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Author Topic: Descending 'the green way'.  (Read 1398 times)

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Offline Deltarider

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Descending 'the green way'.
« on: July 22, 2009, 06:20:36 am »
These days I like to watch the Tour de France . Now, with the etappes in the Alps, every now and then I recognise winding mountain roads I used to descend with the engine off. Silently with only a light sqeal from the frontbrake I loved to overtake cars in a true majestic way. The longest descend I ever did solely by gravity was 14km.
Now in the owner's manual there is a warning not to coast for a long distance with the engine off (inadequate lubrication in the transmission). I've never understood this. Splash lubrication by whatever what turns in the gearbox should be sufficient IMO. Or am I wrong and have I been lucky. I've never damaged my transmission. Or is 14 km maybe too short a distance?
« Last Edit: July 22, 2009, 06:23:07 am by Deltarider »
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Offline GammaFlat

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Re: Descending the green way
« Reply #1 on: July 22, 2009, 06:28:09 am »
Since these bikes have dry sumps, there's not adequate lubrication in the transmission unless the bike is running.  The '73 and forward engines have a larger bearings on the "sprocket shaft" because everyone and their brother was towing the 750's around behind their cars and Honda didn't know why the bearings were failing.  It turns out, Honda was not aware that folks were towing the bikes and were getting warranty claims because of this bearing failure and they doubled the width of the bearing (didn't help).  I think this is in "Thoughts of HondaMan".  There's also a 1 or so HP penalty for the extra bearing surface.  HondaMan was talking about a way to "go back" to the pre-73 bearing arrangement at one point...

I think wet sump bikes would be better suited to lots of coasting.  
« Last Edit: July 22, 2009, 06:30:28 am by GammaFlat »
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Offline Deltarider

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Re: Descending 'the green way'.
« Reply #2 on: July 22, 2009, 07:54:51 am »
Luckily the 500's sump is soaking wet. So maybe that warning in the 500's Owner's Manual is inherited from the 750's manual.
« Last Edit: July 22, 2009, 07:56:57 am by Deltarider »
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Offline GammaFlat

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Re: Descending 'the green way'.
« Reply #3 on: July 22, 2009, 07:56:43 am »
Quote from: Deltarider on July 22, 2009, 07:54:51 am
Luckily the 500's sump is soaking wet.

ahhh, my bad.. didn't look at your sig - I was talking 750's :)
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Offline kslrr

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Re: Descending 'the green way'.
« Reply #4 on: July 22, 2009, 08:56:25 am »
Even with the wet sumps on CBs other than the 750, I dont think the oil comes in contact with the transmission gears.  The pan on my 350F is about 5 inches deep and when filled with the correct amount of oil, is probably no more than 3".
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technojock

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Re: Descending 'the green way'.
« Reply #5 on: July 23, 2009, 01:32:37 am »
Honda SOHC fours have the transmission pressure fed from the oil pump.  I would think that there would be enough residual oil on the shafts to prevent them from galling but it's hard to say.  The gears would be fine with the oil that was still on them since there would be no load, it's the shafts and bearings that would be the possible problem.

Tony
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Offline 736cc

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Re: Descending 'the green way'.
« Reply #6 on: July 23, 2009, 04:33:10 am »
Output shaft spinning from drivechain needs lubrication, betcha its bearing gets hot. They had problems w/ that shaft on early models and changed the part.
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Offline Deltarider

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Re: Descending 'the green way'.
« Reply #7 on: July 23, 2009, 05:28:36 am »
Quote
Honda SOHC fours have the transmission pressure fed from the oil pump.
No, no, not the 500.
Quote
They had problems w/ that shaft on early models and changed the part.
You mean the 750?
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Offline Gordon

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Re: Descending 'the green way'.
« Reply #8 on: July 23, 2009, 09:01:46 am »
Quote from: 736cc on July 23, 2009, 04:33:10 am
Output shaft spinning from drivechain needs lubrication, betcha its bearing gets hot. They had problems w/ that shaft on early models and changed the part.

See Gammaflat's 1st post.
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Offline Mdub

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Re: Descending 'the green way'.
« Reply #9 on: July 23, 2009, 09:48:33 am »
My personal best is 15 miles down from Hurrricane ridge on the Olympic peninsula.  :D
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Offline Don R

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Re: Descending 'the green way'.
« Reply #10 on: July 23, 2009, 04:59:20 pm »
I coasted down a small mountian once and just started it for a few seconds every couple miles.
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Offline IAmCitizenMe

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Re: Descending 'the green way'.
« Reply #11 on: July 23, 2009, 05:14:20 pm »
Quote from: GammaFlat on July 22, 2009, 07:56:43 am
Quote from: Deltarider on July 22, 2009, 07:54:51 am
Luckily the 500's sump is soaking wet.

ahhh, my bad.. didn't look at your sig - I was talking 750's :)

What about 550's? Are they wet or dry?
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Offline Gordon

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Re: Descending 'the green way'.
« Reply #12 on: July 23, 2009, 05:32:34 pm »
Quote from: IAmCitizenMe on July 23, 2009, 05:14:20 pm

What about 550's? Are they wet or dry?

All sohc4's except for the 750 are wet sump, but see Kslrr's post about the 350. 
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Offline honda750k

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Re: Descending 'the green way'.
« Reply #13 on: July 23, 2009, 05:48:30 pm »
in the interest of keeping bearings  lubed while coasting downhill, I"d think just putting it in neutral and letting it idle would do the trick.
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