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 Hiro project this winter
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Rick Bennett
Advanced Member

USA
222 Posts

Posted - 11/23/2019 :  6:56:55 PM  Show Profile  Reply with Quote
I have gone off the deep end this time and am looking at building a Penton Hiro. I now have a nos Hiro motor, one of the ones John bought back in 1974, and a 74 roller. Dale Fisher has provided some welcome information to help out. Seems like a fun project.
Rick

rob w
Advanced Member

USA
3017 Posts

Posted - 11/23/2019 :  9:07:35 PM  Show Profile  Reply with Quote
Rick,
I currently have the same project going on. One day this week, I got the rear wheel that I'm going to use installed, so I will have the sprocket alignment correct.
Then made the tubular part of the upper rear engine mount, that slides over the swing arm bolt, between the two sides of the swing arm.
Then I got the engine located where I want it.
Then took dimensions, made a drawing of the other pieces that will link my upper rear engine bracket to the engine. Making those parts now.
After thats made and bolted to the engine, I will locate where the tabs are welded on for the lower rear engine mounts. Then go to the front engine mounting brackets.
Bob
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Rick Bennett
Advanced Member

USA
222 Posts

Posted - 11/23/2019 :  10:46:11 PM  Show Profile  Reply with Quote
Dale Fisher is also working on one. His is original with lower end intact but no swing arm. I have offered to help him convert the swing arm in return for being able to copy his motor mounts. Keep. Me posted on your progress. I plan on making mine a runner.
Rick
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Pat Oshaughnessy
Advanced Member

162 Posts

Posted - 11/25/2019 :  2:27:11 PM  Show Profile  Reply with Quote
Keep in mind your getting better trans. But a different powerband !
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rob w
Advanced Member

USA
3017 Posts

Posted - 12/03/2019 :  12:23:24 AM  Show Profile  Reply with Quote
Got the motor mounts finished. Hiro engine in '75 Six-Day.

Link to pictures ->
https://photos.app.goo.gl/14jSmiwBMNJ9RiNd9

https://photos.app.goo.gl/GZegzckcWeMgeapVA

https://photos.app.goo.gl/NvXtZprQmA96fEkKA

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Rick Bennett
Advanced Member

USA
222 Posts

Posted - 12/03/2019 :  09:13:11 AM  Show Profile  Reply with Quote
Rob
Great job! A better welding job than original. It looks like the bottom rear tabs have slots, not holes. Isnít there room for a longer tab and hole? Did you use 4130 or mild steel? Have you done the swing arm conversion yet?
Rick
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Rick Bennett
Advanced Member

USA
222 Posts

Posted - 12/07/2019 :  09:45:58 AM  Show Profile  Reply with Quote
At the POG meeting I picked up an original Hiro/Penton from Dale Fisher to copy. Thanks Dale. This is a big help.
Rob...What pipe should be on this machine?
Rick
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Dale Fisher
Advanced Member

USA
1679 Posts

Posted - 12/07/2019 :  10:29:31 AM  Show Profile  Reply with Quote
Some of the originals had a shortened or stubbed earlier '72-ish cone tip and some a slightly modified for angle/clearance '74 standard.

Here is the link to all my Hiro folders on dropbox. Under known originals there are photos.

https://www.dropbox.com/sh/mjlt39b4w95tief/AAD-KMZTTaxjUFDgGvLo2xFFa?dl=0

Dale Fisher
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Edited by - Dale Fisher on 12/07/2019 8:43:13 PM
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rob w
Advanced Member

USA
3017 Posts

Posted - 12/07/2019 :  11:46:59 AM  Show Profile  Reply with Quote
Hi Rick, Dale.
I recommend that before you copy anything, you should check to see if it was done well in the first place. Meaning are the sprockets aligned - and also when transferred over to your frame, are the sprockets still aligned.
I started this project with a half-dozen pictures I once took of the engine mounts, on Pat's original Hiro at Mid-Ohio.
The first step of the fabrication is making the upper rear engine bracket. Which will locate the engine left to right, and also the height up and down.
I can clearly see the dimensions of this piece in my pictures ( + or - 2mm). Unfortunately if I copied that, it would have never been correct. The engine would not have been far enough to the right. The chain would not be aligned, and the kick starter would not have enough clearance to swing.
This really got me thinking, because back in the day / on my original Hiro Penton - more than several times the chain came off. Once when I was leading a Michigan MX State Championshp race, and the last time when the transmission exploded into more pieces than I could count.
Not for certain saying it was made wrong in the first place, the chain came off when landing from a big jump, so maybe it was the swing arm flexing.
Anyway I couldn't copy the original engine mount that I had taken pictures of.
So much more to say - believe this thread may go on for quite some time. Even though this topic hasn't been covered before - hope it doesn't bore the members here.

Edited by - rob w on 12/07/2019 11:50:36 AM
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rob w
Advanced Member

USA
3017 Posts

Posted - 12/07/2019 :  12:04:11 PM  Show Profile  Reply with Quote
For an exhaust pipe, I am starting with a NOS '77 MC5 125 pipe that I got from Al B.

Picture link -> https://photos.app.goo.gl/cEFM22spu34hWJLy8

Takes some cutting and fitting. Had to turn-down the header connection that slides into the exhaust manifold.

Link-> https://photos.app.goo.gl/urH6nP55PKyhFwpw7

Shooting for the length of it to end just in front of the seat mounting bolt hole.

Going to weld it together next, and I'll show some pictures of the results.
Of course fins will have to be cut off of the cylinder head for clearance.

Edited by - rob w on 12/07/2019 12:06:27 PM
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Rick Bennett
Advanced Member

USA
222 Posts

Posted - 12/07/2019 :  10:55:15 PM  Show Profile  Reply with Quote
Dale
I removed the motor from the frame and degreased it so could see better. All four skid plate mounts are broken. Do you want me to replace them? The modifications are pretty well done and if you didnít know better you would think it came from Penton this way. Now I see why the rear lower mount is slotted. You canít put the bolt through the foot peg. It seems to me that the original pipes would be cut down from original 74 pipes since they would have had them on hand. It would be nice to see a photo from the right side.
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Dale Fisher
Advanced Member

USA
1679 Posts

Posted - 12/08/2019 :  1:17:08 PM  Show Profile  Reply with Quote
By broken.... were they removed on purpose? The FMF frame has them missing as well. The second photo doesn't look to have a skid plate on. One was installed in the restoration.

https://www.dropbox.com/s/j15ev6euxb5azij/032.JPG?dl=0

https://www.dropbox.com/s/nln3b7w586pcqpe/Pat%20Mikevicius.JPG?dl=0

https://www.dropbox.com/s/30i4z74uu5appyp/getmediaobject%20%286%29.jpg?dl=0

Dale Fisher
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Edited by - Dale Fisher on 12/08/2019 1:25:30 PM
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Rick Bennett
Advanced Member

USA
222 Posts

Posted - 12/10/2019 :  3:32:34 PM  Show Profile  Reply with Quote
Dale
The tabs, all four, are broken, leaving half on the frame. All have jagged edges. I would say they should be there even if you decide to leave the skid plate off.
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Dale Fisher
Advanced Member

USA
1679 Posts

Posted - 12/10/2019 :  7:50:28 PM  Show Profile  Reply with Quote
Rick, I agree if you have the time and inclination.

Dale Fisher
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