General Lee minibike.

#1
Hello,
This thread will concern the "project and ride" of the General Lee minibike that has just been build. With all of it's problems and ups and downs, like a project is meant to be.
The build can be found >>>here<<<. Pictures of the minibike since it has been build can be found >>>in this album<<<.
Since it's already build, I'll post any ongoing, regarding this minibike in this thread, so here it goes...

This was my first minibike build with a torque converter. A Chinese TAV2-30, if I'm right.
I'm running this torque converter with a 15T sprocket and a 85T rear sprocket (at the moment). I have made the sprocket myself, as I couldn't find any torque converter sprockets for #219 chain.
I really like it compared to a centrifugal clutch, it accelerates much better and doesn't seem to bother to leave with WOT (spinning tire).
So far so good.
After I did a full throttle "burn out" in the dirt, the engine stalled and wasn't able to start again. The torque converter was stuck/engaged.
All of a sudden it was disengaged and I was able to run it again. Problem solved for now.

I did some reading here on the forum and read about cleaning the torque converter and apply dry moly lube, so I ordered a can of CRC dry moly spray of which I think it's the correct stuff?


This is what it looked like after I took the cover off. Lots of rubber. I had already taken the driver off here.


I have cleaned the driver with scotchbrite. The movable sheave didn't seem to have had any dry lube on it, like the other sheave did. Maybe someone in China forgot about it.
I sprayed both (inner sides) with dry moly lube and also the "bushing" where the movable sheave slides over. While these parts were lubed and sat to dry I went onto straightening the back-plate.


I noticed the back-plate was not straight. It wasn't when I mounted it, but I didn't know at that time. Right now I measured it with a straight bar and it was off about 2-3mm. This meant the secondary shaft was not parallel with the crankshaft. That can't be good.


So I made it straight again, the Dutch way! First I marked where I had to bend it and gently used a shop press to put a little pressure where it needed it. I knew the cast aluminium back-plate wouldn't take much, before it would brake, but it didn't need much and didn't brake.


Check, check, dubbel check. Checked it with this tool, a caliper and a straight bar. In my opinion it is as straight as it should have been. Time to mount it again.


I needed to line up my engine with my rear sprocket again. When I mounted the (now straigth) back-plate again, I saw it was not flush with the engine. Because it was now straight it interfered with some engine part that I had to grind a bit to make it flush.

With the freshly lubed (CRC dry moly lube) torque converter it ran great again, without problems. Until...
I noticed that the torque converter was a bit "sticky". I noticed that it didn't always disengage complete back on idle. Sometimes it did and sometimes it didn't. I also noticed a "plinging" sound, before it disengages (the movable sheave jumping back to it's idle position appeared to have made the "plinging" sound).


So I took the driver off, when it was not complete disengaged, and took it apart. And pictured above is what I've found to be the problem.
PS: Is it normal for the driver / the applied dry moly lube to look like this after 1-2 hours of driving?


The problem I'm referring to is the bronze bushing stuck in the movable sheave. With the bronze bushing stuck in here, the movable sheave can't retract complete to it's "idle position", because the bronze bushing "hits" the 4 splined hub driver. This results in the belt to be a bit to tight on idle, or in a worse case it might be way to tight.

I have searched this forum for a similar problem, but didn't find it. I did find a lot of bronze bushing problems, but nowhere that they were stuck.

The bronze bushing's fitment on the inner sheave is made with Chinese tolerances. I guess the outer diameter has grown a bit since it's used, which makes it to fit tight in the movable sheave once the engine revs up and the movable sheave moves towards the bushing.
I mounted the driver again, without belt, to see what's happening when I rev the engine. The movable sheave, moves toward the engine and bushing as rpm's increase and it moves over the bronze bushing when rpm's keep increasing. But with a bronze bushing that has grown or is to tight on the outside; it gets stuck in the movable sheave, which is unable to retract again to it's original position with an engine running on idle.

