Triumphrat

Panthermark · 03-07-2006

Okay, we all know how to change jets. And we know that they are only a small part of the total carb equation. We all know that TBS and Thrux needles are very good. Needles are cake to swap. Most of us know how important shims are. They are just as easy as changing needles. We know there are tricks that can be done with the slides, but some of them cannot be reversed too easily.

However

I've yet to see any posts about setting the float height. Can someone help me out here? I know from the Jenks PDF that the float height has a lot to do with low end power, but I have not seen any instructions on adjusting it. There is some small stuff in the service manual about it, but I'd like to hear from people with real world experience.

Do the carbs have to be removed?
Did it really help?
Pictures?

Getting more ponies at the top end is easy enough, but it's the grunt at the low end that always get left behind. I

Thanks

gm16sw · 03-07-2006

I wanna know too. Sorry...I have know imput but would like some as well.

vitabrew · 03-07-2006

Ok, get some narrow clear plastic tubing (I used hospital IV infusion tubing), need about 4-5 inches. Put bike on center stand, or lift (needs to be straight up). Make sure the petcock is closed, drain the float bowls, attach one end of the clear plastic tubing to the drain nipple on the bottom of the float bowl and bring the other end up to the side of the carb. Open the petcock and the fuel level should rise to about 2mm above the level where the float bowl and main carb body meet, if level is off float height needs to be adjusted. Repeat on other side.

rodburner · 03-07-2006

A hot tub,some wine and Jessica Alba was all it took to adjust my float level. :lgh:

meatwagon · 03-07-2006

Thanks Vitabrew.How do you actully adjust the float hieght?Bend the float tang or arm?Is there a screw adjustment?

vitabrew · 03-07-2006

Bend the float tang to adjust. Haven't had to adjust mine yet.

dazco · 03-07-2006

I don't mean to question the notion that float height will affect power. But could someone explain this to me? The way i see it, the level in the bowl is either too low to where there won't be enough fuel available when needed which should lead to cutting out or stalling, or too high to where it's flooding. in other words, it seems like a "on/off" sorta scenario...it would either be adjusted to where the bike runs improperly, or it would run right. I don't see an in-between or a situation where it would provide more power when adjusted properly vs adjusted a bit improperly but short of causing improper running.

Again, i'm not saying thats the way it is, but thats the way it seems to me. I just want to understand where i'm wrong if i am.

Panthermark · 03-08-2006

Daz,

Page 9 of the Jenks guide.

It refers to setting the float height for low end power. I don't know how much it will help, but it seems simple enough to check and change. As we continue to mod the intakes and exhausts, anything that can be done to help cure flat spots would be nice.

Jenks Carb Guide

03-08-2006

Hey Mark / Vitabrew / Daz,

Vitabrews suggestion is a good one for checking variation. Not sure what the 'about 2mm' measurement is based on - is this the top of the bowl? My memory is that the height set this way is usually based on where the top of the bowl would be.

It is certainly easier than the other way I'm going to describe - which assumes you're removing the carbs to measure carefully...

Remove the carbs, remove bowls and turn them upside down. At the point where the float arm makes contact with the needle pin measure from the bottom of the float tank to the bottom edge of the carb body with a steel rule or a caliper.

They can be done on the bike this way but it is not easy. If you're going to do this or use the tube method - don't try to bend the float adjustment tang without removing the floats. It is delicate work.

Incidentally, mine were out 1mm from one side to the other as standard and this actually generates some vibration at high revs. I measured mine for height and volume (this is a retentive race prep trick). I lowered them 1mm lower than recommended which gives better bottom end response.

Daz. The reason float height makes a difference is because atmospheric pressure acts over the fuel held in the bowl. This pressure amounts to hydraulics by pressure assisting fuel to flow through the jets - once it is flowing through the pilot and main jets. Variation in height varies the hydraulic pressure (more fuel more pressure etc.).

It is a small influence and so is only really noticeable when fuel flow through the jets is smaller (bottom end and cruise). In spite of this small effect - variation in float height does have a reasonable influence on balance at high revs. Having your cyclinders doing the same thing makes a big difference to the potential of your motor.

There is a working range for what works best for the motor. At the extremes - excessively high and it would run out the overflow tubes - excessively low and the main jet might starve for fuel. Both the main and pilot need to be immersed in fuel to deliver constant supply. Woody.

dazco · 03-08-2006

I see. Thanks woody.