Honda 1300 Coupe Forum

General Category => Workshop => Topic started by: RichardH on March 21, 2020, 07:18:00 PM

Title: Valve stem seals and caps
Post by: RichardH on March 21, 2020, 07:18:00 PM
I'm hoping to reduce the heavy smoking of my recent coupe 7 acquisition by replacing the valve seals and caps so I can road test it. I've only removed the rocker cover for this as yet (below). It looks like a fair amount of carbon deposit on most surfaces. The smoke is very thick, pale grey and has a lot of unburnt fuel.

The shop manual's not really clear enough and there are no parts dimensions, however from some research, it looks as if the parts described as the seal and cap are similar to the Honda CB450 motorcycle.

The CB450 stems are apparently 7.0 mm. Has anyone had experience replacing the caps and seals? Do the CB450 parts fit? Any alternatives?
The CB 450 parts seem to be as follows (from CMS and a few other motorcycle suppliers):
Cap, valve guide: 14791-283-020 (The terminology is slighly ambiguous)
Seal, valve stem: 14791-319-005
Images below.

The 1300 Coupe shop manual cites the stem and guide diameters as:
Inlet: 6.975 mm
Exhaust: 6.945 mm
Valve guide: 7.0 mm (limit 7.03mm)

The 1300 Coupe parts list on pages E51 and E52 has the following parts numbers.
Cap, valve: 12217-590-303
Seal, valve stem: 12210-590-000

There's an o-ring seal mid way on the valve guide but the guide has to be removed, not on the immediate agenda.


Title: Re: Valve stem seals and caps
Post by: RichardH on March 24, 2020, 10:19:12 PM
Ian Wright has kindly sent me a valve, valve stem seal and the cap. They're not the same as the CB 450 (by a long shot).

Seal and cap images are attached below, as well as a "roughly" dimensioned drawing of the seal.

The seal seems to be longer than most of the same shape. Though very similar to many, I expect the dimensions, including internals like the seating recess are different to most I've located. Honda D series engines are roughly 5.5 mm, the 1300's are approximately 7.0 mm.

Ian was able to recover seals he already had (in parts motors etc.). He noted he doesn't bother replacing the upper cap, as it gets in the way of most repairs and adjustments and is of limited functionality.

The seal seems to be another of those unobtainable 1300 parts which, though inexpensive if available, can cost many hours searching for  or perhaps improvising.

Any suggestions or known substitutes? It would be great to get a sticky thread going on obscure suppliers, known substitutes and proven workarounds!

Title: Re: Valve stem seals and caps
Post by: RichardH on March 28, 2020, 04:16:33 AM
I moulded the internal cavity of the seal and rechecked/redrew the dimensions.

There are significant changes to the cross-section drawing, now 'REVB'. I previously thought there was a retaining recess, but after a more thorough clean and in better light, I see there isn't. The cup part is cylindrical above the lower angled lip to the upper seating step.

Given the improved representation, it may be that a more experienced person can recall a possible alternative which doesn't require machining the valve guide.

Title: Re: Valve stem seals and caps
Post by: RichardH on March 31, 2020, 09:56:01 PM
I've written to six manufacturers. Only Enginepro responded with a potential and ultimately referred me to Nason's in Sydney. A friend with a Nissan FJ20ET engine also checked and found the seal for his is very similar.
I ordered Nason's suggestion and Nissan equivalents. I'm still waiting for some info so this isn't conclusive.

The Nissan seal, as supplied, seems almost ideal except for the additional length. There's also no internal step as in the original. From the spec sheet
Stem OD  7.00
Guide OD 12.00
VSS Height 15.40
VSS Width 14.40

What I don't have is a guide or the ability to check, as my car's 100km away. Can anyone tell me what the height of the guide above head in the 1300 is?

The shorter "unknown application" seal is much shorter as you see, but may be a contender. The difference in seal diameter is interesting, they're all supposed to be for 7 mm stems, so my 1300 sample must be very worn or Honda made them a looser fit, maybe....

One of these may be "ideal" but I will confirm when I'm sure I can recommend one.

Please add your insights and/or guide info!

ElringKlinger went to the trouble of searching by size and came up with this (thanks to them!):
Manufacturer: ELRING
Part Number: 112.593
Height [mm]: 12,7
Diameter 2 [mm]: 11,5 (ID)
Diameter 1 [mm]: 7 (Stem Dia,)
Diameter 3 [mm]: 16 (OD)
Material: ACM (Polyacrylate)
For Opel/Vauxhall - it's not steel encased but the measurements are extremely close.

Title: Re: Valve stem seals and caps
Post by: IanT on July 12, 2020, 03:35:53 AM
Many years ago i was told cb750 valve stem seals fitted I have a had a valve regrind at a motor cycle repair shop and valve stem seals fitted plus some new and used caps fitted. Motor has been run but car has not on the road yet
Ian Tuttle

Title: Re: Valve stem seals and caps
Post by: RichardH on October 01, 2020, 03:13:16 AM
Hi Ian,
Thanks, the CB 750 looks similar and as you noted have been fitted. I wonder about the lack of outer steel case, maybe it has little effect.
I'll check further and report back when I've had the head apart and/or redone the seals.