Beatrice runs but needs some love

[BobW]

Fuel flow should stop when floats are parallel to the carb body. Bend tang to adjust. Using sidestand can cause oil to flow around the rings. This can cause fouled plug and will cause smoke left side only.
Bring engine to operating temperature before attempting any carb adjustment other than float.
The acorn like thing may well be an acorn. Squirrels like to hide things. Also check for dirt dauber nests anywhere they can get.
Enrichment circuit problems will give hard starting and running on one side when cold.
Bob

[Bamboo812]

Also, the fact that you found one acorn means there may be lots more packed into the muffler/header. Worth pulling off the muffler, at least, to see if it's clear and give a look up the header pipe.

[barryh]

The more I think about it, the left carb wants to overflow. And the smoke is black. And the plug is very dark. The left is too rich. Where should the carb float be set on a '78 R100S?

The usual float bowl depths are a maximum of 24mm for 32mm carbs and 28mm for 40mm carbs.

It might not be the float setting but the actual float being too heavy. Measuring fuel depth in the bowl is a valid method but only for a new float or a float known to weigh close to the same as new. Measuring fuel in the bowl is an inferred method. The actual operational fuel level is much higher and close to the front edge of the bowl because of the fuel displaced by the floats and by the jets and castings. The problem is that heavy floats displace more fuel and therefore raise the level further. It's not that within reason you can't make slightly heavy float work it's just you have to make allowances and you can't set them by using the same fuel bowl depth or by setting them parallel.

I've just gone through this whole exercise of accurately weighing old and new floats and I proved that the fuel bowl depth method is not valid for old heavy floats without deducting something from the fuel depth setting. I can't give exact figures for the impact on actual operational fuel levels but I can categorically say that 12.5 gram floats and 15 gram floats gave radically different mixture strengths when set to give the same depth in the fuel bowl. And the 15 gram floats did still float and were in regular use without flooding. They just produced a much richer mixture when set parallel or at the usual set bowl depth.

If you measure float weight and find them heavier than new I would deduct some thing like 1.5 mm from the expected fuel bowl depth for every extra gram that they weigh.

If they weigh more than 15 grams I would replace them for sure.

[grant81rs]

Gidday,

The ole Bike that needs a little TLC story.... Hearing that a bit lately

Best of luck!!

[George inMinneapolis]

A compression test would tell you if something is up with either rings or valves. Make sure the throttle is open when you test compression. Anything over 125 is decent, though 140 would be nice. I had 140 once, not any more.

[Major Softie]

A compression test would tell you if something is up with either rings or valves. Make sure the throttle is open when you test compression. Anything over 125 is decent, though 140 would be nice. I had 140 once, not any more.

"Open throttle" is not enough with CV carbs, you must also hold the slide open. There also should be no air filter (zero restrictions to air flow. Most people feel they get the most accurate measurement by simply pulling the carbs off the intakes. Also make sure the engine is warmed up. A cold engine with poor compression may be working perfectly at operating temp.

[Ken in Oklahoma]

. . . The problem is that heavy floats displace more fuel and therefore raise the level further. It's not that within reason you can't make slightly heavy float work it's just you have to make allowances and you can't set them by using the same fuel bowl depth or by setting them parallel. . . If you measure float weight and find them heavier than new I would deduct some thing like 1.5 mm from the expected fuel bowl depth for every extra gram that they weigh . . .

Back in my early airhead years I spent a lot of thought and effort trying to accommodate heavy (gas soaked) floats. Probably I didn't give the problem the thought you did, but I did do some serious thinking. I would set the float height to the gnat's ass, and it seemed inevitable that a bit later I would spot gas dribbling from the bowls. In the end I chucked that effort and laid in some new floats in my spares stock and replaced questionable floats when I thought the time was right. Though the new floats aren't cheap, my 'float 'maintenance' went to nearly zero. For me new floats are money well spent. I keep a set of new spares in stock because I know I will need them someday. I also stock things like an alternator rotor, voltage regulator, diode board, coils etc. And this is in addition to the commonly replaced items like points, condensers, fuel lines and such. Perhaps my approach is a bit spendy, but I have a greater sense of confidence that I will be able to finish my ride--and that's worth quite a bit.

My philosophy. Y'all's philosophy may vary.

Ken

[Rob]

By far the most important manual is the parts book. All of the manuals are incomplete, in error and confusing in some parts. You will get better info here over all. You will learn who only has a keyboard and who knows something.

And Bing USA sells a great manual, just for the carbs.
http://www.bingcarburetor.com/manual.html

[Rob]

A compression test would tell you if something is up with either rings or valves. Make sure the throttle is open when you test compression. Anything over 125 is decent, though 140 would be nice. I had 140 once, not any more.

"Open throttle" is not enough with CV carbs, you must also hold the slide open. There also should be no air filter (zero restrictions to air flow. Most people feel they get the most accurate measurement by simply pulling the carbs off the intakes. Also make sure the engine is warmed up. A cold engine with poor compression may be working perfectly at operating temp.

...and a good, fully charged battery...

[Holysmoke]

Adjusted the left float a little and am running through some Seafoam. It seems to be starting and idling better. At idle when I put my hand over the left carb it doesn't affect the idle. The right one will kill the engine. The left cylinder and exhaust get hot, but the right is hotter. Should I check compression next?

Ordered new floats, spark plugs, fuel line and intake boots. Drained and replaced the tranny oil. It was a lighter brown color