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Author Topic: 1975 CB400F Engine knocking  (Read 1311 times)

Offline cxman

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Re: 1975 CB400F Engine knocking
« Reply #10 on: Oct 31, 2018, 21:37:50 »
hope you got the crank ground and the rods checked
1978 CX650 Super Deluxe
1979 XS1100 Special
1974 xl350
1983 cx650 Custom
1973 cb750
1980 cb750
1981 cb650
1982 cb900 c
1974 kawasaki 350 bighorn
1983 GL1100 aspy full dress
1983 GL1100 Nekid
and a bunch of others

Offline bonbons

  • Posts: 24
Re: 1975 CB400F Engine knocking
« Reply #11 on: Oct 31, 2018, 21:45:12 »

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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Offline trek97

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Re: 1975 CB400F Engine knocking
« Reply #12 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

Offline bonbons

  • Posts: 24
Re: 1975 CB400F Engine knocking
« Reply #13 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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Offline bonbons

  • Posts: 24
Re: 1975 CB400F Engine knocking
« Reply #14 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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Offline trek97

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Re: 1975 CB400F Engine knocking
« Reply #15 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. 


Offline 1fasgsxr

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Re: 1975 CB400F Engine knocking
« Reply #16 on: Nov 01, 2018, 13:32:40 »
Wow that exhaust looks super low! 
http://www.dotheton.com/forum/index.php?topic=41083.0

Life is a journey from the maternity ward to the crematorium....

Offline bonbons

  • Posts: 24
Re: 1975 CB400F Engine knocking
« Reply #17 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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Offline trek97

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Re: 1975 CB400F Engine knocking
« Reply #18 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

Offline bonbons

  • Posts: 24
Re: 1975 CB400F Engine knocking
« Reply #19 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.