Rodbolt, I could use your advice on a C40TLRX timing problem

99yam40 · Jun 15, 2009

I have had a post out there for a few days C40TLRX yamaha timing problem but have not had any luck getting any help, could you look at it and give me a reply.

2/12/2010
Just to let others know what I did to fix my problems that you will read about in this thread, I am editing this on the first post for your ease of reading.

I ended up changing the CDI and that fixed the timing problem and allowed me to get a lot better idling because I was able to get the proper RPMs with out having to open the butterflies as much.
I had to change the main jets to eliminate the high speed miss, because someone before me decided to drill out the old ones to get more fuel into the motor.

I hope this will help others as they do searches for problems they are having.When ever you buy used equipment you can never rule out anything as you troubleshoot because you never know what others have done.

rodbolt · Jun 16, 2009

Re: Rodbolt, I could use your advice on a C40TLRX timing problem

bump that post, timing is pretty much fixed on that motor.

99yam40 · Jun 16, 2009

Re: Rodbolt, I could use your advice on a C40TLRX timing problem

Rodbolt,
I checked the other post but did not see your reply.
Maybe you are still writing.
So, are you saying that the CDI unit is the only thing that will change the timing?

99yam40 · Jun 17, 2009

Re: Rodbolt, I could use your advice on a C40TLRX timing problem

Rodbolt,
I still do not see a reply on my original post for the timing problem.
If you sent one maybe something happened to your reply when you sent it, because it is not on the post.
I tried to send you a PM but yours was full, you need to purge your PM folder.

rodbolt · Jun 17, 2009

Re: Rodbolt, I could use your advice on a C40TLRX timing problem

re type your issue then.
your motor uses 3 pulsers and should have a link rod from the carb linkage to the CDI.
dont PM me with a tech question unless I specifically ask as I rarely check PM's.
usually its a mod or a friend ragging on me

.

99yam40 · Jun 17, 2009

Re: Rodbolt, I could use your advice on a C40TLRX timing problem

I set the throttle link like the manual said to and the pointer is pointing at 7 degrees ATDC in neutral low idle and 25 BTDC opened up but the actual timing is over 10 degrees ATDC at idle( maybe as much as 14 ATDC, no marks past 10) when checked with a timing light.

I am able to move the pointer to the 25 degree mark with the linkage disconnected and the motor running and the timing light is at the 25 degree BTDC mark on the flywheel, but at idle and the pointer at 7 degrees the timing light shows over 12 degrees ATDC.

I adjusted the retard stop screw to about 25mm instead of 20 mm just to get the timing to 10 ATDC instead of 14 ATDC and help with the idling. This still allowed for the TSP to move the timing a small amount before moving the butterflies
Checking the WOT timing with timing light showed about 28 BTDC, so I adjusted the advance stop screw to get it back to 25.

The motor still has some random RPM drops from time to time mostly 3/4 to WOT, but it is not due to timing change or fluctuations because I watched the timing while the RPMs were moving around and it stayed steady. I am only going by feel and sound, I do not have a tac.

Rodbolt can you give me your advice about what could cause the timing to be off from what the pointer on the CDI unit is set at?
Have you seen a timing problem like this before?

rodbolt · Jun 17, 2009

Re: Rodbolt, I could use your advice on a C40TLRX timing problem

if the timing isnt changing on all 3 cylinders, while the RPM is fluctuating I would suspect a fuel issue.
if your flywheel isnt indexed for cylinders 2 and 3 simply make marks the same spacing as for number 1 on 2 and 3 and check them to.
if timing on all 3 cyl remains stable hunt for fuel issues.

99yam40 · Jun 17, 2009

Re: Rodbolt, I could use your advice on a C40TLRX timing problem

I will check the other cylinders timing, There are marks on the flywheel. I made sure the marks lined up with the pistons hitting TDC
but why is the timing not at 7 Degrees ATDC when the pointer is saying it is or at least the pointer is at the 7 mark. This is causing major idling problems. I will work on the possible fuel issues once I get the timing where it is suppose to be.

rodbolt · Jun 17, 2009

Re: Rodbolt, I could use your advice on a C40TLRX timing problem

beats me.
other than its not the first time I have seen the mechanical marks not correct when dynamically checking.
first verify the mecanical relationship with #1 at TDC with the pointer, then do 2 and 3.
you will need a dial indicator to do this or with a long phillips and some flywheel rocking you can get close.

99yam40 · Jun 17, 2009

Re: Rodbolt, I could use your advice on a C40TLRX timing problem

I already checked that. All three pistons reaching TDC coincide with their marks.

