whats the best setup

[POORBOY350]

When you hear people talking about 4 mils out running 10 mils with "the right setup" there refering to

how the chassis is set up to get the power to the ground like for instance: size of paddles, # of paddles, gearing, swing arm length, stretched frame, lightend frame, lock out, overide tranny etc.

 

You should invest in a nice compression tester and see where your at.

IMO you if like riding/playing for hours on end and want it to be reliable and fun, run 160-165 lbs of compression and 4* timing, which is proably where your at now with the 20cc's.

 

I run 21cc domes and 4* all day long. I tried 6 and 7 degrees and my plugs backed out twice from the detonation and the bike was noticibly hotter and my pipes discolored. Also running 108 octane.

 

ok thanks man i got ya. so i should just stick to getting some pipes for now? and then a swinger? i do like riding alot tho so i dont want to sacrafice any realiability....

[Titan up]

ok thanks man i got ya. so i should just stick to getting some pipes for now? and then a swinger? i do like riding alot tho so i dont want to sacrafice any realiability....

Yea a set of CPI's or Shearer's and you'll notice more pull in your topend.

I would keep your swing arm how it is. Extended swing arms make the bike harder to turn and you'll lose

traction because the rear tires have no weight over them and less weight transfer to the rear.

Longer swingers are only needed in extreme traction situations like drag racing where your getting all your power to the ground and you can't keep the front end down.

Edited September 29, 2008 by Titan up

[BlntdEyez]

Yea a set of CPI's or Shearer's and you'll notice more pull in your topend.

I would keep your swing arm how it is. Extended swing arms make the bike harder to turn and you'll lose

traction because the rear tires have no weight over them and less weight transfer to the rear.

Longer swingers are only needed in extreme traction situations like drag racing where your getting all your power to the ground and you can't keep the front end down.

 

The reason I suggested a longer swinger is because he stated he wanted to get into more duning and dragging. Its going to be hard to keep that front end down with that swingarm and the power that bike puts out.

[POORBOY350]

its hard to keep it down now but i guess losing my turning wouldnt really be worht it if i need i wil get one if i start doing alot of dragging.

 

would it be worth putting different domes in her??? would 20s to 17s make a big diff?

[Tim Potteiger]

My experience with the 421 Cub is that the best pipe is the CPI for all out horsepower numbers. They are not meant to run high compression, but they do like timing. You can go to +8 on a cub (111 fuel of course). They are fine at 150-165 lbs of compression. The only problem with CPIs on a Cub is the horrible dead spot in the low end. If you look at the power curve on a dyno, you will actually see a horsepower dip before it climbs out hard. CPIs on a +8 timing 421 Cub with 28mm PWKs will do about 93 horsepower. With your carbs, that might go up a bit more. The Cub is a drag motor though, so you will want some more swing arm.

 

For just riding, I hate the Cub motor power curve. It is dead in the low end and pulls so hard on the power band it's scary for tight trails and such. If you are into MX, you definitely won't want CPIs.

[POORBOY350]

My experience with the 421 Cub is that the best pipe is the CPI for all out horsepower numbers. They are not meant to run high compression, but they do like timing. You can go to +8 on a cub (111 fuel of course). They are fine at 150-165 lbs of compression. The only problem with CPIs on a Cub is the horrible dead spot in the low end. If you look at the power curve on a dyno, you will actually see a horsepower dip before it climbs out hard. CPIs on a +8 timing 421 Cub with 28mm PWKs will do about 93 horsepower. With your carbs, that might go up a bit more. The Cub is a drag motor though, so you will want some more swing arm.

 

For just riding, I hate the Cub motor power curve. It is dead in the low end and pulls so hard on the power band it's scary for tight trails and such. If you are into MX, you definitely won't want CPIs.

 

thanks man. so what do i have to do to bump up timing? what will it hurt? do i have to ''retune'' it or anything?

 

as of now it looks like im gonna be getting some cpi's and bumping up the timing depending on what kinda tuning it takes or if i can just bump it up and ride. but i will need to re tune to new pipes anyway so... but thanks for the info keep it coming please... 95 horses sounds good! :biggrin:

[POORBOY350]

what about t5's? and +7 timing? hows that sound everybody... what all would i need to do to do it? just re tune or what thanks.

 

or would cpi and +6 or +7 be better???

[Tim Potteiger]

what about t5's? and +7 timing? hows that sound everybody... what all would i need to do to do it? just re tune or what thanks.

 

or would cpi and +6 or +7 be better???

 

 

That is totally going to be up to you. If you go that high on timing, you will just have to change your fuel to 111. T5s with the timing bump would be a little less drag race oriented. I have seen a Cub with FMF fatties on it, interesting setup, it takes out the "dip" in power in the low end, but peaks at about 84 horse. You will need to recheck your air/fuel once you get new pipes on it. It might not change a ton, but it will most likely change. The best way in my opinion is to dyno it somewhere that has an air/fuel sniffer, so you can get it just right. Doing plug chop checks is an option too, but visible vs. measured with technology.

[POORBOY350]

That is totally going to be up to you. If you go that high on timing, you will just have to change your fuel to 111. T5s with the timing bump would be a little less drag race oriented. I have seen a Cub with FMF fatties on it, interesting setup, it takes out the "dip" in power in the low end, but peaks at about 84 horse. You will need to recheck your air/fuel once you get new pipes on it. It might not change a ton, but it will most likely change. The best way in my opinion is to dyno it somewhere that has an air/fuel sniffer, so you can get it just right. Doing plug chop checks is an option too, but visible vs. measured with technology.

 

thanks for the info man i love hearing and learning all that i can. but 111 is fine for me. and i will most likely get cpi's and i will prob bump my timing up. i just didnt want it to take away from reliability ya know. so how bad is the flat spot or whatever in the low end with cpi's im sure ppl have different opinions on this

[Tim Potteiger]

thanks for the info man i love hearing and learning all that i can. but 111 is fine for me. and i will most likely get cpi's and i will prob bump my timing up. i just didnt want it to take away from reliability ya know. so how bad is the flat spot or whatever in the low end with cpi's im sure ppl have different opinions on this

 

I will see if I can get the actual dyno sheets and post a copy or link to download them later this week. I have a comparison of the FMF fatties vs CPI on the same setup motor. It's pretty interesting really. Some people attribute the dip to low intake velocity which seems like a reasonable explanation but who knows. The people that make the cylinders supposedly have never heard of the existence of this dip or low end flat spot. It really makes no difference for drag racing, but in trail riding, I would see it as an issue I couldn't deal with.