Author Topic: 19.5 hp opposed twin build  (Read 27651 times)

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Offline austinandtina

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19.5 hp opposed twin build
« on: October 12, 2015, 01:55:33 pm »
Hey guys just picked this motor up with a good frame for 20.00. I want to build it to run in my cp that currently has a hot tecumseh. Now this is new ground for me so any help whether advice tips or anything will be greatly appreciated. I was told there is a way to build the stock carb up and I'd like to do billet, crankshaft,rods, bore (to what size ?) Big cam and probably run a spacer in the heads for less compression and a little more static compression....I want this thing to be  a torque god

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Offline PJG56

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Re: 19.5 hp opposed twin build
« Reply #1 on: October 12, 2015, 06:40:08 pm »
Big cam and probably run a spacer in the heads for less compression and a little more static compression....


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What ???????
Paul Guptill  (oppy) #238modX
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Offline austinandtina

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Re: Re: 19.5 hp opposed twin build
« Reply #2 on: October 12, 2015, 08:43:45 pm »
What ???????
I was told these motors don't like high compression so by running a spacer on the heads it will increase the volume of space in the cylinders ...it kind of made sense to me but it doesn't at the same time.. I just need some good quality ideas for this build

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Offline Huffy044

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Re: 19.5 hp opposed twin build
« Reply #3 on: October 13, 2015, 11:09:42 am »
Don't run spacers, flow is what makes flatties run, when you make it flow properly you will loose compression, not a big deal.
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Offline austinandtina

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Re:
« Reply #4 on: October 14, 2015, 08:28:45 pm »
Okay bud I'm trying to get that motor started on the chasis it's on but I get no crank unless I jump the starter at the starter. Crossing the solenoid does nothing

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Offline GRUBDIGGER

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Re: 19.5 hp opposed twin build
« Reply #5 on: October 15, 2015, 07:25:41 am »
BAD GROUND?
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Offline Jeff McKelroy

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Re: 19.5 hp opposed twin build
« Reply #6 on: October 15, 2015, 10:13:27 am »
Are you getting voltage to the solenoid? Check to see also, as Grubdigger said, all your ground connections. Check for voltage to ignition switch/starter button, through switch to solenoid. Also, if your starter solenoid has a dual blade connection, the solenoid is not internally grounded, make a small jumper to one of the bolts that secure the solenoid. There should be an audible click.

Also, make sure the connections from the battery to the solenoid are good.

Offline chavez

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Re: 19.5 hp opposed twin build
« Reply #7 on: October 15, 2015, 10:56:01 am »
Could be some of the original safety switches still in place not letting voltage to get to the starter?
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Offline redline

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Re: 19.5 hp opposed twin build
« Reply #8 on: October 15, 2015, 10:56:30 am »
If your going to modify that engine, why bother spending time to get it to start?
As long as it is complete, and has no ventilation holes in the side, it should be fine.
Once it's all said and done, it will end up making slightly more power than the Tecumseh with it's spark plug removed.
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Offline stvn_VA

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Re: 19.5 hp opposed twin build
« Reply #9 on: October 15, 2015, 04:52:03 pm »
I've been waiting on you Ed to chime in one this one.   Replacing a Tecumseh with the an oppy.
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Offline BIG AL 202

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Re: 19.5 hp opposed twin build
« Reply #10 on: October 15, 2015, 06:09:56 pm »
If your going to modify that engine, why bother spending time to get it to start?
As long as it is complete, and has no ventilation holes in the side, it should be fine.
Once it's all said and done, it will end up making slightly more power than the Tecumseh with it's spark plug removed.
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Offline berthyd

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Re: 19.5 hp opposed twin build
« Reply #11 on: October 15, 2015, 07:31:35 pm »
And to think I had to goad Ed into responding. I would have responded myself, but it sounds better coming from him.

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Offline austinandtina

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Re:
« Reply #12 on: October 16, 2015, 09:39:43 am »
Lol thanks guys and I'm not really replacing I'm looking at having a backup motor to the Ole indian

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Offline austinandtina

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Re:
« Reply #13 on: October 24, 2015, 03:33:59 am »
Sorry it's been awhile been building a hardtail bike on the side too. But anywho where would I start on this build.. ik this may be a dumb question which my opinion the only dumb question is one unasked but could I use my billet flywheel on the oppy if I got a different ring and hub? Also I'm looking to build a low end power motor out of this. What cam should I go with connecting rods pistons valves valve springs keepers and  carb work...mainly how do i get my hands on a adjustable jet also I saw a guy on you tube talking about the stock fuel pump being junk as in the pulse tube goes to the crank case and if fuel pump went bad it could take everything else with it..

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Offline austinandtina

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Re:
« Reply #14 on: October 24, 2015, 03:35:53 am »
Ya sorry if that last post was all over the place ya get the idea I am tired been a long day

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