New cam chain tensioner or not?

[Drew400]

Hello all,

CB400/4 - having shelled out (if you'll pardon the pun) for new crankcase bearings, ground-in my valves, etc. I'm considering replacing all of the cam chain tensioner parts. I read all sorts of stuff about how bad or neglected they were and, having seen lots of evidence of previous engine failures/rebuilds, I'm thinking that, as the engine is out and dismantled, I should play safe and order a whole load of new parts rather than risk reusing stuff.

Any views out there (I'm sure there are lots!). Replace all of the bits or just a few? If so, which ones?

Cheers and thank you, D.

[Bitsa (Ralph Wright - RIP)]

Drew
As a Precaution I have done that with all the bikes I have bought.As usual its in my mind being my age that I am going to keep them so all is new they will out live me.No sad shit intended but once done doubt you will ever do it again unless you do a crap rebuild.Sorry to be a bit morbid but thats my view
All the best
Bitsa

[Trigger]

Drew, if the tensioner is working. You only need to change the blades if worn.

[Lobo]

Hi Drew,

I gave my engine over to an engine rebuilder (Terry Ives)... along with a big box of new DSS parts and a VERY specific instruction, "Terry, I'm a fussy bugger & won't tolerate any fudges etc... please use anything you need, and inform me anything extra (oversized pistons whatever) & I'll get them soonest"

I collected the 45000 engine a few weeks later.... with much of the box of bits back.... unused. I was disappointed (initially) - but Terry was adamant that the engine was beautiful within, "& only just run in" (I'm not saying it hadn't had a complete overhaul by some PO) He didn't see any point in throwing out perfectly serviceable / in tolerance parts for new. And when all's said and done... MY bike will only be riden a few 00 miles a years .... I'll likely never wear it out.

POINT is.... these Honda OEM parts can cost a fortune, and if like me, you'll not be using the bike as a daily commute etc... don't unnecessarily waste cash. The manuals state tolerances everywhere, there is this great site ... by all means the primary chain & cushs, camshaft chain / bits (peace of mind)... but the rest???

Oh... & my engine sounds beautiful... with its new clutch cushs!

[Bryanj]

As long as the horshoe pivots freely and the plunger is free in the casing I would only replace the springs on the plunger as they were only just strong enough when new.

Check the blade for cracking where it bends at the ends and the cushion for rubber loss replace either if faults fond---The tensioner blade can be replaced with just a cam cover off but the cushion needs the head off and barells lifted

[AshimotoK0]

As long as the horshoe pivots freely and the plunger is free in the casing I would only replace the springs on the plunger as they were only just strong enough when new.

Check the blade for cracking where it bends at the ends and the cushion for rubber loss replace either if faults fond---The tensioner blade can be replaced with just a cam cover off but the cushion needs the head off and barells lifted

Agreed Bryan. I have all NOS rubber parts for my 750K0 when I get round to assembling it  but also some really nice used rubber parts, some of which have been off the bike for almost 30 years and kept away from sunlight (i.e no ozone cracking). I guess we will all open up engines which have possibly been apart in fairly  recent times and the parts fitted may not be that old. Sometime,  I am going to take my NOS parts out and measure the rubber hardness on the NOS part and compare with some old, but real nice condition, parts just to see what the difference in hardness is.

Cheers ... AshD

[Clem2112]

I used what I thought was the strongest pair of springs from two engines - there seems to be no specified measurement for free length or condition.

They seem to lose their strength but by how much?

I also checked the plunger for straightness and any sign of wear or ovality on the flat part as that's where they can jam up in the casing hole.
Needless to say, manual tensioning is still needed on mine !

When removing the tensioner blade with the head removed, that cushioned seating piece can sometimes lift out of its pocket in the arm.  Worth a look with a torch to check it's still there when you put a new blade in.

[Drew400]

Thank you all, sound advice as always from people who've been there. You may have just saved me a few bob, not least as this little 400 will be looking forward to a long, dry, easy retirement... if and when I get her running again. This'll not be a daily winter commuter in my ownership!

Cheers for now,

D.

[Trigger]

I agree with bryan. I have built 21 CB400 engines in the last 2 years and everyone has been different. Had one with under 30,000 miles (well that what the customer told me). The oil was like glue, the oil pump was shot and all the tolerances were well past its spec. Had a 98,000 one in that the guy had from new and it had been well looked after with regular oil changes. He had the cam chain changed every 15,000 mile (if he needed it or not).  It was a privilege to work on such a fine example. Only needed rings, chains, cam blades, seals and a gasket set.
I have seen primary chains worn out in 4,000 miles and have seen other last 70,000 before it starts to rattle under 1500 rpm. It is all down to who had the bike before and if they looked after it.

[Drew400]

Thanks Trigger,

Somewhere in the last 10 or so owners it was either abused or neglected then repaired. This is certainly not a well cared for, one owner bike. Hopefully it will feel like one when I get it all back together, albeit with some genuine 'patina' visible.

Hmmm 21 x 400's, eh? This is my first 400 and my first ever engine that involved bottom end stuff. Learning loads and spending too much time in my garage. Great fun in the man shed!

Cheers, D.

[Trigger]

Drew, Built a few 400's over the years. In the 90's we were building 10, CX500 engines a week for the dispatch riders market. Over the years i have lost count of how many Honda engines i have built.

[Drew400]

Loved my CX500... one of only two vehicles that I have bought brand new since 1977 (the other was a Kawasaki GTR1000, oh dear!).

[DayvW]

Hi Drew,
Just to add my penny's worth from my recent 400 engine overhaul (which is also to have an easy retirement) - I figured I'd replace what was needed (and from advice sought from the gurus here).  My cam chain adjuster (the U shaped thing) was jammed and beyond mending .. so I plumped for a nice new shiny one from DS (which is expensive - but has a proper pivot - I have previously posted a pic here) - plus the 2 blades as they were very scored (prob due to the adjuster being jammed).  I didn't replace the springs. On reflection perhaps I should - but then on adjusting a gentle press down through the removable screw seems to be pretty standard for these anyway.  I did also replace the cam-chain (you would wouldn't you).  If the adjuster still worked I would have left it; if the blades were within tolerance I would have left them too.  So - my take is as others here - replace as needed - but don't go mad if you don't need to. For example my main and crank bearings looked pretty good to me - so I saw no point in shelling (to pinch your pun) out £100s for those.  Rings were clearly worn - so they had to go (and lo and behold the eye watering aroma of burning oil when ticking over in my garage (door open is long gone).  And also as documented elsewhere the primary chain was wrecked - so that went (along with the rubbers as advised by OddJob I think - they were indeed old and solid - and relatively cheap anyway).

[Drew400]

Hi Davy,

Thank you again, and for the affirmation (i.e. yes indeed, cam chain, primary chain, rubbers, etc. all renewed). I'll have a look all the other (cam) bits at the weekend, but I feel a little more budget bashing is on the horizon!

D.