Author Topic: Correct location for the longer head bolts-CB650?  (Read 569 times)

Offline andy120t

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Correct location for the longer head bolts-CB650?
« on: December 17, 2019, 04:42:59 PM »
I'm rebuilding my 650 engine...its been apart for a couple of years and I can't recall where the two long bolts go to secure the head to the barrel ( as opposed to the other 10 which are a different size).

Haynes manual and CMSNL parts diagrams font help. I've also searched and posted in the alas site as they have more 650 action, but wondered if anyone here knew - or knows where I might find a manual that tells me?
Thanks!
andy120t

CB650 project
CB400F frame - just missing a few bits...
ZX6R
GSXR 7/11
Triumph 5TA
CB900FZ

Offline Bryanj

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Re: Correct location for the longer head bolts-CB650?
« Reply #1 on: December 17, 2019, 04:55:15 PM »
Does the cmsnl not show different part numbers?

Offline andy120t

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Re: Correct location for the longer head bolts-CB650?
« Reply #2 on: December 17, 2019, 07:25:13 PM »
It shows part numbers, so it's clear there are two different bolt types, but the diagram doesn't show where the bolts go...so I have 10 bolts/ bolt holes but two bolts are  longer and there is no obvious difference in the boot holes ( or none that I can see!). There must be a reason why they are different though.

Nb...it's where the 550 has studs sticking up from the crankcase to take the barrels, the 650 has bolts instead. Pain.
andy120t

CB650 project
CB400F frame - just missing a few bits...
ZX6R
GSXR 7/11
Triumph 5TA
CB900FZ

Offline K2-K6

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Re: Correct location for the longer head bolts-CB650?
« Reply #3 on: December 17, 2019, 10:52:42 PM »
Could you put the bolts into just the head and barrels when off the crankcase to see if any of them are sticking put more/less to find orientation?

If none are spaced differently,  in other words the two long bolts just stick out further in whichever location,  use a vernier guage to measure depth of receiving holes in cases to find the two odd depth examples.

Offline the-chauffeur

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Re: Correct location for the longer head bolts-CB650?
« Reply #4 on: December 17, 2019, 11:49:27 PM »
Just been looking through the extensive Chilton's motorcycle repair manual 1945-84 version because, well, reasons.  There's nothing in there that differentiates the studs.

Without any clear overhead images of the head, it's very hard to say what goes where.  Other models in the same family (like the 350/4, 400/4 and 750/4) had a couple of shorter studs in the front; the 750/4's were the outermost front (corner) two whereas the others were one in from the front corners.  The 650 seems to be the odd-man-out and none of the images I could find showed the top view layout clearly enough. 

If I had to take a guess, I'd start with the two rear outer corner holes (carb side).  With the exception of a couple of the inner holes, the stud holes at the front (exhaust side) are shared with the spark plugs, so it's unlikely to be any of those.  If all 8 of the holes that are only accessible inside the head have the same floor depth (I have no idea whether they do or not), the logical place for longer bolts is in the only two remaining holes, being the outer rear corners.  Looking at images of the underside of the head, those holes also have spaces for knock pins.

That said, 2cm is a fair old difference in length and not something that's going to go unnoticed if you get it wrong - those longer bolts should sit up if they're in the wrong place.  I'm assuming you've already assembled the engine dry to see how the bolts feel in different locations . . .  it should be fairly obvious where there are a couple of deeper holes.
« Last Edit: December 18, 2019, 12:00:01 AM by the-chauffeur »

Offline andy120t

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Re: Correct location for the longer head bolts-CB650?
« Reply #5 on: December 18, 2019, 08:19:47 AM »
 I've tested the depth of the holes and they are a 'll the same....however that was with the head off (so checking depth from the bottom up) - thinking about a dry build, reminds me that for the head itself , the casting is higher  for the two holes either side of the camchain at the back. They are likely to be the culprits.

I'll have a dry run today and see..
andy120t

CB650 project
CB400F frame - just missing a few bits...
ZX6R
GSXR 7/11
Triumph 5TA
CB900FZ

 

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