Pitted tappets, mashed valve ends and a loose primary chain?

[DayvW]

After starting on a clean up of the engine ('76 400-4) I have decided to go the whole hog and strip her down completely for some soda blasting.  In doing so I have found some tappets are pitted and on one or two valve stem ends they seem quite hammered (though the pitted tappets do not coincide with the mashed valve stems).  Has any one seen this before?  I'm going to replace the tappets - but regarding the valve can I grind these back to smoothness (or is there a risk I'll grind through the hardened surface?).

On a separate note - having removed the sump and finding so much gunge in there (mainly, I think, from gasket gunge!) - plus a lump of alloy about 1/4" dia - all of which persuaded me that a full strip down is in order now I have the head off and the engine on a bench  - I poked the primary drive chain on the sprocket (the one that protrudes into the into the sump a little way)  - and it seems so so loose.  Is that how it's supposed to be?  And how long do they last?  The mileage on the speedo reads 23,000 (no idea if genuine of course).  I'll replace it if need be - but they aint cheap.

Any experience of any of the above much appreciated.  Thanks.

[Trigger]

You will have to replace the damaged Valves and Tappets. The engine will need a total strip and any damaged parts replaced.
Your parts list will be long, but it is all worth it in the end.

[Bitsa (Ralph Wright - RIP)]

Plus one with trigger dont cheap skate you get what you pay for trust me
Cheers
Bitsa

[DayvW]

Thanks guys - and yeah - I thought so  - do you think just poorly adjusted tappets may have caused the probs?

And on the primary chain - should it feel loose or would you expect it to be tight -and if so - what is it that makes it tight?

[Trigger]

Dayv, the best thing to do is check all the part and look up the cost. It maybe cheaper in the long run to find another engine. But, can you trust a second hand unit?
Primary chain                                   £75
Cam chain                                        £30
Shells                                               £8 each
Main bearing's                                  £12 each
Oil seal set                                       £30
Gasket set                                       £50 - £95
Piston's                                            £45 each
Piston ring's                                     £15 each
This is just your basic parts you may need. Without any tappets, valves or machine work.The average cost for a CB400/4 is £$??? these days. Any short cuts will bite you back.

[Trigger]

A primary chain has No guilds or adjustment. Just make sure it is not touching the casings. It needs a little play.

[Bryanj]

A new chain when first fitted will have nearly zero play, Ive seen totaled ones at 20,000 and good ones still at 60,000. depends of level of thrash and how well iwas kept in tune (especially carb balance)

[Trigger]

Good call Bryan and Oddjob. I did take the measurements of a new chain for a 400F. But as normal i wrote them on a post it note and now can't find it.

[DayvW]

Thanks again guys.  That tip on replacing bits sounds very sensible .. I was getting there in my thought process (was baulking at the price of a primary chain - but you are quite right - and though I will do OddJob's test - I cant believe its supposed to be as slack as it is (wonder if that was the source of my weird noise the subject of another post?!)) - but advice from people that know is exactly what I need!  Especially useful is advice on how you know when stuff is worn and what to look for (thanks OddJob).  I am planning to take everything out prior to soda blasting - so can look at state of the cam chain tensioner and guides (with the head off the guides look ok - but I will replace them anyway - along with the chain).

Thanks once again!  I will report back on findings in case discussions such as this help others.

[Lynx]

The primary guides, listed here as No. 142 put some tension on the chain when the crankcase halves are together.
http://www.cmsnl.com/honda-cb400f-england_model14639/partslist/E01-3.html#results

[Trigger]

Lynx, these are guide's , not tensioners . I think they are listed as safety guides by Honda. They are to stop the chain chewing the casings, which would result in a blown engine.

[Lynx]

But the chain does actually run on it doesn't it?


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[Trigger]

Yes, it always is in contact with the bottom one,(when worn) running in oil. The top one only makes the slightest contact when new. The protector guilds are held in by 2, 6mm bolts. when the chain is in bad condition the bolt head show marks.