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Post by BritPete on Oct 20, 2022 9:37:50 GMT
Morning all I have been preparing to take the head off SME and have been quite surprised - there appear to be 2 of the 8 bolts with rubber inserts, see diagram below - I was aware on the inserts on earlier bikes but thought they were the inlet side 2 middle bolts Anyone taken the head off an NC, am I correct - I am assuming the rubber will be deteriorated when I remove them Thoughts please - as ever preparation preparation preparation - probably need to source replacements or do I  Lastly CTB and I had a discussion this morning - Haynes recommend if you change the bolts all should be changed - only 5 of the 8 bolts are available - what is the risk if I only change 2 bolts |
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Post by buster on Oct 20, 2022 11:22:54 GMT
its 'proper' practice to change the bolts but I'v never bothered and so far not had any problems.
the rubberised bolts came in around the NA models (I think), the idea being to stop the bloody things seizing in (again I think) I'd definitely replace those two if they are available just for peace of mind.
I keep the bolts in order and replace in order, dead easy to do. as the bolts are loosened lift the outer two up by the bracket, the inners need great care when your only doing the top end, dont drop the copper washers down the engine
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Post by johnfcbn44dx on Oct 20, 2022 11:57:29 GMT
90088 goes at the front 90087 at the back If the seals are good, and your sure the bolts are going straight in, I was thinking to spray the top of the thread and bottom of the barrel shaft for the bolt, with a bit of silicon as a release agent (or the bolt would be glued in). Then put a smear of silicon gasket on the dry and clean bolt seal on final install. But probably best to acquire an 87 & 88 anyway. I think a must have would be the copper sealing washers on all the inboard bolts which should be renewed.  Can't think why you would renew the other bolts unless they had been over torqued and yielded, would not be my intention...they may of stretched a little but not critically. lots of engines with the old bolts back in, and no problem. |
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Post by andy1kenobe on Oct 20, 2022 12:51:25 GMT
I try to go with the manufactures recommendations regarding head bolts. I've replaced plenty on car engines in the past.
But as these are not available, or damn near impossible to source, you have to re-use or even a combination of replace and re-use. I'd hazard a guess there's plenty SD engines with re-used bolts, second hand bolts and even home made efforts (I've done that!) that are running without problems.
Get what you can and re-use what you can't.
Buster and John's advice is sound in my opinion.
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Post by johnfcbn44dx on Oct 20, 2022 14:21:29 GMT
Pete, which bolts were not available just out of curiosity?
The only other thing is the front bolts tend to be more affected by corrosion, but just the zinc depleted, but not a worry, but a slight, thin, scoosh of vht on the long wasted area, before re-installing perhaps.
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Post by johnjones on Oct 20, 2022 14:30:24 GMT
Copper washers on the 4 inner head bolts.
Thin smear of sealer on rocker carrier to head joint face on the 4 inner head bolts.
Do not ( DO NOT ) allow any sealer to enter any head bolt threaded hole else hole will BURST !
Seen this so many times !
Carefully lower all head bolts into Thier holes and start off the bolts...the 4 centre head bolts are open to the outside world's water, salt and grit.
Are there 2 "slits/slots on the cylinders head bolt holes on the cylinder base ?
If yes then seal bolts go into these holes.
Classic bit of honda design so owners can bugger up the engine.
I remember the utter bs at the time suggesting those slits were part of the c/case ventilation system, utter bollocks !
The design team must have had a really bad hair day in that meeting.
Measure the hole sizes in tge cylinder and draw your own conclusion.
Really good bit of honda design designed to cause problems bless them.
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Post by johnjones on Oct 20, 2022 14:34:35 GMT
Lower centre bolts down the holes and start the bolts into the c/case, say 2 turns.
You could now apply a small amount of sealer to the non threaded part of the bolts lower section.
The non seal bolt holes in the cylinder base fill with water,salt, crap etc. and can be the devil to remove without damage...a crap design.
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Post by BritPete on Oct 20, 2022 15:30:46 GMT
90088 goes at the front 90087 at the back If the seals are good, and your sure the bolts are going straight in, I was thinking to spray the top of the thread and bottom of the barrel shaft for the bolt, with a bit of silicon as a release agent (or the bolt would be glued in). Then put a smear of silicon gasket on the dry and clean bolt seal on final install. But probably best to acquire an 87 & 88 anyway. I think a must have would be the copper sealing washers on all the inboard bolts which should be renewed. Can't think why you would renew the other bolts unless they had been over torqued and yielded, would not be my intention...they may of stretched a little but not critically. lots of engines with the old bolts back in, and no problem. 87 and 88 Ordered plus washers for the other 2 inboard bolts |
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Post by BritPete on Oct 20, 2022 15:35:12 GMT
Pete, which bolts were not available just out of curiosity ?The only other thing is the front bolts tend to be more affected by corrosion, but just the zinc depleted, but not a worry, but a slight, thin, scoosh of vht on the long wasted area, before re-installing perhaps. Jon updated  When I dropped the engine out 2 years ago the the upper rear and bottom front mounting bolts were cut off so it is a bit worrying |
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Post by joesoap on Oct 20, 2022 17:52:23 GMT
From what I have read previously by Nick and John, the rubberised bolts for the 250cc are the ones that are very difficult to find.
My understanding is that the 400cc versions are still available, that's assuming that the NC use the same bolts as earlier models. Have you tried the MC0 central number instead of the original 413?
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Post by joesoap on Oct 20, 2022 17:53:30 GMT
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Post by johnfcbn44dx on Oct 20, 2022 18:18:50 GMT
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Post by johnfcbn44dx on Oct 20, 2022 18:20:46 GMT
From what I have read previously by Nick and John, the rubberised bolts for the 250cc are the ones that are very difficult to find. My understanding is that the 400cc versions are still available, that's assuming that the NC use the same bolts as earlier models. Have you tried the MC0 central number instead of the original 413? For the 250 the 90088 is very difficult, managed to get 90087s over a period and at a price! |
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Post by buster on Oct 20, 2022 19:32:04 GMT
next time I come across these barrels I'll weld the grooves in and file the little swines flat, think I got the rubberised bolts for the 450dx engine from silvers if that helps
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