Honda-SOHC
General => New Member Introductions => Topic started by: davidcumbria on February 25, 2023, 06:34:19 PM
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Hi not really a new member since I joined in 2013 and ran a lovely 750 for a couple of years before I caught the two stroke bug and traded it in for a Yamaha RD500. Been away from forum since then. Now I've bought a 74 550k1 with intention of restoring it as a tribute to to the 500/4 which was my first big bike in 1979. Rode that bike to Adriatic coast of Italy and back which was quite an adventure but then gave up bikes until 2008 when i was the typical 50 year old born again biker. I love working on bikes and service my small collection including a Suzuki RG500, Yamaha RD350LC ypvs and my daily rider a Y2000 BMW R1100GS which unusually has been converted to run on carbs.
The 550/4 was supposed to have been fully restored mechanically but my first ride was eventful. I got to within pushing distance of home and it conked out. Turns out by resetting the tappets before I rode it I had disturbed the fuel pipe connections under the tank which were just pushed on with no clip and the pipe had become disconnected. There was no obvious stream of fuel because the restored tank had no internal or external filters and the fuel tap was almost completely blocked.
On my second outing I rolled the bike out of the garage in neutral only for it to stop dead, The only way it could be moved was with the clutch in. Turned out that the plate which secures the selector fork shaft in the clutch housing had been put on the wrong way round allowing the shaft to slide out and drop a selector fork into the sump. operating the gear lever in this condition just locked the transmission shafts. So the complete engine strip had been brought forward !
Ive enjoyed stripping the engine ( my tip is to take the head, block, clutch, starter motor and as much else as possible off when engine is in the frame making it a doddle for two people to lift and manoeuvre out.) Ive found worn out rocker shaft housing , blocked oil restrictors and best of all that the transmission bearing race pins have been driven into the crankcase by incorrect assembly. In one case the pin has cracked the housing under it and in the other actually fractured a chunk out which fell into clutch housing during the strip. Its not pretty but hopefully recoverable with some epoxy eg JB weld. photo below. Any other thoughts or previous experience with this all too common problem ?
Also not sure about the condition of the crank main bearings - look a bit like oil starved or contaminated to to me - what do people think of the photo ?
I have learned so much reading and searching for posts on here since i got the bike a couple of weeks ago and look forward to joining in the discussion which makes this such a useful place
cheers
David
(http://)
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Welcome to the forum, again, David 😊😊😊
Yes, that shell is well and truly fecked. Looks like a mixture of oil starvation, water and worms 😂😂😂
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The bearings look toast. Contaminated oil, standing for a long time and lack of oil changes will do that.
The locating pin on the transmission needle bearings getting driven into the crankcase is a common occurrence, it's why we recommend assembling the engine in the top case as you can seat them properly that way. It does mean putting the primary drive shaft in afterwards but it's generally a lot easier than assembling in the bottom case and trying to get the selector forks engaged whilst not moving the needle bearings, something the last owner clearly didn't manage.
If that was me and you're replacing the bearings anyway I'd look for a set of 550 cases instead of trying to repair all that damage.
What condition is the crank in if the bearings are that bad?
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Thanks no standing on the fence about the bearing then ! Haven’t measured the crank but initial eyeballing and finger scraping suggests it ok. I’ll look into the cases idea. Presumably they are matched so you can’t just buy a single top case ?
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Thanks no standing on the fence about the bearing then ! Haven’t measured the crank but initial eyeballing and finger scraping suggests it ok. I’ll look into the cases idea. Presumably they are matched so you can’t just buy a single top case ?
Yes, they are a machined pair so you need both.
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I bought a couple of 550 bottom ends a while ago, one had so many hanger bolts welded into the case that I ended up scrapping the cases as they were just useless.. The other set of cases seem to be ok and it's possible the crank that goes with them has the correct shells as well, I'd need to check. If they are ok they'll be for sale if you were interested.
The weight of cases and crank prohibit postage however but if you were interested and the price was right I'd be willing to meet halfway.
I'd need to check everything beforehand though. I don't sell crap.
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Am I right in thinking there are no pairing marks on the casings so a seller could mismatch them & you would never know?
Not suggesting for a moment that Ken would do that but I have seen e bay listings showing them priced separately!
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No pairing marks but if missmatched you can frequently feel the missmatch with a fingernail at the bearing.
Pins can be pushed back up and a blob of weld or similar, the shells are shot, probably dirty oil
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No there are no pairing marks Ted, when I said bottom ends I meant a pair of crankcases with cranks in them.
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No there are no pairing marks Ted, when I said bottom ends I meant a pair of crankcases with cranks in them.
I understood what you meant Ken I guess it baffles me that they never stamped both casings with the coding letters during manufacture especially as they were so accurately engineered at the time.
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I guess they never thought anyone would think of doing that Ted. Maybe there are pairing marks, like small blue ink stamps on the inside of the cases which over time have worn off with the oil swirling over the surface.