I will have to look for a new bushing and will need a couple of spare ones also. Perhaps there are other types of bushings that I can make to fit and see how that works out.


I already have 3 spare belts at home. €20,- / 3 pcs including shipping. And some more are on their way, too.

More to come.
 

Li'l Popeye

Active Member
#2
Because the TAV2-30's (chinese) bronze bushing was making the torque converter to get stuck, I wanted to replace it. But as there are several threads regarding the poor quality or broken bushings, I decided to go a different route and make some myself. I had a round bar of bronze in the workshop, so material was there already.
I just made my bushings a bit different. Tighter tolerance to the shaft and instead of 1/2" wide I've made it almost 3/4" wide.


Drilling a hole in the bronze round bar.


Some more work to create my own bushings.


On the right the original bushing, with the 2 new ones I made myself.
On the left is the "flat" sheave that goes on the crank. As this one was not straight/true, I fixed this, while it was off the engine. It won't beat my torque converter belt again.


New, wider bronze bushing installed.


New, wider bronze bushing installed, with the movable sheave over it.

After all installed again, I did some test driving and until now the homemade bushing functions as I wished it would.
 

Li'l Popeye

Active Member
#3
Well, got something else figured.
Since I have rebuild the engine, (swapped crank, rod, flywheel, headgasket) I first installed it on a bike with centrifugal clutch. Noticed more vibrations, compared to the engine as it was stock. Likely caused by inbalance because of different weights of installed parts. I will look into that, later.
On this minibike with torque converter it seems worse. The engine is installed with an incline, which could have contributed.
But after yesterdays driving the vibrations seem to start, when the TC driver is engaging and vibrations continue the entire range. The vibrations seem to flatten out when I open throttle wide open.
And... When I close throttle the vibrations stopped right after the driver disengages. This made me wonder the torque converter is creating vibrations, which I'll have to eliminate first.
I took the driver off, opened it and just sat there looking at it...


The weights in the idle position. No problem.


The weights in the midrange / WOT position. No problem.


The weights in the midrange / WOT position. Not good!

And yes, this is what happens at mine (and probably at others, too), because there are signs of wear at the spots where the metal touches each other.


Signs of wear on both weights.


Signs of wear.

I measured the of center distance of the weights and it comes out to 3mm. 320 grams at 3mm run out...
I guess it's up to the Dutch guy to fix this bad design issue... Not sure how, yet.
 

noseoil

Active Member
#4
Nice posts about your balance problems & the Chinese TAV. With the weights slinging around like that, it's no wonder there's an imbalance at speed. The only thing I might suggest is that the real Comet torque converter is made with better materials & tighter tolerances (of course it costs more!).

I run my older Baja Warrior with a Chinese TAV & no bronze bushing at all. After replacing it several times, I decided that the parts are junk & as long as it runs well enough, I'm ok without it. The first time I looked for it after running for several hours, there was just a smear of bronze powder, rubber & chain lube stuck inside the cover. I don't let it sit to idle for long periods to burn the belt & it seems to work well enough without it. I know, it's the wrong answer, but the bike is still ok & has been for many hours of running like this. Go figure on that one...

If you have run different parts & a lighter flywheel, it's likely that the additional parts are working against the light flywheel to create an imbalance as well. I had asked about this issue when I first build my motor with it's shaking & the most common answer was "yes, the more you modify the motor, the more it shakes" which isn't a very satisfactory answer, but that's what I found from people. I'm still looking into things about my balance issues (the bike's issues are a different matter altogether).

P.S. Your bike turned out really well & looks to be a "first rate" build.
 

