1996 v76x 225 txru missing off idle

[mink30413]

I have cleaned carbs ,replaced fuel pumps, checked and rechecked tps settings,link and sync per yamaha manual,checked pulsar coil and stator output with peak voltage adapter all within specs, swapped cdi and coils with port engine, compression between 105-110, it seems like a ignition miss checked the plug caps and wires all within specs,
The motor seems to run better at wot than at half throttle, it loses 2-300 rpms like a ignition miss, the last time I ran it at the river all 6 plugs looked wet, no visible leaks at fuel solenoids. Any help would be appreciated

[TownsendsFJR1300]

Seems you covered most everything BUT the spark plugs themselves. An old, fouling plug will cause major issues (loosing an entire cylinder from working).

Also, do you have an inductive timing light you can attach over each plug wire and check as the engines running?


Have you checked/adjusted the air screws in the carbs(part #25) ?:

http://www.boats.net/parts/search/Ya...TOR/parts.html


.

[mink30413]

I have adjusted the air screws and I also swapped plugs with the port engine and saw no change, I do have a timing light I will give that a shot this evening.

[99yam40]

timing light with RPM reading capability may be the best way to see if one of the plugs is missing spark,

but any timing light will show if timing is in spec or varying

My guess would be carbs still have a problem if spark and timing is good

[TownsendsFJR1300]

All the plugs being somewhat "wet", I'd probably be double checking to see the idle air screws are within spec..

[mink30413]

I've about worn the screws out taking the carbs apart, I adjusted the air screws out 1 1/4 turns, if I go in is that richer or leaner, I mean is it adding fuel or taking away air?
I also swapped all 6 carbs with the other engine with no change

[TownsendsFJR1300]

I know you posted you replaced the fuel pumps. Just for S&G's, you might check them for any leakage(ie most you pump the primer bulb with the pumps off and check for leaks).

I don't know if yours is the same procedure.

Re air screws, I believe(and may be wrong), turned them in(clockwise), limits fuel fuel flow, leaning them out. There's usually ONLY maybe 1/4 turn adjustment allowed..

Not couting the air adjustment screw, all jets inside are snugged down correct? None left loose?


Question, is the engine NEW to YOU? IE, PO could have dinked with the carbs, put in bigger jets, etc.

[mink30413]

It is new to me, I guess I should have started farther back, we got the boat after it had been sitting up for a long time, the carbs were pretty nasty the first time I went through them, I may need to check the jet sizes because I'm not sure,

[TownsendsFJR1300]

Folks do re-jet for what ever reason, allegedly more horsepower, etc...

It is also possible to drill the jets out BUT the original size # will still be stamped on it, so be aware..

There's some testing you can do but do some research on reading spark plugs.

IE, if the mid and top end of the RPM range, the engine runs fine, their (the main jet) is probably good.

To verify this, some fresh plugs and a hard run WOT for a couple of minutes, then IMMEDIATE SHUT DOWN (anchor up somewhere). Let the engine cool down and pull the plugs. Have a print out of a good burning spark plug to compare it to. Likely, its probably ok.

Do the same at lower RPMs, maybe 1/4 to 1/3 throttle or where its the worst. Kill the engine immediately and check the plugs. If their black with soot, the idle jets are too rich (if you ruled out the fuel pump(s) )

**I'm assuming the oil pump is functioning properly and adjusted properly.**

[mink30413]

I've adjusted the oil rod like the manual says,but with that being said is it possible for the oil pump to have too much output with it properly adjusted?
I have had that thought before.
I've been spending too much time at work I havnt had a opportunity to get to work on it

[TownsendsFJR1300]

I've adjusted the oil rod like the manual says,but with that being said is it possible for the oil pump to have too much output with it properly adjusted?
I have had that thought before.
t

I don't know the answer to that... I haven't ever read it on this forum.

Someone else will have to chime in.

Does it smoke (blue-oil) more now at idle, off idle, where your issues are?

[mink30413]

It doesn't smoke excessively at any time, other than first starting

[TownsendsFJR1300]

Start up smoke is normal.

What's you WOT RPMs?

If its a bit on the low side, not running normally, responsive, etc, possibly choke/cold start system staying partially on?? That'd cause richness but would also affect the upper RPM range.

Looking at the carb parts fisch: http://www.boats.net/parts/search/Ya...TOR/parts.html

looks like choke is 6 solenoids, part #34 (maybe?).. Part #17 is the slow speed jets..

Can you video record and post the engine running crappy and WOT and note the highest RPM's (normal trim), you can get out of the engine?