VFR700 Enrichment/Choke Circuit Jet

Quick question all. I am unable to find the diameter of the choke jet. I have read that using a .01" - .02" wire is the best option for unclogging it. I have .03 wire handy.
My questions .... is the jet uniform diameter through the tube? Or, does it have a taper up in there somewhere?
With my .03" wire, I can only get about 5mm into the tube before I hit on the crap that has hardened in there. Carbs were soaked in a 50-50 mix of Pine Oil and water for 2 days.
I just don't want to route around in there with the wire and ultimately alter the diameter of the choke jet, if I can avoid it.

 

No worries as enlargement is exactly what it needs cuz most are partially clogged.

Best to use a steel wire .010"-.012" diameter in a repeated pecking, poking motion until you can get it gradually in farther--it can take up to about 15 minutes-- to max depth of about 33-35 mm. Blow or suck air into/out of the tube to confirm airflow. Tubes have a uniform ID, but you'll almost always find an obstruction (dried fuel residue) within about the first 10mm. After the first blockage is cleared probing gets easier. :disturbed:

 

I just got back from a music store and they carried strings down to 0.007" as well as 0.008", 0.009" and the 0.010" (0.25mm) that I bought as it seems to be a bit stronger for pushing through. Only cost $1.29.

I picked up a real nice Excel pin vise from a hobby shop for $8.50. It has 2 double ended collets that can handle wire or drill bits up to 3mm in diameter. You can load a short piece of wire in it and gently apply pressure while twisting it.

(I would avoid the aluminum pin vises as they seem to be low quality and have trouble holding things straight)

 

I'm hoping my 0.010" wire will clean out the deceleration enrichment vacuum jet. That tiny hole that the diaphragm indexes to. My 0.015" wire is too big for it.

 

I was going to suggest a pin vice too. Keihin jets are numbered with their aperture, so a 38 idle jet specifies an .038 mm hole. I always use a .035mm drill to open it up, then a little soak in an ultrasonic tank cleans them up nicely. You could use a little throttle body cleaner to finish them up (just don't breathe it and keep it off your skin).

 

Geezus, no carb has been cleaned properly until EVERY brass hole has been probed with a .01" steel wire. Long brass choke pickup tube must be probed to a depth of 33-35mm to clear it entirely. Best description of wire technique to clear is "pecking". If the tube is clear you can get a .012" wire down it about 33 mm. Use carb spray and compressed to aid cleaning.

Jason, that tiny hole is frequently plugged but you can use a .010" steel wire to try clearing it. Soak in carb spray first. No big deal if it's clogged.

 

Not quite. Keihin takes the hole diameter and also factors in the flow rate because of the way the holes are tapered I think. The smaller jets may be closer to exact, but the larger main jets can get tricky.
A Keihin 118 may have an actual hole of 1.12-1.14mm.
Dynojet jets seem to be exactly the hole diameters.
Mikuni are off in the other direction. A Mikuni 118 jet may have an actual hole size of 1.25mm or so.

I think as the jet sizes shrink, their size numbers get closer to their actual hole diameter.

This is why Dynojets kits come with 114 and 118 main jets. The 114 is a little richer than the Keihin 118 and then the Dynojet 118 is another step or two richer still.

Next time I pull my carbs I'm going to measure my jets to make sure I know what's in there. My mains were labeled 118, but it appears I have a dynojet kit in my bike, so those might be Dynojet 118's or they may be Keihin 118's. I know Keihin jets are stamped with their special K and size on the side and I think Dynojets stamp their size on the bottom of the jet.

It's all a bit sketchy. Best thing is to measure them to know what you got.

 

That's some good advice there...I'm adding it to my carb overhaul guide stuff. That's some darn thin wire too - 30 gauge equivalent! A strand of solid core 24 ga. telco wire is twice that size!

 

IT LIVES!!

I finally finished the carbs and put them back on the 87 VFR F2. Cleaned and gapped plugs, ensured the oil was decent, fandangoed a fuel source and gave her full choke. Did not take long for it to fire up.
I have to assume the carbs are set a bit lean(from what I have read on the forums), they were popping back through the top side. I set the fuel mixture screw two turns out at first, I will turn them out another half turn and see how it runs. I do not have balance gauges, so I will set them by feel until I get some gauges. I did not have an air filter or airbox on, I am sure that will slow the air flow some. I will run it with the full intake system next time.
Good news is there was no smoke from the pipes. I bought the bike not running, had not run in about 15 years give or take.
Glad to know it runs now, will continue working and cleaning it up. May make it a track day bike, will see as time passes and I get the chance to work on it more. Not a big fan of the gauge package on the F2 though....

 

It's good to hear you got it running.

