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Blood Sweat Tears and Grease => Engines => Topic started by: bonbons on Oct 04, 2018, 23:15:50

Title: 1975 CB400F Engine knocking
Post by: bonbons on Oct 04, 2018, 23:15:50
Iím currently in the process of tearing down my Ď75 Honda CB400F engine (splitting the case) for the second time to investigate a knocking sound that has been difficult to figure out where itís coming from. It sounds like metal hitting metal as the loudness and pitch of it would be indicative of that...
https://drive.google.com/open?id=1E5MqHdtQRm4Sx8NzEriQ9lVHqyqeydYj
Dropping the oil pan, I find no evidence of metal shavings not shards of anything. No sign of odd wear on the clutch nor stator. Even took a peek underneath and find that everything looks clean
(https://uploads.tapatalk-cdn.com/20181005/4a8172915d3d7399ad5e8c002c61606f.jpg)
On the previous engine tear down I uncovered this shearing on the exhaust side of the upper half on the engine
(https://uploads.tapatalk-cdn.com/20181005/2bc5e01b27ed0b0e02616ace05de3ad0.jpg)
Was this once where the bottom part of cam chain guide seated? Did the cam chain grind it off?

Scratching my head hard on this one (and i bet itís gonna be something really dumb).


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Title: Re: 1975 CB400F Engine knocking
Post by: trek97 on Oct 14, 2018, 17:27:14
Could be the cam chain.

Im starting my 75 400f teardown/ rebuild this week.

Talking w Kanticoy yesterday he told me the 400f is notorious for sticking cam chain adjuster.

So I went ahead and ordered the improved aluminum adjuster, new chain, slipper and tensioner from David Silvers.

Hoping it arrives before next weekend.

Please keep us posted on your build w lots of good pics and any insights you can offer.
Title: Re: 1975 CB400F Engine knocking
Post by: bonbons on Oct 14, 2018, 17:37:15
With a micrometer I measured the journals, crankshaft mains and big end rods:

Main Bearing Journals
1 - 31.9777mm
2 - 31.9862mm
3 - 31.9862mm
4 - 31.9862mm
5 - 31.9887mm

Big End Rod Journals
1 - 31.9887mm
2 - 31.9887mm
3 - 31.9887mm
4 - 31.7830mm (up/down), 31.9887mm (sides)

The bearings spun on #4 and thereís noticeable slop there too, some 0.2057mm worth.
(https://uploads.tapatalk-cdn.com/20181014/416758154367f3f19b296dbcf01814b1.jpg)
(https://uploads.tapatalk-cdn.com/20181014/634b4b60b293c56e9f3919de9601d6b9.jpg)

Iím convinced that this was the source of the knock. Crankshaft replacement is in order. Ended up ordering a whole crankshaft and rods set via eBay that was pulled from a Ď72 CB350F. Sources say that the 350F and 400F of that era pretty much shared the same engine components. Fingers crossed this will fit and work just fine.



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Title: Re: 1975 CB400F Engine knocking
Post by: trek97 on Oct 14, 2018, 18:00:08
Pics of the replacement case I picked up...

(http://www.dotheton.com/gallery/11494-141018155722-45541750.jpeg)

Been chewed on some.  I dont know how deep it was new but its about 5/8 inch now.

(http://www.dotheton.com/gallery/11494-141018155722-4555635.jpeg)

I will have a second example to check by next weekend.
Title: Re: 1975 CB400F Engine knocking
Post by: bonbons on Oct 14, 2018, 18:02:33
Ah! Thanks for those pics. I guess then itís common that piece is worn down via can chain. I doubt that would be any source of knocking, however. It would just get chewed down as a result.


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Title: Re: 1975 CB400F Engine knocking
Post by: trek97 on Oct 14, 2018, 18:09:00
Stinks about your bearings and crankshaft though.

You can get new bearings from davidsilversspares.com
Title: Re: 1975 CB400F Engine knocking
Post by: trek97 on Oct 14, 2018, 18:14:32
I picked up plastigauge at autozone to check bearings one they go into the new case.
Title: 1975 CB400F Engine knocking
Post by: bonbons on Oct 14, 2018, 20:48:48
Good go on the green Plastigauge. Iíve never used the red version...

