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Help The joys of servicing a GB250 Clubman(??)

Discussion in 'Honda 250cc Singles' started by TrickyMicky, Mar 28, 2022.

  1. TrickyMicky

    TrickyMicky Active Member

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    Having taken my latest acquisition out for a couple of runs, I decided to change the oil and filter. I use a small domestic garage, (UK, don't forget!), which also houses a CB400F and a CL160, the latter going under the heading of "work in progress", and occupying the hydraulic ramp. My 75 year old spine and knees were forced into previously unknown positions to locate and remove the drain plug. I then realised that the filter and dipstick opening are on the other side of the bike, Oh Joy!
    The sump was replenished with fresh lube, but the best bit was trying to install the filter along with its spring and outer cover. Have you ever tried balancing 3 snooker balls on top of each other? My dear little Japanese home market machine has learnt some new English words! If I can manage to attach a photo, it would seem I have a slight oil leak from the fitting/shaft under the inlet cam, as marked in pic. Is there any way of renewing the seal without a complete dismantle? Regards, Mike.[​IMG]
     
  2. TrickyMicky

    TrickyMicky Active Member

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  3. Andych

    Andych Moderator Staff Member Premium Member Contributing Member Dirty Wheel Club

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    While the Parts breakdown isnt the best on CMSNL it looks to me to Item 18 (O ring) that goes on Item 11 that would be the culprit....
    https://www.cmsnl.com/honda-gb250-c...0_model50658/partslist/0061.html#.YkGYjzdBzJw

    You would really need to try and get your hands on some sort of workshop manual to see how you can get that out to replace the O Ring as it is a pivot point for what they call the shaft tension lock.. so the lifter tensioner is mounted on there...
    Is that engine used in any other model? As a twin cam?
     
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  4. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    Was the leak there before or after u did an oil change?

    If it was before maybe it was overfilled .... I would clean it all off and see if it continues to seep

    clubman.png
     
  5. Murdo

    Murdo The Good Doctor Staff Member Contributing Member Ride and Events Crew

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    After looking at the diagram of the head, I think you may be able to lift the cam cover and possibily the inlet cam to gain access to the small bolt holding the shaft in place. This will allow you to grab the head of the shaft and slide it out just enough to slip the O ring off and replace with new one. Because these are odd size it is better to get a genuine Honda O ring and use some sealant on it when you fit it into the head.
    While you have the top off you can check/adjust the valve clearances too.
     
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  6. TrickyMicky

    TrickyMicky Active Member

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    Have now owned this 1987 beauty for a whole two weeks, and as it's been unused for a while, the inevitable minor leak has occurred from the shaft carrying the top cam chain sprocket. From what I can make out, the top end is mainly ball/roller bearings meaning that the oil pressure required is fairly low. My first temptation is to carefully apply some pig snot like Hondabond around the edge of this shaft where it is visible on the outside of the head. If this fails, does anybody have the knowledge as to whether the shaft can be withdrawn enough to change the 'O' ring without all the other bits being disturbed in the head. Don't want to sound a defeatist, but I've only just got the thing, Spring is making itself felt here in the UK, and I want to ride it!! Stay Safe and well everybody. Mike. D47CA379-8CC4-4209-9A11-7D0E832B9396.jpeg
     
  7. TrickyMicky

    TrickyMicky Active Member

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    BTW, the photo is not of my bike, it's just a pic. I have used from the internet
     
  8. Andych

    Andych Moderator Staff Member Premium Member Contributing Member Dirty Wheel Club

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    You basically asked the same question in your other thread... but which shaft is it that is leaking. The one that was circled in the previous thread or the shaft for the Top Cam sprocket (centre one)?
    Either way it was to some extent answered. Let us know if you want both threads merged so the relevant info is all in the one place :)
     
  9. TrickyMicky

    TrickyMicky Active Member

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    It's the shaft for the top cam sprocket, just wondered whether it could be eased out slightly to renew the 'o' ring. Yes please merge both threads. Many thanks, Mike.
     
