Hoglet carburetor

[rpf]

Here is Randy's HOGLET built on a Harley Sportster frame. Randy built custom motorcycles. This one was rideable. View attachment 131650
The cylinders are from Briggs and .Stratton off e-Bay. Note the open crankcase and gearbox.

Have you got a larger picture of this? sounds very good!!

 

[dsage]

Andrew:
I sent an email to Mike Rehmus of Model Engine Builder Magazine (where you got the plans) asking him to chime in here with his experience on what has been working for others. I'm sure he has reports of lots of them working down his way in California. I also gave him a link to your Youtube channel to have a look.
Good luck.

 

[AndrewW]

Andrew:
I sent an email to Mike Rehmus of Model Engine Builder Magazine (where you got the plans) asking him to chime in here with his experience on what has been working for others. I'm sure he has reports of lots of them working down his way in California. I also gave him a link to your Youtube channel to have a look.
Good luck.

Many thanks! That's a great idea. I recall I had a bit of an email exchange in August with Mike, but it never dawned on me to ask him.
Thanks again for your help.
Cheers
Andrew

 

[mrehmus]

based on the sound and how well it runs, I don't think the carburetor is the problem. Fuel feed might be though. What was the temperature where you were running it?

 

[doc1955]

The carb I use is the Jerry Howell 2jet carb but I did change it slightly the needles were to blunt and was hard to get a good setting so I sharpened the ends and that helped a lot. But I would guess it is your valve timing I know I had to mess with mine to get it to idle and run. Plus had trouble getting the crank gear to not slip.

 

[AndrewW]

based on the sound and how well it runs, I don't think the carburetor is the problem. Fuel feed might be though. What was the temperature where you were running it?

Hi Mike
Thanks for your thoughts on this. The room temperature was about 10°C. The bottom of the fuel tank is about level with the inlet on the carb. I put a vent hole in the fuel tank filler, but I'm just wondering if it might not be big enough. I will do some more tests.
Many thanks
Andrew

 

[AndrewW]

The carb I use is the Jerry Howell 2jet carb but I did change it slightly the needles were to blunt and was hard to get a good setting so I sharpened the ends and that helped a lot. But I would guess it is your valve timing I know I had to mess with mine to get it to idle and run. Plus had trouble getting the crank gear to not slip.

Many thanks for the advice. I was wondering whether to make a JH 2jet carb. I will need to make two when I tackle the JH v-twin . I'll check valve timing and probably reduce the tappet gap from 10 thou to 3.
Mike thinks it could be fuel delivery, so I will open up the breather hole in the fuel tank. I might try adjusting ignition timing to 20° BTDC too.
I've also found a cheap carb on eBay, so I will try that too.
Yeah that crank gear is quite different to lock.
So I've got a few things to try out now.
Thanks again.
Andrew

 

[dsage]

Andrew:
The vent hole in the tank only needs to be as big as required for air to replace the amount of fuel being burned - which is next to nothing. A 1/16 hole would be overkill.
If the carb has a way to control the air intake volume - like a choke or a variable barrel type throttle opening - within reason almost any carb should work because you have control over both the air and fuel. The fuel with the needle valve and the air as above. So somewhere in there should be a setting that works.
You can reduce your valve lash to a minimum. The amount of lash is only there to allow for expansion of components when hot. So I'd think that a few thou would be plenty. And it can always be checked when hot if you have doubts.
While the engine is running you can experiment with a bit with choking off the air and / or adding fuel with the needle or perhaps a bit of starting fluid when it begins to stall to see what makes it happy to lead you in the right direction.
Keep at it. As you know all new engines requre a bit of fiddling to find out what makes them happy. I wouldn't jump into a new carb right away. The manufactured one you have IMHO should work. As MIke suggested maybe a bit more heat would help.

 

[bluejets]

The Hoglet build docs mention a carb with a conventional barrel type throttle 1/4" dia with a venturi bore of 1/8"

Video 54 at around 24:30 clearly shows what I quoted at 6 to 8mm bore.
Shouldn't make much diffiernce anyhow if you keep the throttle closed a bit more.

