lawn boy duraforce questions?

[Russ2251]

Nice lookin' carb.
Although I've seen chokeless (?) carbs before, I never knew what they were all about.

What does concern me is size of carb. 22.9mm is a little on the large side.
I have several different makes of 1" carbs, non of which could make the transition from low to high speed without running lean and stalling.

 

[Rear engine 86]

Ahh this is not what I want to hear but it is what it is. I guess this is what I get for copying another persons build that as far as I know, never finished.

So I guess I need to find myself a HL-239b carb then.

Oh how I love buying $80 shelf dust collectors!!

Should I even bother trying this carb?

 

[Russ2251]

Try it as it may work. Possible I just had bad luck. .750" venturi seemed as high as I could go without problems.
The HL-239b was discontinued some time ago but they do pop up occasionally on Ebay.

Addendum/edit:
Found one HERE. Possibly a typo.
I only paid $30-35 a couple years ago.

 

[rushking19]

Ahh this is not what I want to hear but it is what it is. I guess this is what I get for copying another persons build that as far as I know, never finished.

So I guess I need to find myself a HL-239b carb then.

Oh how I love buying $80 shelf dust collectors!!

Should I even bother trying this carb?

I Say Try It And If It Dont Work Out Get Another One It's Worth A Try

 

[Rear engine 86]

Ok guys I will stick with the plan and go ahead with this carb. Another thing I was thinking about, will this carb accept a gravity feed fuel supply without flooding?

I hope cold starting won't be a chore with having no choke shutter in the carb.

So I was busy yesterday and I now have the carb mounted with the pulse line hooked up but it always wants to kink, so I have to figure that out.
Tav clock position is pointed down, now that I can see that everything fits and I have it all bolted in place.

I would like to trim more off the top of the mount to more of a square angle profile, not really diggin the curvy look I have going on. The Tav backplate needs to be trimed to clear the exhaust port too.

Im really on the fence here and I would like some input. I feel its a good safe idea to fab up some sort of a third bearing outboard crank support. It would run on the outside of the Tav and link between the crankshaft and the Tav jackshaft to ease the stress on the LB crankshaft and main bearings when the belt is under tension and Im heading towards to moon at high velocity lol.

The whole assembly including the mount, engine and complete Tav unit is still lighter than a clone or any 4 cycle set up.

 

[Russ2251]

will this carb accept a gravity feed fuel supply without flooding

Gravity can not over power pump.
Engine will not flood unless over choked or pop-off pressure is incorrectly set. If carb is unmolested, pop-off pressure should not be an issue.

Also possible...may not need pulse line if gravity fed.

 

[rushking19]

Ok guys I will stick with the plan and go ahead with this carb. Another thing I was thinking about, will this carb accept a gravity feed fuel supply without flooding?

I hope cold starting won't be a chore with having no choke shutter in the carb.

So I was busy yesterday and I now have the carb mounted with the pulse line hooked up but it always wants to kink, so I have to figure that out.
Tav clock position is pointed down, now that I can see that everything fits and I have it all bolted in place.

I would like to trim more off the top of the mount to more of a square angle profile, not really diggin the curvy look I have going on. The Tav backplate needs to be trimed to clear the exhaust port too.

Im really on the fence here and I would like some input. I feel its a good safe idea to fab up some sort of a third bearing outboard crank support. It would run on the outside of the Tav and link between the crankshaft and the Tav jackshaft to ease the stress on the LB crankshaft and main bearings when the belt is under tension and Im heading towards to moon at high velocity lol.

The whole assembly including the mount, engine and complete Tav unit is still lighter than a clone or any 4 cycle set up.

Wow that thing looks so good can't wait to see it in action

 

[Rear engine 86]

Gravity can not over power pump.
Engine will not flood unless over choked or pop-off pressure is incorrectly set. If carb is unmolested, pop-off pressure should not be an issue.

Also possible...may not need pulse line if gravity fed.

Really? I was thinking about why there is a pulse line in the first place and just thought for a momment, "hey this is going to be in my minibike with the fuel tank higher than the carb" and started wondering if I even needed it.

Im a little confused by your term "pop-off pressure"?
Are you referring to the needle and seat air pressure test before it unseats?
Thanks

 

[rushking19]

Really? I was thinking about why there is a pulse line in the first place and just thought for a momment, "hey this is going to be in my minibike with the fuel tank higher than the carb" and started wondering if I even needed it.

Im a little confused by your term "pop-off pressure"?
Are you referring to the needle and seat air pressure test before it unseats?
Thanks

Yes he is

 

[Rear engine 86]

Hey everyone. Was able to make some more progress over the last few days.

I'm going to settle on this third bearing crank support design that I came up with after much thinking. As you can see in the pics the bearing fits in the opening hole in the Tav plate and the inner race is riding on the crankshaft.