  10. Murdo

    Murdo The Good Doctor Staff Member Contributing Member Ride and Events Crew

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    Yes, should be the same deal as I described before.
     
  11. Elliot

    Elliot old enough to know better.

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    Hi Mike, i've nothing to add to your query, just wanted to hi to another GB 250 owner in the UK, not very many of us. that is a beauty of a bike you have there all original by the looks of it. would be nice to be in touch.

    Brian. 100_3330 (2).JPG
     
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  12. T M Fulcher

    T M Fulcher Active Member

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    Hi Mike, I'm another Mike, I have one of these DOHC engines, the bikes were made From 1983 till 1997, Yes & named CB 250 Clubman. My engine number is MC 10 E - 1036837.
    The photo shown of the DOHC & Rocker gear is not from this engine series, The MC 10's camshafts were toothed chain driven & actuated rockers to open Radially placed valves in a true Hemi head combustion chamber, they produced 30 bhp @ 9500 rpm, A beautiful looking aircooled single with twin carbs & exhausts.
    All the best with your project.
     
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  13. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    Looks like a nice design from the blurry pic. I am assuming it is a 1:1 crank to idler gear and the driven gears appear to have a spring loaded backlash gear to cut down the noise.
     
  14. T M Fulcher

    T M Fulcher Active Member

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    Sorry but those pics are not of a CB 250 honda Clubman, I'll take the cam cover off my MC 10 engine & show you why.
    I would like to know what engine that pic was of. Does any one Know?
     
  15. TrickyMicky

    TrickyMicky Active Member

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    I know the blurry photo is not too clear, but if I can manage to load another one, you will see that it is indeed a MC10 engine. The chain from the crank is an inverted tooth type, (Hyvo), and can be seen behind the centre gear wheel. The cams are gear driven from this centre wheel, and yes, the valves are operated by rockers.
     
  16. TrickyMicky

    TrickyMicky Active Member

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    B7254A63-D76B-4086-B6EF-87BECBF546B6_1_201_a.jpeg
     
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  17. T M Fulcher

    T M Fulcher Active Member

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    Sorry Mike please accept my apology, I have just taken the Rocker cover off mine, & yes you are correct the drive is just as you stated, your photos are very clear I must have seen some pics of another engine which showed the inverted chain driving both camshafts.
     
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  18. T M Fulcher

    T M Fulcher Active Member

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    1d7c67223a1b4030459636e776da45f9.jpeg.4afc1007d85703ce01dc22b3277ac6b4.jpeg headcover-packing01-050.jpg.9ebfcf531455840403aa7020931fa240.jpg 1d7c67223a1b4030459636e776da45f9.jpeg.4afc1007d85703ce01dc22b3277ac6b4.jpeg headcover-packing01-050.jpg.9ebfcf531455840403aa7020931fa240.jpg 467aefc3.jpg.182ac2de48ca8c85bf9d0be87a90445e.jpg
     
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  19. T M Fulcher

    T M Fulcher Active Member

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    These are the pics that confused me, they are of Honda's DOHC RFVC 125 engine
     
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  20. TrickyMicky

    TrickyMicky Active Member

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    No apology needed my friend. At 75 years old I am still discovering bikes and operating systems that I didn't even know existed!! The 125 RFVC being a case in question, so I can understand the mix-up. In the name of 'elf & safety, in 1983 all riders in the UK who had not passed their test were restricted to 125cc with a maximum 13BHP. Prior to this, they were all screaming round on hot 250 Japanese missiles. After 1983, once someone had passed their test, they naturally wanted something bigger, meaning the market for 160/175/250 machines was decimated overnight. My reasoning for buying the GB250 being that it's over 100lbs lighter in weight than my CB400/4, plus I think it looks pretty neat. It certainly goes round corners quite well also! Honda UK will not supply any parts for a vehicle which was not intended for sale in the UK, meaning that seeking out and buying parts certainly keeps my ancient grey matter active! I think I am too old now to learn the Japanese language, so I am very grateful for the existance of the internet, and all the helpful people who subscribe to it. Stay safe and well everybody. Mike.
     
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