Engine has poor throttle response down low?

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IMADMAN

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Kinda stumped on why I can't seem to find the sweet spot for the low end throttle response. I've tried every setting from 2-1/2 H to 1-3/4 L down to a little over 1 H to 7/8 L. The mid and top are great with gobs of power, but the take off from a dead stop is really horrible! It seem to take a few seconds for the engine to build up enough rpms/revs. I am running a DS 27 w/ 8000 Rpm clutch spring, shoes reversed, 668 carb and an FG pipe. Any ideas guy's it seems to be getting to much fuel on the L even on the 7/8 setting, once the rpm builds up it runs great. I just don't have the tire spinning power down low.


Any help will be greatly appreciated!


Thanks.
 
IMADMAN said:
Kinda stumped on why I can't seem to find the sweet spot for the low end throttle response. I've tried every setting from 2-1/2 H to 1-3/4 L down to a little over 1 H to 7/8 L. The mid and top are great with gobs of power, but the take off from a dead stop is really horrible! It seem to take a few seconds for the engine to build up enough rpms/revs. I am running a DS 27 w/ 8000 Rpm clutch spring, shoes reversed, 668 carb and an FG pipe. Any ideas guy's it seems to be getting to much fuel on the L even on the 7/8 setting, once the rpm builds up it runs great. I just don't have the tire spinning power down low.
Any help will be greatly appreciated!


Thanks.
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Is the gearing to high? Could be a issue. Pluged airfilter. I have never reversed the clutch shoes, I have read some people do, I don't think it is a good thing. Not the way ther were designed to operate.


Try another carb, it would be the easiest first thing to do.
 
I have seen this symptom before when the idle was to low. I would first just idle it up with the radio EPA or trim on the throttle. If that helps then tighten the idle adjust screw till it hits the plate and set your radio back. If this helps you might have to slightly readjust the low end . I am not saying this for certain fix but is easy try to rule out , and it might fix it.
 
Clubin said:
Is the gearing to high? Could be a issue. Pluged airfilter. I have never reversed the clutch shoes, I have read some people do, I don't think it is a good thing. Not the way ther were designed to operate.
Try another carb, it would be the easiest first thing to do.
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I have 3 to choose from, another 668 a 603 and an 813. I'm running 33/27 (A/B)

Sprint 77 said:
I have seen this symptom before when the idle was to low. I would first just idle it up with the radio EPA or trim on the throttle. If that helps then tighten the idle adjust screw till it hits the plate and set your radio back. If this helps you might have to slightly readjust the low end . I am not saying this for certain fix but is easy try to rule out , and it might fix it.
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Yea I did the idle thing as well, and it's pretty normal, it idles steady and consistent. Adjustments made are noticeable right away. I think i'll switch out the carb. and see what happens, BTW even w/ the stock 23cc it had this issue as well. But I thought it was the MT tires that was killing it. There is no real binding in the drivetrain, w/ the exception of the 25/25 steel gears.
 
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yolonda21 said:
Did you do the fuel tank vent mod? It may be starving itself of fuel. Just a thought. ;)
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It already has the upgraded plug and i've already vented the fuel cap, but I do notice a slight leakage around the plug, i'll try to reinstall it and see what happens.

Clubin said:
27/33 is maybe just a little high for the mt. Try 25/35 before you change anything else.
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I am actually running CEN Assault wheels with Sniper 55 series tires. The diameter is close to the MT size but way less weight.
 
Hey man, I know exactly what you mean with those marine engines. I never really noticed it on my Baja with my rear Dom, side Dom, or Mielke pipe since all 3 of those have a nice bottom end. The marine cylinders really bogged with a high end pipe like the Jetpro V3, moreso than a stock 26 cylinder. I'm now running my DS setup on the Rampage with a side Dom. It too bogs for a second then it's pure balls to the wall crazyness. I got tired of that low end bog so for shits and grins I put the clutch shoes back in the right way. It now performs so much better.


IMO the marine heads do not like stress at low RPM's unless you running a pipe that can make up for it. Don't get me wrong I love my DS setup. Once these engines do "hit the pipe", they are insane. Try putting the shoes back so the engine can get past the bog.
 
catchaser said:
Hey man, I know exactly what you mean with those marine engines. I never really noticed it on my Baja with my rear Dom, side Dom, or Mielke pipe since all 3 of those have a nice bottom end. The marine cylinders really bogged with a high end pipe like the Jetpro V3, moreso than a stock 26 cylinder. I'm now running my DS setup on the Rampage with a side Dom. It too bogs for a second then it's pure balls to the wall crazyness. I got tired of that low end bog so for shits and grins I put the clutch shoes back in the right way. It now performs so much better.
IMO the marine heads do not like stress at low RPM's unless you running a pipe that can make up for it. Don't get me wrong I love my DS setup. Once these engines do "hit the pipe", they are insane. Try putting the shoes back so the engine can get past the bog.
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Thank God, i'm not the only one! Funny thing is the FG pipe w/ a CY29 was pretty nutz in my Firehammer, better than the $250.00 Samba pipe I wasted my $$$ on. Cool, i'll pull the clutch and turn it around the right way, re-check my fuel plug thingy and maybe try another carb and see if it helps, but yea mid to top it screams!
 
Gigitty-Gigitty-Goo- AW RIGHT!!!!!!!!!!!


Well, I finally found the time to flip the shoes back the correct way, and the throttle response has definitely improved! Still working on a tune but it running WAAAAYYYYYYYY better now. Thanks for all the suggestions. I was running the CEN Genesis 55 series assault wheels and Sniper tires, they grab good on short cut grass, unfortunately I did have a minor problem blowing out the right rear, the glue on the bead let go so i'm gonna try and re-glue it again later. For now I bolted up the Excavators and Desperados. Still have a very slight lag on the bottom will try to tune it out w/ the 668 if I can't get that to go, then maybe i'll try a 813 0r 603 and if that does'nt work maybe a gear change, or try my MCD jetpro pipe.
 
IMADMAN said:
Well, I finally found the time to flip the shoes back the correct way, and the throttle response has definitely improved! Still working on a tune but it running WAAAAYYYYYYYY better now. Thanks for all the suggestions. I was running the CEN Genesis 55 series assault wheels and Sniper tires, they grab good on short cut grass, unfortunately I did have a minor problem blowing out the right rear, the glue on the bead let go so i'm gonna try and re-glue it again later. For now I bolted up the Excavators and Desperados. Still have a very slight lag on the bottom will try to tune it out w/ the 668 if I can't get that to go, then maybe i'll try a 813 0r 603 and if that does'nt work maybe a gear change, or try my MCD jetpro pipe.
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813 helped out on the bottom end quite a bit. I got mine used and it leaked fuel from the throttle shaft so I had to put a stocker back in. I liked how the 813 performed but I don't know if I wanna put another back in. Sometimes they can be a female dog to start without the choke.
 
I took my car apart and installed some upgrade parts as well as a lightened flywheel and a 8K rpm clutch spring.


I put the car together and started it.


There is a big difference in throttle response from the get go and it spun the 4 wheels (stock tires) on comncrete. I hope the gears hold.


Now I have to accelerate more to move the car from idle than before so the stock clutch spring lets the clutch engage at lower rpms so that is why the standing start is so letargic.


Tomorrow I am going to take it to our bashing location and see
 
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