First Bike VFR 750

That's exactly what the idle adjuster does... It gives a little "throttle". It is physically moving the cable wheel.

If it doesn't want to idle nicely 1100 - 1200, there is likely still some blockage and/or they need to be synchronized.

BUT... If it runs good other wise, set the idle to 1200+ and get some Techron Fuel System Cleaner or some Seafoam and run a couple tanks thru it before doing anything else.

How you describe it reacting to "choke" sounds normal.

 

Alright sounds good.
We dont have seafoam here but I‘ll find an alternative.

Just to be clear

1. 4000-5000rpms with full choke and warm ist that normal or too much?

2. Is it normal for old bikes like this one to be bumpy when rolling in first gear without giving it throttle (warm) ? As soon as I give it the slightest bit of throttle it smoothens again.

 

Full choke and warm really don't go together. But yes, the RPMs can be quite high when the enrichening circuit is engaged. It is adding more fuel.

As long as you get a pretty good high idle when cold starting with choke, like 2 - 3 grand+, and can start dialing it down as it warms up, sounds normal.

No, really shouldn't be bumpy, That's why I said they are probably still dirty and/or out of synch.

But if it can "idle" and is safe to ride, run some quality fuel system cleaner thru it for a while.

 

If this "jumping" described sounds like loosing a firing here and there it might be bad sync'ed carbs. Leaks in the intake system effect idle more than full throttle. Even with well balanced carbs bad compression (valves/seats/rings) will give unstable idle. If the battery condition is very poor it will also affect idle.
There are many things to check.

 

Might as well check those carb boots … replace if they are cracked or hard as hell


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Back with a small update.
I passed my driving test.

I put half a can carbcleaner fuel additive from liqui moly and fueld it up with premium fuel E5 in europe. I noticed an improvement but still not perfect.

Now a question: with idle set to 1200 are you guys able to take off only using clutch or do you have to give it a little gas?

As to the mosfet RR. Just as @Captain 80s said. It didnt even last 3 days. The following happened.

In slow stop and go traffic or when idling for a few minutes it would get hot. Then the battery gets no charge as per the voltmeter. It reads below 13 volts and even less than 12 with lights on, turn signals and cooling fan. When out on country roads with enough wind from driving, it has good charging voltag 13.5-14volt or when I park for a few minutes to cool it down.
Today it stopped charging alltogether even though the RR still gets hot, the battery doesnt get voltage above 12.5

I got a refund on it and ordered another one as spare. I‘m still looking for an oem one though.

The above symptoms point to a faulty RR right? Any ideas if it could be something else? I know a faulty battery might not charge but as long as its not the stator I‘m happy with it.
The RR getting hot quickly seems like an indicator that the stator is working right?

None of the wires are hot, connectors look good/ not melted or burnt, the inline fuse to battery positive is good.

Also how important is it to bolt the RR on both sides? I got a bolt out of the frame which is too short so I mounted the RR with only one bolt to the frame. That one has no steel plate on the back so heat wont go get transfered that way anyway.

i think thats all for now

 

Typically need to add some throttle when releasing the clutch from a stop if you want a decent, safe launch. But it is possible to do it on level ground without on a properly setup VFR.

Sounds like a shit R/R that gets shittier as it tries to do it's job. Save for a real one and quit dicking around with junk. THEN you can evaluate the rest of your system.

Good luck and congratulations on passing!

 

I always give a little gas just so I don't stall at a light. On my own on level ground I can pull away with idle speed.

+1 on the proper RR. It is only important to secure the RR. I used to race with mine hanging from safety wire. Not recommended, but kept it nice and cool-ish.

If you look at newer bikes the RRs are located in a duct near the head light. I have seen several this way.

 

Or tucked under the tail in the rear wheel well (both my VFR1200, MT-10 have this).

 

Little update for anybody interested.

Finally found an oem mosfet RR Fh012ab out of a daytona. Now the voltage is stable and thus all electrical problems are done.

But of course the hustle never ends. Few days ago i was suriprised by a little puddle of a mixture of gas and I think oil? It‘s a brown/yellowish and oily. Took the fairings off and was welcomed by a small pool of gas leaking from all 4 carbs but found no oil.
Starting the bike also took forever, unless I let the fuel pump prime for like 2 seconds.

It‘s weird because when I cleaned the carbs a month ago, I made sure not to touch any gaskets and also made sure the floats were moveable and not stuck. Also it didnt leak after reinstalling everything.

Last thing I did was add carb cleaner additive to the tank on 3 fuel ups and I can‘t imagine how that could destroy the bowl cover gaskets.

Other than that it drives and handles great. Will give more updates if I find anything

 

Sounds like you get to touch the gaskets that you didn't (and should have) the last time you were in there.

Very common for orings that seem ok, to not be after disturbing them.

Absolutely need to verify where the leak(s) is coming from. Could be the fuel cross over orings in addition to the float bowls.

 

Hey guys I have a quick question.

lets assume the bike is leaking gas from the bowlgaskets, thats the highest part of the bowl, that means fluid should only come out when fuel is constantly being delivered to the carbs.

How come the bowls become empty over night then? The excess fuel on the highest part of the bowl may leak out, but the rest should stay where it is in the bowl no?

Picture: The yellow markings is supposed to be the rest of the fuel that can not leak through the bowl cover gasket.
also the 2 gasoline drops that are hanging out the outlet valves are are drops from the top, which have just flowed their way to that spot. The outlet valves are not leaking and the flatheadscrews are tight

And this is just a general question so I may understand the mechanics better.

 

I vote cross over tubes.

That may be why the gas is a mix of oil and fuel to your description. It is leaking further up and mixed residual oil and gew from the central portion of the carbs as it leaks downwards.

I have had orings that look amazing actually crack apart. I will never trust old ones.

my 2c.

 

Which are the cross over tubes? Do you mean the hose from fuel pump to carbs? I don‘t remember disconnecting or touching any other hoses and tubes apart from the ones ob the tank and the one to the airfilter.

Also doesn‘t explain the bowls emptying over night

 

Did you check the o rings on the drain bolts? Also make sure the float bowl isn’t cracked. I’m not sure if your model has brass tubes pressed into the float bowls ,,, my CBX had a cracked tube once and that exact thing was happening…


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Maybe I have misundersood your question, but the float bowl gasket surface is on quite an angle when the carbs are installed, such that the lowest point is nearly the same height horizontally as the drain screw. If they are leaking around the gasket at that point, the float bowl would very likely fully empty.

 

these tubes with o-rings at both ends. they shrink, crack and get infiltrated by rust dust from fuel tank. any FULL carb service on a vfr includes replacing the O-rings. many times unnecessary if it doesnt leak, while minor service would include jets cleaning and whatever parts needed replacing.