Author Topic: Yankee Doodle not so dandy CB400 rebuild  (Read 1306 times)

Online kent400

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Re: Yankee Doodle not so dandy CB400 rebuild
« Reply #15 on: August 21, 2018, 05:07:17 PM »
The speedo isn't the original, looks like a CB350 Four one. The original would have been marked to 120 mph but one marked to 130 mph was often fitted on those supplied to the USA market. Gauges with crazed faces are often found on bikes imported from the USA, they have sat in the sun too long.

Online Rob62

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Re: Yankee Doodle not so dandy CB400 rebuild
« Reply #16 on: August 21, 2018, 08:38:08 PM »
Great project! Will be good if you can keep it as original as possible i.e. clean and refurb rather than replace..... good luck

Offline Skunky

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Re: Yankee Doodle not so dandy CB400 rebuild
« Reply #17 on: August 22, 2018, 04:27:11 PM »
Is that a crack on the lower fork case.....or a USA cobweb ?

(Attachment Link)

Trust a Nurse to spot a fracture 😂

If you look at this one you can see the crack has slipped down to the mudguard. Scared me for a second though.

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Offline Skunky

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Re: Yankee Doodle not so dandy CB400 rebuild
« Reply #18 on: September 03, 2018, 10:45:12 PM »
Hi All

Started on the project today. First thing was to straighten out the front end to make sure the frame was ok. I loosened the fork pinch bolts and realigned the handlebars and front wheel and it all looks much better. I then put a little oil in each cylinder before completing a compression test and was pleased with the results.

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Offline Skunky

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Re: Yankee Doodle not so dandy CB400 rebuild
« Reply #19 on: September 03, 2018, 11:04:17 PM »
Next I fitted a new ignition switch and put some power on. I turned the bike over on the starter button and it turned over great. The spark was very weak, if there at all. So checked the point gaps and cleaned the points and now got a spark. Thought I would see if she would start but I’m getting fuel leaking from one of the carb overflow pipes. That’s a problem for another day.
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Offline Skunky

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Re: Yankee Doodle not so dandy CB400 rebuild
« Reply #20 on: September 04, 2018, 05:00:32 PM »
The speedo isn't the original, looks like a CB350 Four one. The original would have been marked to 120 mph but one marked to 130 mph was often fitted on those supplied to the USA market. Gauges with crazed faces are often found on bikes imported from the USA, they have sat in the sun too long.

I think you are right Kent. It looks like a 350 speedo to me too. Which means I will need to find a 400 one.  :-[. I didn't believe the mileage looked right and it was odd that the speedo was crazed and the tacho clean. Shit happens though. I do know it has no oil leaks and good compression on all pots. What part of Kent?. I grew up in Swanley.
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Offline Skunky

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Re: Yankee Doodle not so dandy CB400 rebuild
« Reply #21 on: September 09, 2018, 04:36:44 PM »
Why won’t my bike start?. Dear oh dear 😂😂.

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Offline Nurse Julie

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Re: Yankee Doodle not so dandy CB400 rebuild
« Reply #22 on: September 09, 2018, 04:53:53 PM »
Oh dear oh dear indeed 😁😁😁😁
Im a Nurse, trust me, this won't hurt.....much !!!

LINK TO MY CB400/4 ENGINE STRIP / ASSESSMENT AND REBUILD...NOW COMPLETE
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Offline SumpMagnet

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Re: Yankee Doodle not so dandy CB400 rebuild
« Reply #23 on: September 09, 2018, 05:30:21 PM »
Oh ...my....gawd...what the hell IS that in the carbs! I can't believe that was ever petrol.

I think those might need a bit of a clean........
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Offline Skunky

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Re: Yankee Doodle not so dandy CB400 rebuild
« Reply #24 on: September 09, 2018, 07:10:11 PM »
Oh ...my....gawd...what the hell IS that in the carbs! I can't believe that was ever petrol.

I think those might need a bit of a clean........

I’m not sure what happens if you leave fuel in for a very, very, very long time. But I can’t believe it would be sticky. I think there may have been some sort of separation and then new fuel put on top. It’s actually worse than it looks, all of the floats are stuck or rusted in place and there’s a sticky varnish everywhere. I’ve ordered a carb service kit with new jets and gaskets but I suspect I may need to throw the floats too and fit new pins. I may soak it in cider for a few days. Normally makes me feel better 😀. Actually the top ends look remarkably clean.
Any suggestions ?
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Offline Nurse Julie

  • 1973 CB750 UK K2.1977 CB550/4 Mongrel Brat. 1978 CB400/4.
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Re: Yankee Doodle not so dandy CB400 rebuild
« Reply #25 on: September 09, 2018, 07:16:11 PM »
Soak in thinners if you are going to get new floats.
Im a Nurse, trust me, this won't hurt.....much !!!

LINK TO MY CB400/4 ENGINE STRIP / ASSESSMENT AND REBUILD...NOW COMPLETE
http://www.sohc.co.uk/index.php/topic,14049.msg112691/topicseen.html#new

Offline Spitfire

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Re: Yankee Doodle not so dandy CB400 rebuild
« Reply #26 on: September 09, 2018, 07:29:26 PM »
Not as bad as those but I had the same sort of thing on my 750F1, I left it in the garage for 10 years when I was working overseas and when I got back I couldn't open the throttle, couldn't figure out why until I took them apart, they were all glued up inside.
Here's one of the float bowls, and no I did not have to use the hammer !


Cheers

Dennis
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Offline Skunky

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Re: Yankee Doodle not so dandy CB400 rebuild
« Reply #27 on: September 18, 2018, 07:44:25 PM »
The Carburettor kits arrived today  :D. I filled the float chambers with thinners and put the carbs back on top, they have been soaking for 5 days. I have managed to get two of the floats out.

I have invested in a Ultrasonic cleaner and starting tomorrow will begin the strip down and clean up. I will take photos and hopefully I will have them good as new.
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Offline K2-K6

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Re: Yankee Doodle not so dandy CB400 rebuild
« Reply #28 on: September 18, 2018, 08:12:46 PM »
In running a chemical analytical laboratory we'd generally use steam to clean various tarring etc from the lab glass. 

You can use one of those domestic steamers that produce a jet of steam to get an initial clean and possibly free the floats prior to more detailed ultrasonic attention.

Offline mike the bike

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Re: Yankee Doodle not so dandy CB400 rebuild
« Reply #29 on: September 18, 2018, 08:33:37 PM »
Or a steam wallpaper stripper.
German reliability is a myth spread by the Hitler Youth