lawn boy duraforce questions?

[rushking19]

Probably running a little rich

 

[Rear engine 86]

No its the complete opposite.
Boggs really bad and you can hear it surge and then stalls. Pump the primer to flood the carb throat and it will fire right back up until it runs out of that supplied fuel.

I really want this engine to run and idle correctly.

 

[rushking19]

No its the complete opposite.
Boggs really bad and you can hear it surge and then stalls. Pump the primer to flood the carb throat and it will fire right back up until it runs out of that supplied fuel.

I really want this engine to run and idle correctly.

You May Have To Get A More Adjustable Carburetor To Tune It Probably

 

[Russ2251]

Do venturi sizes match up? Or come close?

 

[Rear engine 86]

Do venturi sizes match up? Or come close?

Hey there he is

I will post some pics showing both carb venturi sizes asap. The original one needle diaphragm carb has a much smaller venturi then the dual needle float style Tec HS 50 carb that I tried, perhaps this could be my issue?

I was thinking along the same theory as the LB durafore engine in that Tecumseh supplied this engine intensionally with this undersized carb, just like LB did with those plastic original style carbs.

I have been toying with the idea of mounting a 49cc pocket bike float carb but the mounting ears or holes are to close together so that pretty much scraps that plan. There has got to be a carb that will work on these snow flipper 3 hp two strokes to make it respond like it should!!

 

[Rear engine 86]

You May Have To Get A More Adjustable Carburetor To Tune It Probably

Perhaps but I think it has to do with air velocity and volume. The demands of a piston port 98cc two cycle v.s a 206 cc 4 cycle engine are different I believe.

 

[Rear engine 86]

Here is some pics from left to right compairing my HS 50 Tec carb, stock one needle Tec diaphragm carb and my Tilly HL-334b.
4th pic is showing the removable intake block and how big the opening is.

 

[Russ2251]

...diaphragm carb has a much smaller venturi....perhaps this could be my issue?

Absolutely.
A Yamaha KT100 engine performs perfectly well with a Walbro wb3a carb which has a 1" (approx.) venturi. Engines are actually under 98 cc's.
R*Tek or Duraforce engines (displacement at 141cc's) will never operate with a wb3a even though displacement is much larger than the Yamaha mill.
The same applies to the Tecumseh engines. Go too large and the venturi effect will not kick in...adjustable carb or not.

 

[rushking19]

Any update on the Duraforce?

 

[Rear engine 86]

Any update on the Duraforce?

Still waiting on those carbon reeds...any day I'm hoping now.

 

[Russ2251]

Should've had them by now, I would think.

 

[rushking19]

Should've had them by now, I would think.

Same thing I was thinking

 

[Rear engine 86]

Should've had them by now, I would think.

I'm honestly very surprised they have not shown up in my mailbox yet.

Maybe they are held up at the border for some stupid reason.

Needless to say I'm getting very anxious to continue on with my LB build and to keep you guys updated.

For now I will just tinker with my Tec 3 hp 2 stroke and Im debating on going to pick up a H60 "big block" Tecumseh engine.

Anyone have any expeirence with these engines?

 

[Rear engine 86]

Absolutely.
A Yamaha KT100 engine performs perfectly well with a Walbro wb3a carb which has a 1" (approx.) venturi. Engines are actually under 98 cc's.
R*Tek or Duraforce engines (displacement at 141cc's) will never operate with a wb3a even though displacement is much larger than the Yamaha mill.
The same applies to the Tecumseh engines. Go too large and the venturi effect will not kick in...adjustable carb or not.

This makes perfect sence to me Russ and thanks for explaining.

I would lile to see if I can get my hands on a Mikuni VM16 carb and see if that will wake up that little snow flipper motor.

 

[Rear engine 86]

Were back

I recieved the Carbon fibre reed valve that Russ2251 kindly sent my way and now I can keep you guys updated on my LB duraforce project.
I have a bunch of pics to upload too.
I settled on a very simple style third bearing support for the LB crank that I thought up myself. Hopefully it works as intended as I did not want to go through the time and expense to fab a more complex design.

While I was waiting to assemble the LB short block I got started on the minibike portion of the build. Experimented with some spray paints and I discovered something! If anyone on here has ever purchased so called "chrome" spray paint, only to discover that its just really bright silver, well folks I have a solution to make it work. If you spray semi gloss back on the item to be painted before you hit it with the chrome spray, it somehow creates a backdrop for the chrome paint to reflect. I did my 6" split rear minibike rim and it looks great

More pics and updates on the way!

 

[rushking19]

Awesome finally I can't wait to hear this thing roar to life, and I'm about to get my snowmobile engine running very soon because I'm going to put the rest of the money I need to rebuild the motor in my bank today or tomorrow and order my parts right after I deposit the money

 

[Rear engine 86]

Thats great to hear and I hope everything works out for you the first time you yank on the pullstarter.

I still have some more things todo yet before I'm ready to test fire the LB engine. I need to come up with some sort of temporary exhaust so the piston is not exposed when running.

I assembled the short block yesterday and I will post some pics. Let all the sealant and loctite to cure for 24hrs.

 

[rushking19]

Yeah that is another thing that I have to fix on the snowmobile engine the pull start, And What about The Exhaust I showed you, and can't wait to see the pics

 

[Russ2251]

I need to come up with some sort of temporary exhaust so the piston is not exposed when running.

Actually, engine can be run without anything on exhaust port. Back in the day that was the way we ran our Clinton 2 cycles.
To see fire belching out of the block at night was a sight to behold.
Fuel/air mix may (or may not) need to be slightly richened.

 

[rushking19]

Actually, engine can be run without anything on exhaust port. Back in the day that was the way we ran our Clinton 2 cycles.
To see fire belching out of the block at night was a sight to behold.
Fuel/air mix may (or may not) need to be slightly richened.

True I plan on Running my Rotax 399cc with no muffler just open port