C40TLRX - Scratching my Head, Questioning Manual

[99yam40]

Boscoe read the idle speed adjustment procedure carefully.
how can you take loose the top and middle carbs linkages and then adjust the idle speed on a running motor before closing off the throttle plates and syncing all 3 carbs together?

it reads just like my manual, but it has to be wrong sequence in steps.

OP has not said what his idle or WOT timing is when pointer is on the lines/marks, but mine was about 14 deg ATDC at idle when it should have been 7 Deg. the idle speed adjustment had to be adjusted more to get the proper idle speed and it did not idle well retarded that far.

OP if I remember correctly there is some fluctuation showing up with the light, not steady on the mark

[a387673]

99, ... with you on all those counts:

1- Procedure to set idle in manual appears incorrect.

2- Idle timing with CDI pointer on mark is about 14 ATDC.

3- Idle timing after adjusted to 7 ATDC (throwing other settings, like idle stop screw, throttle, out of spec) jumps around between maybe 5 to 10 ATDC.

I'm going back at it shortly, with a fresh approach, will update afterward.

99, There may not be many who could recall, but calling you "99" makes me think of Maxwell Smart.

[boscoe99]

I take a contrarian view on the SM procedure being incorrect. I have looked at a number of different 40 HP two stroke SM's. They all read the same with respect to the procedure. An older one used to have the idle mixture screw set to a specified value before making the idle speed adjustment, but only that was taken out when the EPA motors were introduced.

The number two carburetor is fixed to the number three. When the number two carburetor is set then the number three is going to follow.

The number three carburetor link is to hold carburetor number two and three at the specified setting.

Then the number one carburetor is linked to the number two carburetor by tightening two screws.

Why not just follow the SM procedure as it is written and see what happens? Without trying to understand it. Remember what our teachers in the past told us (at least me) a million times "don't read anything into the question". Just answer it.

If the motor is running poorly what have you got to lose? Of course do the procedures in the order listed. If the advance lever can't be made to indicate the 7 degrees ATDC position and the 25 degrees BTDC position then there is a different problem that needs to be resolved first.

[99yam40]

99, There may not be many who could recall, but calling you "99" makes me think of Maxwell Smart.

yep was brought up before, I should have been agent 89 I think , but my motor is a 1999.
I remember the show well, and watched it often

[99yam40]

I take a contrarian view on the SM procedure being incorrect. I have looked at a number of different 40 HP two stroke SM's. They all read the same with respect to the procedure. An older one used to have the idle mixture screw set to a specified value before making the idle speed adjustment, but only that was taken out when the EPA motors were introduced.

The number two carburetor is fixed to the number three. When the number two carburetor is set then the number three is going to follow.

The number three carburetor link is to hold carburetor number two and three at the specified setting.

Then the number one carburetor is linked to the number two carburetor by tightening two screws.

Why not just follow the SM procedure as it is written and see what happens? Without trying to understand it. Remember what our teachers in the past told us (at least me) a million times "don't read anything into the question". Just answer it.

If the motor is running poorly what have you got to lose? Of course do the procedures in the order listed. If the advance lever can't be made to indicate the 7 degrees ATDC position and the 25 degrees BTDC position then there is a different problem that needs to be resolved first.

His problem and the one I had was that when you set all of the linkage as listed and the pointers to the marks on CDI the idle timing was off still about 7 deg too much retarded.
If you tried to adjust linkages until Idle timing was correct, you ran out of threads on the linkage and the WOT timing itself was off along with the pointer not aligning with the mark just like the idle timing mark being you had to adjust it because it was giving the wrong timing.

My thoughts were that the TPS that is built into the CDI went bad, so the marks on CDI do not give you what timing it should have while in the idle position.

As for the Idle speed adjustment procedure

The #3 carb throttle plate is activated by the roller pushing on it's linkage and is tied to the #2 linkage.
the #2 and #1 throttle plates are adjustable(to a small degree).
You have to back off the idle speed adjustment screw to allow all of the plates to close completely and sync the top 2 carbs to the bottom one with the plates closed completely.
being the Idle speed adjustment screw you backed off of is on #2 carb,
and you try to crank up and adjust the running motor to get the proper idle speed with the linkages to #1 and #2 loose you will only be running on (con*****ing) the #2 throttle plate with that screw.
the 3 throttle plates not being in sync will not provide a well running motor at Idle RPM. I am not sure you could get it to idle.

I see no way to set the idle speed and then sync the throttle plates as the manual calls for, because you have to back off the speed screw to get them to close to sync them.

Oh yea, from what I remember the #2 throttle plate and #1 each have their own small amount of adjustment with those screws on them that the manual says to loosen before starting the motor and setting the idle speed. the two screws are not just for syncing #1 to the bottom 2.
You make sure #3 is closed completely, then hold pressure to close #2 along with #3 and tighten the screw on #2.
then hold pressure on #1 and 2&3 and tighten screw on #1.
at that point they are synced together and you can adjust the idle speed screw to open each of the throttle plates a little to start and warm up the motor and lastly adjust the actual idle RPM

all of this thinking back and typing makes me want a cold beer,
Is it 5 oclock over there somewhere yet?

