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Author Topic: 1970 hs1 90 cc twin  (Read 2317 times)

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Offline dave c

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1970 hs1 90 cc twin
« on: May 20, 2012, 10:19:38 AM »
Hi Guys

I got an hs 90 and would like to make it a 100 or 125 bike. Is there
a top end that will fit ?? 

Thanks

Dave

Offline dave c

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Re: 1970 hs1 90 cc twin
« Reply #1 on: May 21, 2012, 07:31:41 PM »
30 views and no reply's. I know i'm new but someone knows............... Mark ?, Nathan?, Little Dave ?

Dave

Offline z1 zonly

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Re: 1970 hs1 90 cc twin
« Reply #2 on: May 22, 2012, 08:59:47 AM »
I'd never heard of an HS1 before yours, so I couldn't tell ya.  There is probably enough liner to bore the cylinders to 100cc, but you won't see any dramatic gains.

Consider this:

http://www.ebay.com/itm/02-YAMAHA-YZ-125-COMPLETE-RUNNING-MOTOR-engine-bottom-top-end-KART-yz125-99-04-/261025388979?pt=Motorcycles_Parts_Accessories&hash=item3cc65359b3&vxp=mtr


           RD400F               |               RD350B              |               RD350/H1                  |              SXV550

Offline retaRD

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Re: 1970 hs1 90 cc twin
« Reply #3 on: May 22, 2012, 09:58:24 AM »
What about a twin jet?
I gotta post that video of you Dave.
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Offline JA-Moo

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Re: 1970 hs1 90 cc twin
« Reply #4 on: May 23, 2012, 12:11:09 AM »
You might try and look up the specs, I would bet the strokes are all the same, then you just need pistons and cylinders.
Just because you almost won once at Operation, doesn't qualify you to do actual surgery..........

Offline dave c

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Re: 1970 hs1 90 cc twin
« Reply #5 on: May 28, 2012, 05:57:00 AM »
Thanks for the reply's !!!     :cheers:

Dave

Offline retaRD

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Re: 1970 hs1 90 cc twin
« Reply #6 on: May 28, 2012, 08:15:58 AM »
Dave!  I found an SXV, trying to justify pulling the trigger.
What's new?
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Offline m in sc

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Re: 1970 hs1 90 cc twin
« Reply #7 on: May 28, 2012, 04:48:41 PM »
whats to justify?  :words: :bitchslap:
get off my lawn.

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Offline m in sc

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Re: 1970 hs1 90 cc twin
« Reply #8 on: May 28, 2012, 04:49:44 PM »
dave c.. lets reed that thing and port it. get some chambers and yeah....
get off my lawn.

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Offline retaRD

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Re: 1970 hs1 90 cc twin
« Reply #9 on: May 28, 2012, 06:48:46 PM »
*cough* PV controlled slipper *cough*
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Offline dave c

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Re: 1970 hs1 90 cc twin
« Reply #10 on: May 30, 2012, 03:58:51 PM »
dave c.. lets reed that thing and port it. get some chambers and yeah....

LOL

sounds good to me !!  Ya Nathan , buy the SXV if it 08 or newer !!

Dave

Offline revbone

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Re: 1970 hs1 90 cc twin
« Reply #11 on: June 01, 2012, 01:47:37 AM »
Not sure about compatibility but here are some motor specs from my Clymer's manual:

HS1 (89cc) -
4.9 HP
3.1 ft-lb torque

LS2 (97cc) -
10.5 HP
6.95 ft-lb torque

YL1 (97cc) -
9.5 HP
6.0 ft-lb torque

AS2 (124cc) -
15.2 BHP
9.4 ft-lb torque
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Offline SoCal250

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Re: 1970 hs1 90 cc twin
« Reply #12 on: June 01, 2012, 03:44:22 AM »
This should help... (especially the 2nd one)

Cylinders: 2
Bore x Stroke: 36.5 x 43 mm
Displacement: 89 cc
CR: 7.5
Other detail: piston port, uses two Mikuni VM-16SC carbs

As for part interchange that's a little tougher, particularly since you want to up-size. Most tools/manuals don't account for spec changes, only for matching HW fit or superseding.


EDIT: some additonal info:
the question here is, does the stud pattern line up if the bore is close? Mods will surely be needed.

72 LS2
Bore x Stroke: 38 x 40 mm

RD125 (same as the previously mentioned AS2):
Bore x Stroke: 43 x 43 mm

« Last Edit: June 01, 2012, 03:55:19 AM by SoCal250 »
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Offline sesshomaru

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Re: 1970 hs1 90 cc twin
« Reply #13 on: July 17, 2012, 07:28:14 PM »
The barrels from the LS2 and the AS1/2/3 won't fit as the stud spacing is different.
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