Need Help setting Float Level. 2nd Gen VFR750

Have you had a chance to read through FP's primer on CV carburetor tuning?

CV Carb Tuning Procedures

Also, have you triple checked all the float heights?

 

I checked all float heights and set them all to spec before installing...I double checked them all before putting the bowls back on.

Compression was good when checked.
What's the best way to check for spark?
Should I test the coils?

 

Huh, looks like you have multiple problems going on here.

Right rear and rear left looks like carbon deposits- indicates a rich mixture or weak ignition- causes misfiring, hard starting and hesitation. Recommendations- Check for a clogged air filter, high float level, sticky choke.

Your front right looks oil fouled- oil is leaking past worn valve guides or piston rings into the combustion chamber, causes hard starting, misfiring and hesitation. You will need to run a wet and dry compression test to see what is happening here.

Front left looks somewhat normal.

 

My original problem was the front right plug fouling up and the rear left bowl leaking.

Squirrel had it running good but when I took it home the problem came back.

The one plug doesn't look oil fouled to me....even if it was I'm sure the two techs who worked on the bike would've said something.
I know it looks wet and oily but that's just the picture...it's dry and sooty.

 

All about the carbs, IMO. This said, I have to agree with Tink very long threads get muddled no matter how good the intentions are of the members who are posting.

 

Ok...fair enough.

Quick question though....is there something that can effect only the right bank of carbs/cylinders?

Vacuum line? Something in the carbs?

I understand this thread can get muddled...im just so baffled and exhausted....it's been so long and I've done everything I was told I should do and the exact same problem is back.

First the original mechanic, then Squirrelman, and now me. We all have to be missing something.
:-(

 

Time for DRASTIC measures ! It's all experimental science from here, Matt, with you in the white lab coat !

Since your problem seems mostly on one cylinder, just tune there.

One thing i'd suggest is to try raising float heigh step-by-step betweeen 1-2mm (lowering fuel level in bowl) gradually 1mm at a time until running improves and plugs look right. Do you need a leaner main jet?? Only testing would tell. I could suggest maybe turning idle mixture screws in by about 1/2 turn as long as it runs OK at idle and low speed. Try 10mm float height, ride, and recheck plug.


Float height is listed in fsm as 7mm and also 9mm for '86/'87, same carbs, so why the difference ?? Anyone know ??

After synch is done and with a hot engine try turning in each mixture screw one at a time until the cylinder starts to lose power, then open up each screw about 1 to 1 1/2 turns from there to try running/plugs. Keep opening until you see proppa color at just over idle. Best tool is gas analyzer if you have one. Otherwise, you need to tune fuel (jets/float level) until plug color is right.

 

Yeah, if compression is OK and that plug is just sooty forget about by compression comment.
The previous comment applies.

 

I tried testing the coils as per the Honda manual.

Testing from terminal to terminal was fine but I couldnt get any continuity when testing the wire or where the wire attaches to....tried the other front coil and it was the same deal.

Put a spark plug on the wire and cranked the engine while holding the plug close to the frame and got a weak looking spark on both front coils.

.....great.

Ok....so they are at 9mm right now....move it up to 7mm?

I highly doubt it. Bike ran fine until the first guy started messing with the carbs. Some thing must be clogged, disconnected, torn or something.

The thermostat housing blocks the access to the pilot screws

My Honda manual says the opposite:

Again, cant reach all the screws when carbs are in the bike.

 

Yes, i got that 7/9 thing backward.

Set float on RF to 10mm for a leaner mixture, then ride and inspect the plug. Impovement ?? NO improvement ??

You need a long screwdriver to get to the inside mixture screws, but they are all easy access.

 

Ok....thanks SM. I'll pull the carbs and check 'em again....I'll set the float on the RF to 10mm.

You call that little guy behind the Thermostat housing easy access?? No long screw driver is gonna get in there.

 

The Manual says that you shouldn't swap the Vacuum slides and the needles....does that include replacing them with new ones?

 

no........but did you remove the vaccum slides while you were working ??

 

I didn't before....but I have now.

an update: (incase anyone is following along)

Found gas leaking from the carbs again....upon further investigation I found this:


I pulled the carbs and upon dissasembly found a slow jet very loose...That and the flooded carb pretty much made the descision for me on what I needed to do.

I am carefully going over everything, and replacing pretty much everything. I'll set the pilot screws to about 2.25 turns out and the float level to the stock 9mm.

We just got a lot of snow so it'll be atleast a week before I re-assemble and re-install the carbs.

Fingers crossed. :tongue:

 

Is one of the vacuum slides hanging up? IIRC, weren't these carbs rebuilt a few months back?

 

They've been worked on many times since July....they've probably been apart atleast 5 times.

Would stuck slides cause the flooding? I thought it'd be a Float issue?

When I got the fuel outta that carb the slide was fully down.

The slides do have a bit of wear on the sides but nothing that worries me. If they weren't NLA I'd buy new ones just for peace of mind.