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PHF30 stuck float?

JayDeeca

JayDeeca

Tuned and Synch'ed
GT Contributor
Joined
Aug 21, 2012
Messages
65
Location
Grand Forks, B.C.
Getting the SPII back on the road, and I have had the right carb off twice now in two days trying to solve a problem of raw gas pouring from the carb body as soon as I turn on the taps.
The float is an original black dellorto 10 gram float. I stuck it in the freezer and then submerged it in cold water, and observed no air bubbles from the expanding air. I checked the float weight on a sensitive postal scale and it says it is 10 grams. I also checked that the float hung 18mm on the carb, and that the spring in the needle was functional.
I put everything back together, and still had gas pouring out the carb throat.
The needle and seat (250) were new last year and have maybe 10 miles on them. On a hunch today I stuck in the old needle and seat, but the results were the same.
My schooling says that the only way this can happen is if either the float is hooped/stuck, or the needle is not seating properly. Am I wrong? Is there something I am missing?
Thanks
JD
 
For some reason sometimes the pillars the float needle go through seem to 'Grow'! Don't ask me! I haven't got a clue how or why but that is what *Seems* to happen!

The end result is that the part of the float that the spindle goes through gets 'Grabbed' between the two pillars that the spindle is supported in and although it will appear to move freely when you move it by hand, in service it sticks and won't allow the needle to seat. This is most often seen on carbs with anodised bodies but I've experienced it on non-anodised ones too.

While I can't guarantee this will be the cause the fix is vary simple. Remove the float and get a smooth file and remove a few thou of material from the *Insides* of the pillars that the spindle goes through. It takes only a couple of minutes and may well fix it.

Pete
 
Pete, I shall give that a try. Nothing I had ever heard before, but I learn something every day. I think I will see about getting a new set of floats on Monday as well, never hurts, although it will likely be three weeks getting the darned things. I see MG Cycle float listing is for 8.5g floats. As I indicated, mine are 10g. What difference do the two weights make? \
JD
 
Sounds like something is definately wrong ...how about swapping the two floats between the two carbs... If the symptom follows the float you have the culprit.

Mark the bad one.

You could then hold both floats up in good light, together, the known good one and the known bad one, and compare closely
Compare the float rods, the needle grooves, good against bad etc.
Good luck.

Alex
 
JayDeeca said:
Pete, I shall give that a try. Nothing I had ever heard before, but I learn something every day. I think I will see about getting a new set of floats on Monday as well, never hurts, although it will likely be three weeks getting the darned things. I see MG Cycle float listing is for 8.5g floats. As I indicated, mine are 10g. What difference do the two weights make? \
JD
Click to expand...

I know it sounds like total bullshit but really, its a problem I've observed or st hand on a number of occasions! I have no idea why it occurs as obviously aluminium alloy doesn't 'Grow' but I've seen it and cured it numerous times.

There is of course no guarantee that this is your problem or the fix!

Pete
 
Nope. No joy, Pete. I used a dremel to take down the inside edge of each tower maybe a couple of thou., but on reinstalling the carb I had another major flood. Oh well, it was worth a shot. I have a couple of 8.5g floats on the way, to replace the old 10g floats. Are they to be set up any differently than the 10g?
Tonerj, that is good advice re swapping floats side to side, but I will wait till the new floats arrive.
Thanks
JD
 
Have you tried setting up but with the bowl removed and manually lifted the float to shut the flow. You may have a float that rubs the side of the bowl or just possibly the tab that is used to set the float 'drop' height catches the edge of the seat body where the hex faces (for the spanner) are its very close in there
 
I got the new floats, and went to install them, but realize I still do not know the float height for the 8.5 gram floats. The manuals I have both give the settings for 12 and 10 gram floats. Anyone know what it is for 8.5?
JD
 
JayDeeca said:
I got the new floats, and went to install them, but realize I still do not know the float height for the 8.5 gram floats. The manuals I have both give the settings for 12 and 10 gram floats. Anyone know what it is for 8.5?
JD
Click to expand...


