Went from 5200 rpms to 4800. Issue?

[LEAD PIPE]

1995 150 TRXT
I did a lot of work on this motor and it's running better than it has in years. I noticed that even when it was running rough it would top out at 5200. Now sit tops out at 4800. I don't mind, I usually keep it at 4200. I was just wondering if this was an indication of a problem. All the work I did revolved around fuel and oil. Carbs were removed 3 times for cleaning and rebuild. Do I need to make an adjustment somewhere?

[LEAD PIPE]

When I adjusted the needle screws on the carbs, the manual said 1 turn out, + or - 1/4 turn. I set it at 1 turn. If I opened them another 1/4 turn would that help? Thanks

[erniefish]

Those should not effect the high speed

[LEAD PIPE]

Thanks for the response, any ideas?

[rodbolt17]

first idea?
test spark.
test compression.
fix the fuel system.
preferably before you detonate a piston.

[LEAD PIPE]

I bought a spark tester and everything looked good. Compression was in range and very close together. Everything that can be done to the fiuel system has been done. It runs great. It lost RPMs at the top end. Even when it was running bad I had higher top end RPMs. Everything on/in the engine is better so it must be an adjustment someplace? That seems like the most logical to me. Or should I treat this as a new problem??? Thanks

[rodbolt17]

that six carb smart system has whooped arse on so many trained techs.
you don't stand a chance.
I will tell you you can run the motor with the air boxes off and squirt premix fuel into each carb.
if squiting a bit of premixed fuel makes a difference your on the right track.
remember its an X motor.
a bad T stat on the stbd head will do stupid stuff.

[LEAD PIPE]

Sorry, if I squarted pre mix in the carbs how would I know the difference, like I said the engine runs and sounds great. I just lost RPMs at the top end. I found a tech somewhat nearby, yes he has the certs. But he is 5 weeks back logged. I'm not against bringing it to him. I have a young lad pulling my arm to take him fishing.
The t stat interests me, I haven't considered a water issue. That's something I can check.

Again sorry, what's an x motor?
Thanks for taking the time to respond

[rodbolt17]

the X designates a cross flow motor.
means the top carb on the stbd side feeds the top port cylinder.
and so on and so on.

[TownsendsFJR1300]

If you can do a WOT throttle run (for a short period of time), then kill the engine and anchor up.

Let it cool down and pull the spark plugs. See if they all look the same..

BTW, running a very heavy dose (2-3x's the dose) of Yamaha's "RingFree" can ONLY help(and certainly won't hurt anything).

Its not cheap but works very, very well. Cleans the fuel system and top end..

Regular use of it keeps these issues from happening(fuel issues) along with fuel stabilizer..

[LEAD PIPE]

I have added ring free every time I fuel up since buying the motor in 1999. I can't say if it helps or not but someone I trust told me to do it, so I do. Could a restriction in a fuel line cause this problem? I would rather not tear everything down, but I was thinking maybe a kink in the line someplace. On the spark plug test what would I be looking for? I may have to go out on the old plugs, about a 2 mile run, before I can open it up. I can go out, install new plugs then run it WOT and see what they look like.

[LEAD PIPE]

the X designates a cross flow motor.
means the top carb on the stbd side feeds the top port cylinder.
and so on and so on.

Got it, thanks!