78XS Carb question

[Espiritus]

It's not that I don't think that all of you could help me, but I get all confused when I read threads from folks who refer to carbs other than the one that this monster that I am working on has. . .then I start looking for parts that I don't have. . . kinda reminds me of my old high school locker room when I walked into the wrong side. . .

Anyway, I got my rebuild kit for the carbs and immediately had problems. The kit came with 137 main jets, when what I removed were 140's. Then, when I was looking at the valve seat, I realized that the tip was longer and not tapered the same, and the valve seat assembly didn't have the little mesh ending and the washer was significantly thinner.

So, I installed my old jets, and didn't install the new valves or seat. I guess I shouldn't have been surprised when two of the four floats failed to stop the flow and flooded into the airbox.

Silly me didn't test them before putting them back on the bike.

Pulled them back out. Set them back in the kitchen, came upstairs and got online to read, and read, and read. Here are the questions: Do I go ahead and install the different valves and seat assembly with the thinner washer? Will it matter that they are different? Do I install the 137's or leave the 140's. This bike does have a 4-1 exhaust (which I hate) but the regular airbox (although it has an intake line that pulls out, but it isn't clogged).

I did make sure that my petcock air lines were to the right place, and that I ran the upper T's to the airbox, making sure that the fuel was going to the lower T's. When my petcock is turned to the "on" position, the gas does stop running when the tank is off, so I don't think the flooding was due to the petcocks.

I didn't start it, by the way as it was obviously flooding before I had the chance, and I am pretty confident that the gas didn't make it to the crank, but I will check that before I run it.

Finally, the new idle mixture screws are beautiful. But, how the heck do I know where to set the darn things? I have set all four of them to "just-barely-thinking-about-touching the-hole-that-I-can't-get-them-out-of-it-they-get-stuck-again." Not too scientific, but I have had my fill of broken tips!

What to do, what to do? It's too early in the week and too late at night to drink, but I can replace those valves in about 15-minutes if that is what I need to do tonight (well, provided I don't hit the fridge for that drink. . .)

Oh, I did read a thread that talked about tapping on the bowls while driving to unstick floats. Got a heck of a laugh out of that one! Read another that mentioned "shocking" the carb with a "light blow". . .I am thinking about SHOCKING it by driving it into the Ohio River and seeing if it can swim. . .

Maybe I should have that drink



Cam

[tarzan]

If the new seats screw in ok and the float height remains fairly close use them.Your old needles are obviously leaking.You then just adjust your floats to the correct height. Set your idle mixtures(pilot screws)by screwing them in till they just seat.Use a light touch as it sounds like you already know that.Then back them out
1 1/2 - 2 turns out.If it dont idle there at first back them out a little.

[boyat68]

Espiritus::

According to http://www.xs11.com/forum/showthread...=&threadid=382
You should go up 1 jet size for a 4-1 exhaust, so that is why you probably have 140s instead of the stock size 137s which incidentely, came with the kit. If you ordered the kits from "MIKES" then they don't come with filters on the bottom of the valve seats (mesh) so you would carefully pry off your old "mesh" and put it on the new seats. I do not think that the needles being longer should matter as they are only there to open or close the fuel flow to the carburetors. It is not unusual for new floats to bind and cause leaks so the tapping on the sides of the carbs is only to prove that they are sticking and will release to seal the carbs. Do not be discourage, frustrated yes, as it took thirteen offs and ons to get my own rebuilt carbs to stop leaking and I used the bench test rig before I reinstalled them. The pilots are first lightly seated, then opened to 1-1/4 to 1-1/2 turns. This can be done on the bench before you mount them. When they are lightly seated, you can barely feel the tips protruding through the hole in the top of the outlet plenum. You will do the seating and re-seating many times while synching the bike as you will loose count of how many turns out you have done. As to leaving the 140s in or using the 137s then that is an owners call as to what you want to accomplish.

[red bandit]

There is a tab that prevents the floats from dropping down to far which will cause them to bind with the needle and flood.
Make sure the gasket isn't curved inward and rubbing/holding the floats from moving freely.

[mro]

from a previous post
You will do the seating and re-seating many times while synching the bike as you will loose count of how many turns out you have done.

The pilot screws are not for syncing the carbs.
What I do.... ...
Initial setting of the pilots at 1 1/4 turns out.
Synchronize carbs using the screws that are on the carbs just for this procedure.
Set idle as low as engine will stay running
Turn pilot screw out slowly until engine rpm stumbles, (now too rich condition) Then turn screw in counting turns/partial turns until it stumbles (too lean condition) set pilot screw half way between the two conditions.
After each carb is done may need to lower rpm back down.
When all carbs done set rpm to 950
Re-synchronize carbs
re-check rpm

mro
BTW, would try the new seats/needles, bench test (unless you plan to return em)

[mro]

BWT 2

Use the jets that were in the carbs unless they are damaged as they seldom wear out.
Get bike running then check plug color.


mro