Yeah, seems that my #4 rod journal had gone oval and spun the bearing, leaving wear marks both on the inside and outside. I wonder if the oil passage had been blocked or something. Strange.

Iím awaiting parts from DSS - I wish they had a better package tracking system. Iíll be ordering some crank and rod bearings from them for sure


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Title: Re: 1975 CB400F Engine knocking
Post by: trek97 on Oct 14, 2018, 22:52:34
Good go on the green Plastigauge. Iíve never used the red version...

Yeah, seems that my #4 rod journal had gone oval and spun the bearing both on the inside and outside. I wonder if the oil passage had been blocked or something. Strange.

Iím awaiting parts from DSS - I wish they had a better package tracking system. Iíll be ordering some crank and rod bearings from them for sure

The red is just a bit thicker diameter for wider measures.

Yep I agree, they should offer better tracking.  Not a fan of the $20 flat rate shipping either.  Makes them out of the question for small orders.
Title: Re: 1975 CB400F Engine knocking
Post by: trek97 on Oct 31, 2018, 16:14:33
Anything going on here lately?
Title: Re: 1975 CB400F Engine knocking
Post by: cxman on Oct 31, 2018, 21:37:50
hope you got the crank ground and the rods checked
Title: Re: 1975 CB400F Engine knocking
Post by: bonbons on Oct 31, 2018, 21:45:12
(https://uploads.tapatalk-cdn.com/20181101/89ddbf2546387184b06b353ad52f3144.jpg)
Sorry Iíve not chimed in. Iíve been trying to fine tune the bike now after replacing the entire crankshaft assembly including the connector rods and all the bearings. So far so smooth on that aspect and most importantly, no more knocking!

 New issue has arisen and thatís with 1st gear not engaging right. It clunks dangerously enough for me not wanting me to even try to engage it so Iíve been having to take off while Iím 2nd gear which isnít the funnest. Gonna give this closer inspection thru the week, starting with a clutch adjustment (I doubt this is the issue) and then behind the clutch to check out that part of the shifting mechanism; before I have to go splitting the case again. I think I can split the bottom half of the lower case, right? I dread having to peel off the top cover head and cylinders to get to the transmission below...

Nevertheless, engine knock BE GONE!


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Title: Re: 1975 CB400F Engine knocking
Post by: trek97 on Oct 31, 2018, 23:14:22
Holy Smokes Batman.  You work fast! 

yeah seems the primary shaft, starter clutch and chain.  Would be the biggest stuff w pulling the bottom case. Right?

You've done it more than I have.   ;D
Title: Re: 1975 CB400F Engine knocking
Post by: bonbons on Oct 31, 2018, 23:19:10
Thanks! Yeah, I was pretty fast on this one but as they say, haste makes waste... though I did check things over as I do. Newish cam chain, newish clutch discs, brand spankiní new primary chain too. Iím thinking it could be that one of my shifting forks is bent :-/ We shall soon see.

Meanwhile, I am riding on gears 2 thru 5 trouble free. Bike is smooth as buttah on those gears and is real fun. I hope to get this running at optimum again soon


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Title: Re: 1975 CB400F Engine knocking
Post by: bonbons on Oct 31, 2018, 23:21:07
More details on where Iím at with this build and how itís come along since inception

IDK Numero Dos - 1975 Honda CB400F
 https://r.tapatalk.com/shareLink?share_fid=13548&share_tid=159591&url=http%3A%2F%2Fforums%2Esohc4%2Enet%2Findex%2Ephp%3Ftopic%3D159591&share_type=t


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Title: Re: 1975 CB400F Engine knocking
Post by: trek97 on Nov 01, 2018, 08:58:00
More details on where Iím at with this build and how itís come along since inception

IDK Numero Dos - 1975 Honda CB400F
 https://r.tapatalk.com/shareLink?share_fid=13548&share_tid=159591&url=http%3A%2F%2Fforums%2Esohc4%2Enet%2Findex%2Ephp%3Ftopic%3D159591&share_type=t

Aaaahh Thank you for that.  I went through the whole thread (hit and miss) reading your posts that caught my eye.

That broken tensioner bolt. Ugh.

I was gonna suggest a change in oil.  But I also run the rotella in all my bikes.  Interested to see what you find w the shift forks.

