1969 MTD Trail Flight

[Bbcngineer]

Thanks for adding me to the group. This is my first post. I picked up a 69 MTD without a motor. The guy said that a predator 212 will bolt right in. Well it doesn’t. The motor mount is at an angle so in order to get the motor in the frame I needed to remove the muffler and the air box. No big deal I can relocate that stuff. My bigger issue is the belt rice for the jack shaft. What type of clutch will work with the predator 212 engine? It originally had some kind of torque converter like a snowmobile would use. Has anyone done this swap? What parts do I need?
This is not a restoration project. Just something my nieces and nephews can ride around the property

 

[delray]

just to give you heads up on year of bike . it's more like a 72 and up. you have what i call the second design mtd where the tank is more rounded and the seat too. for example my 71 mtd has the square tank and seat. chain guard is also different. i'm sure other guys will chim in on this with more detail.
good luck on your project.

 

[mustangfrank]

If you can figure out the mounting, get the float bowl level, etc...you can use a Comet 20 series drive and driven clutch, you'll have to measure for the belt, not sure if the original clutch cover and bracket will fit.

Why not find a Tecumseh HS40 or HS50 like original? Much cooler and you can use the MTD exhaust pipe not to mention add value to the mini.

Check out this site...

http://www.pinrepair.com/minibikes/tecumsehmb.htm#partnum

Awesome information and a member on these forums.

 

[Bbcngineer]

just to give you heads up on year of bike . it's more like a 72 and up. you have what i call the second design mtd where the tank is more rounded and the seat too. for example my 71 mtd has the square tank and seat. chain guard is also different. i'm sure other guys will chim in on this with more detail.
good luck on your project.

thanks for the info. I’ve attached a picture of the ID tag. The guy I bought it from said it was a 69. I always like to have the facts though. How can I tell what year it is?

 

[Bbcngineer]

If you can figure out the mounting, get the float bowl level, etc...you can use a Comet 20 series drive and driven clutch, you'll have to measure for the belt, not sure if the original clutch cover and bracket will fit.

Why not find a Tecumseh HS40 or HS50 like original? Much cooler and you can use the MTD exhaust pipe not to mention add value to the mini.

Check out this site...

http://www.pinrepair.com/minibikes/tecumsehmb.htm#partnum

Awesome information and a member on these forums.

OK I've seen the Comet (or comet knock off) systems for sale, but it looks like you mount a plate to the motor that holds the driven clutch and a new jackshaft. Is there a way to use the existing driven and jackshaft?

Kevin

 

[mustangfrank]

OK I've seen the Comet (or comet knock off) systems for sale, but it looks like you mount a plate to the motor that holds the driven clutch and a new jackshaft. Is there a way to use the existing driven and jackshaft?

Kevin

That's a Torq-A-Verter with the plate and that uses Comet 30 series clutches...you can try to use the FM clutches but parts are nearly unavailable and they usually don't work great...You can just buy a Comet 20 driven to replace the jackshaft one in exactly the same configuration and a Comet 20 drive for whatever your engine shaft is, no plate needed. Separate clutches are cheaper and the system you have works great with Comet clutches.

I don't think a plate style would work unless you took off the factory jackshaft, flipped your drive chain side, not to mention the fixed belt size would force the engine to be really far back.

 

[mustangfrank]

thanks for the info. I’ve attached a picture of the ID tag. The guy I bought it from said it was a 69. I always like to have the facts though. How can I tell what year it is?

Start here, downloads of brochures too...

http://www.pinrepair.com/minibikes/mtdinfo.htm

 

[Bbcngineer]

That's a Torq-A-Verter with the plate and that uses Comet 30 series clutches...you can try to use the V-plex clutches but parts are nearly unavailable and they usually don't work great...You can just buy a Comet 20 driven to replace the jackshaft one in exactly the same configuration and a Comet 20 drive for whatever your engine shaft is, no plate needed. Separate clutches are cheaper and the system you have works great with Comet clutches.

I don't think a plate style would work unless you took off the factory jackshaft, flipped your drive chain side, not to mention the fixed belt size would force the engine to be really far back.

OK I guess that was my question. Can i just buy a comet 20 drive clutch to put on the motor and use the existing driven which is mounted to the jackshaft. I don't want to flip all that stuff around.

Does anyone have part numbers to order for the comet 20 clutch and a belt?

