Carburetor problem

[SIZZSAM]

Here is the problem I am having. I have two 78 e's and my brother has one 78 e that he wanted me to work on. I helped him buy it on ebay and even went over to Alabama to test ride and check it out. If I only new. It only had 7000 miles showing so I figured it was a steal. I'm taking the carbs apart and notice they don't look like 78 standard. The jets were all 110's so I figured 80 sg like the manual says. I ran a thread about it and Pete said just tune the carbs for the model and not the make of the bike. One problem is I can't determine if it is a 80 special or standard. The 110 jets lead me to believe it is a special but the jet needles are all 51z7 like a standard g instead of 5gl16 like a special. There are not numbers I can read on the carbs to identify the model. If it is a special with standard jet needles will that be a problem or should I buy some special jet needles? Anybody know the answer. It's probably not a life or death situation but I don't like to leave any doubt as to what I'm doing if I can help it. Any help will certainly be appreciated......Sam

[DGXSER]

Hey Sam,

I am far form a carb guru, so I can only give you my opinion. The 110 jets sound like a stock bike either 80 or 81. The pilots should be 42.5 jets. I am not familiar with the different needles, but I would think as long as the needle and the "needle Jet"/Emulsion tube are matched, it should run ok.

I think what was stated was intended to say to tune or jet the carb based upon the carbs you have and not the year of the bike or engine. However, if you have mods on the bike, they will need to be accounted for in the jetting dependent on what the mods are.

[CatatonicBug]

Maybe some pictures? A few close-ups and the gurus here should be able to point you in the right direction. Are you trying to determine the model/year of the whole bike or just the carbs? The bike can be determined by the VIN. There is a thread around here somewhere that lists the VINs and what model/year they go to. If it's just the carbs, you might be able to tell by the existence of an octy or some other details (to be determined by the gurus).

[SIZZSAM]

carb problem

The bike is a 78 E or standard and the vin# is correct for that. The 78E came in just one color, Macho Maroon. Some previous owner just put different carbs on it. Why, I don't know. I'm pretty sure the carbs are from an 80sg or special but the jet needles are definitely (by the yamaha service manual) for an 80 standard. Both models, 80g and 80sg, use the same nozzle. I guess my question is whether it will run lean or rich by having the wrong jet needles and should I go to the trouble of buying four new sg jet needles. Thank you for your help. Sam

[DiverRay]

I guess my question is whether it will run lean or rich by having the wrong jet needles and should I go to the trouble of buying four new sg jet needles. Thank you for your help.

If it runs well, and the plugs look good, LEAVE IT! That being said, you may have just a bit of "stumble" because of the LEAN mixture of the later carbs. One size up on the main, and an extra half turn on the mixture screw should fix that!

[SIZZSAM]

carb problem

Thanks Ray for the help. It did run pretty good to start with but he had some problems with the gas tank and pet cocks leaking. I haven't started on those yet. I'll check the plugs and if it's too lean I will adjust the air mixture out more. Thanks for the help. I really appreciate it.

[John]

One way to identify Special carbs vs Standard carbs Is to look at the choke lever. On a Special, the black rubber tipped handle should be positioned to the right side of the lever assembly, and the Standard it is positioned to the left, if someone hasn't had to replace the lever with what ever is available.