Motorcycle Repair: Honda 150, honda benly, camshaft bearings

Question
Hi, I have started to restore a 1965 150 baby dream
After I bolted the case up I tried to blow air through the crank shaft to see if the cam would recieve oil.
I have cleaned out all the oil passages in the case but I can not get air to blow through the crank shaft.
From what I can see the oil has to flow through the crank to feed the over head cam.
Do you know if the crank could be pluged up? it looks clean as far in as I can see.
I have an other used junk crank and this one also will not allow air to blow through. I thank you for any help, Randy

Answer
The Honda checklist for oil flow indicates that the test point for oil is the right rear cylinder head stud/nut. This indicates that oil is being pumped upwards around that stud to feed the top end, which is usual Honda practice. I don't have that illustration handy to verify the oil flow path, however. Honda did cut a channel in upper cases, for early models, to promote the oil flow towards the center main, but generally the oil flow is split before getting to the crankshaft.

If you want to send a copy of that page to me, contact me through the website: www.vintagehonda.com to refresh my memory.

Bill Silver



Randy, I can read your question in two ways. I'm not sure if you meant to say that you are testing for air to the camshaft or you typo'd the statement to say crankshaft....?

If you have a copy of the Honda Benly 125-150 shop manual, it shows the oil flow pattern from the oil  pump to the crankbearings and the separate pathway to the camshaft bearings.

I have heard some stories about people having crankshaft failures and finding that the crankshafts were not drilled through all the way, which lead to rod failures. Honda changed the design of the crankshaft and engine cases at least 3 times from 1959 to 1962, do to durability issues.

The oil pump feed comes up through the cases and lubricates the main bearings, which should be drilled through internally to direct oil to the big ends of the rods/crankshaft journals. Oil is separately directed from the pump to the clutch cover/oil filter cover to the oil filter, then turns at the engine cases upwards past the engine studs to feed the camshaft bearings and cam, which is drilled for oil flow internally then out to the small end of the camshaft to lube the end bearing housing.

If engine oil is not kept clean through regular oil changes, or something is overheated to fry the oil, then it can leave deposits that will eventually plug up the oil ways, but this is not a common occurrence.

Bill Silver