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Post by Deleted on Apr 19, 2015 10:50:24 GMT
Prompted by the discussion about Wikipedia accuracy- I am reminded of something that has been bugging me for a while?
What evidence do we actually have that the cubic capacity of the 400 did actually increase from 395cc to 399cc with the CB400NC?
Discuss....
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Post by Deleted on Apr 19, 2015 11:09:22 GMT
399 written on back of cylinder block?
I know - weak....
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Post by Deleted on Apr 19, 2015 15:10:44 GMT
Ok. Anything else?
Any reviews or tests of the day mentioning the increase, any Honda CB400NC brochure stating the new capacity, any increase in bore, any increase in stroke. Any change in piston or crank part numbers? Either the bore or the stroke- or both- has to change to alter the swept volume.
Can you see what I am getting at?
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Post by Deleted on Apr 19, 2015 15:12:41 GMT
Wasn't the 400NC actually down on power when they road tested it? I mean compared to a 1978 model?
I'm sure there is a test somewhere that has this info on it.
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Post by Deleted on Apr 19, 2015 17:28:09 GMT
The early bikes were faster- proven fact. 400NC seems to have gotten 30mm carbs according to Honda, so I guess emission laws slowly strangled the bikes. The same euro NC brochure also gives the bore at 70.5mm and stroke 50.6mm. Which it always was. So....
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Post by Deleted on Apr 19, 2015 17:36:00 GMT
Coming back from town yesterday I saw 75 from my 250 kicker - and I am not joking, honest.
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Post by Deleted on Apr 19, 2015 18:04:02 GMT
Bike Magazine tested the CB400NC against the Yamaha XS400 in September 1982 and quoted the bore, stroke and capacity figures above.
Now- any more evidence for the 399cc available?
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Post by Deleted on Apr 19, 2015 18:59:11 GMT
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Post by greybeard on Apr 19, 2015 22:31:05 GMT
Slightly greater dishing - either on the cylinder head or the pistons?
Just hazzarding a guess, but dishing wouldnt affect bore or stroke but would increase or decrease volume (capacity).
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Post by Deleted on Apr 20, 2015 8:57:23 GMT
Manufacturers did play around with piston tops and combustion chambers to change the compression ratios. 2 stroke fiends never stop fiddling with it. Yamaha changed the XS500 for the final model by putting domed pistons in- it raised the compression ratio from a very lowly 8.5:1 to 9.6:1. It was originally set very low as the Yanks were panicking about the declining quality of their gas. But they also had to change the carbs, jets and ignition advance curves to suit the change. But engine capacity stayed the same at 498cc- compression ratio is only the ratio difference between the cylinder volume at BDC and TDC and nothing to do with the volumetric capacity of any engine.
There is no evidence Honda did anything with the CR of the 400 SD- it stayed at 9.3:1 all the way from the CB400T onwards. Swept volume can only be changed by altering the cylinder bore or the stroke of the piston (crankshaft throw.) The part numbers for the SD piston rings stayed the same throughout- suggesting the bore also stayed the same. That only leaves the crankshaft. Did they change the design and throw of the crankshaft? Seems unlikely as the barrels would have to be slightly longer as well.....
I think the 399cc is looking weak....
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Post by Deleted on Apr 20, 2015 11:42:11 GMT
Surely this was not just a marketing ploy?......or was it? To make the engine sound bigger and sexier?
All 400NC's registered appear to have 399cc on the log book rather than 395cc. After studying CMSNL diagrams a lot of the components in the engine has 449 as the middle part number.
Also, around this time the USA got the CB450T hawk. I wonder what exact CC of that bike was?
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Post by Deleted on Apr 20, 2015 12:03:03 GMT
1982 CB450T Hawk was 447cc Bore and stroke were 75mm x 50.6mm. Adds up using the formula above. i.e. they just bored out the 400 lump and again kept the stroke the same.
Our CB450DX- same again- 447cc and 75mm x 50.6mm. Honda never seemed to change the stroke way back from the original Dream 50.6mm
Even the later CB350S twin we got here was a sleeved down version of the 450 lump again- 64mm bore and still the same 50.6mm stroke. But I am less sure of this ATM.
Why then would they change everything for just one (or 2 if you count the 400ND) versions of one bike model and then go back? Duzzny make sense...
Assuming they had to change the cylinder casting anyway for the 400NC to allow the oil feed changes- I am wondering whether "399cc" just got cast into the mould....
Still happy for any evidence that bore or stroke actually changed though!
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Post by hondapartsman on May 2, 2015 6:20:19 GMT
I was pretty sure all 400s were the same capacity and pistons etc never changed. But I was going from memory now I'm not so sure, I see 447 pistons were fitted, now that code is for the CM400, which we never got here, so there could be a slight difference. 449 by the way is CX500 custom.
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Post by Deleted on May 2, 2015 15:49:45 GMT
I believe the 447 type Pistons differed only in that they had a flatter crown. This went with a cylinder head with re-profiled combustion chamber to suit and to maintain the compression ratio. For us- we got this with the CB400NC but the U.S. Hawk got it earlier. Possibly why the part got a CM400 model code....
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