Torque converter

[evmatt]

I was wondering if anybody here has used the tried and true Comet torque converter instead whatever problematic transmission comes with the grubee kit? I have just finished my 2 stroke 66cc motorized bike and am interested in using a 2.5hp Harbor Freight 4 stroke for the next one. I don't know any other way than using a go kart torque converter?

 

[HoughMade]

I think a Comet Torq-a-Verter would work on that engine as the maximum rpm is about 3600. I would like to try the Comet, but with the more commonly used Honda and Huasheng engines that rev to over 7000 rpm, the 3:1 to .9:1 reduction from the Comet is not enough. We need closer to 3.5:1 to 4:1 from the gearbox (additional reduction from the final drive). If I could find a CVT that gave about 7 or 8:1 down low and 3:1 up top....I'd give it a try.

 

[Youngbird]

Also keep in mind that the smallest Comet is a 3/4" shaft bore and the Honda/HS engines are 5/8" shaft. You would need to sleeve it. There should not be any problems with the setup however so long as your ratios work out right.

 

[HoughMade]

I have seen listings for a Comet with 5/8 shaft (340), but never found anyone who actually had one.

 

[Youngbird]

I dont think they are making a 5/8" shaft 340 any longer. I believe the smallest to be 3/4" unless you can find a 5/8" used. There really is no problem sleeving the crank to accept the 3/4 though.

 

[spad4me]

I think a Comet Torq-a-Verter would work on that engine as the maximum rpm is about 3600. I would like to try the Comet, but with the more commonly used Honda and Huasheng engines that rev to over 7000 rpm, the 3:1 to .9:1 reduction from the Comet is not enough. We need closer to 3.5:1 to 4:1 from the gearbox (additional reduction from the final drive). If I could find a CVT that gave about 7 or 8:1 down low and 3:1 up top....I'd give it a try.

Just a thought .
I am working slowly and cheaply on a cvt solution.
It seems that a thats dax 5 to 1 gearbox guts may fit on a cvt in place of most of the 3 to 1 geared transmission part of a cvt .
This requires a 78 mm clutch and a cvt as well as a thats dax transmission.
No guarantee you will be able to make it work at all. Just a thought.

You may be able to go from engine, to modified cvt, to dérailleur controlled multi speed freewheel.

 

[Youngbird]

Im looking at a Titan coupled with a scooter CVT using DAX's 10 tooth splined sprocket....Im theorizing here. Maybe coupled to a 3 sp internal rear hub.*

* its working for LF.

 

[Dan]

Wondering if going from a 10T (on engine shaft), chain to 30T on the Torque converter mounted vertically behind the seat post, at low RPMs CVT is 3:1 then a 10T from CVT then to a rear sprocket of 54. Even at 10% power loss, with 26" wheel, would do over 30?

At 7000 RPM= 16.20:1 and 33.4MPH (not accounting for power loss due to slip)

At 2000 RPM=48.60:1 (has to be wrong) 3.2 MPH

I am sure I am missing some thing or folks would be building more with them.

 

[Youngbird]

On the Scooter CVT the ratios coming from it are 7:1 in low range and 3:1 in high range. The final drive(cvt to rear wheel) needs to be around 5:1 that wouls be a 10 tooth CVT sprocket to a 48-52 rear wheel sprocket. There is no need to add anything or customize the CVT in any way unless you just want to change the rollers or spring adjustment. Its good as it sits right out of the box. And as stated by LF...."its a bolt up, man!"

 

[Dan]

7:1, thats cool. Thinking of frame mounted engine with the CVT behind and remote so peddles will clear.

 

[Youngbird]

It may be tough to mount the CVT remotely as it needs to bolt to the crankshaft. It has a clutch bell built into it.

 

[Dan]

just read your post. Great lookin' Bike! What I am thinking for that is an "L" plate that mounts to the seat post and CVT mounts to it with 2 shafts coming out. (drive and driven) Really dunno if it will work but always wanted to try one. Have 2 Honda's and they are a joy.

 

[frictiondrive]

I've used Comet converters on mini bikes and my diesel powered GS850. They are okay, but rob a good amount of horsepower due to friction losses. A two speed centrifugal clutch would be nice, but you would have to gear down say, 50% before the clutch to reduce rpm, double the torque and reduce the 2 speeds chain velocity. Without an oil bath for the chains, they would wear out fast at engine crankshaft speed.

Cris

 

[vooodooou]

here is a link to pdf and part # and specs

http://www.islandracing.com/PDF FILES/COMET PDF/340 series torque converter system.pdf

 

[efinitylove]

Go to Grainger dot com
search for this.

Steel Reducer Bushing, Inside Diameter 5/8 Inch, OD 3/4 Inch, Length 1 1/4 Inches, Zinc Plated, With 3/16 Inch Open Slot for Keyway and Setscrew

This way I guess you can mount 3/4 Comet 30 CVT on 5/8 shaft engine.

I have the same idea use Harbor Freight 2.5 HP engine with TAV2. It's good deal for $87 (with coupon) to get engine like this.

I don't know how heavy engine is. I guess I will try to find out next time when I go to the store.

 

[civlized]

I'm not sure about the comet CVT, but some of the cheap scooter cvt's have another gear reduction between the driven pulley and the output sprocket. The one I used reversed the rotation of the output sprocket from the engine direction, which meant that the tire would turn backwards. I spent about a month trying to get all the bugs worked out. I ended up with 2 good rides before everything went wrong. I would suggest paying attention to this when choosing a cvt. If the pics of the cvt show the output sprocket off center from driven pulley, you will have your work cut out for you.

 

[efinitylove]

I got idea from my Go Kart. People often upgrade go kart with comet CVT.

And also you may not need the reduction box. Here is the calculation with custom order 60 teeth sprocket for #35 chain, base on 26 inch bicycle

Low speed is 10.4 mile/hour (TAV2 engage at 2200 RPM with low range radio 2.7:1)
High speed is 50.9 mile/hour (3600 RPM with high range radio 0.90:1)

If you mount this way is very simple. Only need engine,CVT, chain, custom sprocket no need jack shaft or reduction box.

The down side is you need pedal bike to 10 mile/hour before engage CVT.

 

[Elmo]

Go to Grainger dot com
search for this.

Steel Reducer Bushing, Inside Diameter 5/8 Inch, OD 3/4 Inch, Length 1 1/4 Inches, Zinc Plated, With 3/16 Inch Open Slot for Keyway and Setscrew

This way I guess you can mount 3/4 Comet 30 CVT on 5/8 shaft engine.

I have the same idea use Harbor Freight 2.5 HP engine with TAV2. It's good deal for $87 (with coupon) to get engine like this.

I don't know how heavy engine is. I guess I will try to find out next time when I go to the store.

Mine weighs 22# without gas or oil out of the box.
Elmo

 

[industrialphreak]

So the normal torq converters and pocket bike bolt ons will not reverse the drive? thinking about getting a bolt on at ebay. any suggestions?

 

[captianroger]

check out my thread... honda 100cc build i used the comet tav2 torque converter...