Yamiya CB750K0 Fork stanchions

[AshimotoK0]

Anyone used Yamiya early 750 stanchions? I fitted mine but noticed the bottom piston and valve ring was sloppy fit on the stanchions.

The attached pic  is what I found when I measured them.

 Going to take this up with Yamiya but they are hard to get a reply from  as far as I know and I bought them a couple of years ago via Saisei

Opposite to DS ones as his are chromed at the bottom and parts don't fit on

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[UK Pete]

Do you think it's enough to make any operational difference once  assembled and on bike

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[AshimotoK0]

Do you think it's enough to make any operational difference once  assembled and on bike

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I am not sure Pete but the clearance between the  the bottom piston to the alloy fork bottom wall is definitely critical so any play between the stanchion and the inner wall of that piston should also be significant as far as I can tell.  Also how is 0.2 mm extra clearance  going to affect the  operation of the damper valve ring?

I have emailed Yamiya but so far no response. If I get no joy from them,I am not sure if someone could hard chrome just the bottom section and grind to correct size. Another other option would be  to have damper rings and bottom pistons manufactured with undersized bores. Only other more bodgy method may be to Loctite some 0.1mm  shim to the stanchions to take up the extra clearance. I also noticed that the very  bottom circlip was mighty difficult to get onto the stanchion but conversely,the piston/damper ring retaining clips were a looser fit than the originals .

Why the hell can't these people faithfully reproduce the original Honda parts ?  So we have DS selling them that are oversize and Yamiya selling them undersize. To be honest I would have preferred them to be oversize so that I could have machined them.  Should have taken Triggers advice and sent my originals to Phillpots for hard chroming but my old ones were VERY heavily pitted at the bottom yoke clamping region and I assumed the Made in Japan ones would have been spot on correct.

[UK Pete]

I here what your saying ash , it's beyond belief in this day and age of manufacturing tolerances how F-ing hard can it be
I don't think silver's sells them anymore
Lots of originals have very deep pitting and corrosion which is beyond repair so we are having to overcome this bloody problem


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[AshimotoK0]

I have just messaged Philpots to see if they can selectively build up the undersized area and grind back  to correct size.

My Man-in-Japan's wife is Japanese so if I don't get any joy I can probably ask her to speak to Yamiya  directly on my behalf. I can't believe that this has not be talked about before ... unless mine were just a single wrongly machined set....I find that hard to believe though.

[UK Pete]

I have a few sets of new stauntions I bet they are all bloody wrong
With oversize I wonder if I could dip the bottom part in acid for a while to remove chrome

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[AshimotoK0]

Got this response from Yamiya

"Dear Sir,

Thank you for your inquiry.
We checked the picture you attached, but some errors will occur as it becomes a rebuilt item and there is no such thing that we can not install it until now.
We would appreciate your understanding.
Thank you.

Best Regards,
Motorcycle YAMIYA"

[AshimotoK0]

I here what your saying ash , it's beyond belief in this day and age of manufacturing tolerances how F-ing hard can it be
I don't think silver's sells them anymore
Lots of originals have very deep pitting and corrosion which is beyond repair so we are having to overcome this bloody problem


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DS still have them listed Pete  (made in Italy, Yamiya ones are made in Japan.

https://www.davidsilverspares.co.uk/CB750K0-FOUR-1969-1970/part_29393/

[kettle738]

Hi Ash, as you know, I have replaced my original stanchions with Yamiya...my Honda originals are also heavily corroded around the lower yoke area, but I have hung onto them just in case they can be sent to Philpotts at a later date.

Fitting the Yamiya legs was simple enough apart from the snap ring at the foot of the tube which needed a very decent set of snap ring pliers to even have a chance of fitting it.  I think I recall noticing the damper valve etc was not particularly snug, but given my (perhaps misplaced) faith in Japanese produced parts I put it down to me imagining it, and/or wear in my original parts, so I assembled them without a second thought.

I filled and repeatedly compressed both legs before fitting and the damping felt fine (normal)......I did get a pronounced knock when I compressed them hard on the bike which resulted in what I thought was the offending leg being pulled apart again, but that simply turned out to be clearance at the caliper swing arm, dealt with by a shim

I haven't actually ridden the bike since I fitted them  so I can't comment beyond that, so it could still go horribly wrong, but thus far it's situation normal.  You will see them in any event on Saturday.

If I can find my ancient micrometer I will have a go at measuring the swept area of the new stanchions against the old if you think it might tell you anything....

Mick.......... (AKA.... Warren T. Klame)   

[AshimotoK0]

Cheers Mick ..I have sent a reply to Yamiya telling them that I don't think theirs are a "faithful reproduction of the originals' (that's how they normally describe their stuff) and asked them to check their new stock. Wouldn't surprise me if they banned me from purchasing off them again as they get really tetchy when you question the quality of anything they sell. I think the swept area diameter is fine as the top bush is a nice close fit ....in fact I just went and measured and the original and Yamiya are almost identical diameters, if anything the originals are minutely smaller diameter.

I got a pretty hopeless reply from Philpots too ...just a standard reply saying they will grind, rechrome the whole lot, then regrind to size for 185 quid.

I will 'phone Silchrome in Leeds and see what they say. Another thought was to shim the bottom piston  and have  new, undersize,  damper rings made at work. Not sure what material they are made from though. This is all a monumental pain in the ar*e because I rebuilt them and even put in the oil but there was this nagging doubt that the parts slipped on very easily and I remembered the damper ring being fairly tight on the original stanchions. Like all nagging doubts you revisit it to put your mind at rest (well that's me anyway). ...Roll on my CB250K0 projects ...I have oodles of nice original parts to swap around for those which makes life so much easier.

[AshimotoK0]

There is a firm in Sandbach called Dynasurf which hard chromed my CB1300 stanchions recently, cheaper than Philpotts as well. Maybe give them a call.

I'm surprised at Yamiya, the OE tube is clearly not chromed at the bottom, the Yamiya is, which means they've made the stanchions very slightly thinner to accommodate the new chroming, if they'd gone for hard chroming they could have ground down the excess to get a perfect fit, using decorative chroming means you can't.

I think your idea of having them hard chromed and ground back down to original spec is the better option, so long as you give them an original tube to copy I can't see it being a problem.

The Yamiya tube is not chromed at the bottom either Ken. It's just that they are machined down to a smaller size than they should be. I posted on the sandcast site too because those guys use Yamiya a lot.