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Engine Woes...Again

Discussion in 'Technical and Troubleshooting Torque' started by tmg, Sep 11, 2007.

  1. Got a few new problems with my bike. Being old and all, and close to 100,00k's on the clock, the old CB750 is starting to make lots of funky noises. I took it to a motorbike mech yesterday and he said the internal chains (i.e cam chain and cam-to-crank chain) are both stuffed and will be needing replacing very soon.

    He also told me to baby it till I can decide what I want to do with the bike.

    Well, after talking with a housemate today about it (he also rides which is sweet coz I have someone to ride with :)), I would like to see the engine running shmick again. I have another engine sitting in garage which is really needing to be rebuilt and is already is pieces.

    My housemate suggested I take the engine that's in bits and pieces into the mech instead of my running one, and get it rebuilt while I run around on my bike, while it's still going. That way I can stress less about it, and have some form of transport in the meantime. If I DO end up getting the engine rebuilt, I would definitly be wanting forged pistons inside, as well as braided lines for all the fuel and brake lines, just to be complete, as well as a good set of brakes eventually too.

    Thought I would post it here and get some input. I don't want to part with it just yet as I got it from my dad and it's a very sentimental item now. Plus I would like it be all it can be for me too.

  2. Just rebuild it stock. No need for forged pistons, the old ones lasted 100k right?
    Spend the money on new hoses, coils, leads etc when the time comes.

    Regards, Andrew.
  3. Have you looked at the cost to have a mechanic rebuild it for you??
    A new bike would be cheaper....
  4. +1

    yeah i was qouted well over $1k to rebuild a 2 stroke engine a few years ago.

    You best get a quote first. I would suggest buy a running engine from ebay for a few hundred and drop it in.
  5. Cost of a good professional rebuild on an old Jap four? Probably enough to buy you a really nice example of a much better bike (think good to mint GPZ900R).

    Cost of a bad professional rebuild on an old Jap four? Your entire disposable income for the rest of your working life. Or until you decide it's good money after bad and pay a wrecker to take it off you.

    You've got two realistic options.

    1) Have a go at replacing the cam chains yourself. Not a huge undertaking as far as open heart surgery goes, and probably the cheapest route to a working bike.

    2) Sell it for what you can get as-is and put the proceeds and the rebuild money towards something better.
  6. u forgot option

    3) take a week of work and rebuild the engine u have in the shed
  7. Well yes, but I'm an pessimist and tend towards the view that an engine in bits is usually that way for a reason and has stayed that way because something terminal's turned up. Or it's been apart so long it's a three dimensional jigsaw puzzle with all the corners missing.

    It's generally easier to fix something that works but which has reasonably well defined faults, than it is to put someone else's abandoned project back together.

    But then, I'm a glass half empty kind of person :? .

    Cam chain replacement really isn't that horrific. Even if Honda did unnecessarily complicate matters by using two chains where everyone else managed perfectly well with one :) .
  8. If it is now of sentimental value and you don't want to part with it why don't you store it away or use it as a decorative display?

    Keep the the money you would have spent on fixing it up and use it as a way to get a newer bike.

    Ride the other one on speacial occasions.
  9. Haha lots of different comments there fellas. I could rebuild it myself (no non-running one) as I have a Haynes Manual which details how to overhaul an engine, and yeah, I am sorted of clueless as to why Honda used to chains, where the Kawaka ZRX used cogs which would've been way better. oh well.

    I did take it to a bike dealer yesterday, and I've been hearing interesting things about these Hyosoung (spelling?) GT650R's. Who said the brakes are crap??? oh, that's right, them ppls who came off aprilias and ducatis with there nippy brembo brakes. The brakes are fine and the engine - have you heard of an SV650? same engine people!

    I test rode a GT650S as the 650R was predelivered, but not registered, but for $10,300 including all the on road costs, I can have a brand spanker of a bike and it really is a sexy bike! That's my options atm. I will still think about getting my engine rebuilt...and I will not be using it as an ornemental decoration :p
  10. Hyosung :shock: I am sure theres better options out there for that sort of money even if they are not new.Soon as you ride this korean masterpeice it will be worth next to nothing :grin:
  11. It's not the same engine, have you ever seen both close up. I wouldn't touch them with yours, mine just blew up for the second time...
  12. I got a quote a couple of months ago to to an engine rebuild with some big bore pistons (not much more than standard, cost wise) and it come back as $5k.

    I was getting the quote to get an idea of of what I'm going to do in the long run with my bike.

    I'd say, for you, replace the chains in your bike, deglaze the bores and put some new rings in. lap the valves in and put it all back together with a gasket set and ride around for a year or so before you offload it.
  13. You may also need to consider balancing the cost of the rebuild against what you'll get for the bike if you sold it with a rebuilt engine....I doubt if you'll get $5k on an old CB750 as i havent seen many for sale for more than $5k, even with rebuilt engines. If it will cost you $5k to get a mechanic to rebuild the engine, you had better keep the bike forever, or sell it straight away.
  14. Well...I got an update on my bike. It runs, and runs well. How? Well, I was lookin on ebay, and spotted a 900 bol'dor for sale and thought, "hmmm, I could use that", so I went around and had a look and bought it, brought it home and swapped the engine over to mine and now it runs awesome! still have the 750 in the garage and am thinking about rebuilding it, but now my bike is running, I am happy for now.
  15. Personally I'd have run the Bol d'Or instead, unless it was a complete shed. Still, congrats on having a good running bike again. And, I guess, a bit of a sleeper too. I've always liked sleepers, for the :shock: expressions they can create :grin: .
  16. yeah the bol'dor wasn't a complete bike, it was missing the front wheel (which was at the bikeshop and I now have) and the rear light wasn't there, and it had no exhaust system on it, but now it's in my bike it has the KEAG system on it and when it gets goin it sounds like a jet, it's nuts!

    Took it for a run this arvo on the highway and it loved it and so did I :D, it is so smooth now it's great. an oil change made a big difference and now I have the clutch adjusted properly gear changes are smooth and neutral is easy as to find too :D.

    Only thing it's needs is a tune up - it's running a bit rich atm.
  17. Though if you have the finances to rebuild it, and significant sentimental value with it, by all means rebuild it.... Like all restorations, you need more money and less sense....