20 Series Torque Converter Issues

[Smeeneezle]

Hey OldMiniBikes, it’s been a while but I’m finally back and I finally got my Carter 2336ZX 2 seater back on the road with a fully built (my first personal build) Predator 212 and it has a 20 series torque converter on it. Laugh now it you know where I’m going with this. My engine is turning well over 6000 rpms as I have a Trail Tech Vapor (love it!!!) installed which is wrapped around my upgraded msd spark plug wire and boot connected to an upgraded coil. Well before I took this thing out for the first good romping I didn’t realize that this series torque converter was not built for this amount of rpms. I rode it for hours with different kids as my passengers and it rocked with no probs. Later that same day my buddy stops by and I let him take it out for a spin. He rode it for like 2 minutes and the dang thing cut off on him while he was trying to turn around and head back. He proceeds to hop off and try’s to pull the cord to restart it and he noticed that it tried to pull away from him when he pulled it. I run down there and notice that the torque converter is stuck in the engaged position hence why it was pulling away as he pulled the cord. We push it back to my garage and I take the torque converter driver apart and notice that the weights were in fact stuck in the engaged position and twisted slightly which is what was keeping it from retracting. I also noticed that one of the two garter springs was flattened in a couple of sections. It was after that when I started to research the issue that I encountered and discovered that the series 20 torque converters are only rated up to 3600 rpms which explains a lot. So, with that being said, my question is what are my options from this point? I’ve seen the upgraded aluminum weights and different colored garter springs (which seem to only increase or decrease the actual engagement rpm but I haven’t come across and data on what rpms each colored spring goes UP to) which I’m hoping will assist me in this situation as I can not afford a series 40 torque converter at the present time. I’ve seen a tiny bit of info out there that also speaks to some aluminum mod weights but I haven’t found anywhere to purchase them. So, do I have any hope in modifying my series 20 torque converter or is it a must to upgrade to a 40 series or even higher options then that? Thanks in advance for any and all advise/recommendations/comments/suggestions that you all may be able to offer me. Have a great day!!!

 

[TheDullCarbide]

Hey OldMiniBikes, it’s been a while but I’m finally back and I finally got my Carter 2336ZX 2 seater back on the road with a fully built (my first personal build) Predator 212 and it has a 20 series torque converter on it. Laugh now it you know where I’m going with this. My engine is turning well over 6000 rpms as I have a Trail Tech Vapor (love it!!!) installed which is wrapped around my upgraded msd spark plug wire and boot connected to an upgraded coil. Well before I took this thing out for the first good romping I didn’t realize that this series torque converter was not built for this amount of rpms. I rode it for hours with different kids as my passengers and it rocked with no probs. Later that same day my buddy stops by and I let him take it out for a spin. He rode it for like 2 minutes and the dang thing cut off on him while he was trying to turn around and head back. He proceeds to hop off and try’s to pull the cord to restart it and he noticed that it tried to pull away from him when he pulled it. I run down there and notice that the torque converter is stuck in the engaged position hence why it was pulling away as he pulled the cord. We push it back to my garage and I take the torque converter driver apart and notice that the weights were in fact stuck in the engaged position and twisted slightly which is what was keeping it from retracting. I also noticed that one of the two garter springs was flattened in a couple of sections. It was after that when I started to research the issue that I encountered and discovered that the series 20 torque converters are only rated up to 3600 rpms which explains a lot. So, with that being said, my question is what are my options from this point? I’ve seen the upgraded aluminum weights and different colored garter springs (which seem to only increase or decrease the actual engagement rpm but I haven’t come across and data on what rpms each colored spring goes UP to) which I’m hoping will assist me in this situation as I can not afford a series 40 torque converter at the present time. I’ve seen a tiny bit of info out there that also speaks to some aluminum mod weights but I haven’t found anywhere to purchase them. So, do I have any hope in modifying my series 20 torque converter or is it a must to upgrade to a 40 series or even higher options then that? Thanks in advance for any and all advise/recommendations/comments/suggestions that you all may be able to offer me. Have a great day!!!

