CV Carbs and diaphram/spring question

Disassembled things again tonight, and took pictures this time. Good calls pretty much everyone.

Diaphragms are both intact, no tears, and very flexible. Aside from that, cleaning the slides and carb helped, lubing with WD-40 helped, the needles have flat-spots worn in them, and the slides have been drilled, stretched the springs to 8", and that helped considerably. If I blow into the vent, one snaps up immediately and drops immediately, but the other takes far more force for it to come up and stay up, and then it's lazy to drop back down.

First, the slides:


Both look like this, with the black worn off, there are a few other shiny spots as well, and the drill holes are obvious.

The springs are... well soft. Stretched out helped, but I'm going to let them sit, then stretch again, then bake to reset (or just order a Factory Pro 3.0 kit and be done with it).

The needles are stock, shimmed with washers, and both slides appear to seat the needs at a surprising angle. One moreso than the other. This is the one that's not smoothly moving.



I have a whole set of photos here at flickr (CLICK ME!!) that shows the needle sliding against the side of the passage it reaches down into.

That takes me to the flat-spots on the needles. One is just worn through the brassy coating into the steel, the other is notched enough to catch when you slide your finger down the length of the needle.




At this point, I just want to take it all down to metal, and drop it in dip for a while, and then scrub the snot out of it as best I can. It's very clean, or at least it seems clean, but going over the chambers and slides with 0000 steel wool and WD-40 really cleaned things up nicely (all the wool fibers are removed, so they don't damage the diaphragms; but I really need to pick up synthetic that won't shed).

 

It is always difficult to follow somebody else on carburetor work. You never know what they have done, or why. Looks like you're getting it narrowed down, though. The needle with the notch in it is classic! Sounds like it was not running right for many thousands of miles.

I tried to look at the photos per your link, but I'm on a dial-up connection (long story) and got tired of waiting. I don't think that the needles are not worth salvaging...

 

In general, following someone else's mods on a vehicle is... interesting. Both of our bikes are modified, but not by the last or next to last owner. All either of us knew about each was "new exhaust", and "rejetted". I really need to pull the VFR carbs and see what the jetting IS. But my bike runs super smooth, aside from some bogging under 5-6K at anything over half throttle. I'm guessing that's just how it's cammed.

Flickr is very much NOT dial-up friendly.... sorry about that.

Anyway, I guess I should ask some directed questions based on the photos:

1) the needles need to be replaced, correct?

2) the slides have been drilled, and this seems like it's not a good thing from my digging at HawkGTForum

3) the springs are likely also shot, or at least need a number of rounds of stretch/compress to get them to stay at 8", and then some baking to "set" them there.

4) I can only imaging that the needles are designed to sit at an angle like that, and the tip of the needle is supposed to be the wear-point with the passage the needle fits into. Both slides are the same in this regard, at first I thought it was an angled shim, but now I'm not so sure.

5) If my geometery is correct, on the hawk carbs, the needle doesn't fit directly into the needle jet, but into a passage that is connected to the needle jet's end?? The angles seem wrong.

6) A full carb dip and clean, installation of a Factory Pro 3.0 kit with a call into them for their jetting recommendations on the Muzzy and K&N pods seems like a quick and easy out of everything aside from the drilled slides. But I'm sure I can seal the drilled holes with some ingenuity. JB Weld might actually be ok for this, or tap and insert an aluminum plug, and grind smooth. At $90/each, seems like taking a "modify" route over the replace route would be worth it.

7) How likely is the choke circuit to be contributing? I've been poking at it, and the cables are very stiff, and have a fair bit of resistance to pulling the ends back out, after moving the lever back to the closed position.

8) What's everyone's favorite cable lube(s)?

thanks much.

 

Every constant velocity carb I have ever seen is supposed to have the needle centered in the discharge tube, or at least be allowed to self-center. But I have never had a Hawk carb apart. Perhaps KC-10 will have some input here. The needles should not rub while "in use", meaning that if they contact without the engine running, but have enough play to self-center, it shouldn't be a problem.

