2000 C40TLRY 40 hp 2 stroke

[swamphox]

I have a couple issues with this motor that ran well 2 years ago. New carb tuned by shop that installed it, ran very well. A year later I ran it and got water in the gas. Shop fixed it and stored it after not running it all summer. Started it this summer and ran well with a hose hookup. Then it quickly developed an idling issue. Gas is new with a fuel/water separator. Sart it up and in about 15-20 seconds it conks out, or idle increases or it really decreases rpm and then conks out. I am very mechanically inclined but for some reason I have little GOOD luck with 2 stroke motors. Where is a good place to start as it seems it may be an electrical issue with what I have read here and other forums. I have read that the CDI may be bad but that is a $400 part and I would like to see if I can determine somehow as to the wellness of that part before I replace it. The other issue is with this motor and the telltale water indicator. Is there something wrong with the design of these impellers that would prohibit water circulation?

 

[brodmann]

When was the water pump last replaced? I replace mine every spring. Go to an auto parts store and get a spark gap tester. Under $20. Set the gap to about 3/8" and try it on all cylinders. If the spark can jump that gap, than your ignition system is fine. If the spark is fine then you've got a clogged jet in the carb, or a fuel delivery of some type. To check for fuel delivery problems try choking it when it starts acting up. If it revs up when you press the key in, then it's starving for gas.

 

[99yam40]

measuring peak voltages into and out of the CDI is the best way to see if it is working as it should.
your service manual has all the specs.

a timing light hooked up to the plug wires will show if timing is where it should be along with if there is current heading to the spark plugs.

I lost #2 piston/rings this past wed on mu C40TLRX, so I man looking for a motor like yours if you decide to get rid of it

 

[swamphox]

The motor is like new with a brand new carb(3). The water pump issue is strange. I burned up three impellers on this motor trying to figure it out before I brought it to a mechanic. The waterpump thing is mystifying. The water system is clear but it does not PUMP the water like it should or at all at times. I had the carbs checked out even though they are brand new OEM. The mechanic said it is a known issue. He said you need to raise and lower the motor by trimming, it seems to work but even when it does get going the stream is not consistant, even when the thermostat is removed. Of course when I bring to the mechanic it works like it should.

 

[swamphox]

I don't have a service manual. I guess I am going to have to get one. Best price I could find is about 95 delivered. The last time the motor ran and it ran well at the shop with the mechanic was last year. I ran it out of fuel and just started it the other day. Started right up and ran well but took more time than I like to see water out of the telltale. After a minute or so it started run poorly. Inconsistent with rpms, conking out, just not running well.

 

[99yam40]

did you drain the carb bowls after running the fuel out before putting away?
running until motor dies still leaves fuel in the bowls, then the gas evaperates, but leaves oil and gas residue in there that will plug up jets/passages.
This motor does not have a choke,
At start up the prime start system adds extra fuel and the timing is changed also.
once warmed up the timing changes again and the extra fuel is turned off.
if the pilot jets/passages are plugged or restricted the motor will not run well.
as I said before use a timing light to see what the timing is doing and if it is in spec.

you may have scale or other debris in the cooling passages plugging off circulation or even the tell tale.
Have you tried blowing some compressed air up the TT while the motor is idling with water to it to see if that clears out the system and gets the TT flowing better?

hove you pulled the stat and tested it for proper opening temps in a pot of water ?
what do the passages look like around the stat?

the block needs to fill up before much pressure is put on the TT.
the TT indicates the water pump is pumping, but does not indicate if water is flowing properly thru the motor itself.

 

[swamphox]

The stat is tested and works and I did run it without it and still there were problems. I know to run for very short periods until I see TT. I was going to ask about a choke, this model, no choke. I think I lost my timing light 20+ years ago and I have mostly had four stroke yamaha since and it never had a problem for its first 15 years.

 

[swamphox]

I will perform the test suggested and repost when I have completed them. thanks

 

[99yam40]

buy, beg , borrow, or rent a timing light to see what the CDI is doing to the timing.
I had a problem with mine when I got it in 2008, turns out I could not get the timing at idle to hit spec without messing with the WOT timing. so I bought a new CDI and that took care of the timing problem.

 

[swamphox]

I won an old induction timing light on ebay for about $25. Hope to get it tomorrow.