SOHC.co.uk Forums > CB350/400
Engine rebuild Parts list
Dolomite_:
--- Quote from: Bryanj on February 25, 2024, 05:34:45 PM ---Have you priced a rebore recently, the last four sets of 500 i did did not clean at 0.25 as the bores were "barelled" had to go to 0.5
--- End quote ---
I've not had to rebore anything yet. Im guessing its going to be atleast a couple hundred pounds. I'm going to contact an engine machine specialist near me tomorrow.
McCabe-Thiele (Ted):
--- Quote from: Dolomite_ on February 25, 2024, 06:16:47 PM ---
--- Quote from: Bryanj on February 25, 2024, 05:34:45 PM ---Have you priced a rebore recently, the last four sets of 500 i did did not clean at 0.25 as the bores were "barelled" had to go to 0.5
--- End quote ---
I've not had to rebore anything yet. Im guessing its going to be atleast a couple hundred pounds. I'm going to contact an engine machine specialist near me tomorrow.
--- End quote ---
You might already know, it's worth mentioning that whoever does your rebore should be aware of the fine tollerances Honda used on these engines. Ideally the engine specialist should be someone with Honda specific motorcycle engine experience.
Laverda Dave:
I agree with all the above and would add a caveat to the rebore work and that is be very wary of the man down the road who is used to reboring car or British motorcycle engines. Japanese motorcycle engines run very tight tolerances. The individual pistons should be measured and numbered. The bores are machined to suit the individual pistons.
I second Ted & Bryanj's recommendation, get the rebore done by someone who knows what they are doing with regards to these engines. The specific tolerances are in the Haynes manual.
I had a Honda CB250RS rebored by a so-called specialist five years ago. Despite giving him the tolerances he decided to do it his way as he thought the tolerance was too tight and the piston would sieze. Guess what, this is exactly what happened but not because it was too tight but because the 'specialist' bored it out as he would a British bike and didn't tell me. The engine used a litre of oil in the space of 50 miles, the bike sump only holds 1.5 litres, result a full seizure on the M40 motorway on a newly rebuilt motor. There was a big hole in the top of the piston on inspection.
Only use people who are recommended by others on this forum to save yourself a lot of pain and money👍
Dolomite_:
--- Quote from: Laverda Dave on February 26, 2024, 12:05:31 AM ---I agree with all the above and would add a caveat to the rebore work and that is be very wary of the man down the road who is used to reboring car or British motorcycle engines. Japanese motorcycle engines run very tight tolerances. The individual pistons should be measured and numbered. The bores are machined to suit the individual pistons.
I second Ted & Bryanj's recommendation, get the rebore done by someone who knows what they are doing with regards to these engines. The specific tolerances are in the Haynes manual.
I had a Honda CB250RS rebored by a so-called specialist five years ago. Despite giving him the tolerances he decided to do it his way as he thought the tolerance was too tight and the piston would sieze. Guess what, this is exactly what happened but not because it was too tight but because the 'specialist' bored it out as he would a British bike and didn't tell me. The engine used a litre of oil in the space of 50 miles, the bike sump only holds 1.5 litres, result a full seizure on the M40 motorway on a newly rebuilt motor. There was a big hole in the top of the piston on inspection.
Only use people who are recommended by others on this forum to save yourself a lot of pain and money👍
--- End quote ---
Good point Laverda Dave. Ive had a quick search through the forum but couldnt find any mentions, do you know any places in the Northwest you would recommend?
Laverda Dave:
I would contact either Nurse Julie & Graham (Trigger) or Bryanj both are on this forum. It goes without saying they are both the best at what they do and having been around Honda sohc's for ever they know what they are doing. Graham has just rebored my cylinders with some NOS Honda pistons and rings I purchased from Ted and replaced the valve guides and some valves. The postage cost to send the barrels and head to Graham was £9 via Royal Mail, next day delivery. Quicker and cheaper than going by car to your local rebore man!
Going back to a point made earlier by Bryanj, my barrels had 43k on them (or so I was told by the PO) and were on standard bore. They had to be bored out to .50 so unlikely you will get away with a 0.25 rebore on yours but until they are propely measured by whoever does the rebore you won't know so dont jump the gun and buy a piston kit yet as you may be wasting your money.
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