Carb Float Level

Retiredgentleman · Posted: June 25, 2007, 2:01 am Post subject: Carb Float Level

I just cleaned and rebuilt carbs on 78 XS650 SE. Set the Float height to 24 mm ( .940 in)...........Since the fuel level in the float bowls is so important I'd like to hook up a manometer to the float bowl drain plug using clear plastic tubing. I expect I can get a bolt of the same thread and just drill it out.
Anyone done this before? How did you do it? When viewing the manometer, what is the correct level for the fuel?

grizld1 · Posted: June 25, 2007, 9:37 am Post subject: Re: Carb Float Level

You're not really using a manometer (instrument for reading pressure)there, just a simple tube vented to atmosphere that lets the fuel rise to its level. You're on the right track--get a spare float bowl plug, drill it out, and attach a barb. Fuel level should come to the bottom of the flange on the float bowl with the bike level. It's not necessary to run the engine while you do this.

Retiredgentleman · Posted: June 28, 2007, 1:50 am Post subject: Re: Carb Float Level

Drilled out a float bowl drain plug and connected plastic tubing. Set up carbs level on the bench. ....................Interesting that when I set float height as per the Haynes manual @ 24 mm or .940 in. the actual fuel level as seen in the plastic tubing is 3/16 in. above flange of float bowl,(Rich)

This time I started by adjusting the float until I had the correct fuel level at the bottom of flange on float bowl. Then when I measured the float height it was 26.6 mm or 1.047 in.This is where I will leave it.

I think everyone would be wise to set their float levels using a plastic tube from the drain plug. Taking a measurement from float bottom to gasket surface is error prone and will not necessarily put your fuel level at the correct spot.

xsjohn · Posted: June 28, 2007, 8:05 am Post subject: Re: Carb Float Level

How does it run now and what are your head temps.....

John

Retiredgentleman · Posted: June 28, 2007, 10:03 am Post subject: Re: Carb Float Level

John;............Not ready to run engine yet; parts coming from mikesxs such as master cyl. rebuild kit and oil sump filter. Hope to have it running soon and will update my posts. I don't have a laser thermometer but your postings on head temperatures are making me think about buying one.

xsjohn · Posted: June 28, 2007, 11:37 am Post subject: Re: Carb Float Level

Sure could save the farm in the summer if things arn't just right.....Rode mine for 7 years with a hot cylinder and can't tell you how may times I had to fix it before I figured that one.........30 bucks for a infrared thermometer seems like nothing now...

John

80xs650 · Posted: December 14, 2008, 3:18 pm Post subject: Re: Carb Float Level

How did the non-spec float height work out? Did you have to change it? Thanks.

xsjohn · Posted: December 14, 2008, 3:28 pm Post subject: Re: Carb Float Level

Brass float settings 80.........23MM is about stock when set with the spring depressed...........use the allens and the floats and bowl and jets can be accesed on the bike........stock needles suck.............that in combination with timing and compression will beat the thing to death........been there and done that..........

xsjohn

Retiredgentleman · Posted: December 14, 2008, 3:54 pm Post subject: Re: Carb Float Level

80xs650;
Setting the float level with a clear plastic tubing from the drain valve is the most accurate, with no chance of error. Yes, I left my 38mm CV carbs as set in June of 07. Engine has started perfect and run extremely well ever since.

xsjohn · Posted: December 14, 2008, 4:14 pm Post subject: Re: Carb Float Level

As long as you know what the level is really supposed to be on these.........

xsjohn

80xs650 · Posted: December 14, 2008, 7:28 pm Post subject: Re: Carb Float Level

Thanks to both of you gentlemen for the replies. I'm going to replace the butterfly shaft seals on my 1977 650D soon (the right carb is chirping loudly), so I think I'll rebuild them at the same time, and get everything set properly. If the budget allows, I'd like to put them back together with a set of John's needles as well.

One other question: When measuring from the "gasket surface", is that the carb body where the gasket sits, or is it with the gasket in place? The last time I had the carbs apart, I set the floats at 24mm without the gasket.

Thanks again.

xsjohn · Posted: December 14, 2008, 7:44 pm Post subject: Re: Carb Float Level

Getting the screws off the main bar is fun........should heat them......I have broke off 2 so far......they used some kind of super loctite on them....once they break off I would have no idea how to get the stud out.....tried everything......had to drill and tap it larger.....bad day....

xsjohn

xsleo · Posted: December 14, 2008, 8:26 pm Post subject: Re: Carb Float Level

the yamaha factory manual i have shows how to do the drain plug /clear hose like this.

xsjohn · Posted: December 14, 2008, 9:25 pm Post subject: Re: Carb Float Level

God I am blind......knew I should have quit that sooner.......

xsjohn

Jake68 · 650Rider Supporter Joined: Mar 23, 2007 Posts: 841

xsjohn wrote:

Brass float settings 80.........23MM is about stock when set with the spring depressed...........
xsjohn

JOHN!!>..Wow..I've been looking for this Data...is there data like this for the 77 Carbs some idiot put on my 78 Smile

..adjusting on the bike I mean...

xjwmx · Posted: December 14, 2008, 9:55 pm Post subject: Re: Carb Float Level

xsleo wrote:

the yamaha factory manual i have shows how to do the drain plug /clear hose like this.

You have to be careful there's no bubbles in the tube, else it will read way wrong. I open the tap with the hose pointing down a bit and let the tube fill, which seems to keep the bubbles from forming. The engine should be idling.

xsjohn · Posted: December 14, 2008, 10:03 pm Post subject: Re: Carb Float Level

Jake.....make your own data.......set the floats to factory then measure to the body with the float spring gently depressed till it bottoms.....note that measurement.....see a few posts above.........posted that over 2 years ago.........been doing that for 40 years.......based on lazyness I guess...allens in the float bowl.........like a girl in a dress....play without ripping everything off Laughing

xsjohn

Retiredgentleman · Posted: December 14, 2008, 11:31 pm Post subject: Re: Carb Float Level

Important to have the carbs level, when setting float levels with the clear tubing method. If doing this with the carbs on the bike, it would be done with the engine off.

Jake68 · 650Rider Supporter Joined: Mar 23, 2007 Posts: 841

Yeah John, I spotted the Allens tip..its a cracker..off to get me some tomorrow Smile

tweedy64 · Posted: December 15, 2008, 11:28 am Post subject: Re: Carb Float Level

Ye jake allens in your float bowl makes life sooooo much easier, did mine awhile ago. cheers tweedy

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