You've done a bunch of good work to the machine.  Pods can be a pain in the ass to tune.  lol. 

I know your shooting for the "LOOK" but Im keeping things stock.  Its just easier and reliable for me.  I aint getting any younger here.

Please Keep the updates coming our way. 

Title: Re: 1975 CB400F Engine knocking
Post by: 1fasgsxr on Nov 01, 2018, 13:32:40
Wow that exhaust looks super low! 
Title: Re: 1975 CB400F Engine knocking
Post by: bonbons on Nov 25, 2018, 04:56:26
The picture may be a bit misleading but yes, the exhaust does ride low. No off roadiní with this bike and Iím careful over speed bumps and dips.

The exhaust is handmade from Outex (Japan). I like it a lot.


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Title: Re: 1975 CB400F Engine knocking
Post by: trek97 on Nov 25, 2018, 10:55:18
Long time no see bro.  Hows things going?

I got busy yesterday and actually got a short ride in.

Check it out when you find the time...

http://www.dotheton.com/forum/index.php?topic=75640.msg912689#msg912689
Title: Re: 1975 CB400F Engine knocking
Post by: bonbons on Nov 25, 2018, 13:25:08
Long time no see bro.  Hows things going?

I got busy yesterday and actually got a short ride in.

Check it out when you find the time...

http://www.dotheton.com/forum/index.php?topic=75640.msg912689#msg912689
Awesome! Congrats! Though, at the least I'd say put a front brake on that thing!
Get these bikes out on the road!

Things with my 400F are meh; things can always improve. Still getting some rides in. Because of the air pods and aftermarket exhaust, I had to upside my jets (88 Mains; 75 is stock). I recently discovered too that it's important not to mix/match manufacturers of these carb parts. Since I had an aftermarket main jet, I kept its constituent parts stock (i.e. needles and emulsion tubes were Keihin which didn't seems to fit well with the aftermarket mains). This time I tried swapping out those parts to try to keep consistent with the aftermarket mains. It was noted in some other posts (TwoTired on the sohc4 forums) around that the needle taper and point/mating profiles are important to consider when messing with jetting. So I swapped out those carb parts and it is definitely a lot more steady and doing carb sync is seemingly a lot less laborious. Will get some more ride time in to see for certain.
Meanwhile, I'm anxious to drop my oil pan as 1st gear is still a big unruly. The way that gear behaves makes me thing that those gears are somehow out of round in the way that the bike feels like it oscillates at 1/4 to 3/8 revs. Strange.

Ride on.
Title: Re: 1975 CB400F Engine knocking
Post by: trek97 on Nov 25, 2018, 17:48:03
Yeah that does seem strange.

I kept my stock airbox just to keep things simple.
Title: Re: 1975 CB400F Engine knocking
Post by: bonbons on Nov 27, 2018, 00:24:37
(https://uploads.tapatalk-cdn.com/20181127/5b50541fca7de85f001486938f9251c4.jpg)
So hereís proof that this can be done - splitting the case while leaving the top-end on. I donít like this method. It makes working with the engine a tad unwieldy. If you want to inspect/replace bearings or maybe the primary shaft drive/chain, con rods, can chain tensioner or gears, you probably have no business digging into the lower case like this. But since I am, eh once again, working on rebuilding this darn thing I just wanted to see if it could be done.

These screws were a bear to remove. All else are accessible from above and below:
(https://uploads.tapatalk-cdn.com/20181127/3fb141e7696ed354a03538cc212f04f6.jpg)
As you can see I had to use a swiveling drive extension that can get into it at an angle. Not fun.


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Title: Re: 1975 CB400F Engine knocking
Post by: trek97 on Nov 27, 2018, 07:45:52
After completing assembly I realized I had installed the tension arm bolt incorrectly.   ::)

I had to pull the bottom case off to re-orientate.

The SS Allen cap screws made it easy as the heads are small enough to just slip past the jugs.

Correct, w mark on head facing out...

(http://www.dotheton.com/gallery/11494-121118105644-46611419.jpeg)

M.E.K. is nasty stuff but it cleaned the Hondabond off nicely. 

Then a fresh coat of Hondabond applied.