You are right on track with the aluminum weights. A 40 series won't give you the rpms you need as they only have three choices for rollers and two garters (up to 3100rpm engagement if I remember correctly) and they have a structural limit of 5600rpm. 20s and 30s have an 8000rpm structural limit.

Stick with the 20 series for now.

What cam does your motor have?

I never found the garter information online either. This is a scanned paper I've had in my archives. Stock TAV2s use zinc weights with blue garters. I'd imagine 20s use the same.

View attachment Comet Garter Chart.png

 

[Smeeneezle]

You are right on track with the aluminum weights. A 40 series won't give you the rpms you need as they only have three choices for rollers and two garters (up to 3100rpm engagement if I remember correctly) and they have a structural limit of 5600rpm. 20s and 30s have an 8000rpm structural limit.

Stick with the 20 series for now.

What cam does your motor have?

I never found the garter information online either. This is a scanned paper I've had in my archives. Stock TAV2s use zinc weights with blue garters. I'd imagine 20s use the same.

View attachment 104665

Thanks so much TheDullCarbide, this is great information from you and from that sheet of paper from Comet.

I’m running a DynoCams Mod2 cam.

The 20’s do in fact come with the zinc weights and Blue garter springs. Have you seen the Mod. Aluminum weights for sale anywhere, anyhow, anyway? Am I correct in thinking that the higher the spring engagement rpm the higher the max rpms that those garter springs can tolerate?

Thanks again. I look forward to hearing back for you.

 

[TheDullCarbide]

Thanks so much TheDullCarbide, this is great information from you and from that sheet of paper from Comet.

I’m running a DynoCams Mod2 cam.

The 20’s do in fact come with the zinc weights and Blue garter springs. Have you seen the Mod. Aluminum weights for sale anywhere, anyhow, anyway? Am I correct in thinking that the higher the spring engagement rpm the higher the max rpms that those garter springs can tolerate?

Thanks again. I look forward to hearing back for you.

I don't think the aluminum weights are for sale. They might have been a custom modification from Comet for a specific application. The weights you ordered are 146.8g. You could take a shot at drilling the weights but be extra careful to keep them balanced and equivalent.

The garters don't determine the maximum structural rpm, the weights and therefore balancing does. The lighter the weights, the lighter the rotational mass, the higher it can rev before . The 8000rpm figure is for the die cast aluminum.

Heavier garters will obviously raise the engagement rpm but they will also raise the shifting rpm. That is to say, the belt will grab at a higher rpm AND the TAV will shift at a higher rpm. For example, if you take a stock TAV2 (engagement @ 2200rpm, shift @ 3400rpm) and throw white garters at it, it will engage at 3100rpm and shift at 4300rpm, give or take.

Beware that the blue/silver garters can have a tendency to snap because of how stiff they are. Avoid them if you can but keep a good stock if you must.

 

[Smeeneezle]

Thanks again for your assistance with this TheDullCarbide. You are appreciated. So, with all of what you said, seeing that I am getting the die cast aluminum weights, I’m thinking I will go down in color as I like the engagement rpm just over 2000. Does that sound like a smart way to go or should I go stiffer on the springs?

 

[TheDullCarbide]

Thanks again for your assistance with this TheDullCarbide. You are appreciated. So, with all of what you said, seeing that I am getting the die cast aluminum weights, I’m thinking I will go down in color as I like the engagement rpm just over 2000. Does that sound like a smart way to go or should I go stiffer on the springs?

But I thought you wanted to shift at 6000rpm? If you engage at 2500rpm, there's no chance you could shift above even 4500rpm.

 

[TheDullCarbide]

Thinking about it, I know exactly what happened. You took a stock 20 series setup and spun it up to the top ratio then let the engine rev to 6 grand. That's what smashed the inside garter.

