70 Rupp Roadster build blower housing

It has been a few months since I last posted. I am working on bringing back to life my 70 Roadster I purchased back in Nov 1970. (actually a Xmas present from my parents). The old bike, ( see pic find and current) has been hiding my my dads shed for 40 plus years. Missing a few parts and of course a hole in the engine block. Learning alot thru this project, but much more learn. A question I have has anyone successfully modified blower housing from the nut-serts to studs. I have most of the internal parts to the engine as well as the lighted flywheel and no blower housing. Last winter I found an old snowblower with a 4 hp Tecumseh in excellent shape. From the things I have read it requires the added clearance which means the studs for mounting the recoil. Any tricks or ideas to convert this blower housing. I don't want to ruin a good part. Thanks dalpan.


I think the mounting holes are correct because of the 20 degree angle mounted engine on the 70 roadster. Which puts the orientation @ 10 o'clock.
This is where I read about the 10 o'clock position. http://www.pinrepair.com/minibikes/tecumsehmb.htm#flywheel
Maybe I'm missing something. Still learning all the little details. Would either orientation work?

Starter mech positions: To add to the blower housing confusions, there's yet another thing to consider... the position of the starter mech. Notice these two rounded (old style) blower housings have the pull start mech in slightly different positions: 12 oclock (left) and 10 oclock (right). Technically speaking, the 12 oclock position is for flat motor mounted minibikes. The 10 oclock position is for 20 degree angled mounted motors. A small and probably meaningless detail, but one I thought we should probably cover here.
Thanks for that, never noticed it before. I looked at pics of Hs40 engines and could not find that style.
I had always figured people had drilled the holes and that they were not factory


Well-Known Member
For some reason, I thought it was the 12 o'clock orientation, but I was wrong. From what I was told years ago, not having them in the right orientation on a slanted engine will cause damage to the blower housing. Here's the original engine from my 1970 Rupp

2015-05-08 10.46.13.jpg

you can get 1/4-20 studs on McMaster Carr and Ebay. I've never done this, but it seems like you should be able to grind out the nuts from the inside and tack-weld studs in




Well-Known Member
1/4-28 is the correct thread pitch for those, little tougher to find new though. I have cut them out/off of later 70's and up shrouds to reuse for this.....I just throw those shrouds in the garbage most of time anyway.

you can get 1/4-20 studs on McMaster Carr and Ebay. I've never done this, but it seems like you should be able to grind out the nuts from the inside and tack-weld studs in




Well-Known Member
I know 1/4-28 is the correct thread, but they are hard to find in stud size.

I have converted blower housings (remove the inside nuts, put in studs.) The way i do it is this... cut off the old internal nuts (pretty easy, you can use a dremel with a cut off wheel, or sometimes you can just knock them out.) Then just use 1/4-20 or 1/4-28 bolts (3/4" length), mounted from behind. TIG weld them in place from the inside. Then using a flap grind, you can take down the heads a bit. You don't have to grind off much to make it work. I do this all the time, it works fine. On the length 5/8" bolts are ideal. But i use 3/4" length. If you're using a kick start you will need to use 3/4" length!

Also I use 1/4-20 bolts. And then use 1/4-20 nylon lock nuts from the front. But Mark is right, 1/4-28 is the correct thread. Yet nylon locknuts in 1/4-28 are harder to find. So i use the more common 1/4-20 threaded parts. Again it works fine, but make sure you use locknuts. They use 1/4-28 to make it hard for vibration to loosen the nuts. But with nylock nuts, this isn't a problem.

On the position of the starter... either 12 or 10 oclock works fine on a flat or 20 degree situation. They both work. The mount position is for ergonomics only.
Appreciate the feed back. I'll start the surgery this weekend. I'll post a pic of my progress. @markus, you mentioned in my first post, "you need to be patient and you'll find the parts", some parts are pretty darn hard to find. @capguncowboy that looks like a nice engine, you don't have a spare diaphram carb?ha Again thanks for the info.
There is no reason to settle for a 1/4-20 set up, and no reason to use a TIG unless that is all you have. It's a simple spot weld.

I am a long time customer of Bolt Depot, they are excellent, shipping is fast, and prices reasonable on a wide variety of hardware, especially chrome and stainless.

I use 1/4-28 bolts that I've shaved the heads down on, but these would work better: Socket button head, Zinc plated alloy steel, 1/4"-28

1/4-28 nuts are easy to find, I use them in several applications on karts and mini bikes.

Here are several examples of nuts you can chose from, without making a special trip to the hardware store.

Hex lock nuts nylon insert
Flange nuts serrated, Stainless steel
Flange nuts serrated, Zinc plated steel
Prevailing torque lock nuts, Zinc plated grade C steel


Well-Known Member
Keps nuts are what tecumseh used originally, they are are the same as the nuts that hold the carb onto the intake......They are reusable locknuts, once you loosen it from tight they spin off easy, not like a nylocs or other pnched locknuts that tear themselves or the stud/bolt up to lock them up and are tight to remove, They also dont normally tear up paint too bad......plus they are clean and look factory :)


Well-Known Member
These are all good options I agree. The nylon lock nuts do work fine. I’m not removing the pull start, pretty much ever. So once it’s on, it’s on. It is good to use the original hardware, if that’s an option. But my hardware store does not have that stuff, so I go with what they do have. In the end it’s the same result, and works just as well. But I agree if you can get or have the exact stuff, that’s always the best way to go. Just that’s not always an option. I was just providing an alternative technique to achieve the same goal


Well-Known Member

yea those are the ones, I've seen them in the hardware store locally, Usually take 2 or more engines to make one around here though so I save them off the donor engines and usually have them at the ready in the bin.

heres the OG ones, and set of the studs I pulled off a squaretop shroud I have saved for a lighting coil engine build:



Well-Known Member
What’s with the telephone handset Markus?
Its a mid 1930's western electric phone I am redoing. Much like an old mini bike, someone had spray bombed the entire thing....right over corrosion, dirt, rust, the dial, and even the bakelite handset, etc... I just got done stripping all the paint, thankfully to find the porcelain face, and chrome parts on the dialer mech still actually good, and was able to strip and polish the Bakelite handset pieces. cast aluminum body had corrosion and some pitting so I Blasted and did some priming and sanding to get it back into shape. Getting ready to mix up some black and spray the body. I will have to find the center placecard that goes on the dial as that was MIA and some period correct cloth phone cord as they also cut the old cords off it for something they could get at the hardware store...becuase it was "Just as good" :D