Cannot rev past 6500 RPM under load

[Radioguylogs]

I into tried to think how it could happen re-building carbs, and I wondered if the mechanic accidentally dropped a small screw or bolt into the intake.

 

[baceti]

Hello from Bulgaria. First of all, I apologize for my bad English - I use google translate I read the thread and decided to give some direction because I understand that your problem has a point of contact with my problem This summer I started building brand new instruments for my V-Max ( odometer, tachometer, etc.). My idea was to dismantle the original ones, but without doing interventions on the motor. I.e. at any moment to be able to return the motorcycle to factory condition. So in this line of thoughts, actions and the fact that my bike is the worst possible modification: 3UF - I ran into the same problem as you. The only difference is that everything works fine for me, but when I changed the odometer I got a limit of 6500rpm. I researched a bit...it turned out that the speedlimiter in the odometer is the problem. I did the "reverse engeneering" and now have a device replacing the blunt limiter. As far as I understand, you have a CDI from just such a motorcycle (3UF) - for Japan or France. They are limited and the CDI - it receives a signal from the odometer - at a speed between 10 and 180km/h the restriction is not active, but if you go out of this interval the CDI deactivates 2 of the cylinders at over 6500rpm. I am currently trying to find the pinout of my CDI. I live far away from where I keep the motorcycle and therefore I "work" on the matter only on the Internet So far I can find almost nothing about this cdi (3uF). The only thing I found out is that those pins that are missing in your installation (but there are them on the CDI) are precisely for the limiter. Hope I was helpful. Greetings.

 

[n00bzi11a]

Hello from Bulgaria. First of all, I apologize for my bad English - I use google translate I read the thread and decided to give some direction because I understand that your problem has a point of contact with my problem This summer I started building brand new instruments for my V-Max ( odometer, tachometer, etc.). My idea was to dismantle the original ones, but without doing interventions on the motor. I.e. at any moment to be able to return the motorcycle to factory condition. So in this line of thoughts, actions and the fact that my bike is the worst possible modification: 3UF - I ran into the same problem as you. The only difference is that everything works fine for me, but when I changed the odometer I got a limit of 6500rpm. I researched a bit...it turned out that the speedlimiter in the odometer is the problem. I did the "reverse engeneering" and now have a device replacing the blunt limiter. As far as I understand, you have a CDI from just such a motorcycle (3UF) - for Japan or France. They are limited and the CDI - it receives a signal from the odometer - at a speed between 10 and 180km/h the restriction is not active, but if you go out of this interval the CDI deactivates 2 of the cylinders at over 6500rpm. I am currently trying to find the pinout of my CDI. I live far away from where I keep the motorcycle and therefore I "work" on the matter only on the Internet So far I can find almost nothing about this cdi (3uF). The only thing I found out is that those pins that are missing in your installation (but there are them on the CDI) are precisely for the limiter. Hope I was helpful. Greetings.

Hi baceti.
It's not my case, since the engine had this behaviour in almost every gear, well bellow 180 km/h.
Hell, I could only reach 160, 170 km/hIf I really insisted.

In the end the engine seized after being worked on by an recommended mechanic...

 

[baceti]

That's exactly what I mean. You have a limit on each gear because (I assume) your speedometer is not one of the limited ones, and your CDI is for a limited model. It "thinks" that you are always above 180 km/h, because the board inside the speedometer is missing, and that's why it cuts at 6500 rpm. This is what the limiter in the speedometer looks like:

I guess you are missing this.

In the end the engine seized after being worked on by an recommended mechanic...

Sorry about that

 

[Yvonne Blaz]

Such a sorry sad reality to face . Yamaha builds the best motorcycle on the planet and then we have to read that certain governments that should allow their people to enjoy everything life has to offer , goes and puts limits on the finest piece of machinery ever sold in the world . Probably under some disguise of freedom !

