Author Topic: CB400 Rebore question  (Read 677 times)

Offline GregShiv

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CB400 Rebore question
« on: June 24, 2018, 09:07:25 PM »
Hi all,

I am getting a 0.5mm rebore done on my 400F and have a Cruzinimage piston set.
Is the piston clearance .001 inch as there are no guidelines supplied with the pistons?

I am thinking of taking the work to be done at HT Howard in Slough, anyone used them?
1983 Suzuki GSX550ESD
2013 Aprilia SL750 Shiver
1976 Honda CB400F

Offline Nurse Julie

  • 1977 CB550/4 Mongrel Brat. 1974 UK 500/4 K1. Honda CD250u.
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Re: CB400 Rebore question
« Reply #1 on: June 24, 2018, 09:12:23 PM »
Cruzinimage piston clearance is 1 thou. But, it has to be rebored to match each piston as the pistons will all measure slightly different.
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Offline GregShiv

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Re: CB400 Rebore question
« Reply #2 on: June 25, 2018, 05:48:58 PM »
Thanks Julie.

The machine shop said they match the bore to the piston and then mark the pistons accordingly.

One more question, my crankshaft has no markings to indicate the journal size but I have measured each one with a micrometer and they all measure at 31.98mm and the crankcase is marked as BBBAB.
Can someone confirm what crankshaft bearings I will need please?

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1983 Suzuki GSX550ESD
2013 Aprilia SL750 Shiver
1976 Honda CB400F

Offline hairygit

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Re: CB400 Rebore question
« Reply #3 on: June 25, 2018, 05:59:09 PM »
You need it measured far more accurately than that for a start! The difference in shell sizes are so minute in reality, 2 decimal points is not accurate enough. Get some plastigage and do it that way. If you don't know how to use it, find a GOOD engineering workshop that are experienced with Japanese motorcycle cranks and get them to measure it up for you. Errors in measurement can wreck an engine in a few seconds.
If it's got tits or wheels, it's hassle, if it's got both, RUN!!!

Offline GregShiv

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Re: CB400 Rebore question
« Reply #4 on: June 25, 2018, 06:37:41 PM »
For the measurements tolerance I was going by the Honda workshop manual which only shows the specific ranges in 2 decimal places.
If it needs more precise measurements I will have to get a better micrometer or as you suggested Hairy find an engineering shop who can measure beyond 2 decimal places.

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1983 Suzuki GSX550ESD
2013 Aprilia SL750 Shiver
1976 Honda CB400F

 

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