Boggs down and wants to stall at around 1900 rpm

[toddingalls]

1990 Yamaha 115 hp 2 stroke
Idles good and runs good until I hit about 1900 rpm.
Then it Boggs down and wants to stall after about 1900 rpm.
I cleaned the carbs about 3 months ago.
Good spark, good compression, seems to be getting fuel, primer bulb stays hard... Any ideas?
No alarm sounding.
Goes over 1900 rpm when neutral, just not when in gear.

[99yam40]

Not sure on motor that old, but the newer ones limited RPM by retarding timing while in safe mode. You could monitor timing to see if it is advancing like it should. Also check to make sure the alarm system if functioning properly.

3 months ago is no guarantee of clean carbs, if the compression is good right now,and spark is good at Problem RPM on all cylinders(inductive timing light will show this), along with the timing, then it is time to clean carbs again

[toddingalls]

Thanks for the reply.
Tore into the carbs today.
I think I found the problem.
Cracked and torn rubber rings on 3 of the jets. (at least I think those are the jets)
What do you guys think? Would this cause the symtoms I am having?
Not sure what the actual name for the part that I need to order though.
See pic.
These were rebuilt about 3 months ago. i think I may have gotten the wrong size rubber rings for my carbs.

[99yam40]

my thoughts are that you did not use Yamaha parts the last time and the fuel ate them up

[toddingalls]

Yes I agree. Thanks for your reply.
Hard to believe that stores would sell o-rings that will start to disolve in fuel after only 3 months! Will go with yamaha orings this time if I can find them.
I think some pieces of the rubber were blocking the fuel flow... do you agree? I guess there's one way to find out for sure.

[99yam40]

Agreed, it does not take much to plug things up

[toddingalls]

Well back to the drawing board (Dang it!)
Replaced the shot carb o-rings and still have the same problem.
What's next?
Runs fine on muffs, and will go over 1900 rpm on muffs too. But take her out and test under load and she will still bogg down at almost exactly 1900 rpm.
What else could be causing this?
Fuel related? Or timing related? Or.... ?

[mitch]

check your fuel pump for holes in diaphram

[99yam40]

like I said before compression,spark, and timing are easy to test.
If all is good, then you are left with fuel

[toddingalls]

Like I said in original post... tested compression spark and fuel.
Will test timing again I guess. Fuel pump looks okay.

[jb123]

if those orings look like that there are most likely pieces clogging carbs..... youll get real good at cleaning them by the time it runs normal
you can also run on an aux tank ball and hose to check for a supply side issue... what is the cond of the ball when it bogs ??
do you still have the quick disconnect @ motor ?? if so, delete it
bogging under load is the classic symtoms of dirty carbs

[toddingalls]

Well looks like I had 2 problems.... bad CDI unit and rotten o-rings on the main jets.
Carbs are clean, and installed fresh o-rings.
I tried to put the elect meter on the CDI to confirm, but I got all confused (going by the clymer manual). I know... I need to order the Yamaha manual. Is there an easy way to test the CDI to confirm?... I am not quite grasping the Clymer manuals description of how to test the CDI. I will also run a search 'testing the CDI'.

[99yam40]

What makes you think the cdi is bad?

Did the timing advance like it should while problem is occurring?

Does you alarm sound when tested?

are you loosing spark at higher RPMs?

Testing CDI consists of taking input and out put vlotages and comparing them to the specs in the manual.What parts do you not understand?
Are you using the proper peak reading volt meter or a DVA adapter to take voltage readings like the manuals say?

[toddingalls]

Timing is advancing okay.
No alarm going off.
Interitent spark on 1 and 3. Coils test okay.
I just have an ohm meter. Sounds like I will have to get a peak reading volt meter or a DVA adapter to properly test the CDI.
My confusion was where exactly to hook up the leads of the multi-meter and what setting to use on my multi-meter. But it sounds like I need the DVA adapter first anyway.

[99yam40]

Timing is advancing okay. Did you see this while the problem was occurring? You need to be looking at the timing while the problem is occurring.

No alarm going off. Did the alarm sound when testing the alarm or did you even test to see if it does sound?

Interitent spark on 1 and 3. Coils test okay. how did you see the intermittent spark?Timing light or something else?

sorry Not sure if you are giving enough info so I ask more questions