73 MTD Trail Flight need new converter

[Bbcngineer]

Folks,
I bought this old minibike without a motor. The jackshaft is there as well as the secondary clutch pulley. I am putting a 212 Predator engine on this bike and am looking for the easiest way to get this up and running. I need help with the primary clutch and the belt. What primary clutch (part number and manufacturer) do I need for the predator engine that will interface with the OEM secondary? What belt do I need for the recommended primary?

Kevin

 

[mustangfrank]

Folks,
I bought this old minibike without a motor. The jackshaft is there as well as the secondary clutch pulley. I am putting a 212 Predator engine on this bike and am looking for the easiest way to get this up and running. I need help with the primary clutch and the belt. What primary clutch (part number and manufacturer) do I need for the predator engine that will interface with the OEM secondary? What belt do I need for the recommended primary?

Kevin

MTDs had both asymmetric and symmetric clutch setups depending on year and model. Post a picture of your clutch from at least two angles if you want better advice, include a good pic of the sheaves to see the angle.

Unless you're going to find an original primary you should replace both clutches, the belts don't generally work between the vintage and new clutches.

 

[Bbcngineer]

MTDs had both asymmetric and symmetric clutch setups depending on year and model. Post a picture of your clutch from at least two angles if you want better advice, include a good pic of the sheaves to see the angle.

Unless you're going to find an original primary you should replace both clutches, the belts don't generally work between the vintage and new clutches.

I am OK to replace both primary and secondary with a new belt. That makes perfectly good sense.

What parts do I need? does anyone know the part numbers that work?

 

[ELT]

I'm running a 30 series clutch a secondary on my mtd. I had to used a longer jackshaft with this setup.

 

[mustangfrank]

Mine has Comet 20 series primary & secondary, I'm using the factory clutch cover, the old clutches ran the same orientation.

 

[Bbcngineer]

Mine has Comet 20 series primary & secondary, I'm using the factory clutch cover, the old clutches ran the same orientation.

Do you know what parts you bought? Was it a kit with a belt? I know nothing about these bikes and don't want to buy the wrong stuff?

 

[mustangfrank]

In the case of MTDs the clutches are purchased separately and you'll have to measure for a belt. Again, without knowing your original setup I can't say whether a 20 or 30 series would be correct.

All the normal minibike retailers sell them but I like the online charts and clutch info here:

https://www.gokartsupply.com/mobile/

 

[Bbcngineer]

OK now I'm starting to understand this stuff. My original clutch is a symmetrical design, so I need Comet 20 series clutch correct? To measure center to center distance I am a little confused. My motor mounts have very long slots for adjustment. Should I position the motor in the middle and take the measurement or position the motor on either extreme and take the measurement? Or look for the belts available and pick one that fits my center to center?

mustangfrank,
what part numbers did you use for primary, secondary and belt?

Kevin

 

[ELT]

OK now I'm starting to understand this stuff. My original clutch is a symmetrical design, so I need Comet 20 series clutch correct? To measure center to center distance I am a little confused. My motor mounts have very long slots for adjustment. Should I position the motor in the middle and take the measurement or position the motor on either extreme and take the measurement? Or look for the belts available and pick one that fits my center to center?

mustangfrank,
what part numbers did you use for primary, secondary and belt?

Kevin

The origonal system required the engine all the way to the rear of the slots.

 

[mustangfrank]

OK now I'm starting to understand this stuff. My original clutch is a symmetrical design, so I need Comet 20 series clutch correct? To measure center to center distance I am a little confused. My motor mounts have very long slots for adjustment. Should I position the motor in the middle and take the measurement or position the motor on either extreme and take the measurement? Or look for the belts available and pick one that fits my center to center?

mustangfrank,
what part numbers did you use for primary, secondary and belt?

Kevin

If you have the original clutch cover I would fit the engine so that the cover slots will align well first...if not I'd bolt the engine in the middle to leave a little adjustment just in case the belt measurement is a little off when you get it.

I don't remember what part numbers I used and the bike is in storage for the winter but:

Comet 20 series driver (3/4" or 1" whatever size your engine PTO shaft is)
Comet 20 series 6" driven (5/8" or whatever measurement your jackshaft is)
Comet Symmetric belt (measure CTC distance)

 

[ELT]

Here's some pages out of the owner's manual. Mtd used a fairbanks morse asymmetrical torque converter on some bikes and a symmetrical torque converter on later bikes.

 

[Bbcngineer]

Here's some pages out of the owner's manual. Mtd used a fairbanks morse asymmetrical torque converter on some bikes and a symmetrical torque converter on later bikes.

awesome information. Mine is a symmetrical design. I have it all apart and in the parts washer. I'm going to put it all together and see it the parts work with a new belt. If it works well ill keep it if not ill buy the comet 20 replacement driver and driven.

Kevin

 

[1971_MB1A]

awesome information. Mine is a symmetrical design. I have it all apart and in the parts washer. I'm going to put it all together and see it the parts work with a new belt. If it works well ill keep it if not ill buy the comet 20 replacement driver and driven.

Kevin

If you want to make it a bit easier on yourself go to beltpalace.com. They have a conversion chart you can view to help figure it all out.

 

[Bbcngineer]

OK folks here is what I have so far. Secondary is 6 inches in diameter. Center to center with the motor as far to the rear as possible is 8 1/8. I chose comet belt number 203581A. I'll try to put it together with my old parts and see how it works. I think it will be fine as I'm not planning to put 100,000 miles a year on it.

Thanks to all of you for sharing your expertise, resources and opinions on the topic. It has been a really fun time.

Kevin