Heymow - Lawnmower Racing Forum

Engine Help => Other Engines => Topic started by: austinandtina on October 12, 2015, 01:55:33 pm

Title: 19.5 hp opposed twin build
Post by: austinandtina 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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Title: Re: 19.5 hp opposed twin build
Post by: PJG56 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 ???????
Title: Re: Re: 19.5 hp opposed twin build
Post by: austinandtina 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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Title: Re: 19.5 hp opposed twin build
Post by: Huffy044 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.
Title: Re:
Post by: austinandtina 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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Title: Re: 19.5 hp opposed twin build
Post by: GRUBDIGGER on October 15, 2015, 07:25:41 am
BAD GROUND?
Title: Re: 19.5 hp opposed twin build
Post by: Jeff McKelroy 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.
Title: Re: 19.5 hp opposed twin build
Post by: chavez 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?
Title: Re: 19.5 hp opposed twin build
Post by: redline 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.
Title: Re: 19.5 hp opposed twin build
Post by: stvn_VA 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.
Title: Re: 19.5 hp opposed twin build
Post by: BIG AL 202 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.
SOUNDS CORRECT TO ME!!
Title: Re: 19.5 hp opposed twin build
Post by: berthyd 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.

Bert
Title: Re:
Post by: austinandtina 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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Title: Re:
Post by: austinandtina 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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Title: Re:
Post by: austinandtina 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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Title: Re: 19.5 hp opposed twin build
Post by: PJG56 on October 24, 2015, 09:02:21 am
I have just the cam for you..
Title: Re: Re: 19.5 hp opposed twin build
Post by: austinandtina on October 24, 2015, 12:18:37 pm
I have just the cam for you..
Are these single or twin cam motors and what do u have for me

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Title: Re: 19.5 hp opposed twin build
Post by: BIG AL 202 on October 24, 2015, 01:56:14 pm
BEEN THERE
Title: Re:
Post by: austinandtina on October 31, 2015, 04:18:25 pm
Well guys I got the twin mounted wired up and lines ran. It starts but won't stay running I'm sure carb needs cleaned. Couldn't really figure out the governer linkage almost seems as if it is missing parts. I bypassed it for my last non points race tomorrow and just see how she fairs in the stock form. ...ik flywheel can't take the rpms as well as rod and crank but I'm geared pretty tall and our track is 90 ft straights so I won't be in it long anyway

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