CV Carbs and diaphram/spring question

These are HawkGT carbs, not my VFR (the Hawk's the one that's currently strewn about the garage, getting re-assembled). But, sample principles, right?

The slide is pushed down by the spring, correct? With the carbs off the bike, the springs should cause the slide to move to the closed position, with the needle all the way into the needle valve, correct?

I can reach in, move the slide, and one will sit wherever I leave it. The other will slowly, ever so slowly move back towards closed, but won't make it all the way to closed before it stops.

This wasn't what I expected, given those big springs that are in there.

The bike had been running very rich before we pulled the carbs (as we tore the whole bike down). 144/42 jets, 2.5 turns out, front and rear (with a Muzzy glass-pack and K&N pods). Doesn't seem like that should be too rich from my reading online. I'll also be checking that the choke control was correct as well.

 

Something isn't right, the slides should snap back down as soon as you remove pressure. You might check for varnish buildup on the sides of the carb body and slide. If it takes too much pressure to raise the slides you might check the vent holes to make sure they aren't plugged, but that's pretty unlikely IMO. My guess is that there is buildup of some kind on the carb body walls.

 

Check to see if the needles have been shimmed, and if so, that they are "floating" rather than rigid. I have seen more that one occurrence where the needles have been shimmed upwards, and whatever sort of retainer that is used (normally a screw-in plug) is holding them rigidly in the piston body. The needles need to be able to self-center, so they will not restrict the piston movement.

If they have been doing it for a while, you'll find wear marks on the needles. It would also explain it running rich, particularly right off idle.

 

Thanks for the confirmation. I'd opened the float bowls to inspect what the jetting was (I'd been assuming the previous owner was overly optimistic about required jetting, but it's honestly very mildly jetted for the intake and exhaust mods (#144 mains vs. 150-162 as I've seen with similar mods).

I'll open the diaphram covers, and see what I find. I can move the slides up/down with my fingers, not a lot of resistance to movement. I'm almost expecting to find no spring (or a rusted into nothing spring) on one of the carbs, based on how it feels (no resistance to opening up the slide, and little resistance to one finger in sliding it back closed.

I'll also check the needle for wear.

I guess I'll find out when I pull the diaphgram/slide/needles if anything other than the main jets were replaced. It's a smooth tapered needle (like oem or Factory Pro needles for the Hawks, not a dynajet need (with a step in it).

Thanks for the info!

 

Wow, what a freaking coincidence. After months of frustration, I finally got my Hawk up & running. And boy, does it run now. No more coughing, sputtering, stalling, rough idle, etc... It starts right up with a single turn of the throttle & half choke. It warms up to no choke required in about 3 minutes & I can ride away with the choke on in about 1 minute.

Here's what I did & recommend that you do.

1) Call Factory Pro @ 1-800-869-0497. Do this even if you don't have their carb kit. Tell them each & every thing that is done to the motor. I'm talking like "I have full M4 headers but a Scorpion muffler, a Factory Pro ignition advancer, stock air box with K&N drop in, stock pistons, etc" They will tell you exactly what each & every component in the carb should be. In this day & age of calling a company & speaking to Tarbash Babaganoosh in some far off land, I was shocked at how friendly & capable their staff was. If you are in need of anything, Factory Pro will make a kit to your specifications.

After a 1 hour conversation, I received this reply, it was really this in depth:
Front Cylinder 142 Main & 42 Pilot
Rear Cylinder 138 Main & 42 Pilot
Factory Pro needles set at 2d position from the top
diaphram spring stretched to 8"
screws 2 1/2 -- 3 turns from full out

2) Take the float chamber apart. Make sure you take out the float valve & ensure the float screen is spotless. Unless your carbs are clean enough to eat out of, take this chance to scrub the crap out of it with a brush & carb cleaner. Gun brushes work the best. Install the jets as recommended. Use ONLY Keihin jets or whatever brand of carb it is. I have 3 Factory Pro jet kits & all 3 have Keihin jet in them.

3) Take the diaphram chamber apart. GENTLY clean the diaphram with WD40. If it is even slightly torn or ripped, order new ones. Stretch the springs to whatever Factory Pro says & then bake them in the oven at 350f for 15 minutes or so. This makes the stretch hold. Again, clean EVERYTHING until it's spotless. Inspect the needles for nicks & such. Drag a cotton ball up & down the needles. If the cotton catches at all, your needles need attention. If they have any rough spots on them, either get new ones or polish up the old ones with emery cloth.

4) Check your plugs since everything is out of the way. If you put in new ones, make sure they are gapped correctly. Shine a light into the heads to see if they look OK.

