1999 Yamaha c40tlrx issues.

[Tsbeast1991]

Hey guys, so my motor “was” running good and started to slowly run like crap… I rebuilt the carbs added new plugs, and after a few months I was messing with it checking timing on the cdi and fine tuning the carbs. Somehow I bumped my emergency enrichment knob to “on” and it blew my mind trying to figure out what happened. Lol well i put it back to normal, and upon just messing with it, I tested spark which I have, new plugs were black and very wet, has good compression, but I checked the timing with my timing light and it’s showing what it looks to be like 14 atdc. Manual calls for 7, the cdi pointer points to 7. I plan to adjust the cdi to get the timing correct, and I’m going to get a dial indicator tomorrow to find “TDC”. What sequence do I follow to find TDC other then just turning the flywheel clock wise to find its most extending point? I have read where someone said to turn clock wise, find TDC and mark flywheel. Then turn counter clock wise and mark TDC on flywheel, then the middle of those two marks is the very most TDC point. Any help is appreciated . Could my carbs mayne gotten junked up from running it on emergency enrichment unknowingly and affect timing somehow? I’m sort of new to this. I just know it idled very poorly and when I try to turn my idle adjust screw in it will bog and cut off.. I will post a video of how shitty it runs and what my timing light pointed to. Thanks guys! I also want to make sure the adjustable timing pointer is pointing at the right flywheel marks!https://ibb.co/bvd6R0s

[99yam40]

the flywheel should be marked for TDC for all 3 cylinders.
it helps to mark with white paint to see better while using the light, mark the 7 and 25
you can check the pointer by using a pencil or other wood dowel shoved into the spark plug holes.
even a screw drive will work, but may damage threads or other things if not careful
check it both ways to see what the difference shows

probably will end up with a new CDI like me if reading that far off

[Tsbeast1991]

99yam40 it’s definitely off, because my idle screw is in pretty far and it still idles low lol. There is TDC, tdc2 and tdc3, what are the other two for? Plugs 2 and 3 should show the same reading as 1 correct? I moved the wiper lastnight to 7 atdc and I could tell my idle screw was in real far cause the idle was then pretty high hahaha. I will mess with it some more, and hopefully my cdi linkages can extend enough to set it per light spec. Ordered new plugs aswell. This pic is where my timing sits at idle. It doesn’t look like the timing pointer has ever been moved so I feel good about just basing it off the mark and not checking TDC myself to verify marks cause it seemed to run really good but high when I turned the wiper and the timing light showed 7

[99yam40]

99yam40 it’s definitely off, because my idle screw is in pretty far and it still idles low lol. There is TDC, tdc2 and tdc3, what are the other two for? Plugs 2 and 3 should show the same reading as 1 correct? I moved the wiper lastnight to 7 atdc and I could tell my idle screw was in real far cause the idle was then pretty high hahaha. I will mess with it some more, and hopefully my cdi linkages can extend enough to set it per light spec. Ordered new plugs aswell. This pic is where my timing sits at idle. It doesn’t look like the timing pointer has ever been moved so I feel good about just basing it off the mark and not checking TDC myself to verify marks cause it seemed to run really good but high when I turned the wiper and the timing light showed 7

the other 2 just give you a reference that you can look at with a timing light also to make sure they are hitting correctly too.
your motor has 3 pulser coils telling the plugs when to hit.
makes it easy to see if one or more is not doing what they should be.

When mine did this, I could not get the idle and WOT timing adjusted to where they should be at the same time.
I replaced my CDI, hope you have better luck

[Tsbeast1991]

99yam40 ohh okay! So cylinder 2 should be showing “tdc2” on flywheel and tdc3 for cylinder 3? Sorry it’s been soo long since I’ve had to adjust timing. Or should all 3 show the same @ the 7 degree mark after I adjust the cdi box to get #1 to hit 7 atdc? And thanks man I hope I don’t aswell!!! I see there is a blueish looking cdi box made by cdi that references my part number and then the all black one like what I have now. Both same part number compatibility any difference? I see eBay has a few for around 220ish used that have a 90day warranty.. and then the blueish cdi brand for like 375$ new.

[99yam40]

the blue one is made by CDI El;ectronics & is an aftermarket.
when I bought my Yamaha CDI it was around $400 about 10 years ago if my memory is still OK

Yes adjusting the wiper linkage adjusts timing for all Cylinders.
I have no idea what went wrong on mine or yours but to guess it would be the integrated TPS(throttle position sensor)
guessing it is a variable resister.

did you check price on this web site, click on the Yamaha Parts on top of page for a new Yamaha part?

[Tsbeast1991]

99yam40 yep the new cdi is 549$ Im gonna hope and pray that I can adjust it enough. To see if the wot throttle will match spec can I use my idle throttle lever all the way up whilst it’s in a barrel of water? Or do I have to put it in gear all the way forward? Thanks yam! Also, is there any other components that could be retarding my timing like this? https://www.boats.net/product/yamaha...6c1d361bbc3f54 63D-85540-00-00 Ouch!

[99yam40]

with motor off after you have adjusted the idle timing to 7 degrees, advance the throttle controls normally and mark on the CDI where the wiper pointer is getting to. You can try to adjust that, but I do not remember if you can adjust it different than what is at.(only one threaded linkage to CDI wiper).
this is where I ran into problems if my memory is correct.( WOT timing will be off with no way to correct it)


then disconnect the linkage to wiper, start up motor on muffs or in a bucket while leaving throttle at idle,
advance the wiper on CDI to the mark you made earlier while looking at timing with a timing light.

or you will have to do it while running WOT across the water with a helper to look at timing with light

[Tsbeast1991]

99yam40 very good idea… we’ll I got the timing at 7atdc idle will see what wot is reading, I do believe I tested it for a quick second and it was reading like 29 btdc…. Not sure though! Will have to check it for sure using your method. Hopefully I can adjust it by the retard screw….. also, as for ignition coils, primary resistance is the coil harness plug and ground with a ohm meter and secondary resistance is coil harness plug to the boot wire correct? Plan to check my coils aswell I’m reading primary should read .18 - .24 ohms and secondary should read 2.72 kohm- 3.68 kohm in my manual. Motor runs pretty good at idle now and pilots are 1.5 turns out on each carb, not sure how to adjust those to fine tune the idle. I really need to get a rpm gauge but idk which one to get.