Honda HRB476c Blade brake clutch problems

[snoopster]

I have recently inherited a european Honda HRB476c SXE that has a couple of problems with the blade brake clutch.

1. It emits a single loud knock each time the blade is engaged.
2. The drive belt fouls the clutch housing

Problem 1 - I have stripped down the clutch and can see no issues with it. It has all the correct components assembled correctly and in good condition (plenty of friction lining left, both bearings run smooth, spring assembled the right way around). A couple of slightly unusual observations is a) the crankshaft has 2 'keyways' machined in it, but is only fitted with one woodruff key. Should the key go in the upper or lower keyway on the crankshaft?
b) the end float on the crankshaft is more than I would expect. I measure approx 0.6mm. Does anyone know what it should be on a GCV160?

Problem 2 - The drive belt is just fouling the upper clutch housing (the one bolted to the engine that contains the thrust bearing). The belt and gearbox tension spring have been changed with honda original parts with no success.
A couple of guesses to the reasons for the belt fouling
a) The pulley/clutch drive plate (75160VE1R40) is mounted too high up the crankshaft. I am not sure how as all the correct parts are fitted in correct order and orientation. However the honda parts diagram does show the pulley/clutch drive plate component fitted upside down for this model compared to others like the HRB536c that uses the same part no. This must be an error as doing this would mean there is nothing for the friction lining to contact with?
b) maybe the problem is caused by the fact that the pulley on the gearbox is so small (Approx 7cm on this model, approx 15cm on the hydrostatic models).

Any insight into these problems would be really appreciated.

 

[robert@honda]

I am not sure how as all the correct parts are fitted in correct order and orientation.

Take a look at these pages from the parts catalog...hope they can help. (see attached)

 

[snoopster]

Hi Robert,

Thanks for these. These are the exact same parts diagrams i am using and all components shown align with how this mower has been assembled, apart from the pulley..........................i know what you are thinking.............BUT Experience with other HRB models tells me the pulley on this mower is installed the right way up.

(Note Part '25' must be drawn upside down. It makes no sense to install it this way up if you want the friction lining to engage with the driven disk. I note it is drawn the correct way on parts diagrams for sister models like the HRB536c that share the exact same clutch assembly.)

 

[robert@honda]

Hi Robert,

Thanks for these. These are the exact same parts diagrams i am using and all components shown align with how this mower has been assembled, apart from the pulley..........................i know what you are thinking.............BUT Experience with other HRB models tells me the pulley on this mower is installed the right way up.

I think you may be correct; the pulley shown in the parts catalog does seem to be opposite that of the one shown the shop manual (at least for USA models)

Here are the factory shop manual pages for USA-spec HRM/HRB models. Early production and later production used slightly different designs. Can't say for sure what might have been used on the HRB476c you have, but these may help:

Early HRM/HRB:

Later HRM/HRB:

 

[snoopster]

Thanks Robert,

Yes mine is the earlier HRM version you show in these diagrams, (minus the thrust washers as it has a replacement pulley/clutch) The only other difference is the clutch arm hinge and clutch pin holder have been combined into a single plate (what I call the upper clutch housing) that the crankshaft passes through via a thrust washer and bearing (as shown in the parts diagram). But otherwise identical. I am glad you concur with the verdict on the errored parts diagram.

Stripped the clutch down again today and did not really find anything. Upper clutch housing had slightly more play than usual, so added a 0.75mm washer to the flange bolt (Part no 12 on your parts diagram). This removed the play on the housing, moved it a further 0.75mm from the belt.

Reassembled, started it up, engaged blade (without the blade fitted), no knock. Refit the blade and do the same and the knock reappears. So no improvement. Though the belt hardly rubs now.

Can you tell me what the endfloat should be on the GCV160 crankshaft? I am convinced this knocking is related to crankshaft endfloat ('drift')

 

[robert@honda]

Can you tell me what the endfloat should be on the GCV160 crankshaft? I am convinced this knocking is related to crankshaft endfloat ('drift')

:wink::tongue::wink::laughing::wink::laughing::tongue:

 

[snoopster]

:wink::tongue::wink::laughing::wink::laughing::tongue:

So its official, the royal stamp, my axial clearance is within spec!