Author Topic: Almost finished (I think)  (Read 1226 times)

Offline Dave487

  • SOHC Associate
  • Posts: 53
    • View Profile
Almost finished (I think)
« on: June 05, 2017, 03:49:11 PM »
Got the 400-4 on the road and passed the MOT last week. It seems to run ok but has a lot of transmission noise on both acceleration and overrun. I haven't ridden another one so don't know how they normally sound. The noise is not there when running in neutral but it sounds a bit clunky if I unscrew and remove the oil filler whilst it's running. Still quiet if I engage first gear but the noise starts when I feed in the clutch even before starting to move off. It sound like it could be from the clutch / primary gears and there was a bit play in the cush drive when I assembled it. I have a feeling it might be the primary gears not meshing correctly. Does anyone know where I can get new cush rubbers from. I have tried to contact ttr400 but did not get a reply.

Offline hairygit

  • SOHC Jedi
  • Posts: 2708
    • View Profile
Re: Almost finished (I think)
« Reply #1 on: June 05, 2017, 04:02:41 PM »
The primary "gear" is actually part of the crankshaft on a 400 four, and is not replaceable on it's own, new or replacement crank is the only answer if it is damaged. That said, I have NEVER seen a primary sprocket on one actually damaged. Have you balanced the carbs properly, as all the SOHC fours clatter horribly if they are out of sync. What have you done to the engine, or did you just get it going without stripping it? The primary chain can make horrendous noises if worn, but my money is on the carbs being out.
If it's got tits or wheels, it's hassle, if it's got both, RUN!!!

Offline mike the bike

  • SOHC Jedi
  • Posts: 2652
  • CB400F, Royal Enfield Interceptor.
    • View Profile
Re: Almost finished (I think)
« Reply #2 on: June 05, 2017, 05:31:30 PM »
Although it's always worth synchronising the carbs, a thought occurred to me;  does it still make this noise with engine off, just rolling down the hill?
Where's that 10mm socket got to?

Offline Dave487

  • SOHC Associate
  • Posts: 53
    • View Profile
Re: Almost finished (I think)
« Reply #3 on: June 05, 2017, 06:53:33 PM »
Thanks for the replies Hairy and Mike.
Yes the engine and gearbox has been stripped and checked but the primary chain looked ok so was not replaced and the carbs have been synchronised to less than 1 inch Hg.
 The noise I'm worried about is more of a whining noise (I didn't make that clear originally) like 2 gears not meshing correctly and i think it's coming from the clutch side.
The clunky sound at idle may well be primary chain noise but I don't think that's anything to be concerned about at this stage.

I haven't tried running it downhill without the engine running as Mike suggests but will at next opportunity that's a very good point.


Offline hairygit

  • SOHC Jedi
  • Posts: 2708
    • View Profile
Re: Almost finished (I think)
« Reply #4 on: June 05, 2017, 07:12:01 PM »
Clutch release bearing grinding/whirring is a possible cause of the noise. How did you determine that the primary chain was okay? The basic test is to lay it on a table or other flat surface, and if any links from the top run touch the bottom run, replace it. Generally I insist on replacing it anyway if splitting cases on any Honda four, just because of the hassle of doing it twice hoping to save a few quid! If people moan about it I tell them to find someone else to do it!

Sent from my X6pro using Tapatalk

If it's got tits or wheels, it's hassle, if it's got both, RUN!!!

Offline Dave487

  • SOHC Associate
  • Posts: 53
    • View Profile
Re: Almost finished (I think)
« Reply #5 on: June 06, 2017, 12:32:04 PM »
I tested chain as Hairy suggested (learned from a previous post) but maybe it would have been better to have replaced it anyway. However I still think its the clutch gears not meshing properly and intent to buy another clutch unit complete, de-rivet it and try to replace the cush drive.

Offline mike the bike

  • SOHC Jedi
  • Posts: 2652
  • CB400F, Royal Enfield Interceptor.
    • View Profile
Re: Almost finished (I think)
« Reply #6 on: June 06, 2017, 03:58:08 PM »
The cush drive inside the clutch is unobtainable.   Ivealready ground off the rivets and looked into replacement rubbers.  The rubbers wouldn't cause a noise like that anyway, don't waste your time.
Where's that 10mm socket got to?

Offline Dave487

  • SOHC Associate
  • Posts: 53
    • View Profile
Re: Almost finished (I think)
« Reply #7 on: August 04, 2017, 04:33:47 PM »
I'm still concerned about the whining transmission which seems to be getting worse, particularly on overrun. If I pull the clutch and stop the engine the noise changes so I think it's likely to be on the primary drive.
I'm so bothered by it that I've split the cases again to have another look.
There's nothing obvious but a few things may be contributing.