Slides usually have at least one hole that dampens/tunes their upward movement. The old racer's trick of drilling them out lets them open up quicker, at the cost of low RPM stumble if the throttle is opened quickly. On a street bike, it can be annoying, particularly if they open quickly enough to cause a backfire through the carb due to the sudden lean-out of the fuel mixture. A high velocity airstream has to be maintained past the needle/discharge tube for it to supply fuel at the proper rate, and if the slide goes up to quickly, no more or very little fuel flow. The difficulty is in plugging them and re-drilling them to the original size, as they do need to be located properly. Somebody here may have done this before. And as far as I know, perhaps the Hawk carbs do not have a hole in the slide from the factory.

The worn needle might be usable, but the notched one, even with the notch polished out, will always have an unpredictable fuel mixture.

I use the "cable life" spray (green can), but I have never been able to get the special leak-proof adapter to work. I make a little funnel (sort of) out of aluminum tape, wrapped around the control end of the cable, and spray in lube/let it drain/repeat until I get tired of it.

 

I fully expected a centered needle. The heavily angled needles were surprising. Further, it appears it's the hole in the slide for the needle that's angled. And I can see the shimmed needle putting more spring-pressure to reduce it's ability to wiggle correctly.

It's certainly NOT centered. When the slide is fully raised, the needle tip is touching the side of it's passage, and held against it with spring pressure from the slide.

This pic here shows how the needle hole in the slide appears to be at an angle (from the factory?):



I don't have any other references for how the Hawk needles are supposed to sit (or even know of that passage is actually angled, and so all is well)...

I'm really tempted to cross-post over to HawkGTForums, I know at least Squirrelman is also on that forum, with lots of Hawk carb info over there.

 

That's a weird one. I'd go to the Hawk forum and find out. If you do, a follow-up post would be great. It never hurts to know about these things.

 

if the needle won't wobble freely you need to remove the retaining peice and file or cut down the center plastic nub ( under the spring) about 1mm

the grooved needle is in need of replacement

 

I moved this over to HawkGTForum.com, as it appears to be down to specifics of the Hawk carbs vs. cv carbs in general:

Carb Problems (running VERY rich) - Honda Hawk GT Forum

Squirrelman, KC, see you guys over there?

I'll post back here when I get it resolved. Although I may have one breakthrough I need to go test.

 

if by very rich you mean VERY, VERY rich.....then you likely have a misadjusted float in that carb.

 

1) That one needle is absolutely shot. I don't know for certain if the needle would self center if I just dropped it in & let gravity do it's thing. I remember the needle was fairly easy to move around. Did your needle retainer have a small spring under it? Both chambers in mine had what looked just like the spring from a ball point pen.

2) Since you said your daiphram springs are less than springy, I would say the full kit would be a wise choice.

3) I don't see any reason why you wouldn't be able to fill those holes in the slides with a plug & then machine them down like you said. I won't lie, I don't know nearly enough about the issue to say whether it would or would not work. I only know that from a metal working or machining point of view, it should be fairly easy.

4) I would recommend getting the adjustable needles. Like LGN001 says, shimming the stock needles can cause them some difficulty.

5) Any time you use the pods, you can usually use the same size jets in the front & rear cylinder. With the stock air box, you will usually see a larger jet in the front since the front header is almost always longer. With the pods, the cylinders can breath independently. If you use the same size jets with the stock air box, you will get a very noticable burp every time you hit the gas & the rear cylinder will usually run hotter.

6) This is just a guess here, but I'm thinking, based on your statement of using pods with a Muzzy exhaust (full headers or just a slip on?), that you will be recommended to use:
150M, 45P, 8" springs, screw 2.5 turns, adjustable needles either 2 or 3 from the top.

7) I'm not digging the Hawk in the link. I like the Hawk for what it is, elegant simplicity. It is a completely basic bike with enough hi-tek to keep the inner geek in everyone happy. When they get super modified like that one, they kinda stop being a "Hawk". On mine, I really want to find a way to hide the Fox Racing resevoir since I hate the way it looks in plain sight. It messes up the clean looks of the bikes. I hate the Givi windscreen on mine but my Wife insists on some wind protection.

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