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  1. #11
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    As I said, this isn't really a "drag" bike, but I like toying around with stuff like this. I'll swap out the TC sprocket for a smaller one when I don't feel like 50 mph at 6000 rpm is appropriate for the style of riding I'll be doing.

    I built the engine with a NR cam described as "serious torque" but it is still a racing cam. The cam is for kart racing on small tracks. Russel said it should pull from about 4k to 7.5k. The idea behind this build was to make a mini that went faster than the last one. It will mainly be just a fun bike. I do stupid stuff with these. Take them in the snow. Take them to off road parks. I honestly didn't have too many issues with the last minibike and 30 series TC with 6" pulley. It was an 11:1 CR, Black Mamba Jr, gx390 carb - Hemi 212. Stock Driven Spring. Middle Hole. It handled 7000 RPM ok. 145/70-6 tires. Had to go back to find this stuff.

    When it was geared 54:8 it did the 1/8 mile is about 11.2 sec @ 47 mph (7050 RPM) and was at max speed by the 1/8th. It would also flip over backwards with a heavy throttle blip when stopped. LOLOL
    60' 2.25 sec 20mph
    330' 6.6 sec 40mph
    1/8 11.2 sec 47mph

    Only data came from cell phone gps app and I didn't get a "drag slip" after I swapped sprockets, but top speed was around 54mph - 55mph (6.4k - 6.5k RPM) when geared 54:10 (so 4.86 :1 with 6" 0.9:1 Overdrive).
    Last edited by bob58o; 09-18-2017 at 11:47 PM.

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  3. #12
    delray's Avatar
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    TheDullCarbide. i also wanted to clarify something i said about unwanted vibration and to anybody else that read this? engines that i did the testing on both had aluminum flywheels. now just in the last couple days i have been doing some changes to a bike with a comet 30 series and gearing and that bike has a cast iron flywheel with a billet rod,cam,coil....etc.. and was not getting any type of unwanted vibrations at all?
    thinking the cast iron flywheel(heavy) was absorbing the unwanted vibration. most people may never notes this problem? one they may not use a comet setup on a race engine that turns high rpm's with a aluminum flywheel and if they did they wouldn't have the option to change over to a performance driver unit and thats where i stumbled across this problem and notes there was a big difference in the performance driver unit that was machine out aluminum over the heavy stamp out steel 30 series driver unit.
    i also was installing a clone/7" driven and decided to try the yellow stiffer spring on one more time...... man this bike too does not like the yellow spring. all it wants to do is make the motor try to rev and spin the belt when i get on the gas real hard.. with the factory red/clone spring installled the driven works just fine.
    belt i was testing this with was a bando belt and length of the setup was the factory spec's, 6 7/8 center(crank) to center(driven).
    one other thing i notes with the clone 7"driven keyway slot. seams to have just little to much excess play in it. almost like it's machine out to 15mm. i will have to mill out a new keyway stock if i want this problem to go away....

  4. #13
    Senior Member TheDullCarbide's Avatar
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    Quote Originally Posted by delray View Post
    TheDullCarbide. i also wanted to clarify something i said about unwanted vibration and to anybody else that read this? engines that i did the testing on both had aluminum flywheels. now just in the last couple days i have been doing some changes to a bike with a comet 30 series and gearing and that bike has a cast iron flywheel with a billet rod,cam,coil....etc.. and was not getting any type of unwanted vibrations at all?
    thinking the cast iron flywheel(heavy) was absorbing the unwanted vibration. most people may never notes this problem? one they may not use a comet setup on a race engine that turns high rpm's with a aluminum flywheel and if they did they wouldn't have the option to change over to a performance driver unit and thats where i stumbled across this problem and notes there was a big difference in the performance driver unit that was machine out aluminum over the heavy stamp out steel 30 series driver unit.
    i also was installing a clone/7" driven and decided to try the yellow stiffer spring on one more time...... man this bike too does not like the yellow spring. all it wants to do is make the motor try to rev and spin the belt when i get on the gas real hard.. with the factory red/clone spring installled the driven works just fine.
    belt i was testing this with was a bando belt and length of the setup was the factory spec's, 6 7/8 center(crank) to center(driven).
    one other thing i notes with the clone 7"driven keyway slot. seams to have just little to much excess play in it. almost like it's machine out to 15mm. i will have to mill out a new keyway stock if i want this problem to go away....
    That vibration problem could definitely be caused by the flywheel. As for the keyway, there seems to be a metric and a standard keyway. I've already had a 6" that came with two different keyways machined into it. It's just hit and miss.

  5. #14
    delray's Avatar
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    TheDullCarbide
    I've already had a 6" that came with two different keyways machined into it
    thats just crazy, i like to see that. one of the reasons why i am not sold on clone torque converters.
    something wong

  6. #15
    Senior Member TheDullCarbide's Avatar
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    Quote Originally Posted by delray View Post
    TheDullCarbide
    thats just crazy, i like to see that. one of the reasons why i am not sold on clone torque converters.
    something wong
    This one came off my Ty-Rail. When we got the kart, it had a very worn Comet TAV2 so my dad bought an off-brand TAV2 and threw it on. The driver on the off-brand flew apart all over the yard because the outer face of the pulley climbed over the washers holding it on. I ended up putting the worn OG back on and it still runs today. I took apart a Yerf-Dog CVT for the 7" driven and threw it on my Ty-Rail.

    If you don't want to read that, it means this is an off-brand 6" driven:

    100_4267.JPG

    I also got the pictures of the so called "shaft extension". The 1 1/8" hex on it is a lifesaver when you need to hold the crank still:

    100_4268.JPG

    100_4269.JPG

    100_4270.JPG

  7. #16
    delray's Avatar
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    wow,one side keyway does look bigger.

  8. #17
    Senior Member TheDullCarbide's Avatar
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    Quote Originally Posted by delray View Post
    wow,one side keyway does look bigger.
    Yuuuppp...One fits a 5mm key and the other is for a 1/4". I just keep 5mm on hand and get creative with a belt sander to make my step keys.

 

 
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