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  #16 (permalink)  
Old 3 Weeks Ago
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Location: Pembrokeshire Wales
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Many thanks for comments, will check valves today. Are there any anodes I can get at with the head off? How tricky is it to change the valve seals? Is it worth dismantling and checking the oil pump?
I am always wary of "fixing something that ain't broke".....
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  #17 (permalink)  
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Quote:
Originally Posted by cleddau1 View Post
Many thanks for comments, will check valves today. Are there any anodes I can get at with the head off? How tricky is it to change the valve seals? Is it worth dismantling and checking the oil pump?
I am always wary of "fixing something that ain't broke".....
Did you download the manual from the link? Everything is in there to completely rebuild your engine if so desired.

I see one anode in the head, but it is not clear if the cams have to come out to get to it.

You will need to remove the cams and need a valve spring compressor tool to get to your valve stem seals. Can be a bit fiddly getting the springs compressed and the keepers back in.

If it was not using oil and the valves themselves are sealing good....I myself would not bother doing the valve stem seals. But that's your choice of course.

Cheers
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  #18 (permalink)  
Old 3 Weeks Ago
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Thanks Panasonic, the manual refused to download to my tablet or laptop, probably due to the firewall, will try again with different computer and net access.
Just did the heads on my daughter's 1973 VW camper and last year did the one on my Fiat Punto. My 1968 Lancia Fulvia Coupe awaits a similar fate so have all the kit and, now partially retired, plenty of time although it is amazing how family members find all sorts of things for me to do that they managed to cope with when I was busy working.
But am unfamiliar (or was) with the anatomy of 4-stroke outboards.
This Yamaha drives my 32ft Iroquois Sailing Catamaran. It is such an excellent sailboat that the motor is only used when dead calm (a very rare occurrence in West Wales) and to get on and off the mooring. Saltwater always although the motor is completely out of the water when sailing or moored. Lack of opportunity for fresh water flushing except at end of season probably explains all the gunge.
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  #19 (permalink)  
Old 3 Weeks Ago
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You must have your firewall settings on high...as it is only a PDF file that you are trying to download. ..lol

There is a job for one of your family members...get them to download it for you...while you fix their stuff.

If you got the kit to do the work then changing out the Valve stem seals would be a good thing...seeing you are already in there.

Running your engine on a regular bases, even if you don't need to, will help keep it working good as well.

Good luck
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  #20 (permalink)  
Old 3 Weeks Ago
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Update: filled both combustion chambers with paraffin and after 24 hours considerable loss from one, none from other. Topped up and blew compressed air into ports showed significant leak from one valve only. All rockers had been slackened right off.
Will dismantle cylinder head and lap in all valves and can the also replace anode.
Managed to download manual, problem was several people using very slow internet connection, solved by downloading at 4 am.
The Clymer manual is just the right thickness when placed under one side of my outboard stand to bring the tilted engine horizontal........
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  #21 (permalink)  
Old 3 Weeks Ago
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Glad you found that valve while it was apart!

I'd check the valve guide for any excess slop..
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  #22 (permalink)  
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Well glad you have your manual now...and the Clymer is in the right place...not being used.

Let me guess exhaust valve leaking?
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  #23 (permalink)  
Old 2 Weeks Ago
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OK I have lapped all valves, replaced valve stem seals, replaced oil seals and also removed the cover from the exhaust side and cleaned all the water passages there and am now ready to fit the cylinder head.

It would be easier to adjust the valve tappet clearances while the head is on the bench but the manual advises that all rocker adjusting screws should be slack as the head is bolted down. Providing the pistons are at BDC this should not be necessary as long as I ensure the timing mark on the camshaft drive gear is lined up as for TDC before bringing the pistons to TDC and fitting cambelt.

Am I missing something?
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  #24 (permalink)  
Old 2 Weeks Ago
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Well, being a simple screw and lock nut VS shim adjustment, I'd just do it by the book...

IMO, with all you've done, I wouldn't cut a corner now...

BTW, what was the leak, a burnt valve, or just needed re-seating?
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  #25 (permalink)  
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tolerances may move when the head is torqued down.
after all it is not heavy cast iron
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  #26 (permalink)  
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The head will move slightly when torqued down as Yami said....so your valve tappet clearances may change from your bench settings. OR they may not.

Seeing that they are not hard to get at...I would install the head as per the manual and then set the tappets as per.
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  #27 (permalink)  
Old 2 Weeks Ago
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Makes sense; will do
It was an inlet valve that was leaking but not obvious why, all valves pretty good shape really, some carbon on the exhaust valves but cleaned up easily.
As there was water in the oil I spent some time flushing all the remnants of the old oil out of the block.
Once reassembled will spin motor on starter with plugs and fuel disconnected to circulate the new oil and then change oil again before starting for real. The LU is off and will have new impeller and oil.
Currently on hold until houseguests leave and then have to repair daughter's washing machine......
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  #28 (permalink)  
Old 1 Week Ago
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You are a busy man and will have one well looked after little engine there. Ready for many more years of service.
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  #29 (permalink)  
Old 1 Week Ago
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Quote:
Originally Posted by panasonic View Post
you are a busy man and will have one well looked after little engine there. ready for many more years of service.
+100^^^^^
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  #30 (permalink)  
Old 6 Days Ago
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Prior to fitting head checked with straight edge and there does appear to be some warping so will have to get this skimmed. Is there some way of knowing the maximum the head can be skimmed?
The block seems to be OK.

Also on the diagram here:

1998 T9.9MLHW Yamaha Outboard CYLINDER CRANKCASE Diagram and Parts

There is an O ring part number 34. Where does this go?

Although the new gasket has built in sealant is it worth using some extra and if so what?

Any advice would be appreciated.....

Last edited by cleddau1; 6 Days Ago at 01:21 PM. Reason: error
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