Turns out a 6304-2RSL bearing is a near perfect fit for my application, only slight hand fitting was required. I love when things work out like that!
The width of the added support bearing is almost perfect to space out the Tav driver for proper belt alignment.
I also trimmed the mount on the top and made clearence for the exhaust flange. Lol Im so sick of aluminum dust and bits everywhere!

I found a piece of saftey glass to resurface my head and block as per Russes instructions. Im very happy with the results and what an excellent tecnique.

Just waiting on the arrival of the Carbon fibre reeds Russ hads sent me and we can reassemble the short block. Its getting closer and I still need to figure out my exhaust and throttle cable hook up ( not going to be easy) and to test fire the engine.

 

[rushking19]

Hey everyone. Was able to make some more progress over the last few days.

I'm going to settle on this third bearing crank support design that I came up with after much thinking. As you can see in the pics the bearing fits in the opening hole in the Tav plate and the inner race is riding on the crankshaft.

Turns out a 6304-2RSL bearing is a near perfect fit for my application, only slight hand fitting was required. I love when things work out like that!
The width of the added support bearing is almost perfect to space out the Tav driver for proper belt alignment.
I also trimmed the mount on the top and made clearence for the exhaust flange. Lol Im so sick of aluminum dust and bits everywhere!

I found a piece of saftey glass to resurface my head and block as per Russes instructions. Im very happy with the results and what an excellent tecnique.

Just waiting on the arrival of the Carbon fibre reeds Russ hads sent me and we can reassemble the short block. Its getting closer and I still need to figure out my exhaust and throttle cable hook up ( not going to be easy) and to test fire the engine.

Nice To See A Update On The Duraforce Project, I Was Starting To Wounder What You Was Up To ,And I Love The Way You Cut The Torque Converter To Better Fit The Exhaust, Hope You Get The Carbon Fiber Reed Valve Soon So I Can Hear This Beast Roar, This Is Practically Like A Single Cylinder Snowmobile Engine Now With That Torque Converter Lol

 

[Rear engine 86]

Yeah I dont want other members thinking Im getting burned out cuz I am going to finish this.
Thanks man and I really didn't want to have to trim the Tav backplate but I had no options.

Yeah they should be in my mailbox in the next day or so and yes indeed this is like a single cylinder sled powerplant.

Im trying to figure out on how to arrange the throttle cable hook up and still not quite sure on how I want to configure the exhaust. I dont want this to be really loud when all said and done but not to be so restrictive that its hurting performance either.

 

[rushking19]

you could use this its a rlv racing clamp on exhaust, i run one on my orange go kart that has a briggs and stratton 6.5 hp ohv it quiets it down and its unrestrictive and gives it a deep throaty exhaust note, and its used on tones of race motors Honda and briggs and stratton with 20+hp, its cheap and all you have to do is clamp it on.
http://www.ebay.com/itm/Clone-Header-Muffler-4104-Go-Kart-Briggs-Raptor-Racing-Engine-Animal-Intek-/201069436310?hash=item2ed0ac1d96&vxp=mtr

 

[Rear engine 86]

Yes.Rushking19 that is a great idea and I like the looks of this.
Once I get a headpipe made up and then I would like to make a mini bike specific mid pipe that
would be held to the head pipe with springs and then have this RLV muffler clamped at the end under the seat of my Sprocket minibike.

 

[rushking19]

Yes.Rushking19 that is a great idea and I like the looks of this.
Once I get a headpipe made up and then I would like to make a mini bike specific mid pipe that
would be held to the head pipe with springs and then have this RLV muffler clamped at the end under the seat of my Sprocket minibike.

You're Welcome, I Can Imagine It Now

 

[rushking19]

Here's A Video Of A Briggs And Stratton Animal Motor With An RLV Muffler
https://m.youtube.com/watch?v=nOklYOPvZaQ

 

[Rear engine 86]

That exhaust will sound pretty good I bet with my 141 cc 2 stroker exhaling through it.

Im a little short on funds atm but I will post more updates and pics asap. Hopfully the carbon reeds Russ sent me are in my mailbox. I will post a step by step assembly of the new factory fresh Lawnboy Duraforce short block.

I'll be back!

 

[rushking19]

OK Great To Hear

 

[Rear engine 86]

Still waiting on the arrival of the carbon fibre reed valve Russ had kindly sent my way. Hope to have some updates real soon.

In the mean time I have picked up this 3hp 2cycle engine to tinker with. Its a Tecumseh snow flipper engine and I need to find a carb that will work for a minibike application.

 

[Rear engine 86]

Here is a pic. I tried to get better throttle response and to get it to idle using my HS 50 carb but it ran terrible or not at all.