Lean cough? or too rich?

[TownsendsFJR1300]

Plus 1 ^^ on both posts.

ALL THE JETS have to be REMOVED and you should be able to SEE LIGHT THRU THEM.

If not, their NOT CLEAN and WILL cause running issues.

Also, the orifices they screw into, you should be able to squirt brake or carb cleaner thru them and see the fluid come out elsewhere (depending on the orifice).

And unless you have paper gaskets, all your O-rings, etc, should be fine to reuse


Last week I had a 90cc Yamaha 4 wheeler with a badly clogged carb. The idle jet is so small my jet cleaning tip were too big...

Ended up using a pulled wire from a hand held wire brush.

Even with that, took me easily two hours, carb cleaner and 150 PSI to finally get it open... And if I had not cleaned that jet, the idle would not have been good. Once done, nice steady idle, ran like a top.. You can see the main jet in the pic, the idle jet was behind it:

[walleye1]

If that engine has one carb for two cylinders they need to be flow tested after cleaning

[pstephens46]

If that engine has one carb for two cylinders they need to be flow tested after cleaning

How do you flow test carbs?

[99yam40]

I do not understand flow testing 2 cylinders coming though one carb

[TownsendsFJR1300]

I do not understand flow testing 2 cylinders coming though one carb

Cause it's absolute BS.

Harleys (air cooled) all have one carb or throttle body that divides into TWO cylinders...
So do most V twin MC engines, larger lawn equipment machines....

It's simple common sense. How does cleaning a clogged jet NOW change how a carb flows??? Simple, it DOESN'T.

Start grinding up the inside of a carb for some reason, sure things will change...


BTW, the Ops engine has 3, two barrel carbs:http://www.boats.net/parts/search/Ya...TOR/parts.html
Not that that makes a difference..

[99yam40]

I was thinking flow testing was fuel flow maybe, but do not see how that could be tested or even air flow for that matter unless there was a separate carb for each cylinder

[boscoe99]

[zenoahphobic]

Maybe if you have two carbs going to one cylinder, you would have an argument that they need to both supply the same amount of air each. But then you can only adjust linkages at idle and it is assumed they keep in sync all the way to fully open. Yes I can hear someone saying why use two carbs and where is that done?

Back to conventional one carb supplying more than one cylinder, it is generally relied upon fixed physical things non adjustable. That is the Y tube has been manufactured symmetrical and the insides of even texture. Uneven cylinders can be difficult to balance. The problem for example becomes important in adjusting for a smooth idle, one cylinder is always going to try to run faster than the other. To correct this corrections need to be made somewhere between the carbs and the input valves, the flow can be tested with vacuum gauges in each "path". Things like polishing or smoothing can be done. Often the small "machining" can improve for consistent idle but has negligible affect on peak power of each cylinder, where output plumbing would be given attention. Of course it is far more complicated and difficult determining individual cylinder power output.

My 2 cents to stir the pot.

[zenoahphobic]

Some of that seems to have come from a medical journal referring to old age male urology.

[99yam40]

OK I was not thinking about a double carb.
For some reason I was concentrating on a single barrel carb feeding 2 cylinders like the old twin cylinder small motors

Should have looked back to see what motor we were talking about

[walleye1]

These carbs half to be flow tested, if not your time is wasted. you are going to waste the customers money.

[99yam40]

you could have said these double barrel carbs need to be tested to make sure fuel flow was not restricted into the carbs, that would have made more sense to me

[TownsendsFJR1300]

Flow testing is usually associated with AIR FLOW...

Checking to see that fuel flows from the FUEL inlet in thru the inlet seat IS PART of the cleaning... (Or it should be if your doing it correctly).

Goes without saying IF your doing it correctly... I do that on every carb (but use fuel) and if there's any doubt of the needle / seat leaking, put a vacuum gauge on the intake line, flip the carb upside down(needle closed) and check it does hold a vacuum.

For testing, I have a small, (maybe a quart), old mower fuel tank with a fuel on off switch. I use gravity to allow fuel to flow and observe same.

A garden hose (pictured above-unless noted elsewhere), is going to have WAY MORE PRESSURE than your FUEL PUMP. Gravity on the other hand, MUCH less and easier to see any obstructions...

This is BASIC STUFF..

If it's NOT flowing, still clogged, your doing a "do over" , (at your expense and time for doing a half a$$ed job).

FLOW TESTING:

[99yam40]

when one was not big enough to feed that cylinder.
there are ways to make thing more complex if you really wanted to

I crawled into a crankcase one time to help set a piston and rod to the cylinder and crank.
but it was a compressor, not a motor

[walleye1]

It is two floats per carb, one float per cyld. top carb handles #1 nd #2 cyld and so on. CHECK?