1) The bush on first gear is a bit worn which allows the gear float about and touch the mating one. So I'll replace it.
2) Hi-Vo chain appears to be ok (see photo) but I'll replace it anyway this time.
3) The cush drive rubbers in the primary gear have a bit of slack but are very hard, not sure how soft new ones come but I'll replace them anyway.
4) My main concern are the primary chain guides as these are very hard and worn at the ends particularly the bottom one(see photo) but the chain is not touching the attachment screws. I could make new ones out of Nylon66 or Tufnol but the originals have a metal backing even though they're like a brittle plastic.

Does anyone know what a new one feels like, are they like a neoprene rubber or more like nylon?. I can't a find source of replacements at the moment.

Maybe I'm a bit fussy having never ridden another one, but a bit concerned about something locking up and chucking me down the road.



Offline CBNelly

  • Newbie
  • Posts: 18
    • View Profile
Re: Almost finished (I think)
« Reply #8 on: December 11, 2017, 10:40:57 PM »
Hi everyone
I've just joined the forum and currently have my 400/4 engine in bits
Reason for strip is a whine from the clutch/gearbox when under load in gear
I've seen a few threads and even a Youtube clip with the exact same noise
Has anyone found a reason for this noise yet?
I've quickly checked all my bearings and gears/cogs and all seem fine
Only issue I have is the first gear seems loose on the shaft but not sure what tolerances apply
Any help anyone can give to resolve this noise would be much appreciated!

Offline Dave487

  • SOHC Associate
  • Posts: 53
    • View Profile
Re: Almost finished (I think)
« Reply #9 on: December 12, 2017, 02:03:46 PM »
As I said on the previous post I took it all apart, replaced the primary chain and cush drive rubbers and made a new bush for the first gear pinion, I also managed to source a better bottom primary chain guide and I re-checked all bearing races in the gearbox but couldn't find a noisy one.
 I had previously changed complete clutch for one with less play in the clutch damper but I can't find any replacement damper rubbers at the moment.
 
None of this made a significant improvement to the transmission whine but it did give confidence that I'd done it right the first time. I've done about 400miles since re-assembling it and don't really worry about it anymore although I may take the clutch cover off during the winter have another look at the clutch drive gears (ie. checking for correct meshing etc.) as I still suspect that the noise is somewhere in the clutch drive.

I've dismantled the old clutch by drilling out the rivets but the damper rubbers are an awkward shape to make and really need to be moulded. I was in contact with TTR400 some time ago but he doesn't have any stock now so anyone has a source of supply please let us know.

Offline CBNelly

  • Newbie
  • Posts: 18
    • View Profile
Re: Almost finished (I think)
« Reply #10 on: December 12, 2017, 07:03:01 PM »
Hi Dave,
I read through your suggestions and wondered if any had made a particular difference
I want to do all the checks, etc. before reassembling the engine again
Like I said all my bearings seem OK but I will focus more on the clutch as noise seems more pronounced when being slipped
I've had my noise for a while and bike runs OK but always the nagging thought in the back of my head
I'll keep looking over the engine and if anything comes up I'll be sure to post
Thanks

Offline Clem2112

  • Midlife
  • SOHC Expert
  • Posts: 282
  • CB400F1 1976 R1200GS 2016 Matchless G80 1955
    • View Profile
Re: Almost finished (I think)
« Reply #11 on: December 12, 2017, 08:29:37 PM »
Pretty sure the "whine" is typical of straight cut gears , not sure if there are any in the driveline apart from the primary chain gear on the crank and the intermediate shaft.
Back in the day when these bikes were popular, my mate's f1 was very whiney in 1st but had a very sweet engine that revved well past 10,000.

My only evidence for what is the likely cause of the noise :-
Mini Coopers had straight cut gears in the box and were very whiney / noisy.
Later Hondas had hy-vo cam chains that whined at high revs, my NC31 (400 Super Four) being one.
Gear-driven camshaft bikes like the CB-1 400 also made odd noises.

Offline Dave487

  • SOHC Associate
  • Posts: 53
    • View Profile
Re: Almost finished (I think)
« Reply #12 on: December 12, 2017, 10:13:03 PM »
I think Clem2112 has got a point all the gears including the main clutch drive have straight cut teeth and the large gear on the clutch basket has a bit of play so it may not mesh correctly with the drive gear. I'm not quite sure how this can be corrected without new parts.

 

SimplePortal 2.3.5 © 2008-2012, SimplePortal