TAV-30 Max speed limit?

xBrent92

xBrent92

New Member
#1
#1
Just wondering if 42mph is the absolute fastest i can go with a TAV-30 and if i can do anything to help it gain more RPMs but i must first say i have the Yellow driven spring and i drilled a 4th hole and it helps a big noticeable amount on acceleration but i can still only go 42mph. Any suggestions?

I wonder if this $20 clutch i have could handle a modified engine.
This setup i have now gets me to 42 mph in about 4 - 4.5 seconds.
 
MikeBear

MikeBear

Active Member
#3
#3
Put a smaller sprocket on your drive wheel, even just a couple less teeth will help change the drive ratio. Smaller sprocket = more revolutions = more speed. Or, find a TAV sprocket that's 2 tooth smaller.

Just don't go too crazy, or you will lose POWER on the other end.

With all that being said, 42mph is pretty good already with a smaller minibike.
 
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xBrent92

xBrent92

New Member
#4
#4
i'm on a 4:1 gear ratio. It should go faster than that for sure.

and P.S. i had the Driver double pre-loaded to try and gain RPM but all it did was give me more torque.I would like a stiffer-than-yellow spring.

my specs:
.290 lift camshaft @ 104LSA .246 duration
gx390 caburetor ,rejetted for more fuel.
30degrees ignition timing.
26pound valve springs.
4:1 gear ratio was tested. It does the same for 3:1 gearing. and yes if you were wondering the engine is able to power 3:1 flawlessly. i have video proof.

Oh, me and the ride only weigh max estimated 220 pounds .
 
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ole4

ole4

#6
#6
That cam should make good power from 4000 to a max of 8000 what rpm were you turning at 42mph? I have my performance engines geared from 5-1 to 6-1
 
xBrent92

xBrent92

New Member
#7
#7
ole4 said:
That cam should make good power from 4000 to a max of 8000 what rpm were you turning at 42mph? I have my performance engines geared from 5-1 to 6-1
Click to expand...
i checked out the speed calculator and if my ear-judgement is correct, 3800rpm sounds about right.

With the gx390 carburetor i am using a .044 main jet.

Problem:
_I was trying the .0625 main jet for test run and it gave me a big power increase when off idle but it seemed to GULP the whole fuel bowl in 1 second even with a 14 LPH Mikuni fuel pump.
_So i took off the bowl, drilled the pilot to 5/64 hoping that was the issue, plugged part of a spare hose on the fuel inlet of the carb, sprayed some carb cleaner in the hose with the fuel valve open, and the cleaner verrryy slowly moved down and out of the carburetor.
_Now i know there is a flow problem in the fuel passage. It is VERY hard to blow through also. Even with 85psi of air pressure through the hose. i compared by blowing through the stock carb and the stock flowed VERY easily. But i want the 390,not the stock.
_ How do i clean that area? i tried poking with wire. I see there is a tiny Welch Plug? i tried drilling on it but it seems harder than steel and keeps slipping and grinding the carb.
 
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FirePowerMinis

FirePowerMinis

Active Member
#8
#8
Geared too tall, likely. It's shifting in to overdrive before the engine starts making good torque, and it can't overcome the drag.
And/or the carb issue...
 
xBrent92

xBrent92

New Member
#9
#9
FirePowerMinis said:
Geared too tall, likely. It's shifting in to overdrive before the engine starts making good torque, and it can't overcome the drag.
And/or the carb issue...
Click to expand...
lol "before makes good torque". This thing will slide out from under me like a magician pulling a tablecloth from under wine glasses if i don't firmly grip the steering. It's a light weight kart with half a seat by the way.
If this thing can make more torque i am all in.

I'm thinking about making this work by drilling around the area, cleaning it out, soldering it all back up and should be better than before.
 
FirePowerMinis

FirePowerMinis

Active Member
#10
#10
That "thing" isn't light, and of course with the TC in low it can spin a tire.
Again, still, making too many wild guesses at a time with tuning.
The path to power is well traveled. Follow it.
3800 RPM with 240+@.050 is not in the torque curve, especially with rototiller compression.
 
xBrent92

xBrent92

New Member
#13
#13
lol K.
I'm just going by what i've already done acceleration-wise. i don't know speed difference between 4:1 and 3:1 yet. Acceleration was about the same.
 
jeep2003

jeep2003

#14
#14
im curious to what you find out. if youre not maxed out on the rpms then youre just out of power. going up on the gear ratio might help or might not. the tav kinda compensates for that either way. going to a centrifical clutch might be the answer for more speed in that case but youll have to start over with the gear ratio. I dont know anything about the mods youve done it might just not be making any power up high.
 
xBrent92

xBrent92

New Member
#15
#15
jeep2003 said:
im curious to what you find out. if youre not maxed out on the rpms then youre just out of power. going up on the gear ratio might help or might not. the tav kinda compensates for that either way. going to a centrifical clutch might be the answer for more speed in that case but youll have to start over with the gear ratio. I dont know anything about the mods youve done it might just not be making any power up high.
Click to expand...

I will do my best to video record acceleration from first and/or 3rd person perspective.

And i am thinking if the TAV its self is maxed out on revs, then gearing up should gain more speed with the same revs. I'm excited to find out.

i also drilled a main jet to .0625 for more fuel so that will help acceleration-wise.
I will be occupied these next couple of days so until then we gotsta wait.
 
yalipito

yalipito

Member
#16
#16
I have reached 60 mph on my mini with a TAV2. Gearing and a few tricks to the tav made the difference. 3:1 will not help you unless you go on a long downhill.
 
xBrent92

xBrent92

New Member
#17
#17
yalipito said:
I have reached 60 mph on my mini with a TAV2. Gearing and a few tricks to the tav made the difference. 3:1 will not help you unless you go on a long downhill.
Click to expand...
Teach me oh wise one.

I do have the ability to gear for 5:1 and theoretically go 60mph @ 6750RPM with 15" tires.

`I did notice the TAV-2 had the white spring and the TAV-30 doesn't. I wonder how much effort it would take to bend the other side of the White spring to make it fit the TAV-30.


I was told by several people that 4:1 gearing wouldn't move anything. But i took it one step further and did 3:1 gearing and all of the torque was still there. Still waiting to do a top-speed comparison.
 
FirePowerMinis

FirePowerMinis

Active Member
#18
#18
2.68:1 ratio multiplier in the TC low range is allowing you to get away with the tall gearing. 10.7:1 at low speed using 4:1

When it shifts to the .9 overdrive, your 4:1 goes to 3.6:1, like hitting a big hill. Remember, your 5:1 will be 4.5:1 with the overdrive.

These low-end TC setups are not as tuneable as sled/JrDrag stuff, so they're more of a 2-speed than a CVT, IMO
 
FirePowerMinis

FirePowerMinis

Active Member
#20
#20
Mark G said:
LOL, years ago a buddy of mine had a couple of Ram Air Trans Ams , both had the 6 speed and you are right on the money, 6th was just about useless:laugh:
Click to expand...
For top speed, absolutely, but it let me get 28mpg@78mph cruise setting on the x-way between Chicago and Omaha once a week for a year.
 
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