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Metering Spring Mod for More Fuel Supply to Carb for all motors.

Discussion in HPI Baja Engine and Exhaust forum, started by Timmahh.

Daves Motors
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  #161  
Old 12-28-2015
sprnt22m sprnt22m is offline
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Great Results

Did this mod to my kid's 30.5 King and used the pressure regulator and gauge. Should have jotted the numbers down but was getting like 25-27 psi to get the needle to pop off the seat. I then closed off the pressure so there was no additional pressure but the gauge would still read line pressure and allowed it to leak down and was getting 10-12 psi for a hold pressure.

Cut off about 4-5 windings off each end of spring so there was like 1-2 full coils left on the spring so it would still sit straight. Used a utility knife against steel bench vise and it easily cut it off nice and clean. After the mod I was seeing like 18 psi for pop off and it then leaked down to 8-10 psi.

Previously the motor was lazy off the bottom and was hard to tune but this made the thing really wake up and responded very well to a tune. Its been a while since I ran it and have an OBR 30.5 in my HPI Baja and this King motor sounded almost as good. I've had issues with tuning both of them once in a while when they get warm and have seen this empty primer bulb issue so I'm expecting this mod to solve that too. Idle quality was great and what was nice is I could tune the idle mixture to a nice lean idle so it doesn't load up but it was never boggy even with the lean idle mixture. Tuned the high speed so it was just getting blubbery so the kid doesn't burn the motor up and it was still super clean off idle with great throttle response... I was impressed

Going to do this mod to my OBR in the next couple of days so I'm looking forward to seeing the improvements it does to it. Will try to shoot before/after video. I spend a lot of money on pipes trying to get rid of the flat spot off idle so this thing would wheelie on demand... pretty sure this mod would have saved me a lot of money.
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  #162  
Old 05-16-2016
jcflyer jcflyer is offline
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I would like to ask what is the purpose of this mod? Why not just open the low needle for more fuel instead of cutting the spring? Also if I am breaking my tires loose on cement wouldn't that indicate that I have enough low end power?
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  #163  
Old 07-03-2016
nitroheadjones nitroheadjones is offline
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because you can never have enough horsepower but you can always throttle back when you need too.
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  #164  
Old 07-03-2016
jcflyer jcflyer is offline
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Quote:
Originally Posted by nitroheadjones View Post
because you can never have enough horsepower but you can always throttle back when you need too.
I have to disagree, too much horsepower breaks things and for me creates lots of wheel spin. I drag race and too much wheel spin is not good...
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  #165  
Old 07-04-2016
jbooker82 jbooker82 is offline
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Quote:
Originally Posted by sprnt22m View Post
Did this mod to my kid's 30.5 King and used the pressure regulator and gauge. Should have jotted the numbers down but was getting like 25-27 psi to get the needle to pop off the seat. I then closed off the pressure so there was no additional pressure but the gauge would still read line pressure and allowed it to leak down and was getting 10-12 psi for a hold pressure.

Cut off about 4-5 windings off each end of spring so there was like 1-2 full coils left on the spring so it would still sit straight. Used a utility knife against steel bench vise and it easily cut it off nice and clean. After the mod I was seeing like 18 psi for pop off and it then leaked down to 8-10 psi.

Previously the motor was lazy off the bottom and was hard to tune but this made the thing really wake up and responded very well to a tune. Its been a while since I ran it and have an OBR 30.5 in my HPI Baja and this King motor sounded almost as good. I've had issues with tuning both of them once in a while when they get warm and have seen this empty primer bulb issue so I'm expecting this mod to solve that too. Idle quality was great and what was nice is I could tune the idle mixture to a nice lean idle so it doesn't load up but it was never boggy even with the lean idle mixture. Tuned the high speed so it was just getting blubbery so the kid doesn't burn the motor up and it was still super clean off idle with great throttle response... I was impressed

Going to do this mod to my OBR in the next couple of days so I'm looking forward to seeing the improvements it does to it. Will try to shoot before/after video. I spend a lot of money on pipes trying to get rid of the flat spot off idle so this thing would wheelie on demand... pretty sure this mod would have saved me a lot of money.
It's a night and day difference. I did this to a Gizmo modded WT-1048 big bore carb on my T.S. 30.5. I did the mod before running the carb.

Another thing I like to do is get some threaded rod and make a couple carb studs. That way you just slide a gasket, carb, another gasket, and then the air filter mount on to the studs. That way it all stays in place / lined up while putting it back together.
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  #166  
Old 07-04-2016
jcflyer jcflyer is offline
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So if you did the mod before running the carb. how do you know it was a night and day difference?
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  #167  
Old 07-09-2016
jbooker82 jbooker82 is offline
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Quote:
Originally Posted by jcflyer View Post
So if you did the mod before running the carb. how do you know it was a night and day difference?
Sorry should have been more clear, from the stock WT-990 to the modded WT-1048 on the same T.S. 30.5 engine. Usually when you go to a larger carb you loose low end throttle response. The modded WT-1048 has a crisper off idle snap than the non modded WT-990.
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  #168  
Old 02-15-2017
Mikee36 Mikee36 is offline
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This thread has some great info. Made a few of my cars run surprisingly better.

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