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

[99yam40]

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

The manual shows the linkage is correct for the C40TLRX.

 

[Grew2maxum]

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

My CDI box looks the same except the timing marks are on the arched part where yours are on the box. Yamaha must have changed it with the later/different models. They list different CDI part#s for the 2 motors. Mine is running great with the timing set with a light ignoring the box marks.

 

[99yam40]

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

Did you ever check to see what the idle timing was with the light when the pointer was at the 7 degree ATDC idle mark?
I have yet to find someone that has said they had and their idle timing was off like mine is.

 

[Grew2maxum]

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

Here's what i did with my 89 PRO50:
The timing specs are 4-6 ATDC at full retard (idle), and 24-26 BTDC at full advance (WOT).
Marked flywheel with whiteout type correction fluid at cyl1, 4-6ATDC and 24-26BTDC to make the marks easy to see under the timing light.
Running and warmed up on a garden hose adapter with timing light hooked to cylinder one, I adjusted the full retard screw untill the light indicated the 4-6ATDC mark. The full retard adjust screw on mine at this point was almost at it's full extended position. I then marked the CDI box at this pointer position. (It was a good 1/8" from the original mark). I then shut off engine and removed the snap on link from the CDI box pointer allowing it to be moved independant of the throttle. With throttle untouched (still at idle position) I started the engine again with the CDI pointer set to the new idle retard mark I then got back on the timing light and slowly adjusted the CDI pointer until the light indicated my 24-26BTDC mark on the flywheel (engine speed still at idle without touching throttle controls). The idle increases with the advanced timing but not to an unreasonable level. I did not run the engine at this advanced idle for more time than it took to set the pointer (this is easily and quickly done). I then shut off the engine and marked the CDI box at this new full advance pointer position. I then adjusted and re-attached the link so the pointer was at the newly marked full advance mark on the CDI box with the throttle arm against the full advance stop. As there is no mechanical advance dependant on engine rpm this works. I then lake tested the boat with a driver at WOT and the timing mark remained at the 24-26ATDC mark. Sounds like an strange method and i'm sure there will be feedback but in reality it works and the motor now runs great.
PS: on mine I did have to slightly advance the full retard idle timing just a bit (extend the screw 1/2 turn) to get a bit better idle at cold startup. This does not affect the WOT throttle timing.

 

[Grew2maxum]

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

In my last post a few minutes ago near the end of my paragraph I incorrectly put 24-26ATDC where it should have been BTDC as earlier in the post.

 

[99yam40]

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

I did that also but then someone said to not worry about the idle timing just the WOT so I put the Idle timing back on the original mark because there was not much thread left on the link with it adjusted all the way back to the 7 Degrees ATDC by timing light.

What did your idle timing look like with the pointer on the idle mark on the CDI unit before you adjusted it? Was it real far off or just a few degrees?
Mine was 14 degrees instead of the 7 it was supposed to be.

Let me know if changing your CDI box brings your timing and timing marks back to where they are suppose to be.

 

[99yam40]

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

Here is a sketch of a DVA I located out on the web, does it look like one anyone has used before?
Are they really this simple of a device?
do yo think this will this get a reading close enough to factory specs to troubleshoot the ignition system on CDI units?

 

[tal]

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

Grew2maxum,

I just did the same thing you did today, well almost. I actually was able to test mine at 4500rpms or WOT, whichever you prefer, in a test tank I setup at home. I used an old horse trough and placed boards on it with weight while I held the rpms long enough to check. This of course took 2 people cause things happen fast, water would still fly out and steering wheel would turn, etc.

Anyhow, I realized that (on the pro 50) once your throttle position hits a certain point, it is already at full advance, usually before WOT. So in a sense, it doesn't have to be fully WOT. If you observe the CDI pointer when moving the throttle, which rides on the large plastic foot, it reaches full timing before WOT.

I did attempt to do as you said, and adjust that full advance at idle (since the Seloc wasn't quite clear as to idle or 4500rpms) but it didn't feel right revving it up like that. I ended up blowing water out the old trough about 4 times before I got it all right.

I need to take it to the lake and test now, but it seems to run a hell of alot better when I shower down on it. It use to stumble and stammer around. Now it seems to get quick. FWIW, I've been messing with the timing and carbs on this thing for around 4 years on and off..I think I'm much closer now though. My full retard screw is like one thread of fully bottoming out along with my CDI pointer being to it's full extent (screwed on by 3 threads) as well. I can't wait to see what it does in the water now.