Li'l Popeye

Active Member
#5
If you would say a real Comet would be trouble free, it would be worth it. But as I've seen pictures of it, I think the Chinese made an exact copy of the Comet torque converter TAV2 that is. So I guess in a Comet the weights can cause an imbalance, too. I think the design of the driver (loose weights held in place with some springs) could be better.
Okay, in China they have other tolerances. As I have a complete workshop, with lathe and mill, I have no problem with some modifications and I like doing it. I always learn something of it.
Untill now, my "selfmade" bushing holds up very good. I think I made it a bit to tight, as it is turning inside the belt, but it can freely rotate on the shaft. I'm okay with that.
I also figured it isn't worth to spend a couple of €'s for a new bushing that holds up for a couple of hours, that's why I've made my own improved ones. But apparently I can do without, with care.

Well, today I had another day at my minibike workshop!
To tackle the issue with the weights being able to run out 3 mm of center, I decided to modify the stock parts.


These are the stock weights. 305 grams as pictured.


These are the weights in the lathe. Turning the hole diameter from 41,.mm to 47 mm. The point where the 2 solid bars are at.


70 Grams of non magnetic material removed.


On the movable sheave I've made a bushing (proudly made in the Netherlands). Tight on axle (and locktite) and a tiny bit shorter.
The outside diameter is 47 mm. The same as the inside diameter of the weights and the distance between the 2 pins. The weights can't move sideways anymore, at least not 3 mm...

Vibration problem solved?!
No...I did make a testdrive after this modifications. Engagement rpm is a bit higher, which is ok. The minibike really leaves from the spot right now... And if my hearing is ok, the engine makes more rpm's during the entire torque converter range.
The vibration wasn't as bad as before during the testdrive, but there was still some vibration, caused by the Torque converter driver pulley weights. I know this, because I also ran the engine without belt mounted, with and without weights in the driver pulley. Without the weights there is just "normal" engine vibrations, which occur during certain rpm ranges.
With the weights... On idle all ok. As soon as the weights are likely starting to move outboard, things start to vibrate during the entire rpm range.
As I know the weights are not able to move sideways, anymore I assume that the weights don't move equally outboard, causing the vibrations.
This can be caused by sheaves that are not straight/true. I will have to look into that.


Pictured on the left: an all ok driver with 2 sheaves equal/true to each other. Both weights equally centered.
Pictured on the right: a driver with 2 not equal/true sheaves. This leaves a greater opening on 1 side, causing weight no 1 to move more outboard as weight no 2. It can be seen as weight no 1 is a bit outside the green line. Weight no 2 is inside the green line. This will cause vibration and this is hard to solve.
If 1 sheave is a tiny bit not true, this will already contribute to vibration as it creates more space for 1 weight.
I can imagine if the minibike would drop on the outboard side sheave, it will likely have some vibrations afterwards.

So what to do next?
Not sure yet, how to solve this, as the design of the driver pulley is not very well thought out.

Design wise I would make it different.

Something like pictured above. A stationary plate, attached to the crank. Arms, springs and weights on it, which in turn press against the movable sheave. Because the weights are connected to arms, they will all be centered equally. This design eliminates vibration, in my opinion.
Design wise. Price wise, likely not.
 

noseoil

Active Member
#7
Good thing you have all those tools! I can't imagine having to pay for the stuff we do with these bikes & motors. As you said, it's all about learning & thinking about things, so it's all good. I'd like to see you design a better clutch assembly, but the time it would take in design & manufacturing would be a lot.

I'm sure it launches much faster with the lighter weights & revs more freely now. Make sure you hold on when it gets going!
 
#8
If you coat the pins with dry moly lube this might allow the weights to center up while in use. the taper on the sheaves should lead the weights naturally to a centered position. If one pin is in a bind, the weights will open unevenly and the weights will move off center.
 

delray

Well-Known Member
#9
nice to see that you too also did some testing with the comet and notes unwanted vibration that a comet can create with billet flywheels.
unfortunately your not going to re-engineer the driver. having two pieces of cast material with two springs ramp around them and then trying to expand evenly in between two uneven stamp pieces of steel isn't going fly well.
also got to remember the comet was design back when small engines had only heavy aluminum or cast steel flywheels. it's a whole nothing ball game with these new ohv engines that people want to build with billet flywheels and run with a comet torque converter.
 
