Hi everyone,

I got a Evinrude engine from a friend to check it out, he told me it
ran bad. I took off the carb and cleaned it out after that it ran
fine.
Now not long after that during (has been going good that day) a small
boat trip engine started to run rough especially when running at
higher rpm. It's harder to notice it when I try to run it idle.
Coming home I took off the float chamber and noticed a dusthair in the
main jet. Removed it and being convinced that would have caused it
put things back together, also installed a simple fuel filter to
prevent this from happening again. (does this engine has a filter in
the carb?).
But on a fishing trip yesterday after about 5 minutes the engine
started to do the same again.
I checked out the newsgroupes but the answers vary quite a bit.
Since my engine is so simple of construction I suspect a simple answer
for this problem. It's a 2 stroke, 2 cylinder, 4 HP Evinrude from '86
with one carburator.
By the way, I find only one adjusting screw on the carb, where is it
for and how many turns out should it be?

Your help is much appreciated,

Jan.
(Honda CB 400N '79)
(Honda CB 750 Sevenfifty '92)
(Yamaha TDM 850 '98)

4 HP Evinrude from '86
with one carburator.
By the way, I find only one adjusting screw on the carb, where is it
for and how many turns out should it be?

Jan.... The filter is in the gas tank. The fuel hoses may be deteriorating,
allowing debris to enter the carb (check the carb again). The carb adjustments
are as follows:

(Carburetor Adjustment - Single S/S Adjustable Needle Valve)

Initial setting is: Slow speed = seat gently, then open 1-1/2 turns.
Start engine and set the rpms to where it just stays running. In segments of
1/8 turns, start to turn the S/S needle valve in. Wait a few seconds for the
engine to respond. As you turn the valve in, the rpms will increase. Lower the
rpms again to where the engine will just stay running.

Eventually you'll hit the point where the engine wants to die out or it will
spit back (sounds like a mild backfire). At that point, back out the valve 1/4
turn. Within that 1/4 turn, you'll find the smoothest slow speed setting.

When you have finished the above adjustment, you will have no reason to move
them again unless the carburetor fouls/gums up from sitting, in which case you
would be required to remove, clean, and rebuild the carburetor anyway.

Joe (30+ Years With OMC)

Hi,

Joe, thanks very much for the reply.
I had that needle out way too much.

So this rough running is a sign of starvation? You can hear the engine
wants to go but it is holding back all the time.

I put on a new fuel hose when I first started to use the engine after
I got it, some weeks ago. Yesterday I pulled out the fuel hose
connection out of the fuel tank and saw that the little filter was
damaged, not sure if I did it but I found some corrosion in there as
well. I assume I need to buy a whole new connection here with filter.
I guess, this might have lead to the problem.
I better clean the carb again as well.

Jan.
(Honda CB 400N '79)
(Honda CB 750 Sevenfifty '92)
(Yamaha TDM 850 '98)

Hi,

I found after I pulled of the cylinder head a lot of carbon (kind of
wet) on piston and cylinder head, could this cause a problem as well?

Many thanks,

Jan.
(Honda CB 400N '79)
(Honda CB 750 Sevenfifty '92)
(Yamaha TDM 850 '98)

Yes, recommend you tear down the carb and verify clean and float set
properly.
Clean the head and piston good.
Install new plug
Run brand name gas and OMC, Merc, or Yamaha oil TCW3. Cheap oil tends to
not burn properly and cause carbon buildup.
The amount of oil and gas you burn in that engine - you won't save any real
money on cheap oil.

--
Tony
My boats and autos - http://t.thomas.home.mchsi.com



"Jan" wrote in message
...
Hi,

I found after I pulled of the cylinder head a lot of carbon (kind of
wet) on piston and cylinder head, could this cause a problem as well?

Many thanks,

Jan.
(Honda CB 400N '79)
(Honda CB 750 Sevenfifty '92)
(Yamaha TDM 850 '98)

Jan wrote:

All as already suggested & ........

Hi everyone,

I got a Evinrude engine from a friend to check it out, he told me it
ran bad. I took off the carb and cleaned it out after that it ran
fine.
Now not long after that during (has been going good that day) a small
boat trip engine started to run rough especially when running at
higher rpm. It's harder to notice it when I try to run it idle.

Hmmm this sorta rules out the idle jet, it's the adjustable one, so
at high rpm the engine is running mostly on the non adjustable main jet.


Coming home I took off the float chamber and noticed a dusthair in the
main jet. Removed it and being convinced that would have caused it
put things back together, also installed a simple fuel filter to
prevent this from happening again. (does this engine has a filter in
the carb?).
But on a fishing trip yesterday after about 5 minutes the engine
started to do the same again.
I checked out the newsgroupes but the answers vary quite a bit.
Since my engine is so simple of construction I suspect a simple answer
for this problem. It's a 2 stroke, 2 cylinder, 4 HP Evinrude from '86
with one carburator.
By the way, I find only one adjusting screw on the carb, where is it
for and how many turns out should it be?

The wet interior you mentioned to Tony tends to indicate lack of
spark in that cyl?? It has 2 coils so when you put the head back on make
sure the coil connections & particularly their earthing is all tickety
boo.

If it persists, disconnect each lead in turn when running (should
then be grounded but .....) & determine if it is losing spark on one cyl
after a little running + heat. If so swap the bits & pieces from cyl to
cyl till the fault follows to the other cyl, to ID the offending
component.

K



Your help is much appreciated,

Jan.
(Honda CB 400N '79)
(Honda CB 750 Sevenfifty '92)
(Yamaha TDM 850 '98)

Hi everyone,

Thanks very much for replying on my questions. It was a couple of days
since I checked for new messages and in the meantime I found a
workshop here in Uppsala (Sweden) where I took the engine after
confirming a serious ignition problem, as suggested here in the n.g.
Had to go there cause I had no flywheel puller. After we took the
flywheel of he suggested me to clean the breaker points using very
fine sandpaper (800-1200). One of the spark plugs was again completely
fouled. He noticed the spark plug where still the original ones, cause
the old paint was still on there, so we bought a new set of those as
well( Denso plugs).
Coming home we cleaned the breaker points and put in the new spark
plugs, when we tested them you could actually hear the spark wich I
couldn't notice testing the old ones and the spark was a lot clearer.

So that night we went out fishing and the engine behaved perfectly
with all the power available. Still a lot of fun with a 4 hp engine!

Still, one little question. Under the cover and bolted to the carb
sits a plastic lever wich is actuated by the throttle and connects to
the butterfly valve in the carb. In it sits a screw (allen key), where
exactly do you use this one for?? Is this for high rpm adjustment? And
how to adjust?

Many thanks,

Jan.

(Honda CB 400N '79)
(Honda CB 750 Sevenfifty '92)
(Yamaha TDM 850 '98)