intermittent vibration at about 3500 to 10000 rpm

hi all .  my baby's not well ,she's developed a vibration when i get to about 10 miles in on a ride out   ,    if i give her a rest for a bit (30 mins and a coffee for me so the feeling in my fingers comes back) she pur's like a kitten all the way to red line..... ok things i have done so far but still no good,,,stripped the carbs down and cleaned (ultrasonic clean) new carb insulators x 4 (one off the old ones was split a bit ) cleaned coil connections, cleaned pickup connector, checked coils and pickups as per service manual(ohms with in spec when cold) new spark plugs fitted, carbs reset up and balanced. air filter cleaned and reoiled(k and n type). pretty sure voltage regs ok as its a yamaha one and reads 14.3v all the time (on tickover and at high rpm) any one got any idea's whats going on, any help or info on this would be appreciated ..

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if you somehow lost or displaced the rubber buffers at each side of the fuel tank, it can vibrate/resonate at certain frequencies.

thanks for the info squirrelman ,just checked and there both still in place.

something may be loose, so go around and check nuts and bolts holding things together.

If it only happens after 10 minutes then you want to look at two things: 

1. Are your carb floats set too low or is there fuel starvation of sorts? Is the filter gummed up? That might take about 10 mins to manifest as the fuel supply slowly decreases 

2. Is it something to do with thermal expansion once the engine has warmed up? For instance check if the exhaust isn’t properly seated on the heads or if your intakes have gaps etc. Some issues only manifest when engine is warm as gaps are still snug when cold

Any other symptoms? Does it run better on choke? Does it run ok at WOT on the motorway? Does it smoke? Leaking fuel? Is there a distinct noise when this happens? A smell? 

will have a look around tomorrow  10 pm hear now and got to get up at 5am for work ,will check back tomorrow,🧐

@stray  ,floats are set at 9mm which is correct for this year, forgot about the fuel filter it was new last year but will change it just in case,as for wide open still vibrating all the way but i can back the rpm down to about 3300 and it smooths out again but when i twist the wrist its seams like its lacking some power and the vibration comes back. 

oh also cant see any real smoke ,water level ok ,dosent smell rich,

just a thought is there any easy way to prove that the tank breathers working correctly,

the chances that these vibes could be a result of carb imperfections nears zero.

Have you checked the coils and pickup when warm? You don't have any vibrations when cold, so the error needs to manifest itself before diagnosing is possible. Would be my guess anyway, but I'm not nearly as experienced as for example squirrelman.

9 hours ago, Wot4y

just a thought is there any easy way to prove that the tank breathers working correctly,

Open the fuel cap when experiencing vibrations. Is the vibrations suddenly gone? Then you have a breather problem. If not, the breather is at least not the main problem.

Measure the Vac output with engine cold and hot  over pairs of the yellow wires (unplug the RR)

Another thing, are the fuel lines ok? They could be on the limit fuel flow wise, and when the rubber gets warm and expand slightly they could possible restrict fuel flow enough so that you get starvation. But since you've changed other rubber parts maybe you've changed the fuel lines as well recently?

10 hours ago, Dutchy

Measure the Vac output with engine cold and hot  over pairs of the yellow wires (unplug the RR)

Can someone expand on this ,I might be being a bit thick here but what's the RR mean

The RR is the voltage regulator.

The altenator in the engine (under the round cover on the left hand side) produces alternating current, Vac. Like the stuff coming from a wall socket. The engine needs direct current Vdc. So the RR converts Vac into  Vdc. As the engine revs up, the Vac level increases. As the battery doesnot like >15Vdc very much, the RR will have to "get rid" of excess. It does so by generating heat.

So if the RR and/or the altenator is faulty, it will have an impact on the electric circuits....

As the engine heats up it impacts the altenator and RR.

56 minutes ago, Dutchy

The RR is the voltage regulator.

The altenator in the engine (under the round cover on the left hand side) produces alternating current, Vac. Like the stuff coming from a wall socket. The engine needs direct current Vdc. So the RR converts Vac into  Vdc. As the engine revs up, the Vac level increases. As the battery doesnot like >15Vdc very much, the RR will have to "get rid" of excess. It does so by generating heat.