I'll try and give you some info on these bikes.

The fuel pump voltage is regulated through a safety relay that has a tachometer wire going to it (actually, the 87 bikes have a different igniton box so the tach signal comes from one of the ignition coils). The higher the rpm, the more voltage or 12v pulses as the case may be, goes to the pump. So don't expect the fuel pump to work with the key on and engine not running. It does not "prime" like when you turn the key of a fuel injected bike. You can bypass the relay and feed 12v to the pump with a jumper wire to allow the carb bowls to fill up with fuel. Or just crank the motor a lot if you battery is healthy.

The jetting etc... in the carbs with stock intake and exhaust is pretty darn good. When they rolled out of the factory the pilot screws were adjusted on the lean side to improve emissions and then capped so you can't adjust them. Nowadays folks uncap them and set them a bit richer (about 2.5 turns out) for better start up and for better overall running.

The filter and airbox restrictions play an important roll in carb jetting. If you modify them the bike usually runs poorly until you make jetting changes to compensate. So don't ride it unless the filter and airbox is installed, snorkel too.

I hope you did a bench top sync of the carbs when you had them off to get the linkages pretty close. It can run pretty good with just that, but it might rattle at idle. Unfortunately you can't really do a good carb sync by feel. A proper vacuum sync on a running engine will make it idle real nice and fix several issues. I'm building a 4 bottle sync tool right now and have less than $20 invested in it. Once it's finished I'll post up some pictures. You can also search on YouTube for carb sync and look for the 4 bottles with blue liquid in it. That's a great design with no chance of ever sucking liquid into the engine.

 

Fuel pump working A ok. Initial test was run through the pump from the get go. The bike is some time from being ridden. Needs a lot of TLC to say the least. It is as if the previous owner coated the bike in an oil mist before he set it aside for ... ever.

 

Hey, oil mist. Sounds good to me. Better than letting it rust. eaceful:

It sounds like you need to change all fluids including brakes and clutch. You might need to take apart the calipers and clean seals and pistons to make sure your brakes are working good.

Hopefully there is not much rust in the tank.

I got my 86 as a basket case as well and got it running and fixed up. It's a lot of work.

 

Awesome! Glad to hear it's running. Oil mist? Was he preserving it from the elements?

Here's a tip for all the early carbie V4 Hondas (at least in my limited experience)...you can cycle the fuel pump once by toggling the kill switch when the ignition switch is on. It's a good little test I use to see if the fuel cut relay, wiring, fuse and fuel pump are all working. It's a little tiring to prime the carb bowls that way as it takes like 100 cycles to fully fill the bowls...but it'll work in a pinch. It doesn't test the spark boxes though.

 

Apologies for hijacking thread but need to send "squirrelman" a PM and he is over his limit for messages.

 

***WARNING - MESSY SHOP AHEAD, PLEASE LOOK AWAY IF YOU CAN'T STAND A MESSY WORK AREA***

Here is one of the carbs when I first started working on the bike....nice shinny lacquer. The project F2 in its unnatural habitat. And the exhaust venting system to significantly reduce being yelled at by the boss while testing.

 

Had to toss this one in of the F1 before yesterdays ride. A fantastic and fun 100 miles around Chelsea, Leeds, and Pell City Alabama yesterday. Indy cars were practicing at Barber and viewing was free. Amazing day, high was 80F/27C and sunny. Today is much the same. Soon it will be too hot and humid for this fella, but I am going to squeeze in as much as I can before the southern furnace cranks up.

 

That's what mine looked like, I have a spare set of carbs (clean) except main jets #40 are from gummed up carbs. I used lacquer thinner to get rid of gunk, but still couldn't get a wire through any of the four.

I am sending my carbs to "squirrelman" as soon as he clears his mailbox!!!

 

OK,me mates, i finally got the message and jolly-well cleared the decks again for more action.

So whomever needs to complain about one of my posts is welcome to do so at this time.

Thanks for any carb work. I try to do excellent work at low prices cuz if you guys had money, you'd mostly be ridin newer bikes, right ? I have alot of time and no responsbilites, access to a great shop always could use a few extra buck$ to buy 'cycle tires since SS is my only income.

Basically, and by default, doing carb work is my wintertime cycle-related hobby......which is also my job, my only job. I'm able to begin work on any set of carbs the day they come in, find whatever its problems were and call or email the owner with the details, then schedule a return delivery date. And i never mark-up prices if i need to order any replacement parts.

Dealer-shop techs usually don't do great carb work unless you find a guy over 50+. Most shops take short-cuts and don't spend the time on the details it takes for a proper refurbishment.

Agree with Jason, engines won't run proper without airbox and filter in place.