[a387673]

Confession

I did have to change the spark plugs again, and the other settings I mentioned on the full retard stop screw and the CDI pointer (TPS) are not in spec versus the manual, and I had to adjust timing settings, but at the end of the day, I had to do a thorough rebuild of the carbs, new inlet seats, etc., to get this engine squared away (I hope). I had been into the carbs several times, and they were clean, no clogged jets, but what I believe happened is that one of these portable EPA tanks that doesn't vent fumes out had swelled up with such pressure that it had compromised my inlet valves/seats/seals. I have been unplugging the tank from the engine, but it was found in this condition when I picked it up at the shop, weeks ago..... been chasing my tail since........... it wasn't straight-forward, cut and dried, as there were other "symptoms" or items out of whack, but I would have been well-served to have torn the carbs all the way down sooner.

(chorus of "told you so's")........ Thanks again for the feedback..... my manual did me no favors on a couple of items...... but learned some more........ gained a couple of diagnostic tools.......

[a387673]

Confession

I did have to change the spark plugs again, and the other settings I mentioned on the full retard stop screw and the CDI pointer (TPS) are not in spec versus the manual, and I had to adjust timing settings, but at the end of the day, I had to do a thorough rebuild of the carbs, new inlet seats, etc., to get this engine squared away (I hope). I had been into the carbs several times, and they were clean, no clogged jets, but what I believe happened is that one of these portable EPA tanks that doesn't vent fumes out had swelled up with such pressure that it had compromised my inlet valves/seats/seals. I have been unplugging the tank from the engine, but it was found in this condition when I picked it up at the shop, weeks ago..... been chasing my tail since........... it wasn't straight-forward, cut and dried, as there were other "symptoms" or items out of whack, but I would have been well-served to have torn the carbs all the way down sooner.

(chorus of "told you so's")........ Thanks again for the feedback..... my manual did me no favors on a couple of items...... but learned some more........ gained a couple of diagnostic tools.......

[99yam40]

are you saying you got the timing set to 7 and 25 properly?

[a387673]

Timing

Yes, by adjusting the full advance stop screw, I set the full throttle timing to 25* BTDC. The CDI pointer was still a little off the mark to get the full retard timing to 7* ATDC (pic).

[99yam40]

So you got the timing light showing 7 and 25 but the pointer was not on the marks, correct?

I could not do that with mine, when I moved the idle stop and linkage to get 7 ATDC the 25 was way off and I could not adjust to get it back.

When I replaced the CDI the marks and timing all agreed with spec

I also found only one of my crankcase re-circulation check valves was checking. I replaced all of them when I replace the crank due to main bearings getting pitted.

My prop now is allowing more than 5500 WOT where before it would not get over that with just me in boat, so I just watch my tach

[a387673]

"So you got the timing light showing 7 and 25 but the pointer was not on the marks, correct?"

Yes, Sir. That's correct.

I hope my idle adjustments and clean carbs will stop the plug fouling trend I observed. Pre-adjustment pics show a relatively clean plug from Cyl # 1, and from the other cylinders, one of the plugs that was apparently fouled enough to cause rough running....... I think the carbs were flooding those two cylinders, but not sure if that aligns with their appearance...... I know I had to put fresh plugs in to get it to run right.

[Tsbeast1991]

I think I have the same thing going on….. I rebuilt my carbs, and lately, it’s ran like crap. However tonight I checked timing and it was like 14 atdc idle… supposed to be 7. It doesn’t idle well at all and will eventually bog down and cut off. How did you go about finding TDC on each cylinder? I may pick up a dial indicator tomorrow to put in the plug holes to find where tdc is, do I just spin the flywheel clock wise till I get tdc? I also want to verify my pointer is accurate because it’s adjustable and I know the previous owner fiddled with some things. I’m also fouling my plugs. Verified spark on all 3 cylinders and compression is good. And same as you said, if u try to. Advance the idle screw it’ll just bog out. Any help is appreciated I’m gonna pick up a dial indicator tomorrow to find TDC but idk what to do, I read where one guy says turn flywheel clock wise, find TDC, then mark flywheel. Turn counter clock wise, find TDC, mark it. Then the center of the two marks is your true TDC? Lol

[Keithbaja]

Happy 4th to all. A seloc is great for starting wood burning stoves and open fire pits. That's about all its good for...I would suggest you get a Yammy service book for your motor and nothing else. Same with Chilton's except they are known to burn a little hotter....,...,..

[a387673]

Beast, I did not verify timing marks on flywheel to TDC with a dial indicator. I think I did a visual check to confirm it was at least in the neighborhood. The flywheel on mine has marks for all 3 cylinders..Good Luck.

[Tsbeast1991]

Yup same here! I got it in timing now. Guess a cdi box is in my future