Topic: CB750 emulsion tube mod?

[slowjo]

This past spring after sitting all winter in Ohio my 1972 CB 750 K1 gave me nothing but problems. It just would not want to run right. So after I gave it the old 3000 mi tune up and pulling and cleaning the carbs many times as per Hondamans book it finally started to run better, still rich at idle but better. Now that winter in N.E. Ohio is near I'm thinking about pulling the carbs again. I did modify the emulsion tubes as per Hondamans suggestion.  If by chance I did drill out the emulsion tubes too big should I try to find replacement ones? The carbs are 7A's with 40 slows and 120 mains. I do have a set of 110's to try. Should I buy a complete carb rebuild kit for all four carbs? I see that some kits have more replacement parts than others. Any suggestions?

[slowjo]

 We have a break in the weather so I'm off for a quick ride. Its about 55 and sunny.

[ekpent]

The big question would be what kind of air filter and exhaust system are you running or other mods. Also your description was a little confusing as you called it a 1972 - K1  1972 would be a K2 and 1971 is K1.

[Danno]

if you drill out the holes in the emulsifier tube too big they can be soldered closed again after cleaning but you have to make the inside back to the correct size by running an appropriate size drill bit down it by hand and cleaning the tit of lead off the inside of the tube try not to scar up the inside of the tube also the lead on the outside needs to be sanded flush too they can then be redrilled to the correct size after that or you can get emulsifier tubes still my friend can still get them and the jets he owns all brands cycle in muskegon michigan but I honestly believe if you followed instructions they will be fine

[slowjo]

I'm sorry for this late reply to my question. Three weeks ago my 6 year old daughter was bitten by the neighbors dog. Once on both legs and once on the face. It has been a rough few weeks for my family. As for my motorcycle, the build date of 6/71 . After the 6th month Honda titled it as the next year. It has all the older parts that came on earlier models than the ones that came on the 1972 K2. From what i have read it is considered a 1972 K1. Then again I have been known to be wrong before.

[MCRider]

I'm sorry for this late reply to my question. Three weeks ago my 6 year old daughter was bitten by the neighbors dog. Once on both legs and once on the face. It has been a rough few weeks for my family. As for my motorcycle, the build date of 6/71 . After the 6th month Honda titled it as the next year. It has all the older parts that came on earlier models than the ones that came on the 1972 K2. From what i have read it is considered a 1972 K1. Then again I have been known to be wrong before.

This issue comes up periodically, and here's the poop. For the CB750, the "K" series follows the calendar years, but only loosely and only by coincidence. K1s of other models may not be anywhere near 1971. Honda itself did not use calendar years before 1974. The model year in the US was assigned by the dealer and or Bureau of Motor Vehicles where, and when,  it was sold.

So you could very legitimately have a 1972 K1. But realize when talking about it you'll get raised eyebrows from those not familliar with what was going on back then. And also realize that when you buy parts, you'll need to use the serail number, denoting K1, and not the model year.

Honda got sued over this, and lost, and starting about 1975, they standardized model changes with calendar years.