Just checked the timing on all 3 cylinders at idle and the all show the same timing. ( all looked the same distance from the TDC mark).I then removed the linkage and adjusted the pointer until I got the timing light on #1 to TDC and then checked the other two cylinders and they both were on TDC marks for there cylinder also.
Could it be the CDI unit?
or is there anything else that would affect the timing?

It will run like this but does not idle as well as it should.
I do not know if it will cause problems with the timing not being proportional to the butterflies as it is coming up to RPM. I think it will be retarded a little more than it should be coming from idle which will affect the power until it reaches the 25 BTDC

Don S · Jun 17, 2009

Re: Rodbolt, I could use your advice on a C40TLRX timing problem

Pull the flywheel and check to see if the woodruff key is sheared or stepped.

99yam40 · Jun 17, 2009

Re: Rodbolt, I could use your advice on a C40TLRX timing problem

The timing looks good on the high end. If the key was a problem I think that the timing shift would affect the top side also. but I will check it out

JustJason · Jun 17, 2009

Re: Rodbolt, I could use your advice on a C40TLRX timing problem

If your WOT timing is correct then its probably not the flywheel. What kind of timing light you using? If it's not a good one try another one if you can.

99yam40 · Jun 17, 2009

Re: Rodbolt, I could use your advice on a C40TLRX timing problem

Snap-On timing light.
Always work fine back when I was automotive mechanic.

I bought the boat used last year and it has been running great, but about 3 weeks ago it started giving me some problems with surging and I went through the carbs, filter, and looked at the fuel pump diaphragms fuel lines and connections. Did not make a difference.
I had a poling platform Installed on the aluminum boat and the next time I took it out it started acting up about 10 minutes after launch. It idled and ran good until that point but then did not want to idle well anymore and still had a little surging on the high end.

JustJason · Jun 17, 2009

Re: Rodbolt, I could use your advice on a C40TLRX timing problem

Have you done this specifically.....?

http://forums.iboats.com/showthread.php?t=283269

99yam40 · Jun 17, 2009

Re: Rodbolt, I could use your advice on a C40TLRX timing problem

No, I have not tried all of this, but I will see if I can find the gauges needed. I had some at one time but have not seen them in years.
Are you telling me not to worry about the timing being so far off at idle?

JustJason · Jun 17, 2009

Re: Rodbolt, I could use your advice on a C40TLRX timing problem

you can get the gauge at sears... and all the fittings and lines at home depot.
I just had to read through your other threads.... it be nice if they were all merged into 1.
You should be able to set your base timing without even running the engine... only with cranking. Its only a mechanical adjustment.
Yank all your plugs, put all the leads on a spark board and set it that way... just cranking.
Did you happen to mess with the pack wiring at all and maybe get the 1 and 2 triggers backwards?
A lean misfire will cause all sorts of funny things. And from your previous post of a misfire at 3/4+ throttle i'd definitely do the fuel test. Once you have the tools it takes all of 10 minutes to do.

99yam40 · Jun 17, 2009

Re: Rodbolt, I could use your advice on a C40TLRX timing problem

I have not messed with any wiring at all. Just checked the timing with the timing light after having trouble with the idling and moved the linkage a little.

I am not sure that checking timing on a prime start motor with the advancing from the CDI will work when only cranking the motor over without starting and letting it warn up first. It is controlled by the cdi at start up and advances the timing until the temp. switch tells it it is up to temp. and even starts after that it advances the timing for a short period during that time.
The old mechanical timing was strait forward but not this newer stuff .
I know I need to address the high speed RPM drop but I was trying to address the timing problem before I fell back to that.

99yam40 · Jun 18, 2009

Re: Rodbolt, I could use your advice on a C40TLRX timing problem

Is there any info on what the timing should be during cold start along with RPM?
This is reading 4 Degrees BTDC for a short while (tempatures here in the 90's so it does not take long to warm up) them drops back to 10 ATDC with the retard stop screw adjusted to 25 MM instead of the 20mm called for in the manual.
I would think that this info should be in writting somewhere showing timing and RPM or throttle position. Even something about how far the CDI advances and retards the timing under certin conditions would be very helpful during troubleshooting.
If anyone has seen any info like this please chime in.

JustJason · Jun 18, 2009

Re: Rodbolt, I could use your advice on a C40TLRX timing problem

ahh.. i didn't realize the cdi advaced the timing... i thought it was just mechanical.
Count me out of this one then... sorry i couldn't help.

Rodbolt, I could use your advice on a C40TLRX timing problem

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