The weights flung out to the outside of the driver to get to top ratio and then when the engine kept revving, the weights crushed the garters against the inside of the driver housing.

 

[Smeeneezle]

But I thought you wanted to shift at 6000rpm? If you engage at 2500rpm, there's no chance you could shift above even 4500rpm.

Thinking about it, I know exactly what happened. You took a stock 20 series setup and spun it up to the top ratio then let the engine rev to 6 grand. That's what smashed the inside garter.

The weights flung out to the outside of the driver to get to top ratio and then when the engine kept revving, the weights crushed the garters against the inside of the driver housing.

Hey TheDullCarbide, I really appreciate all of your insight. Now I may sound like a dummy here but this is the first I’m hearing about this “shifting” on the torque converter. Being that I have the 20 series converter with the zinc weights and blue garter springs, I’m engaging at about 2200 rpms. From there I do not know what your meaning by shifting and are you able to tell me at what rpm I would be shifting with my stock converter setup that I am currently running? I do not want to shift at 6000 rpms (unless that would be better) but I was just saying that my engine is turning well over 6000 rpms. And your description of how my converter “exploded” is exactly correct. Now with that being said, what would you recommend from here if this was your build?

Thanks again and again and have a most excellent day!!!

 

[Richard Trotter]

The Driver and Driven clutches work as a pair. Increasing the spring rate of the driven clutch may help.

 

[TheDullCarbide]

Hey TheDullCarbide, I really appreciate all of your insight. Now I may sound like a dummy here but this is the first I’m hearing about this “shifting” on the torque converter. Being that I have the 20 series converter with the zinc weights and blue garter springs, I’m engaging at about 2200 rpms. From there I do not know what your meaning by shifting and are you able to tell me at what rpm I would be shifting with my stock converter setup that I am currently running? I do not want to shift at 6000 rpms (unless that would be better) but I was just saying that my engine is turning well over 6000 rpms. And your description of how my converter “exploded” is exactly correct. Now with that being said, what would you recommend from here if this was your build?

Thanks again and again and have a most excellent day!!!

Considering you have a MOD2 cam it would make sense to shift the engine higher. That cam likes to rev. Now I hope that you have an aluminum flywheel and a good eye for your conrod or else you DO NOT want to rev that engine.

Anyway, if it were my setup, aluminum weights, blue or white or one of each garters (dependent on what type of riding you do), green contra in the third hole.

If you're into reading, here's an old post of mine on the subject. It was originally about a TAV2 (30 series) but for getting to know the 20 series it'll do. Just don't quote numbers. Also, disregard the 6" vs. 7" driven talk:


Okay...(glad this is part of my rare areas of expertise ). The TC has four modes:

idle
engagement
shift (or I sometimes call it acceleration)
top end

At idle, the TC is disengaged. The driven is totally closed (belt on the outside diameter) and the driver is totally open (not even touching the sides of the belt). The belt is sitting on the bronze bushing between the driver halves. This bushing keeps the belt from grabbing the crankshaft when it's all the way down in the driver pulley.

To get to the engagement point, you must rev the engine enough (2200rpm with zinc weights and blue garters) to get the weights spinning in the driver to overcome the force of the garters holding them together. the weights start moving outward from centrifugal force, riding up the back of the tapered movable driver half, pushing that half against the belt. The belt gets squeezed in the driver and starts to transmit power to the driven. Now here's the first fun part, as the engine spins faster, the driver puts more tension on the belt. Back to the driven, the driven needs a certain amount of force (which translates to belt tension) to start to open, sort of like an extension spring. The engagement point is that region of rpm where the driver is putting enough tension on the belt to transmit power, but still not enough to start to open the driven pulley and start shifting. In a stock TAV2, this region is between 2200rpm and 3400rpm.