 

[99yam40]

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

well it seems no one will post what there timing was at idle or WOT before trying to adjust it , so it does not make any thing when reading this thread.
it may help others if they would give this info

 

[tal]

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

99yam40,

I do have timing info before adjustment. On my pro 50, the timing at idle was 2* ATDC. I then checked the WOT and it was all the way up to 32* BTDC.

I'm pretty sure the large advance curve was causing my problems. Funny thing is though, it seemed to idle really well at 2*, almost better than what the book calls for. After setting my idle timing I readjusted the carb mixture screws and idle speed screw.

 

[99yam40]

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

so, it seems your idle timing was only off 2 degrees but the WOT timing was off 6-7 degrees. Most manuals call for+ or- 4 so that does not seen that far out. But it is not good to go over on the WOT.
THANKS FOR THE INFO

 

[tal]

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

Ok, just an update, but it seems the idle and WOT timing setting does not affect the way my powerhead performs. I have what appears to be intermittent misfire from idle or just above to 4500 rpms or so. WOT seems to run without a lick, but bad thing is, I use alot of gas at full throttle and it sucks running the little motor that hard all the time.

One thing I did notice after running the boat this morning and letting it sit until evening fish, when I went to start the engine it acted as if it were seized. I removed all plugs and turned the engine over to find that #3 was full of fuel?

How does only one cylinder fill full of fuel sitting for 7 hours? I have been through these carbs I don't know how many time, dipped, rebuilt and regasketed..I have noticed that the steel yamaha tanks build pressure from time-to-time, but if everything is right it shouldn't pull fuel through the carb?

Hate to hijack the thread but I'm about done with this yamaha...any thoughts to save it before I make a shooting target out of it?

 

[BadBowtie4wd]

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

Wow I am glad that I am not the only one with this exact problem. I have a 99 c40TLRX that was converted to a tiller.

Just above idle it will stay running, at idle it sneezes (misses?) and dies. Seems like WOT it run fine on the water.

There for a while I could only get the motor to start while in enriched mode (open).

Have cleaned the carbs, replacing the gaskets from carbs to intake in next.

Any one else got a fix? I have always had Mercury's, I may go back to them.......

 

[99yam40]

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

Ok, just an update, but it seems the idle and WOT timing setting does not affect the way my powerhead performs. I have what appears to be intermittent misfire from idle or just above to 4500 rpms or so. WOT seems to run without a lick, but bad thing is, I use alot of gas at full throttle and it sucks running the little motor that hard all the time.

One thing I did notice after running the boat this morning and letting it sit until evening fish, when I went to start the engine it acted as if it were seized. I removed all plugs and turned the engine over to find that #3 was full of fuel?

How does only one cylinder fill full of fuel sitting for 7 hours? I have been through these carbs I don't know how many time, dipped, rebuilt and regasketed..I have noticed that the steel yamaha tanks build pressure from time-to-time, but if everything is right it shouldn't pull fuel through the carb?
Hate to hijack the thread but I'm about done with this yamaha...any thoughts to save it before I make a shooting target out of it?

More than likely you have a bad fuel pump letting fuel into #3 through the pulse port and your tank should have a vent to keep it from pressuring up, check to make sure it is working

 

[99yam40]

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

Wow I am glad that I am not the only one with this exact problem. I have a 99 c40TLRX that was converted to a tiller.

Just above idle it will stay running, at idle it sneezes (misses?) and dies. Seems like WOT it run fine on the water.

There for a while I could only get the motor to start while in enriched mode (open).

Have cleaned the carbs, replacing the gaskets from carbs to intake in next.

Any one else got a fix? I have always had Mercury's, I may go back to them.......

Sounds like your idle jets or circuits are still plugged or you have not done the sync and link like the manual shows along with adjusting the carbs.
Also the prime start circuit must be plugged if you have to switch it to open to make it start.
How is the timing at idle and WOT? That is what this thread is about.
Start a new thread,do not just throw something on the end of a old thread

 

[BadBowtie4wd]

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

Sounds like your idle jets or circuits are still plugged or you have not done the sync and link like the manual shows along with adjusting the carbs.
Also the prime start circuit must be plugged if you have to switch it to open to make it start.
How is the timing at idle and WOT? That is what this thread is about.
Start a new thread,do not just throw something on the end of a old thread

Thanks, Will do.