Honda CB750 First Start Prep After Engine Rebuild | Exhaust, Oil Tank, Carbs & Throttle Cable | 24
In this video I get my CB750 SOHC Cafe Racer project bike ready to start. I do the necessary final preparation of my CB750 SOHC Cafe Racer Project Bike for first start after its engine rebuild, or top end rebuild at least.
When I got this bike I found that the engine, although it had been rebuilt, needed to be stripped and some, a lot, of the parts replaced. Now I am ready to start it again.
Things that I used:
Brass Barrel Cable Nipple 6mm OD x 8mm Length: ebay.us/eEoZFF
20w-50 20w50 Mineral Car Engine Oil: ebay.us/kIrUMY
Before you start any engine after a rebuild it is important to make sure that you haven’t missed anything that will cause, either damage, or for it to fail to start. Obviously checking that all of the parts have been put back, and that everything is reconnected is important, but this is closely followed by ensuring that the engine has good lubrication right from the start.
The CB750 SOHC engine is a dry sump engine with an oil tank. Although a lot of these engines let the oil drain from the tank down into the sump. They aren’t supposed to but the check valve doesn’t always work as designed. This doesn’t seem to cause any problem, unlike some other bikes which will try to pump the oil out of breathers when the engine starts.
When you are starting an CB750 SOHC engine after a rebuild it is a good idea to make sure that the sump has some oil in it, so that the oil pump is already pushing oil around. During the rebuild the oil pump was checked and primed with oil, so it should be ready to go. To help this even further, I put a half litre of oil through each of the outside inlet rocker covers, so that it would give the top end some more lubrication, and it would run down into the sump.
I used standard 20w 50w motor oil. Modern oils are a lot better than they were 40 years ago, and I know some of the additives can cause some problems. But I have tended to use this type of oil in my older bikes for a long time, and I haven’t yet had a problem. The manual recommends 10w 40w oil for CB750 SOHC engines, but does give 20w 50w as an alternative, and as I am in a colder climate I think going for the slightly heavier oil is a good idea.
I had given the carbs a refresh, and these needed refitting. I warmed the, relatively new, manifold rubbers in hot water to make them soft. The carbs went on really easily, with old rubbers it can sometimes be a bit of a battle.
When I fitted the throttle cables I noticed that the close, push, cable was too long. I shortened it and soldered a new nipple on. I wanted to put a new nipple on the open, pull, cable to replace the temporary one that is in place, but I haven’t got one in stock so I needed to order one.
I would normally spend some time setting the ignition on a newly rebuilt engine. But I knew that I had set this up quite well the first time that I started the bike, so apart from checking it I decided that it would be OK.
In the next episode I should be starting the bike. Exciting times ahead 🙂
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