5) Ohm check your plug wires. This is almost certainly the single most overlooked step in troubleshooting. I mean really, how many can say they've actually checked their plug wires for proper resistance?

6) Reasemble the float chamber first & then the diaphram chamber. The single hardest step is to make sure the diaphram is not pinched & installed correctly. Take the time to install all new o-rings. It's cheap insurance.

7) Find an old law mower fuel tank or get one of these: Motion Pro - Auxiliary Tank

8) Ops check everything. The aux tank is great since you dont need to take the fuel tank off repeatedly if something isn't right.

9) As long as everything is as it should be, sync the carbs & reassemble.

10) Flog the crap out of the bike.

KC-10 FE out...
lane: :usa2:

 

KC,

your thread about your Hawk carb-work turned up in my investigations, it was definitely a pleasant surprise. The Hawks are such amazingly FUN bikes, yeah my VFR is faster, but my wife's hawk is more fun (until I get on the freeway).

Factory Pro is definitely on my list of people to talk to. Such good reviews, and such good resources, it's really awesome. Glad someone's realized that you can't farm out customer service and expect it to still be good.

Inspecting the heads won't be hard. They're currently lying upside down on the "dirty" workbench where I've been removing 1/8" of carbon build-up from them and the pistons.:frown:

Granted, they're now nice and VERY shiny, still with the grainy finish from the casting, but the surface of the grains are very smooth, and well cleaned.

Like I said before, I'd assumed it was stupid jetting tricks, but now I'm thinking things are actively broken somewhere. All the plugs were carbon fouled, too.

Gun brushes... that's a good idea.

 

After I re-jetted, my problem was 2fold. Actually, I'm kinda of glad that all this happened. Necessity is the mother of invention. I learned more about carbs in the last week than I ever did & I was a mechanic for 9 years.

1) The clip fell off the needle for the rear cylinder. The clip or needle can't go anywhere but it certainly wasn't doing any good in this configuration.

2) Some how, the idle screw migrated it's way to full in. When I finally got it to run, it would rev straight up to 3500-4000.

Now after all the swearing, throwing of tools, troubleshooting, etc, the bike runs like a freight train. On my favorite deserted backroad, I was able to redline 1st thru 4th.

KC-10 FE out...
lane: :usa2:

 

Popped the diaphragm cover off, and to my surprise, there was actually a spring in there. Although it was so weak it was unable to lift the cover off with it's own strength.

The slide's surface is pretty rough (milling marks), and worn shiny in two spots where it's been wearing against the sides of the carb. No sign of any grunge in sight.

Lubricated with a thin layer of WD-40, the slide snapped closed pretty quickly, but as the WD-40 dried, it went back to stalling out, if it tried to close at all.

The spring was 6-3/4" in length, a tad over stock, but not by much. I'm guessing the stretched springs help out a lot with closing the slides back quickly.

I also pulled the needle retainer, and it's the stock needle, shimmed with a thin (~1/64") washer.

And, I found an extra washing stuck to the inside of the diaphragm cover. No idea where it came from, unless it had been under one of the screws as a shim. I'll double-check it when I pull the other side to compare.

Thanks for all the tips.

Beginning to sound like I just need to really clean this well, and upgrade it to a full jet kit from the partially upgraded state it's in for something that better matches the intake/exhaust mods (new needle, with proper clips to shim it correctly).

And I wish I'd found the source of the running rich. About all that's left is the enriching circuit, and poor spark leading to incomplete combustion.

 

Not to beat this to death, but was the needle floating instead of rigid? When the little washers are used on the stock needles, it usually raises them high enough so that the retainer holds them solidly in position. When that happens, the slide and needle (as you know) do not fully seat. Right off idle, and through the lower RPM range, the motor will run really rich due to the slide/needle being too high and exposing too much area in the discharge tube that the needle should be partially blocking.

If you have the threaded plugs that retain the needles, try loosening them to let the needles move around just a bit, and then check the slides for operation. If the stock needles are the type with the really thick heads on them, they can be used satisfactorily if you grind down the top of the head the corresponding amount to compensate for the thickness of the washer.

If you do get an aftermarket jet kit, and haven't used one before, they usually recommend that you drill out the air passage holes in the slide body so it raises faster. It is sometimes a good idea not to enlarge the holes in the slide body until you try the jetting mods first. Don't ask me how I know...

And, in my limited experience with the jet kits, it has been my experience that the replacement needles are a bit too rich, even at the highest clip setting on the needle.

