Ever have a problem with these needle valves ?

[tz375]

I checked the 72 550 VM28 floats and 74 BS40 and 76 BS40 and a set of 73 GT750 VM32 and they all look the same to me. YMMV.

[pearljam724]

I checked the 72 550 VM28 floats and 74 BS40 and 76 BS40 and a set of 73 GT750 VM32 and they all look the same to me. YMMV.

Good to know. Thank you, sir. I'll have to open my 550 carbs and give them a try to verify this being the problem or not. I cross referenced some floats and I found that the early GS model floats from the 450/550 and 850 if I rememeber correctly are the same as the late model GT 750 floats. But, when I look at fiches for the GT 550 and 750 float part numbers they are different ?

[tz375]

I agree that the part numbers are different but I could not tell the difference. I used a calibrated lab grade eyeball to determine that they are the same and it is quite possible that the tangs are slightly different but the difference appears to be minor ie I didn't spot a difference. They are close enough to try a set if you have them available.

If they don't work then let's look at alternatives.

[Knut]

Met a similar problem when we were working on the 550 carbs for the GTR. The needle valves were aftermarket, and the carbs flooded even if set correctly. I got some original Mikuni needles from a spare set of H1 carbs, and compared. They are visually identical, BUT, the spring loaded "tap" inside acted differently. On the aftermarket needles they could be pushed all the way in. On the Mikuni needles they stopped about 1mm before, so they didn't go all the way in. Installed the stock ones and no more flooding.

I always go for stock Mikuni parts for carbs. It can save a lot of hassle and grief.

[Suzsmokeyallan]

TZ375 said

I used a calibrated lab grade eyeball

That sounded vaguely familiar so I went and did a search on Wikepedia and all was confirmed. Those lab grade viewing devices were the type I used to have before I switched over to scanning electron microscope HD eyeball.

You really should upgrade Richard its a whole new world.

Since the reference to the early GS750 was mentioned that float should also be found in the first GS425/450 carb as well.

When rebuilding my carb sets (I'm working on a spare set as well) for the 77 project Buffalo, I knew what was coming as I've had the blessing of it bestowed on me before.
So,,,,,all new gaskets, all new o-rings, all new float valves, all new floats, all new screws, and all new jets. Previous owners seem to love to destroy these parts in their bid to make future owners buy new ones.

Richard how good are the Keyster float valves in the kits from Sudco? did you ever test any?
I have a few new Keyster float valves put aside and I wondered if you had good results with them in your testing.

[pearljam724]

Met a similar problem when we were working on the 550 carbs for the GTR. The needle valves were aftermarket, and the carbs flooded even if set correctly. I got some original Mikuni needles from a spare set of H1 carbs, and compared. They are visually identical, BUT, the spring loaded "tap" inside acted differently. On the aftermarket needles they could be pushed all the way in. On the Mikuni needles they stopped about 1mm before, so they didn't go all the way in. Installed the stock ones and no more flooding.

I always go for stock Mikuni parts for carbs. It can save a lot of hassle and grief.

That is the exact thing I noticed. Didn't think it would be a problem. The new K&L needles push all the way to the head of the needle body. Where I'm pretty sure I remember my stock ones also stopped a mm or maybe even 2 mm from the body. In noticing the comparison, I thought I made a good choice in replacing the stock ones because they didn't completely compress like the new ones. Right there might be the winning cause. Or losing cause, however you want to look at it. With " Knuts " comments I think I know how to fix that. With the K&L's pushing all the way to the base. When the tongue is adjusted to float height, it angles down on top of the needle. Not shutting the fuel completely off because a mm or 2 is not compressed because of the angle of tongue when it meets the needle. With Mikuni needle being short of the base a mm or 2, it works fine in conjunction with angled tongue. What I think may just work for the K&L's. I need to flatten the tounge where it meets the head of the needle when adjusting the float level so that the tongue lays flat against the head of the body that holds the needle.

[pearljam724]

My carburetor problem wasn't the floats or needles after all. I'm ashamed to admit what turned out to be the problem. Anyhow, the bike is running like a champ now. Just have to work out a couple small electrical issues that I hurried to get finished. The next time I have a moment, mess with the air mixture screws as it doesn't want to idle at 1,100 rpms. It will idle however at 1500 rpms. So, I know I'm very close. Little stuff. But, It's running very well. No more fuel leaks, all cylinders consistently firing, great throttle response now down low and up high. No hesitations. I rode it for a couple of hours today. The chambers make it sound and feel like a 2 stroke should. Put a big smile on my face. Everything is now good in Buffalo land.

[T350guy]

Put a big smile on my face. Everything is now good in Buffalo land

That's good to hear