 

[mustangfrank]

OK I guess that was my question. Can i just buy a comet 20 drive clutch to put on the motor and use the existing driven which is mounted to the jackshaft. I don't want to flip all that stuff around.

You can just get a new drive and try it out with the existing driven, the belt/sheave angles are close if not the same...you'll end up replacing the driven sooner or later though.

 

[Bbcngineer]

You can just get a new drive and try it out with the existing driven, the belt/sheave angles are close if not the same...you'll end up replacing the driven sooner or later though.

OK I'll just buy both now.

 

[mustangfrank]

My same original driven was workable when I got it and I had a Comet drive clutch in my stash but the original spring loses tension and there isn't any adjustment like the Comets...belt gets sucked down in the sheaves and doesn't come back so you're stuck in high gear.

Enjoy the project, the MTDs are fast little minis with factory 4:1 gearing!

 

[Havasu Dave]

OK I guess that was my question. Can i just buy a comet 20 drive clutch to put on the motor and use the existing driven which is mounted to the jackshaft. I don't want to flip all that stuff around.

Does anyone have part numbers to order for the comet 20 clutch and a belt?

No, you can not use a Comet 20 driver with the existing driven IF it is a Comet 30 or Cat 99. The 20 uses a "Symmetric, 3/4" Top Width belt," and the 30 uses an "Asymmetric, 3/4" Top Width belt."

Note that the earlier Cat 99 series, also made by Comet was the same as the current 30 series. The angles on that Cat 99 or Comet 30 belt and sheaves are 2.5 degrees on one side, and 18 degrees on the other. A noticeable difference.

You don't need, or want a "torque-a-verter" as those are the ones that come married to a plate. You are going to be using the jack shaft on the bike, or since it's probably going to be a pain in the ass to get the driven off of it, I recommend getting that replacement 3/4" keyed jack shaft, a replacement chain sprocket if needed, and a new Comet 20 driver and driven, and from what I read, the Chinese knock offs seem to work fine. After that, you measure your distance, and get that belt to specification.

Your biggest challenge is how to modify your Chinese engine to fit, and dealing with 20 degrees of engine angle with a float carb- which isn't that hard either.

 

[Bbcngineer]

No, you can not use a Comet 20 driver with the existing driven IF it is a Comet 30 or Cat 99. The 20 uses a "Symmetric, 3/4" Top Width belt," and the 30 uses an "Asymmetric, 3/4" Top Width belt."

Note that the earlier Cat 99 series, also made by Comet was the same as the current 30 series. The angles on that Cat 99 or Comet 30 belt and sheaves are 2.5 degrees on one side, and 18 degrees on the other. A noticeable difference.

You don't need, or want a "torque-a-verter" as those are the ones that come married to a plate. You are going to be using the jack shaft on the bike, or since it's probably going to be a pain in the ass to get the driven off of it, I recommend getting that replacement 3/4" keyed jack shaft, a replacement chain sprocket if needed, and a new Comet 20 driver and driven, and from what I read, the Chinese knock offs seem to work fine. After that, you measure your distance, and get that belt to specification.

Your biggest challenge is how to modify your Chinese engine to fit, and dealing with 20 degrees of engine angle with a float carb- which isn't that hard either.

I got the engine to fit in by removing the muffler and the air box. Both of these components are readily available after market, but will fabricate my own parts because I want to use the existing MTD exhaust pipe. Its such a cool feature. I have been reading that some folks are mounting the motor at an angle and they are running fine. Just need to make sure oil level is right for the angle. Any ideas if this is true? I suppose I could machine some 20 degree wedges to level the motor.

 

[mustangfrank]

No, you can not use a Comet 20 driver with the existing driven IF it is a Comet 30 or Cat 99. The 20 uses a "Symmetric, 3/4" Top Width belt," and the 30 uses an "Asymmetric, 3/4" Top Width belt."

Note that the earlier Cat 99 series, also made by Comet was the same as the current 30 series. The angles on that Cat 99 or Comet 30 belt and sheaves are 2.5 degrees on one side, and 18 degrees on the other. A noticeable difference.

You don't need, or want a "torque-a-verter" as those are the ones that come married to a plate. You are going to be using the jack shaft on the bike, or since it's probably going to be a pain in the ass to get the driven off of it, I recommend getting that replacement 3/4" keyed jack shaft, a replacement chain sprocket if needed, and a new Comet 20 driver and driven, and from what I read, the Chinese knock offs seem to work fine. After that, you measure your distance, and get that belt to specification.