I gave it about 30 minutes to dry before reassembly.  To help prevent it from squishing into the crank bearings.
Title: 1975 CB400F Engine knocking
Post by: bonbons on Nov 30, 2018, 22:21:53
Trek97, one note about using stainless steel hardware on your engine (aluminum) is that galling can occur since SS is a harder metal than aluminum. Zinc-plated hardware may be the better option. Use Helicoils where you can and always try torquing to spec. Also try not to use that impact driver for torquing and casual removing of hardware - try to do everything by hand if you want to maintain your threads


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Title: Re: 1975 CB400F Engine knocking
Post by: trek97 on Dec 01, 2018, 06:31:00
Solid advise and info.  Thanks bud.
Title: Re: 1975 CB400F Engine knocking
Post by: bonbons on Dec 01, 2018, 10:17:32
Trek97, one other note on the cam chain tensioner bolt that you had to twist around to show that the mark was facing outward... perhaps more important would be to make sure that the flat on that shaft is facing outward toward the hole where the bolt locks that part down. Hopefully, thatís not what that line you have facing outward corresponds with, otherwise youíd have to spin that back around 180į. Iíd take a peek thru the lock bolt hole to make sure that the flat is oriented correctly.


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Title: Re: 1975 CB400F Engine knocking
Post by: trek97 on Dec 01, 2018, 10:19:04
Trek97, one other note on the cam chain tensioner bolt that you had to twist around to show that the mark was facing outward... perhaps more important would be to make sure that the flat on that shaft is facing outward toward the hole where the bolt locks that part down. Hopefully, thatís not what that line you have facing outward corresponds with, otherwise youíd have to spin that back around 180į. Iíd take a peek thru the lock bolt hole to make sure that the flat is oriented correctly.


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Set up as per the Honda workshop manual.  But I will double check on that.  Im pulling carbs off so it wouldn't be too much of an ordeal to yank engine and re-do.
Title: Re: 1975 CB400F Engine knocking
Post by: bonbons on Dec 01, 2018, 10:25:05
Though your tensioning bolt does look like OEM, that marking is on rubber that is fused onto a piece of flat metal, which over time can slip or knock itself off. I would not rely solely on that mark and thereís no harm in checking that the flat surface is facing in the correct direction which would be outward toward the bolt hole


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Title: Re: 1975 CB400F Engine knocking
Post by: pidjones on Dec 01, 2018, 12:24:15
In my experience, Helicoils are also SS,  and SS will pressure weld to SS easily. ALWAYS use some type of anti seize on SS into Helicoils. We had a bunch of SS valves with SS Helicoils @ ORNL, all fine thread. Too many times I had to replace Helicoils that had pulled out when removing bolts that had not been coated with anti seize. Our crafts preferred the copper coat type, while I preferred graphite in isopropyl alcohol. Both worked well, mine was just less messy and if any got into vacuum systems would just evaporate and leave carbon behind. Copper coat is probably better in aluminum as the graphite would make it too easy to strip all of the threads out. Take care to reduce torque when using either! Luckily, most of our flanges were tightened until we saw a certain compression of the copper sealing gasket. Torque wrenches were seldom needed.
Trek97, one note about using stainless steel hardware on your engine (aluminum) is that galling can occur since SS is a harder metal than aluminum. Zinc-plated hardware may be the better option. Use Helicoils where you can and always try torquing to spec. Also try not to use that impact driver for torquing and casual removing of hardware - try to do everything by hand if you want to maintain your threads


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Title: Re: 1975 CB400F Engine knocking
Post by: bonbons on Dec 01, 2018, 12:43:12
Agreed on the SS Helicoils. Although I am with you on using some type of anti-seize (I use a zinc-type compound, this one goes up to 750įF! https://www.amazon.com/dp/B004HMLCLI/ref=cm_sw_r_cp_api_oARaCbSAQQ2NH) I also find strangely contradictory that an anti-seize be applied to hardware that you want to be sure fastens and doesnít back out (i.e. engine bolts). Though Iíve not tried, Helicoils also come in the option of a ďscrew lockingĒ type where the threads on the Helicoils are slightly distorted to allow some binding (or locking) of the bolt you have fastened to it. Perhaps something like this coupled with a good anti-seize to prevent galling might be beneficial to use to insure that these engine bolts donít back out?


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