Ok this comes up probably once every few weeks, so i dug thru and gathered the information neccessary to do the Metering Spring mod on your carbs.
for those that dont know, you can adjust the pop off pressure of the metering valve, which dictates amount of fuel flow into your carb at any point in the rpm range. by lessening the pop off pressure, you allow for less fuel pressure to be needed to enter the carb, thus makeing it easier for fuel to flow into, thus thru the carb, maximizing fuel available for the motor thru the entire rpm range.
This can be a very important mod on a Reed case motor, but due to all carbs being slightly different, it may or may not be an effect you have, or will ever have. but its good information to know, if your maybe having some quirks that you cant track down initiallly, and your swayed to think its fuel supply. a good indication your pop off pressure is too high is if your primer bulb is constantly being emptied out after a long run.
your primer bulb should basically be 1/2 full or more pretty much all the time. if you run, and see your primer bulb is empty or near empty, you will likely see great benefits to lowering your popoff pressure, thus increasing fuel flow, thus fuel supply to the carb and motor.
here are some of the posts quoted by the original poster, on their mods and subsequential results. at the end, you ll find a link to the relavent thread where i dug this information out of.
i took a bit of time and dug up the relavent thread and subsequential posts. these will help you imensly. Im actually going to make a new post on just this topic in the engines/exhaust section.
Originally Posted by SSNOS
I just started another thread with issues with my 813 and TS metering spring. The metering spring is under the primer bulb housing. If you take off the housing, you'll see the main needle and metering arm and the spring goes under the arm. I've had some tuning issues with this setup so my reccomendations would be for you guys to wait and see what TS says about my problem first before you try this combo. I think the spring is only meant for teh stock carbs.
Originally Posted by stubby686
Update: The pump/gague set up I'm trying to use is less than fair to say the least so I'm just doing it the old fashion way ..... trial & error
I'm taking single coils off the spring then running it to see if there is a difference. The first 5-6 coils didn't do a thing at all. I went for broke today and took 5 more coils off all at once. What a difference that made. It's not 100% ripping out of the hole on pavement but about 3-4 feet out it's all that & then some. On dirt with less traction about 1 foot out if that and all hell is unleashed !! The way I see it now it's perfect (for me). Who woulda thought snipping a few coils off a tiny spring could make such a huge difference. I was just about to dump 300 into a top end. According to Trevor the stock springs in the WT carbs need aprox 25psi to open the metering needle and the "sweet spot" is 12-14psi.
Thanks everyone !!! This thread saved me some coin , put a huge grin on my face seeing this thing rip & hopefully helped out someone else be it now or in the future !!
Originally Posted by stubby686
Thats the one. #48 (NOT #48A). It can be done with the carb still on the motor. Just take off your roll cage & air filter.
Carb how it will be on motor , take cap off tank to release any pressure first
Take 4 screws out & remove bulb, white part of carb & diaphram (black gasket) Fuel line can stay on
Take the phillips screw out and you'll have the metering lever & spring in hand. It's a really crappy pic of the spring but the two ends where the coils are close together is what your after. I took about 5 coils off each end. That was aprox half of the total (close together) coils on each end. This is a 668 carb & looks to have a different spring than the 813 I've been messing with. My 813 spring had more coils wound close together on both ends but was shorter in total length so in theory would make it stiffer having more coils in a shorter spring. Anyhow all springs will be different as will personal set-up's so it's whatever works for your app and not a "coil count" as what to take off. I found a utility knife works best to cut the coils off. Lay the spring on something metal and put the blade in the spring where you want to cut it and rock the blade back & fourth while pushing down. The nail clipper way spreads the coils apart and bends them and was a PITA IMO. Good luck !!
Originally Posted by KUN114
This is what I came up with. Not sure how accurate it is, but seems to work. I took a Ball needle, slid about a 1" piece of antenna tube over it. Then the fuel tubing over that and wrapped it all with some vinyl tape. Hooked it to my low preasure motorcycle suspension pump.
Stock spring popped at 30psi
Cut off 5 coils from each side brought it down to 26psi
Cut all close coils from each side= 20psi
Cut two more coils from each side and it's about 14psi
Installed the spring in the carb on my 5T and fired her up. Notice a major difference just running on my short driveway. To bad we just got 30" of snow yesterday, so it will be a while before I can give it a proper test run.
Another question. Will this spring mod benefit performance on any engine or just the reed port engines?
and the original thread link.
maybe this can be stickied up. would be a great sticky imo for anyone with a TS motor, or other Reed induction motor. as well as pretty much any motor that just doesnt seem to be all it should be.