Heald Super Bronc progress.

[Sprocket86]

Getting lots done on the Heald VT-8

I wasn't really digging the looks of the mismatched pull start and fan shroud on my newly acquired Bronc. I wanted the classic white engine as these were when new.

I was given 2 additional HM-80 engine and one is from 1971! Classic off white tins and the flywheel mesh screen that so many engines utilized at one time.

I swapped them over to the current engine. I wanted t swap the whole engine but unfortunately the 3/4" PTO does not have a tapped 5/16-24 threaded hole. I thought about drilling one but it has to be spot on.

The white 1971 engine even has the 3 pin charging/lighting coil vs the engine that's in the bike now is the later design with electronic ignition coil and 1 pin with a lower output coil for just a single lamp like on a snowblower.

The auxiliary fuel tank that came with the bike started to leak fuel after a few days. The mount holes have stress cracks. I mounted up the white engine mounted fuel tank. I plan on getting the tank plastic welded and have both.

 

[chrisr]

They make drill guides to help center the hole when drilling the PTO. Maybe someone on here can share such a guide. I use a socket over the PTO and mark center that way and drilling the PTO is pretty soft. Just need to be careful taping and drilling. Let us know how it goes.

 

[Sprocket86]

They make drill guides to help center the hole when drilling the PTO. Maybe someone on here can share such a guide. I use a socket over the PTO and mark center that way and drilling the PTO is pretty soft. Just need to be careful taping and drilling. Let us know how it goes.

I have thought about using a 3/4" OD, 5/16 ID bushing as a pilot guide as there is a large pulley currently on the crank from it's snowblower days that protrudes past the end of the crank by about an inch. The bushing would sit dead center in the pulley 3/4" ID and would guide the drill bit parallel with the crank. Would I need a 5/16-24 starting and bottoming taps to thread the hole?

 

[chrisr]

A 5/16-24 fine thread tap is what you want, and you want the bolt to go into the PTO appox ~ 2 inches and the bolt used to secure the driver should not bottom out in the hole. When drilling and tapping, you would want to use safety glasses and use oil. While taping, you should backup a 1/4 turn after going forward a turn and be sure to clean out the hole good of debris before inserting the bolt. Hope that helps.

 

[Sprocket86]

A 5/16-24 fine thread tap is what you want, and you want the bolt to go into the PTO appox ~ 2 inches and the bolt used to secure the driver should not bottom out in the hole. When drilling and tapping, you would want to use safety glasses and use oil. While taping, you should backup a 1/4 turn after going forward a turn and be sure to clean out the hole good of debris before inserting the bolt. Hope that helps.

Yes it does for sure! Thank you.

 

[PatrickCraik]

A 5/16-24 fine thread tap is what you want, and you want the bolt to go into the PTO appox ~ 2 inches and the bolt used to secure the driver should not bottom out in the hole. When drilling and tapping, you would want to use safety glasses and use oil. While taping, you should backup a 1/4 turn after going forward a turn and be sure to clean out the hole good of debris before inserting the bolt. Hope that helps.

2" way too deep. You want much meat on the crank as possible. 1" hole plenty deep with a 3/4" long screw, flat washer
large enough to cover boss of driver or clutch and a lock washer. It's just to keep a driver from sliding off. Hell, my '04 Lil Indian with a 6HP OHV Tec never had a bolt before I bought it,lol! It had 2 set screws holding on the clutch and never budged

 

[creia]

I 100% agree with Patrick's post above^^^^. I have drilled MANY and never over 1" deep. Furthermore, on every engine I have ever seen with the drilled and tapped crank end (from the factory) they are NEVER over 3/4-1" deep. By the way, you do not need a "bottoming tap"- just a regular tapped will work just fine.
Michael

 

[Mr. Pink]

Here's how I drilled and tapped the crank on my vintage Briggs.
It was a bit scary to do, but was easier than I expected.

 

[Sprocket86]

2" way too deep. You want much meat on the crank as possible. 1" hole plenty deep with a 3/4" long screw, flat washer
large enough to cover boss of driver or clutch and a lock washer. It's just to keep a driver from sliding off. Hell, my '04 Lil Indian with a 6HP OHV Tec never had a bolt before I bought it,lol! It had 2 set screws holding on the clutch and never budged

I thought 2" might be a little to deep myself. The bolt and large flat washer does more then just stop the driver clutch from sliding off. when the driver weights start to move outward, considerable tensile force is placed on that bolt and washer.

 

[Sprocket86]

Here's how I drilled and tapped the crank on my vintage Briggs.
It was a bit scary to do, but was easier than I expected.

View attachment 298591


View attachment 298592

Thanks for sharing that. How did you drill out the 3/4" OD dowel dead center?

 

[Mr. Pink]

Thanks for sharing that. How did you drill out the 3/4" OD dowel dead center?

I have a wood turning lathe.

 

[Sprocket86]

I have a wood turning lathe.

I need to get a lathe to really up my fabrication skill sets.

 

[Mr. Pink]

I need to get a lathe to really up my fabrication skill sets.

I fabricated a disc sander attachment for the lathe.
The sander works quite well for wood, plastic and metal.

 

[Sprocket86]

I fabricated a disc sander attachment for the lathe.
The sander works quite well for wood, plastic and metal.

View attachment 298617

That's a great idea and would come in handy for many things no doubt.

 

[Sprocket86]

Getting more things accomplished on the Bronc.

I was able to get the leaky fuel tank plastic welded up and hopefully it holds. I'm concerned the vibration will be the Achilles Heel on this type of repair. we shale see. How did the Bronc's plumb their fuel line when they used the 2 tank set up?

The front wheel bearings were dry as a bone and the axle was not centered. I debated making an internal bearing spacer like I did for the rear wheel but I felt it's not as necessary. Lubed up the wheel bearings and centered the axle. Now on to the next big challenge!!

At some point in the Broncs life the left fork spring broke half way and got jammed (so I think) in the upper portion of the fork leg. The red outlined section in the photo shows how much is all balled up in there. Someone decided it was a good idea to weld through the spring bolt hole and make a big porous junk mess to hold it all in there. The tube is all ground down and looks thin. Hopefully this tube is not an oddball OD and thickness.

I would like to try and fix this and make it appear like it was factory. Any ideas? This is my green area in the mini bike hobby.