THIS MONTH IN THE GARAGE...
This month Dan gets to grips with punctured floats and a very dirty fuel tank.
I’ve never taken the time to investigate why the white floats in Dell’Orto carbs seem to have such a high rate of failure, but they do. Nothing is 100% guaranteed or bulletproof, so even other floats will still have some level of failure, but I see more of the white floats ending up perforated than I do any others. Is it because there are more white floats in circulation and therefore, as a percentage, we are bound to see a higher number? Who knows (I’m sure somebody does) but regardless of the reason why they fail, Dell’Orto seems content to send the majority of its carbs out with them so all you can do is run them until they fail.
When I’m buying replacement floats, I go for either the black Dell’Orto floats or the red MB ones, they both seem to work very well and I haven't seen any failures with either yet. The MB ones are self-explanatory, but the black Dell’Orto ones need to have additional consideration, as they use a different plastic to the white ones, and therefore have a different buoyancy for the same weight, hence I usually go for a slightly heavier black float than the white equivalent.
A case in point happened this month when a customer brought his scooter in for dyno and we saw exactly this problem. I’ve seen it on a lot of white floats, and both went on my Targa Twin within a very short space of time of each other. When they fail, a small perforation and a partially filled float will just cause rich running but if the float fills entirely or both sides go, you end up with fuel spewing out of the carb overflow and that’s not a good thing. So, my advice to anyone running a set of white floats is just to carry a spare set of the red MB ones in case you need them.
Shit from tank to carb…
I don’t know what the precise chemical make-up of the offending material is, most likely some sort of fine metal flake/ silt/paste, but my ‘technical’ approach is to say: “You’ve got some shit in yer carb mate!”. And that’s exactly what I said to Stu Mawson when he popped in for a dyno last month. However, and I told Stu this, I’ve never seen a carb that knackered from tank contamination. Clearly, something had come through from the tank, clogged up the filter in the carb, but still allowed the finer particles through, which had acted as a grinding paste on his carb and decimated the internals. The slide looked like someone had been at it with 40-grit sandpaper or even a rough hand file, it was particularly messed up.
I forget the exact jetting details that we ended up with, but I seem to recall that a lot of the rich spots were ironed out just by replacing like-for-like components because the old ones had worn so badly that they were running rich, and new ones took up the slack and tightened up the jetting nicely.
I’ve no idea if there was any damage to the cylinder, that wasn’t one of the jobs for us to do, but thankfully cylinder compression and power were still up in the right ballpark so, luckily, just a few new carb bits got things sorted. I also advised Stu to strip the tank when he got back home, as the fuel tap and filter would also need cleaning out, most likely, not to mention the tank itself also needing a good wash out.
Our method for that is to put some clean fuel in the tank, along with a handful of nuts and washers, and then simply shake the whole tank back and forth, in every direction for a minute or two (you soon get tired!) and then drain it out and repeat. You have to keep going at this until the fuel you empty out runs clear and is free of debris. It’s a mundane task, but well worth doing if you don’t want to destroy your carb and, potentially, your cylinder.
My ‘technical’ approach is to say: “You’ve got some shit in yer carb mate!