Author Topic: Oil pump and cylinder studs  (Read 1151 times)

Offline Fenderfreak

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Oil pump and cylinder studs
« on: November 29, 2018, 05:24:56 PM »
Looking for a bit of advice on the oil pump for my 250k3 and cylinder studs

If you have a look at the attached photo you can see that the edge of the pump body has been worn away! Can not find any reason for this, any ideas? Also the piston and bore measure just over 19mm where as the manual states 16mm, is this the right pump?

Two of the cylinder  studs in the photo are devoid of the small thicker part as shown in the parts list.

Is this correct? Was there a later mod or has the previous owner fitted the incorrect studs?

Thanks in anticipation.


Honda CB250K3 1971
Honda CB750FZ 1979
Harley Davidson XR1200 2008

Offline AshimotoK0

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Re: Oil pump and cylinder studs
« Reply #1 on: November 29, 2018, 06:14:47 PM »
It may be that the manual refers to an early pump fitted to the 1968 K0  Honda seemed to produce a shop manual for the 1st version of a bike and never update it. See attached but I reckon the pump is correct . As for wear, if badly scored I would get a replacement if in doubt. i don't really understand the question on the studs. I know that pair  of the  K4 model only,  studs had bits of rubber moulded onto them.

Hope this helps

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“Alright friends, you have seen the heavy groups, now you will see morning maniac music. Believe me, yeah. It’s a new dawn.” Grace Slick, Woodstock '69 .. In the year of the Sandcast.

Offline Fenderfreak

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Re: Oil pump and cylinder studs
« Reply #2 on: November 29, 2018, 06:56:34 PM »
Hi Ash, makes perfect sense, didn’t realise the thicker part of the studs were moulded rubber. The moulding seems to be shown on the K3 as well, so may get a couple of replacements as they must be there for a purpose, perhaps to stop vibration

I’ve bought an new pump off of Frank in Germany as old one is badly scored. I was concerned about the wear to the external portion of the pump body as to what caused it. You can just see it on the outside of the pump in the photo.

Thanks again for your help 👍
Honda CB250K3 1971
Honda CB750FZ 1979
Harley Davidson XR1200 2008

Offline AshimotoK0

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Re: Oil pump and cylinder studs
« Reply #3 on: November 29, 2018, 10:26:12 PM »
No worries ... I just checked a CB250K0 oil pump and it has an  alloy body with 19 mm plunger. So I learned something today ... Honda probably fitted a smaller piston oil pump very early on in production .. compiled the manual based on that early pump and did never updated it.
“Alright friends, you have seen the heavy groups, now you will see morning maniac music. Believe me, yeah. It’s a new dawn.” Grace Slick, Woodstock '69 .. In the year of the Sandcast.

 

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