1964 CB72

toastyhamster · Post by **toastyhamster** » Wed Feb 03, 2010 11:22 am

Damn this bike is fighting every inch of the way, it just not want to be fixed!

After quite a bit more work earlier this week I was ready to start it for the first time. Would it fire? Not even trying to start, nice fat healthy spark (after cleaning the point faces for the nth time). Taking the plugs out and they were dry, so I suspected lack of fuel. After a trip to buy some "cold start" spray I could get it to run briefly on the right hand cylinder. After a bit more investigation I put the wires to the points on the right way round and it fired up on the button. Doh. But only on the right hand cylinder. Checking the left hand carb and I'd put the float bowl on upside down - dick! Fitted that the right way round and the carb float bowl leaked, and then right hand carb started to overflow, then after fixing the float bowl leak the left hand carb started to as well. Spent an hour or so trying to fix both before admitting defeat and ordering a couple of rebuild kits. And a new condenser as there's more spark at the points than I'd like.

Still it ran pretty well on one cylinder.

Oh and I connected up the horn but that didn't work either (loom fault somewhere)

One day this will be finished!

davomoto · Post by **davomoto** » Wed Feb 03, 2010 4:33 pm

Perserverence. patience, and lots of time and money. These bikes are amazing to own and ride when properly tuned and prepped. make no mistake, it not a modern, fuel injected, 100 horsepower, thumb the starter and go bike. To me, that's what makes them so special. Re-use your stock jets and jet needle . The bowl gaskets, float needle and seat and top gasket are all that I use from the aftermarket kits.

davomoto

Spargett · Post by **Spargett** » Wed Feb 03, 2010 5:02 pm

Toasyhammer, I've definitely been where you are. Don't worry, it's got nothing to do with you, just the initial nature of generally neglected and very old bikes.

The carbs require an incredible attention to detail. The float height must be PERFECT, the gaskets solid, the floats not catching the gasket, etc. etc. Every step of the carbs has to be dead on for them to function correctly.

As far as the right side not firing, are both carbs getting fuel? I'm sure this will sort itself out. Just a process of elimination. Keep your work solid and the information clearly explained on the forums and you'll have a running bike.

toastyhamster · Post by **toastyhamster** » Wed Feb 17, 2010 7:28 am

Dammit now the floats are leaking! grrr!

teazer · Post by **teazer** » Wed Feb 17, 2010 11:39 am

Carbs are very that way and cause a lot of frustration as you chase problems, but the good news is that once fixed, they stay that way for a long time.

We use CB77 carbs on one of or race CB160s and sure as fate at least once per season, one or other will start to spew raw fuel everywhere - just because they can. I started to replace old leaky brass floats with CB750 plastic floats which just drop straight in and don't leak.

Get a rack of SOHC CB750 carbs for about $20 from a swap meet and you have two pairs of floats.

Spargett · Post by **Spargett** » Wed Feb 17, 2010 11:40 am

Great tip.

teazer wrote:I started to replace old leaky brass floats with CB750 plastic floats which just drop straight in and don't leak. Get a rack of SOHC CB750 carbs for about $20 from a swap meet and you have two pairs of floats.

toastyhamster · Post by **toastyhamster** » Wed Feb 17, 2010 12:22 pm

$20 from a swap meet, or in UK prices about 50 quid.

Ordered a couple of new floats off ebay so hopefully that'll be one more problem out of the way.

Just got to be patient again while the post comes from the US.