SOHC.co.uk Forums > CB750
Taking engine out burning oil
yozzer74:
Well I've managed to get three sets from cmsl and David silvers had just one set . David silvers said that the F2 had two different part numbers for the rings on the F2 so didn't know which pistons mine had does anyone know if the pistons are different or they just changed the part number .??
bytio:
This company does pistons and rings up to +4mm
http://www.scheuerlein-motorentechnik.de/motorrad/Honda/700-799-ccm-h7/cb750four-modelle/cb750f1/
Excellent quality, I used them on my F2, (they have them for Ks and F1s as well) I had the same oil burning problems went through 2 over size steps new guides etc, still burning, the cause eventuall found the machine shop boring he Barrells made the clearances too big, I did lots of research and consulted Hondaman (and his book) I insisted on this clearance, the shop said it would seize, and wrote a disclaimer. I got the clearance I needed, the bike ran perfectly, and never used as to of oil, oh and it didn't seize.!1
philward:
Heres a similar link refererence 'Hondaman' info -
http://forums.sohc4.net/index.php?topic=89779.msg1005284#msg1005284
I used the recommended smaller clearance on my 836 cruzinimage big bore kit - 850 miles and so far so good. I am not sure what clearance the guy who bored my barrels used on my CR750 current build - he may have used the standard tolerences (I am now doubting myself whether I insisted on the smaaler clearance as I did on the last build) - time will tell when I start it up!
royhall:
--- Quote from: bytio on March 27, 2017, 07:57:16 PM ---This company does pistons and rings up to +4mm
http://www.scheuerlein-motorentechnik.de/motorrad/Honda/700-799-ccm-h7/cb750four-modelle/cb750f1/
Excellent quality, I used them on my F2, (they have them for Ks and F1s as well) I had the same oil burning problems went through 2 over size steps new guides etc, still burning, the cause eventuall found the machine shop boring he Barrells made the clearances too big, I did lots of research and consulted Hondaman (and his book) I insisted on this clearance, the shop said it would seize, and wrote a disclaimer. I got the clearance I needed, the bike ran perfectly, and never used as to of oil, oh and it didn't seize.!1
--- End quote ---
I agree. My 350F was left to the engineer to fix the boring size, just left him the barrels and 4 new pistons. Although he did a good job I am now thinking its going to need boring again. Smoking on two cylinders and using oil. I'm pretty sure he's bored it to a standard clearance as he's more used to doing British iron and that has about 5 thou clearance. What is the recommended clearance on a 350F, Hondaman recommends .0010" to .0012" but that's for the 750?
bytio:
0.0008-.0010 anything more then it will burn oil (that's what he recommends for the 750 and worked perfectly for me. I don't know the 350
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