Author Topic: Hirth 634 Mod  (Read 10264 times)

Offline moosenelson

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Hirth 634 Mod
« on: September 01, 2010, 11:07:41 AM »
 I usually do not post my projects as I have a tendency to take way to long to follow through. I seen to be easily distracted by new projects and this is no different as I have a couple other projects at this time. The reason I am starting this post is that I think there will be some interest from the Arctic Cat crowd.
 A bout a year and a half ago I purchased a 634 Hirth from a guy who needed cash. Not being a big Hirth fan at first I was not interested but when he said $50 I decided to take a look.


 When I saw the intake I knew it was a good deal so I offered him $40 and he accepted. I stuck it on a shelf in the storage shed and forgot about it until this spring. In March I decided to see if I could sell it so I brought it to the garage and started cleaning it up. While looking it over I saw through the exhaust ports that it had some unique pistons.


  I checked the compression and it has 185 lbs. on each cylinder. As it is missing the shrouds I decided I would cut down the housing and make it a free air. Thought as long as I was at it I might as well tear it down an put in new seals and gaskets.
 Well to my surprise when I took the cylinders off they were Mod ones with the finger and piston ports.


 And when I split the casings the crank is welded and the casings have fillers too.



 I think the right thing to do is find a 634 Chassie to put it in when I am done.
 
 Moose, Proud Member of the CCVSC?   uK#!**

God Damn that thing must be fast cause you were going like hell when I passed ya.

Offline 69 MOD

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Re: Hirth 634 Mod
« Reply #1 on: September 01, 2010, 11:25:18 AM »
Wow great buy!!

Slap that baby in a 634 Puma chasis and hang on!

B.A.
"Show me a man that can be bothered to do little things,
I'll show you a man who can be trusted to do big things."
Laurence "Larry" Bell

Offline panther634

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Re: Hirth 634 Mod
« Reply #2 on: September 01, 2010, 12:18:18 PM »
So, I take it you do not want to sell it now? I am interested in it if you are, I am quite fond of the Hirths. s#n

Offline GreenBlood800

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Re: Hirth 634 Mod
« Reply #3 on: September 01, 2010, 07:11:49 PM »
Very cool!  Nice find there!

 2utp

Will work for beer and Viking snowmobiles!

Offline Invader440

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Re: Hirth 634 Mod
« Reply #4 on: September 01, 2010, 07:32:24 PM »
Nice find.
Too many vintage events and not enough weekends!

Offline Nutter

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Re: Hirth 634 Mod
« Reply #5 on: September 02, 2010, 08:39:51 PM »
Cool motor Moose  2utp

Bring the flywheel over any time.
Let's ride.

Offline 69 MOD

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Re: Hirth 634 Mod
« Reply #6 on: September 02, 2010, 10:26:32 PM »
Hey Moose I might have some parts you need (if you need any that is)

Let me know if you do...

B.A.
"Show me a man that can be bothered to do little things,
I'll show you a man who can be trusted to do big things."
Laurence "Larry" Bell

Offline moosenelson

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Re: Hirth 634 Mod
« Reply #7 on: September 03, 2010, 10:22:41 AM »
  Thanks B.A., at this time I think I have all the parts except exhaust which I am thinking of making a set of pipes for it. I appreciate the offer and will get a hold of you if anything comes up missing.

 uK#!**

God Damn that thing must be fast cause you were going like hell when I passed ya.

Offline Nutter

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Re: Hirth 634 Mod
« Reply #8 on: September 04, 2010, 07:00:51 PM »
Made Moose's 634 flywheel into a Free Air flywheel today  uK#!**

Moose already had all the fins cut off:



There was a big flange that wasn't needed with no fins and no electric start, so I removed it.



Then I smoothed out the rest as best as I could. There were some low spots from the fin removal that I left. If I was to do it again I'd want to remove the fins myself.

Let's ride.

Offline moosenelson

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Re: Hirth 634 Mod
« Reply #9 on: September 04, 2010, 08:47:24 PM »
Gotta say thanks again Nutter, not only for the machine work on the flywheel but for the pizza too. I might have to hang out at your place more often.  d.r.i.n.k. Nice to meet the family and have a couple beers with Snowball, T-Bone, and you.
 No luck finding a jackshaft Puma but think I found a 634 Panther.

  Moose, proud member of the CCVSC!!!   uK#!**

God Damn that thing must be fast cause you were going like hell when I passed ya.