Your biggest challenge is how to modify your Chinese engine to fit, and dealing with 20 degrees of engine angle with a float carb- which isn't that hard either.

He's got a Fairbanks Morse on it and he's replacing it anyway now...did they make those in both symmetric and asymmetric? His is mounted backwards if it is asymmetric...my jackshaft is 5/8" too, not 3/4" so better measure if you think they also had 3/4" jackshafts.

Pictures are of my old one, same vintage mini, sheaves are worn out but symmetric.

 

[Havasu Dave]

He's got a Fairbanks Morse on it and he's replacing it anyway now...did they make those in both symmetric and asymmetric? His is mounted backwards if it is asymmetric...my jackshaft is 5/8" too, not 3/4" so better measure if you think they also had 3/4" jackshafts.

Yes, they made them both ways. The photo is too tiny for me to see, but I commented to get him to consider replacing both driver and driven as a unit, and not to piss with trying to pull that driven off of a stuck JS. Also, the FM belts (assuming it's a symetrical) is (I have read) different width.

My comment on procuring a 3/4 jack shaft was based on the bore options of the Comet 20. but I screwed that up, thinking it only came in 3/4 and 1" when in reality it comes in 3/4 and 5/8, of which I have bought plenty, so disregard everything I say in this thread.

https://oldminibikes.com/forum/index.php?threads/help-with-mtd-clutch-please.50892/

https://www.oldminibikes.com/forum/index.php?threads/fairbanks-morse-tc-setup-asymmetrical.135411/

 

[Havasu Dave]

I got the engine to fit in by removing the muffler and the air box. Both of these components are readily available after market, but will fabricate my own parts because I want to use the existing MTD exhaust pipe. Its such a cool feature. I have been reading that some folks are mounting the motor at an angle and they are running fine. Just need to make sure oil level is right for the angle. Any ideas if this is true? I suppose I could machine some 20 degree wedges to level the motor.

Yeah, I've never had an engine die going up a 20 degree incline either. There are better carb options, but I don't mess with Chinese engines on mini bikes. Plenty of info here on that. The oil level is not an issue either- since we also don't seize engines going up a hill. Upside down, not so much. Sounds like you have it figured out. That drive stuff is easy. Since you;re not restoring, you probably have a ready market for that driven.

 

[mustangfrank]

Yes, they made them both ways. The photo is too tiny for me to see, but I commented to get him to consider replacing both driver and driven as a unit, and not to piss with trying to pull that driven off of a stuck JS. Also, the FM belts (assuming it's a symetrical) is (I have read) different width.

My comment on procuring a 3/4 jack shaft was based on the bore options of the Comet 20. but I screwed that up, thinking it only came in 3/4 and 1" when in reality it comes in 3/4 and 5/8, of which I have bought plenty, so disregard everything I say in this thread.

https://oldminibikes.com/forum/index.php?threads/help-with-mtd-clutch-please.50892/

https://www.oldminibikes.com/forum/index.php?threads/fairbanks-morse-tc-setup-asymmetrical.135411/

Good point on the jackshaft, my bearings were sloppy so I ordered 2 bearings, shaft stock and a gear for a little over 20 bucks shipped...my clutch came off fairly easily after soaking in penetrant but it'd suck to be ready to put the new one on and struggle with the old one.

I tried to mic my original belt for reference but it was pretty dry and worn...measured under 3/4" width but who knows where it started.

 

[Havasu Dave]

Good point on the jackshaft, my bearings were sloppy so I ordered 2 bearings, shaft stock and a gear for a little over 20 bucks shipped...my clutch came off fairly easily after soaking in penetrant but it'd suck to be ready to put the new one on and struggle with the old one.

I tried to mic my original belt for reference but it was pretty dry and worn...measured under 3/4" width but who knows where it started.

Good move, and congrats on getting the clutch off. I seldom have that kind of luck. I've even had to drill the old Jack shaft out, to rebuild the clutch.

I am almost positive those belts were 5/8 top width. I know folks use the larger 3/4 belts if they have a Comet driver on the FM or Cat88 driven, but I don't. I've heard that the Chinese knock of Comet 20 copy drivers and driven work well for general purpose, and they are definitely cheap, and your method of replacing the works, and replacing both clutch halves are what I'd do.