The shifting starts to happen when the engine revs to 3400rpm, putting enough tension on the belt to open the driven. The driven is opened by belt tension alone. It's this point when the engine can run at a constant rpm while road speed changes. Now for the second fun part, the movable half of the driven pulley twists backward as it opens. The engine's torque wants to fight the driven opening because it wants to twist it closed again. I absolutely love this feature because it allows TORQUE SENSING. Torque sensing allows the engine to run at different speeds in relation to the torque it's outputting. When you're cruising in a car with an automatic transmission, say the engine runs in 4th gear at 2100rpm. But as soon as you floor it, it downshifts into 2nd gear at 4800rpm. That is the equivalent of torque sensing in a TAV2. Another reason for torque sensing in a TAV2 is that when you run at WOT, you need more belt tension than at half throttle to avoid slippage. Remember, engine rpm is the only thing that affects belt tension, so by revving the engine more at high throttle, you're tensioning the belt more.

Top end is when the TAV2 runs out of shifting range. At this point, the driver is fully closed and the driven is fully open. If you want to go faster beyond this point, the only way is to rev the engine more. Racers use this to their advantage because their engines need to rev to get to their peak HP. The shifting of the torque converter gets them off the line and out of corners better than a clutch, but still allows them to rev beyond top end on the straights. You won't have to worry about revving because the governor will limit the fun after top end to 3600 rpm (or if you do the mod, 4200rpm).

Just as a side note, there are two different types of drivens. 6" and 7" OD. The 7" revs better after top end because the belt doesn't ride very low in the driven at top end. It can also handle more HP because is contacts more of the belt. The 7" is better for racers. The 6" has a wider shifting range, but doesn't rev as well. The 6" is better for low(er) HP karts and ATVs. A stock TAV2 comes with the 6".

Soooo...The end effect of this all is:

Starting from a dead stop, accelerating at WOT the TAV2:

Acts like a 2200rpm clutch until the belt can engage the driver without slipping.

The engine revs in low gear (2.68:1) until 3400rpm.

The TAV2 maintains 3400rpm as it shifts. The ratio is varied in order to maintain engine speed. This engine rpm can be varied by the amount of throttle applied due to torque sensing (ex: 2900rpm @ 1/4 throttle, 3200rpm @ 1/2 throttle).

The engine maintains 3400rpm until the TAV2 hits top end.

When the TAV2 hits top end, the engine will start to rev again in high ratio (0.9:1). The TAV2 cannot shift anymore to compensate for the increasing road speed.

The engine revs to 3600rpm (4200rpm with the mod) where the governor limits your fun.

 

[Smeeneezle]

Considering you have a MOD2 cam it would make sense to shift the engine higher. That cam likes to rev. Now I hope that you have an aluminum flywheel and a good eye for your conrod or else you DO NOT want to rev that engine.

Anyway, if it were my setup, aluminum weights, blue or white or one of each garters (dependent on what type of riding you do), green contra in the third hole.

If you're into reading, here's an old post of mine on the subject. It was originally about a TAV2 (30 series) but for getting to know the 20 series it'll do. Just don't quote numbers. Also, disregard the 6" vs. 7" driven talk:

I do have an ARC billet flywheel and a ARC billet rod. What exactly do you mean by “a good eye for your conrod?” It is billet and it is an ARC.

Would you mind elaborating on what riding conditions would call for the blue or the white or one of each? I do ride around the streets in my neighborhood but I also take it off road, mostly grassy areas and a little dirt trail action. Also by green contra you are referring to the spring in the driven, correct?

Thanks for sharing that info from your previous post. That helps with the understanding of it all from a technical stand point.

I’m still waiting to get my aluminum weights and still need to order the garter springs that I’m ultimately going to use. I cannot thank you enough for all of your assistance and knowledge.

 

[TheDullCarbide]

I do have an ARC billet flywheel and a ARC billet rod. What exactly do you mean by “a good eye for your conrod?” It is billet and it is an ARC.

Would you mind elaborating on what riding conditions would call for the blue or the white or one of each? I do ride around the streets in my neighborhood but I also take it off road, mostly grassy areas and a little dirt trail action. Also by green contra you are referring to the spring in the driven, correct?