#11
If you coat the pins with dry moly lube this might allow the weights to center up while in use. the taper on the sheaves should lead the weights naturally to a centered position. If one pin is in a bind, the weights will open unevenly and the weights will move off center.
These pins seem to have a lot of play.
 
#12
also got to remember the comet was design back when small engines had only heavy aluminum or cast steel flywheels. it's a whole nothing ball game with these new ohv engines that people want to build with billet flywheels and run with a comet torque converter.
I assume they also designed it to be easy mass fabricated.
 
#13
Let me share with you what I have done to all my China T/C drives to make them operate smooth and otherwise behave...
1. Cut a chamfer on the outside of the bushing and break the edges with emery cloth so the sheave will slide over the bushing without binding.
2. Rub baby powder on the sides of the T/C belt for smooth engagement and smooth change of drive ratio.
3. Dry molly lube on sliding surfaces. (as you have already done)

That sliding sheave is always in some sort of bind due to the belt not being in contact with the sheave all the way around its circumference. With use these parts eventually wear in and the sharp edges will wear off. These units are not the precision units found on scooters and ATVs that are machined and balanced to run perfect, the low initial cost just won't allow for such precision. To make these run really good the whole outside end of the driver would have to be made on a lathe and held to close tolerances for smooth action and acceptable balance. I hope my tips will help solve your T/C problems for now, if not, I guess it will be back to the drawing board to improve on what mass production has blessed us with!
 

delray

Well-Known Member
#14
li'l popeye,see why you have a unwanted vibration. big chunk unbalance material spinning on one side of the crank and super lite piece of aluminum on the other side trying to absorb vibration going though the crankshaft.


take that lite flywheel off and go with a reg-billet flywheel,but may not fix the problem either as long you are still using a 30 series unit. my opinion a lite flywheel is good for one thing and I don't think your application would be good at all for it.

here is something I thought you would like to look at. it's a torque converter that use roller barrel style weights. it would be interesting if a guy could incorporate this setup in a comet unit. only if a guy had a lathe....lol. i'm sure the the barrels would have to be a different size and the single spring tension(stall) would have to be figure out. the end result would probably still create a unwanted vibration with all that dead weight spinning? unless you had maybe a heavier aluminum flywheel. one thing for sure the the rollers would never hang up like the comet weights would.

there is one other torque that would work with a reg-billet or lite flywheel,but that's another story and they don't make it anymore and your not going to find it or the correct parts to make it work good for any high performance built small block clone,honda,briggs..etc...
kind of surprised that no companys have step up and try building a true machine out billet torque converter for a minibike. the jr dragster stuff is all over kill torque converters for a minibike that runs a built small block.
 
#15
Hello.
I do not believe the flywheel is creating a vibration problem. I agree that it is light and can't absorb much vibration. I did run the engine with the stock steel flywheel. It didn't make much difference. The vibration was still there.
I am certain it is caused by the weights in the tc driver. Like you said held together by some springs.
The roller driver you mentioned... well It can cause little vibration when the sheaves are not equaly placed or untrue. All rollers are held in place by a single spring. Each roller should have a seperate spring.
I have searched the internet, but didn't find any aftermarket clutch drivers (that work well and do not cause vibration) for this tav2-30 that is widely used in go karts and minibikes. Strange.
Looks like this Dutch guy has to make a decent Tav2-30 driver clutch.
 
#16
I found a Comet 103HPQ clutch on internet. Now that's what I mean. This will likely not cause vibration as the "weights" are hold in place by arms.
I will not buy it. To expensive for this poor guy and it doesn't fit.
Enough ideas!
Gr.
John
 

noseoil

Active Member
#17
Yes, a "Bully" type of clutch setup for the sliding member of a torque converter would be the way to make it balance & run correctly, but the cost in machining, research & development, trial & error would be staggering.

