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Hi , its been a long time since on forum, various reasons but this may help people with the old niggling problem with carb running issues on early slide type t-dubs? as you will see if you look through forums there are various fixes , non of them really worked for me ?
A very good worksheet done by qwerty which i did use (some help there well done for your time and effort)
I seem to have sorted the problem just about renewed the whole carb now trying new parts on it, but its worth mentioning that i renewed the complete choke plunger unit which made it run better when hot alot less hesitation (did not make any difference spraying it with carb cleaner around seals or plunger but on visual insp the barrel was showing wear/tear after just 2,500miles from new? not a cheap part to try £70:00 great british pounds +20% tax.:(
The next bit of advice i can give is too set float bowl height on min height spec so that the float bowl is carrying max fuel level this has made a massive difference and no surge 30-50mph in any gear on light/partial throttle, still pulls like a train all the way up to max throttle, this advice was given to me by a friend who tunes motocross 250cc bikes for race teams, now maybe the early carbs just had a small float bowl fitted for space reasons to fit in frame (i don,t know) but had in initialy set up in the middle of min/max height specs, anyway thts worked for me. there is no fuel resriction from tank too carb used aux portable tank when testing
pilot jet #42 from xt 350
main " #116
needle shimmed (stainless washers smoothed down 0.022" standard airbox/exhaust
 

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Somewhere here Lizrdbrth outlined the procedure for checking the float bowl fuel level that is simple.

You want the bike level and attach a clear line to the drain outlet. Open up the drain screw so fuel flows through the clear tube. Curve the clear tube up to the float bowl seam and the fuel in the line will show where your fuel level is in relation to the float bowl. I believe you want it just below the gasket. Mine was just about half full in this test and after setting the float height my surge problems disappeared.

GaryL
 

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Thanks for the props, but I can't take credit for that'n. It's older than dirt, and in fact the procedure is actually outlined in the TW manual.

I would like to restate that the static float level listed for our carbs (or any carb, for that matter) are only ballpark. A lot of folks don't realize this. They aren't and never were intended as gospel. They're a means of getting it close on a freshly re-assemble carb, after which you're supposed to check the actual level with the tubing.

A couple of the reasons for this is that the floats themselves are a mass-produced, manufactured item and can be of varying weights, and often they aren't perfectly parallel, either. Either will cause one to "float" higher or lower than the other in the float bowl, affecting ACTUAL fuel level. So check them via the tubing method and be prepared to tweak and repeat a time or two til it's right.

Make sure that the plastic float chambers themselves are as clean as the rest of your carb. That film of fuel residue has weight. Might be hard to wrap your head around, but even a fairly light coating of it will affect your float level.
 

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Thanks for the props, but I can't take credit for that'n. It's older than dirt, and in fact the procedure is actually outlined in the TW manual.

I would like to restate that the static float level listed for our carbs (or any carb, for that matter) are only ballpark. A lot of folks don't realize this. They aren't and never were intended as gospel. They're a means of getting it close on a freshly re-assemble carb, after which you're supposed to check the actual level with the tubing.

A couple of the reasons for this is that the floats themselves are a mass-produced, manufactured item and can be of varying weights, and often they aren't perfectly parallel, either. Either will cause one or the other to "float" higher or lower in the float bowl, affecting ACTUAL fuel level. So check them via the tubing method and be prepared to tweak and repeat a time or two til it's right.
Hey, It was your fault that I finally got my bike running right after you wound me up and pointed me in the right direction. I had already set the float height with a ruler and the carb up side down and all looked good until I attached the clear tube and found my float bowl was only about half full and the engine was starving for fuel when ever I got on it.

I will always blame you!:icon_biggrin:

GaryL
 

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Always willing to take the blame if it makes me look smarter than I really am:p.

It was worse back in the day when floats were made of soldered brass. If Elmer out on the assembly line made your left float and Luigi made your right float and Elmer liked using lots of solder but Luigi didn't them Elmer's float would make Luigi's side sink like a rock. lol.
 

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Carb dynamics

Somewhere here Lizrdbrth outlined the procedure for checking the float bowl fuel level that is simple.

You want the bike level and attach a clear line to the drain outlet. Open up the drain screw so fuel flows through the clear tube. Curve the clear tube up to the float bowl seam and the fuel in the line will show where your fuel level is in relation to the float bowl. I believe you want it just below the gasket. Mine was just about half full in this test and after setting the float height my surge problems disappeared.

GaryL
This Is good sound carb mechanics 101, glad to see it propagated here on the forum:eek:ccasion14:
 

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The reason they run lean with low float is not that they are running out of gas. The higher the level of gas the more pressure you have on the jet. I use this to tune the two carbs on my 47 Ford Flathead. If you are running a little rich just lower the level a tiny bit. To lean raise the level a bit. If the carbs are running out of gas it would be burning a lot of gas or leaking or not running from the tank as it should.
 
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