 

[AndrewW]

Thanks to everyone for the advice.
I've now got a list of things to try.
All the best!
Andrew

 

[Basil]

Thanks to everyone for the advice.
I've now got a list of things to try.
All the best!
Andrew

Hi Andrew
I agree on the timing @30deg. This sounds like an aweful lot for such a small cylinder. What does that work out to mm piston travel BTDC? I would think 15deg would be plenty.

 

[dsage]

Don't forget valve lash figures into your VALVE timing. A lot of lash will make your VALVE timing later.

 

[propclock]

Well I have had a lot of fun with my Hoglet. I cheated and used
a carb from a Saito 450 4 cycle. I can give the model # and pictures if interested. Last time I looked ~80$
I added a venturi reducer and it took
quite a bit of adjustment to get all it right. My contribution
here is to make the timing easily adjustable. I have a long knurled
handle on mine. Start retarded advance as desired , or my favorite get it running REAL STRONG and advance the throttle
and retard the timing. Then it sounds very realistic practically
firing out the exhaust. I had an Indian Scout with left handed throttle and right hand ignition advance/ retard.
For a small engine it sounds very realistic when very retarded.
I added a handlebar throttle
and work the timing on the side. That and the kick start is a real
crowd pleaser at shows.
Just my 1.414 cents worth.

 

[mrehmus]

I think the ignition timing is quite a bit too soon. As my old mentor said, if it has compression , fuel and proper spark timing, it will run.
Another thing to check: Could it be heating up and binding? Some folks have had problems in that regard with o-rings.
Here is the drawing page on the use of O-rings by Tom Stuart in Issue # 15 of Model Engine Builder magazine.

 

[coulsea]

One problem might be that the fuel tank is too high. the fuel level must be below the venturi / jet or it will flood, you should have to choke it by putting your finger over the inlet for a second to get it to start.

 

[AndrewW]

Hi Andrew
I agree on the timing @30deg. This sounds like an aweful lot for such a small cylinder. What does that work out to mm piston travel BTDC? I would think 15deg would be plenty.

Thanks for the advice - added to my list of things to check/change.

 

[AndrewW]

I think the ignition timing is quite a bit too soon. As my old mentor said, if it has compression , fuel and proper spark timing, it will run.
Another thing to check: Could it be heating up and binding? Some folks have had problems in that regard with o-rings.
Here is the drawing page on the use of O-rings by Tom Stuart in Issue # 15 of Model Engine Builder magazine.
View attachment 131717

Thanks for the info Mike - very useful. As luck would have it I don't think I'm far off the dimensions quoted. I was previously concerned that my o-rings might be on the small side, as they are only a few tenths of a thou bigger than the cylinders (similar to my Farm Boy which has good compression). I think the piston grooves are pretty close to that suggested in the article too - but I will double check.

 

[Majormallock]

Hi, Sorry late to the Thread... I have built a Hoglet. used cast iron rings, as i do on all my engines,... tried and tested method.. find attached a drawing of the carburettor used. I used the float chamber,but you don't need to! for me it just gave extra flexibility of where to mount the fuel tank.

 

[AndrewW]

Hi, Sorry late to the Thread... I have built a Hoglet. used cast iron rings, as i do on all my engines,... tried and tested method.. find attached a drawing of the carburettor used. I used the float chamber,but you don't need to! for me it just gave extra flexibility of where to mount the fuel tank.

Thanks - very interesting! I've just purchased a cheap carb and will give that a try first. This could be my 'Plan B'!
Cheers
Andrew

 

[Harglo]

Thanks for the info Mike - very useful. As luck would have it I don't think I'm far off the dimensions quoted. I was previously concerned that my o-rings might be on the small side, as they are only a few tenths of a thou bigger than the cylinders (similar to my Farm Boy which has good compression). I think the piston grooves are pretty close to that suggested in the article too - but I will double check.

Any chance you could post the drawing of your carb?
thanks
Harvey