Triumphrat

DaleE

I'm in the middle of swapping out the pilots and mains on my 2K TBird in an effort to achieve that little extra horsepower rush that many of you have talked about.

I've put in the new jets, and will be re-installing the carbs tomorrow. My question is, should I worry about float height, now that I've got the carbs off the bike? I have no complaints about the way the engine currently runs, and no reason to think that anything is wrong with the old carb setup, but should I be measuring float height as a part of this modification? And if so, how do I go about that without a special tool?

jimmyj900

Check your float height before you consider adjusting. If they're all the same height then leave them alone and just enjoy the ride.

If your engine shuts down like the ignition was turned off when you hit reserve then the float heights are even. If you get a misfire on one cylinder for a while before the next starts misfiring then you're probably due for a float height adjustment.

To measure the float height, remove the float bowls and stand the carb rack on it's side so that the float pivots are up and the bowl mating face is vertical. Gradually tilt the rack until the float tabs lightly touch the spring pins in the float needle valves. Measure from the bowl mating face to the tops of the floats making sure that your ruler is square to the mating face.

The Haynes manual gives 14.5mm (all models) as the float height which translates to 9/16" with a 0.008" error.

Factory Pro gives a 17.5mm float height that translates to 11/16" with a 0.0015" error.

Now, 3mm is a pretty big difference. The first time I measured the float heights on my Keihins they averaged to 16.5mm but since I was installing the FP kit I set them all to 17.5mm.

NOTE: The Triumph shop manual checks the float bowl level using a transparent gauge tube attached to the float bowl drain with the carbs installed and the bike level. You hold the gauge next to the float bowl gasket line and check the fuel height in the tube against the gasket line. Triumph specifies 1.5mm over the line plus or minus 1.0mm.

The higher you set the float height, the lower the fuel in the bowls and the leaner the engine will run.

MEASURE THE FLOAT HEIGHT FIRST! If all three are set the same or within the Triumph 1mm range then you're probably better off leaving them alone. Otherwise, the choice of setting is up to you but I'd recommend averaging the current settings so as not to create any major differences in engine behavior.

To set the height you have to bend the float tabs that contact the bowl needle valves. This is a very delicate operation because if takes a bit of force and if you bend anything other than the tab the floats may not pivot properly. There's also a large multiplication factor in the adjustment so take it easy on the adjustments.

Don't attempt to bend the tabs with the floats in the carbs! Push out the float pivot pin with a paperclip or similar to remove the floats. I use the corner of a block of wood in a vise and gentle pressure to bend the tabs.

Any other questions, just ask!

Jim

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jimmyj900

Forgot to mention...

The local Home Depot has a section of blister-packed small hand tools and one of them is a 6" stainless steel ruler by General. It's got a 'T' slider with a pocket clip that's ideal for checking float heights and if I remember correctly that's what it was sold for years ago in automotive supply shops.

Jim

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Woody1911a1

"If your engine shuts down like the ignition was turned off when you hit reserve then the float heights are even. If you get a misfire on one cylinder for a while before the next starts misfiring then you're probably due for a float height adjustment."

excellent jimmy ! never would have thought of that . with all the talk about jetting , it's great having such an informative post on float height .


Mick , this needs to go up in proven setups

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DaleE

Wow, thanks, Jim.

jimmyj900

[quote=Woody1911a1;946338...never would have thought of that...[/quote]

It's really scary.

Jim

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Woody1911a1

however ............ carb balance would have an effect .......and the degree of it's effect would be determined by throttle position during the running down of the remaining fuel in the bowls after hitting reserve .........

just a thought

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jimmyj900

That's true but carb balance has it's greatest effect at idle, so the farther off idle you're running the less effect it has.

It's still scary as hell when you crest a hill at about 5,000 rpm, the engine just quits completely and you've no idea what happened!

Jim

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Woody1911a1

ahhhhhh so that's what you were referring to :P

and i was just about to adjust my floats .

thanx bud , always look forward to your posts

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