I'm thinking the light flywheel is also a factor, as Delray has said. We all seem to be chasing the "magic bullet" to make things better, but it's a long, slow, costly & sometimes a painful process, to be sure. A heavier flywheel would help dampen the vibration, but it's still there no matter what you do. You can reduce it, but never eliminate it completely. Looking forward to your next mods to see what works.
 
#18
Yes, a "Bully" type of clutch setup for the sliding member of a torque converter would be the way to make it balance & run correctly, but the cost in machining, research & development, trial & error would be staggering.

I'm thinking the light flywheel is also a factor, as Delray has said. We all seem to be chasing the "magic bullet" to make things better, but it's a long, slow, costly & sometimes a painful process, to be sure. A heavier flywheel would help dampen the vibration, but it's still there no matter what you do. You can reduce it, but never eliminate it completely. Looking forward to your next mods to see what works.
The "Bully" type of clutch, to operate the movable sheave is the way that I'm looking into, yet. There's 1 problem with it and that's: with a normal clutch it only has to "travel" 1 mm or so (clutch clearance). What I want it to do is to move it 19 mm as that's the distance the movable sheave has to move.
I have also seen the 40 series clutch, with the 3 roller weights in it. Looks to me as a better design as the TAV2 or 30 series. Not sure what would happen with those when sheaves are not true.
Well I'm currently working out several options on my computer.
To calculate centrifugal force I'm using this formula: F=M X (V X V) / R
F=Force (N)
M=Mass (kg)
V=Velocity (M/sec)
R=0,5 x diameter (M)
My stock
 
#19
li'l popeye,see why you have a unwanted vibration. big chunk unbalance material spinning on one side of the crank and super lite piece of aluminum on the other side trying to absorb vibration going though the crankshaft.


take that lite flywheel off and go with a reg-billet flywheel,but may not fix the problem either as long you are still using a 30 series unit. my opinion a lite flywheel is good for one thing and I don't think your application would be good at all for it.

here is something I thought you would like to look at. it's a torque converter that use roller barrel style weights. it would be interesting if a guy could incorporate this setup in a comet unit. only if a guy had a lathe....lol. i'm sure the the barrels would have to be a different size and the single spring tension(stall) would have to be figure out. the end result would probably still create a unwanted vibration with all that dead weight spinning? unless you had maybe a heavier aluminum flywheel. one thing for sure the the rollers would never hang up like the comet weights would.

there is one other torque that would work with a reg-billet or lite flywheel,but that's another story and they don't make it anymore and your not going to find it or the correct parts to make it work good for any high performance built small block clone,honda,briggs..etc...
kind of surprised that no companys have step up and try building a true machine out billet torque converter for a minibike. the jr dragster stuff is all over kill torque converters for a minibike that runs a built small block.
Polar style clutch used in junior drag racing operates by using ramps and rollers. You can adjust by using different rates of ramps and different sized rollers. This is clutch is really wide though so prob not a good choice for a minibike.
 
#20
Polar style clutch used in junior drag racing operates by using ramps and rollers. You can adjust by using different rates of ramps and different sized rollers. This is clutch is really wide though so prob not a good choice for a minibike.
Yes, It's a lot bigger I think. And more expensive. But I do like how it's designed. With the ramps, rollers, etc. And not the weights that are supposed to be held in place by garter springs.

Design of improved TAV2-30 series driver clutch is in progress.
Goal is to come up with something that eliminates vibrations, caused by unevenly moving weights, to nearly zero.
With the use of:
Stock sheaves; stationary and movable.
Stock splined driver hub. (maybe slightly modified)
Stock pilot washer and bolt.
The stock weights and the garter springs can be thrown away...
Some kind of "bolt-on" performance piece...

It will take some trial and error, but would be nice to get it to function.
This is what I have come up with so far.

It's not complete yet, as the other parts need to be figured out.
 

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