So if the RR and/or the altenator is faulty, it will have an impact on the electric circuits....

As the engine heats up it impacts the altenator and RR.

Ok got you I'm on the same page now ,right I have only checked it when warm (14.3v to the battery not checked the ac side yet.it's not a standard one,it's a Yamaha solid state one,voltage stays constant throughout the Rev range),I will have to give it a run tomorrow and check it when hot also coils and pickups(320 ohms when cold on the pickups).dont have any time tonight to play. Found the bit in the manual about fuel pump test. So will give that a go to, 

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11 hours ago, SweViffer

Open the fuel cap when experiencing vibrations. Is the vibrations suddenly gone? Then you have a breather problem. If not, the breather is at least not the main problem.

Will give it a go tomorrow,also will do a fuel flow test aswell found the info in the service manual..

Ah!  That RR indeed doesnot look like a OEM VFR one!

The "YELLOW" wires appear PURPLE  :goofy:

so with the engine heated up well (the altenator gets "cooled"with engine oil, so as the oil heats up, its cooling properties diminish), shut down the engine, set your multimeter to Vac, unplug the RR (the white plug) and start your engine. then measure over the combination of 2 purple wires. Best if you can keep the multimeter propes in so you can rev the engine to say 5000rpm. Write down the measurements you get from each reading. 

7 minutes ago, Dutchy

Ah!  That RR indeed doesnot look like a OEM VFR one!

The "YELLOW" wires appear PURPLE  :goofy:

so with the engine heated up well (the altenator gets "cooled"with engine oil, so as the oil heats up, its cooling properties diminish), shut down the engine, set your multimeter to Vac, unplug the RR (the white plug) and start your engine. then measure over the combination of 2 purple wires. Best if you can keep the multimeter propes in so you can rev the engine to say 5000rpm. Write down the measurements you get from each reading. 

Ya it's not standard, got you on the ac side 3 phase setup ,still got the original RR in place so can unplug Yamaha one and go back to honda(had one fail )wires are blue there go back across the frame to the original plug ( yellow wires).

Dutchy, 20 May 2019 at 8:05 PM

Ah!  That RR indeed doesnot look like a OEM VFR one!

The "YELLOW" wires appear PURPLE  :goofy:

so with the engine heated up well (the altenator gets "cooled"with engine oil, so as the oil heats up, its cooling properties diminish), shut down the engine, set your multimeter to Vac, unplug the RR (the white plug) and start your engine. then measure over the combination of 2 purple wires. Best if you can keep the multimeter propes in so you can rev the engine to say 5000rpm. Write down the measurements you get from each reading. 

Ok. Quick update,done a fuel check and I'm getting 200ml in 5 seconds so 2.4 litres per minute, removed tank breather from filling cap and tested it (working ok).checked alternator when cold and got 19-20 v on tick over and 55-65 at 5000rpm,

ok think I've found a problem with the pickup wires  ,seem to have lost a wire in the loom,I will try to explain,at the pickup plug end I have (white/yellow-yellow with black squares =pickup 1-3) and white/blue-yellow with squares=pickup 2-4)see pic[image: image.thumb.jpeg.97abc7b3586d3ada44dc7b2c82665861.jpeg]s

at the other end (cdi end) seem to have lost the connection  and a wire? Only have one yellow with squares ,see pic[image: image.thumb.jpeg.e2a09917c24cd34f1d850892bea9a10a.jpeg]

checked both plugs on the cdi and only have one wire connected from pickup 2-4. 

Now the wiring diagram I have is the one for the rc24 gen1 and the wire colours don't seem the same and the cdi unit has 3 plugs on it ( my cdi unit has two 6 pin plugs) .

does anyone have a diagram for a FJ FK 1988 vfr .

update ,OK bike in bits now ,found a low quality pic of the FJ FK wiring dia,you can't read the colours but you can just about follow the lines,striped all the cover tape off the wire harness from the pickup connector to the cdi unit and found the yellow wires are joined withe a crimp ,so soldered them up .found 2 more spliced wires so did them to.now reading 322 ohms from the pickups at the cdi end ,so going to tape it all back  and give it a go ,fingers crossed [image: image.thumb.png.84c961279c1ac7a082ba940dfef9dd4b.png]