 

The needle was free to move, yes. I looked for that. The retainers are the quarter-turn variety, to lock into place. I don't think that the 1/64" shim added that much pressure on the needle over stock, but I will definitely be going over everything very carefully looking for problems. The slides still don't move as freely as I think they should, and I'm going to put them in without the needles, to see if the needle is dragging in it's passage.

 

I would say that it's fairly easy to get your jets to a satifactory condition. Other than the floats not working, it's pretty hard to screw up screwing in a little brass plug.

Factory Pro sells a kit that includes the diaphram springs. If the ones you have are that flimsy, I would recommend spending the $90 & getting the entire kit. All 3 Factory Pro kits I have do not require any drilling.

If you have worn spots in the actual slide chamber, about your only option is dressing it with steel wool, the finer the better. If it's the slides themselves that are worn, your only real option is to get new ones. The local parts guy tells me that these things are not readily available. Good thing is, the slide & diaphram are a single unit. Consulting RideNow online parts finder reveals that this will be $86 X 2 + shipping.
Online Microfiche for Honda, Yamaha, Suzuki, Polaris, & Sea-Doo Motorcycles, ATV, Watercraft

Another thing I would try is to put the needle back in, aftermarket or stock, & try to wiggle it side to side. The actual needle socket itself might be worn. The local mechanic says that, other than incorrect jets, would be a very likely case of running rich just as LGN001 pointed out. If you had 1/8 of carbon build up, I'd say you got the rich part.

Get that bike running, the world needs more classic hardware running around.

KC-10 FE out...
lane: :usa2:

 

stretch the stock springs to 8"- 8 1/2"

lubricate slides with WD-40 and clean the area where they slide with green Scotchbrite and WD-40

needles should be free to wiggle about, not too tight

 

we're definitely classic hardware riders:

His: '86 VFR700F, RWB
Hers: '88 HawkGT, Silver

and it's so nice working on metric bikes, I only need half the sockets (just the metric ones).

 

i just helped truck 4 Hawks (one RC 30 setup) from DC area to Buffalo this weekend, nice mix of wheels, Ohlins shocks and forks, bits and pieces, pipes and pegs to build ONE JEWEL of a Hawk over the long winter........with 3 bikes left over.

 

Awesome! One of my coworkers is looking to start riding, and asked about starter bikes for he and his GF (one shared bike for now). She's 5'1".

I had a pretty simple answer, and then found this:
Honda Hawk GT NT650 - Super Clean!

 

You know what I would like to see?

I want Honda to re-invent the Hawk GT. I think Suzuki has it a little too easy with the SV650. I want it to be exactly like it is now, 360 lbs wet, raised clip-ons, SSSA, single round head light, simple & uncluttered. I would like the following upgrades.

1) 680CC & FI. The exact engine, all the way from 1988, has morphed over the years into 680CC with FI in the new DN-01 & the European Deauville.
2) 4-4.25 Gal fuel tank
3) 6 Speed Trans
4) Modern tire sizes, 120/70 & 160/60
5) 65HP at the wheel.
6) 60MPG

Build that & charge $6000 out the door & it sort of makes the Ducati Monster 695 irrelevant doesn't it?

On a side note, since my mutual fund tanked & is now worth less than the newpaper at the bottom of a parakeet's cage, I guess the little red beast is no longer for sale.

KC-10 FE out...
lane: :usa2:

 

That'd be one hell of a nice bike, KC.

And sorry to hear about the mutual fund... I'm feeling pretty lucky about mine right now. You're fund company go under, or just tank in value?

 

Tanked in value.

KC-10 FE out...
lane: :usa2:

 

Seems like a good time to throw more money into it, if you have any expectation of it going back up again. Mine have been glued to ride that the S&P500 and DowJones have been on, so I'm not too worried about it long term (but then, I'm in for another couple decades, so I'm not too worried, period).

Anyway, back to bikes. I found this rebuild thread on the HawkGTForum last night, and was just in bliss:

Honda Hawk GT Forum - View Single Post - My Bad Hawk New paint pics added!

It's got me thinking about spending some rainy afternoons on the Hawk's frame with the aluminum polish. I have all the tools, just need the right polishing compounds for the random-orbit buffer, I have the right bonnets.

The black engine is definitely sweet. The silver paint is flaking off ours in a few places.. Not sure whey they painted the aluminum crankcase sides, cylinders and heads with silver metallic paint, and then polished the crankcase side covers...

 

hey, KC, in woking on carbs more than 25 years i've seen mixture screws migrate out, even fall out, but NEVER migrate in against spring pressure..........?