 

[jaws]

Seems like 6500 rpm are cursed for some bikes.
Our 3uf suffers from a similarily strange problem.
Bike runs great most of the time except the following:
Let's say I'm cruising at 4k rpm in 3rd gear, I have to overtake a car so I downshift to 2nd and twist the throttle...engine revs happilly till 6-6.5k rpms and then bogs and won't pass 7k rpm. Now, standing at the red light, waiting to go green... I start moving, shift to 2nd and going wot, the bike gets mad and revs like crazy....until cruising...and the problem comes back.
- Carbs cleaned up thouroughly
- Hayabusa c.o.p's
- shindengen sh 775 rectifier 14.3 volts charge
- New fuel pump
- New spark plugs
- Pick up coil tested o.k
- Cleaned ground wires
- New battery
Seems to me, that it's a fuel starvation problem, today I swapped carb slides and needles, and tci but the problem, persists.
Is it possible the fuel relay to be the cause? What about the diode?

 

[baceti]

Hi, if it's a lack of fuel, the engine feels like you're closing the throttle....and if it's from the stupid limiter, it feels like 2 of the spark plugs stop. I don't know how to explain it. The limiter works as follows: When you start the engine, 2 conditions must be met. One is that the speedometer is at 0 km/h, and the other is that the neutral light is on. After that, when you start the speedometer produces a movement signal (the reading is between 0 km/h and 180 km/h) only then the limiter is not active. Otherwise it cuts the engine at 6500rpm - not sure but I think it disables 2 of the spark plug coils. If you run the engine with the neutral light off (for example, in 1st gear with the clutch engaged)...the limiter will limit constantly regardless of speed.

 

[baceti]

..... What about the diode?....

It is possible, that the signal from the neutral passes through one of the diodes in the diode assembly. They need to be checked.

 

[jaws]

The problem is that it looks like a limiter, the engine continues to accelerate but it's sluggish like there is a lack of fuel. No black smoke coming from the exhaust by the moment it does it...
Today I swapped the diodes and the fuel pump relay from a friends 3uf vmax, but nothing changed...
I'm really disappointed!

 

[jaws]

Update:
I found the problem, yesterday night, after hours!
The pickup coil plug, had corrosion on its two contacts, resulting in high ohm readings on the tci plug. I cleaned the contacts with contact cleaner spray and the bike, runs like a charm.......for now

 

[Fire-medic]

Kroll is a good remedy but prcey, but you want to ride your bike don't you?
(For others having poor electrical connections).

 

[jaws]

Kroll is a good remedy but prcey, but you want to ride your bike don't you?
(For others having poor electrical connections).

Price is not a problem, when it comes to a solution.
Problem is, that I don't know what Kroll is... I found on google the Kroil spray, if it is the one you mean.

 

[MaxMidnight]

Another good contact cleaner (and again pricy) is Deoxit.

As a quick fix just make and break the connector several times. Provided they are not burnt or loose this will clean the contact area sufficiently to remove any corrosion.

 

[jaws]

I used loctite 7039 and the result was really good. If the problem comes back, I will use the deoxit, which I can find here in Greece.
I forgot to mention that, I bent slightly the two contacts and did the "make break" technique, and the multimeter readings became steady at 118 ohms on the tci connector.

 

[baceti]

For problematic electrical connections, I use the most common contact spray, then clean with isopropanol and finally apply this contact grease so that it does not oxidize over time: https://electrolube.com/product/cg53a-contact-grease/
It is used by car manufacturers in car switches, buttons, etc.

 

[jaws]

For problematic electrical connections, I use the most common contact spray, then clean with isopropanol and finally apply this contact grease so that it does not oxidize over time: https://electrolube.com/product/cg53a-contact-grease/
It is used by car manufacturers in car switches, buttons, etc.

I didn't know about electrolube! And from a little search, there is no retailer here in Greece! There are so many useful products out there. Maybe I should try to find an equal substitute...

 

[Fire-medic]

MaxMidnight is right on the Deoxit, Kroll is a Liquid Wrench/PB Blaster type product penetrating oil. Acetone & ATF mixed 50/50% is also an effective penetrant.

I use a small tool to pop loose the connectors from the nylon male/ female blocks to be able to sand them shiny bright if they are badly oxidized upon disassembly. A small dab of Dielectric grease helps to promote continued good contact between connectors.

A set of torch cleaner tips is also a good way to scrape through oxidation tubular interference fit electrical connectors.

 

[MonteG]

Kroll is a good remedy but prcey, but you want to ride your bike don't you?
(For others having poor electrical connections).

I'm guessing you meant KROIL, Absolutely the best rust penetrant I've ever used! Never tried it on electrical connectors, though...

https://www.kroil.com/product/kroil-original-penetrant/