Tried to find the 8.5 spec, but no luck. Start with the 10 gram height. If the carb leaks, raise the floats a little. It doesn't need to be exact. You need enough fuel in the bowl to supply the engine, but not so much that it overflows.
 
john zibell said:
JayDeeca said:
Tried to find the 8.5 spec, but no luck. Start with the 10 gram height. If the carb leaks, raise the floats a little. It doesn't need to be exact. You need enough fuel in the bowl to supply the engine, but not so much that it overflows.
Click to expand...
Click to expand...

Thanks John, much appreciated.
JD
 
Re: PHF30 stuck float? - still

I am still chasing the fuel overflow problem from the right carb PHF30). I have replaced the needle and seat and the float with new components. I have adjusted, measured etc, and still I get a severe overflow from that carb. I am starting to suspect that the way the fuel lines connect the two carbs may be the issue. Is that possible? Can anyone tell me what the original set up for fuel lines was on the SPII? Was it the same old X fitting that the Eldo had? Currently on the SP each tap goes to the carb below it. The carbs are also connected to each other, and I am using dual barb connections, so there is a fuel line running across the top of the trans from one carb to the other. Is it possible that this set up is causing the problem? I am grasping at straws.
Thanks
JD
 
The fuel lines aren't the issue, That is the same connection pattern I'm using on my MkV. It is something with the carb. Did you open up where the float attaches as Pete recommended? It is possible for fuel to go around the seat if the mating isn't perfect. Are you sure it is not that?
 
John Z
I did indeed take Pete's suggestion, and relieved the inside of the float legs a bit. Although there was no evidence of the floats having been binding, I did it anyway just to make sure.
I agree with your take on the fuel line; I have that same set up on my Eldo now, with now issues. And it should not make any difference so long as the needle is seating properly. However, I have tried three separate needle and seat set replacements to no avail, so I am stumped.
One other thing that is a possibility is that I replaced the cable operated enricheners to flip-tops last fall. From my understanding of how the circuit works, I can't see how a stuck enrichener would cause a flood of gas out of the carb, especially when the engine is not running. However, I mention it because it is a change I have made to the carbs. I had the flip-tops off again the other day to compare them to the old ones and can see no difference.
John D
 
The flip tops aren't this issue either. I had a problem with a BMW/5 that I rebuilt the carbs (Bings). No matter what I did, I couldn't get the left side to work properly. Ended up I had to replace the left carb as over the years, the body had actually gone bad. Different carb body,same rebuild parts and the problem went away.

Have you tried just setting the floats a little lower? BTW, it is good practice to turn off the petcocks when you stop somewhere.
 
Re: PHF30 stuck float? RESOLVED

I solved the issue today. I pulled the left (non-leaking) carb today and thoroughly cleaned all jets etc, and installed another new needle and seat. I also replaced all the nylon fuel line with German made black braided line and new hose clamps. I also removed the flip tops and put the old cable operated enricheners. The flip tops were a pain to reach anyway. Dumped the gassy crank oil, refilled with Rotella T 15/40, warmed the bike up, dialed in both carbs with the Harmonizer, and bingo it runs like a top!. A non-gas leaking top! I went for a 40 mile tear and the bike runs just great. The feel of this SP is so different than my Eldo and Quota. It seems more visceral or something.
I cannot definitively say what I did that corrected the problem, but I suspect the left needle and seat and the fuel line.
Thanks for everyone's help and patience!
John D
 
You should be running a multi weight oil such as 15W50. The 40 is a little light for these engines.
 
john zibell said:
You should be running a multi weight oil such as 15W50. The 40 is a little light for these engines.
Click to expand...

Can you make a recommendation? Something that is commonly available? I have been using the Rotella Diesel oil because of the ZDDP content. I| was just about to drop the oil in the Quota and refill with the Rotella. Maybe \I will wait till I hear what you recommend.
TIA
JD
 
My oil of choice is Mobil1 15W50, but any of the full synthetics available should be just fine, even for the hydraulic valve engines. The two valve engines are as choosy as the 4 valve engines. I'd only possibly be concerned about lower ZDDP in racing applications. Again, this is just my opinion based on observation.
 
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