runout of the shafts was all good at 0mm,
•   runout of the valve heads range from  .06 to 1.04mm,
•   valve contact surfaces range from 1.87 to 2.4.
While the gasket looked ok in the photo, they both began delaminating on removal.
There was some valve slop in two of the guides and a couple had cupping on the contact surface.

I was not sure if the removal and replacement of the guides was easy or difficult
I noted that the faces of the heads were scratched see photo
And I noted some corrosion in the water pipe from the head to the thermostat see photo.
I think I should purchase new valves, springs and guides and either do the replacement myself or take them to the engineers shop and get them to do it.

I seek your opinion
Should I have a crack at installing the guides or send it to the engineers?
Should I replace the water pipe, or will the O ring compensate for the poor surface of the pipe?
Should the surface of the heads be shaved?
If the rocker arm should be a smooth operation?
Anything else I may have missed?

Thanks again and hope to hear from you
gm

CX PHREAK

Re: Erratic revs
« Reply #54 on: 25-Jul-21, 15:08 »
The discolouration on the shafts may be indicative of overheating or is simply baked oil.

The sticking point on your rockers is wear to the rocker shafts. It is not usually an issue.

The shafts can be swapped inlet for exhaust so that the current bearing surface is moved to the top and the unworn top side moved to the bottom where the thrust is taken.

Have you given the valves a test lap to check their seating? Don't use coarser than medium compound. Aside from being to coarse for the job generally coarse has large enough lumps of abrasive to roll on the low spots, cleaning them and making it appear there is more contact between valve and valve seat than there really is.

The sloppy valves were exhausts?

If going the route of guide and seat replacements I'd put it into a workshop capable of the work if you can afford it. You'll never have to look at them again then.

The coolant pipe is fine.


gm

Re: Erratic revs
« Reply #55 on: 26-Jul-21, 15:24 »
thanks CXPHREAK
Not sure what you mean by swapping the valves.  The inlet valves have a head diameter of about 31.9 and the exhaust are about 21.9. I hope this is normal for the 650E.  The exhaust valve heads are bent out about a millimeter. I can't imagine they will ever form a seal again.
Yes it  is the exhaust valves that are sloppy.
What did you think of the scratches on the surface of the head?
GM


CX PHREAK

Re: Erratic revs
« Reply #56 on: 26-Jul-21, 15:29 »
As for the swapping - I meant the rocker shafts and not the valves.

I expected the exhaust valves would be the sloppy ones as intakes are generally OK.

The head gasket should handle the scratches in the head face but personally I would face them out. If you'll be putting the heads in to a workshop to be done maybe they can also give the gasket faces a quick reface.


gm

Re: Erratic revs
« Reply #57 on: 26-Jul-21, 22:53 »
Thanks again CXPHREAK
I will need to wait untill Sydney's lock down is over before I can get to the workshop.
I will let you know how it goes.
GM

RAM

Re: Erratic revs
« Reply #58 on: Today at 13:50 »
Should I have a crack at installing the guides or send it to the engineers?
Should I replace the water pipe, or will the O ring compensate for the poor surface of the pipe?
Should the surface of the heads be shaved?
If the rocker arm should be a smooth operation?


Replacing guides also requires valve seat cutting. A job for the engineers.
A soft new O ring and rubber grease should seal OK.
Shave heads if they are warped otherwise light clean with a smooth block with medium grade wet & dry and kero.
Hylomar sprayed on gasket is another option.
Rocker arm operation should be as smooth as possible. Clean and polish shafts.
I hope you can solve all problems easily.

gm

Re: Erratic revs
« Reply #59 on: Today at 15:17 »
thanks RAM
I'll let you know how it goes
gm

 


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