Thanks for sharing that info from your previous post. That helps with the understanding of it all from a technical stand point.

I’m still waiting to get my aluminum weights and still need to order the garter springs that I’m ultimately going to use. I cannot thank you enough for all of your assistance and knowledge.

1) Awesome job on the flywheel and conrod. You wouldn't believe the amount of people who want to rev an engine to 5 grand on stock internals. You did it right.

2) For applications like climbing hills and towing stuff where you'd want low-end torque the lighter, blue garters would keep the engine at low rpms and make it grunt up hills. For more racing and high speed riding, the white garters will let the engine produce power higher in the rev range to ultimately go faster. A combination of a white and a blue would do the obvious and give you the in-between. This is more of a starting point for your tuning so considering the stock already has blues, order whites if you ride fast, pinks if you ride hills. Once again, the best I can do is give you an educated guess behind my computer.

3) You're very welcome. My pleasure.:thumbsup:

 

[Smeeneezle]

Hey @TheDullCarbide I’m finally getting back around to this project. I’m good to go on everything except you mentioned a green contra for the 20 series driven however I can only find the stock blue spring anywhere. You know where to find it by chance? Thanks in advance.

 

[Smeeneezle]

Hey @TheDullCarbide I’m finally getting back around to this project. I’m good to go on everything except you mentioned a green contra for the 20 series driven however I can only find the stock blue spring anywhere. You know where to find it by chance? Thanks in advance.

Ahh ha I figured it out. The green spring is for the 30 series and blue is for 20 series.

 

[TheDullCarbide]

Ahh ha I figured it out. The green spring is for the 30 series and blue is for 20 series.

Yeah I forgot about that too. Ride on!

 

[riverjohn]

https://www.bmikarts.com/PDF/Comet_TAV2_Torque_Converter.pdf

I hadn't heard about crushed garter springs til now, have always used
the lighter weights/blue spring @3300.
However, putting together a TC with spare parts for a drag set-up in process
I am left with stock weights and a blue-silver garter @3600 that will
see about 7000 rpm... NOT! Ordering the alum weights; seems the Comet
literature would have addressed the crushed springs issue as a technical/safety concern.
Thanks for sharing.

 

[Smeeneezle]

https://www.bmikarts.com/PDF/Comet_TAV2_Torque_Converter.pdf

I hadn't heard about crushed garter springs til now, have always used
the lighter weights/blue spring @3300.
However, putting together a TC with spare parts for a drag set-up in process
I am left with stock weights and a blue-silver garter @3600 that will
see about 7000 rpm... NOT! Ordering the alum weights; seems the Comet
literature would have addressed the crushed springs issue as a technical/safety concern.
Thanks for sharing.

Hey @riverjohn, yea pretty crazy about crushing the springs. I just got the aluminum weights, pink springs, white springs and blue springs to mess around with this weekend as well as a new 7” comet driven that I’m going to put blue spring into hole 3. I’m super excited to check it out and tweak away the weekend. Have fun with your dragster build and be careful as I’ve heard those blue/silver springs are super stiff and have been known to snap because of it. Ride on!!!

 

[jeep2003]

Sounds to me like you need a higher gear ratio. Unless you drive at very low speeds all the time and it sounds like you dont. There is no use having the low gear ratio there if you dont use it.

 

[riverjohn]

OK friend, let us know how that big 7" pulley works out.
I'll be trying an alum/ blue/white @3650 setup soon,
TC's are a great invention!

 

[Smeeneezle]

Sounds to me like you need a higher gear ratio. Unless you drive at very low speeds all the time and it sounds like you dont. There is no use having the low gear ratio there if you dont use it.

Hey @jeep2003, would you mind elaborating as to why, and how, this would help my setup out? I’m still fairly new to this game and am still trying to learn as much as possible and would just like to know what makes you suggest this. Pick your brain kinda deal. Thanks in advance.