90 degree V-twin engine

[gbritnell]

Hi everyone,
Just a quick update on the running of the engine. I have almost 20 minutes of running time on the engine. Not all at one time but in 4 or 5 starts. I'm discovering things that needed to be redone. First of all I made a new needle for the carb. I made it out of a large sewing needle so it has a much finer adjustment. Next up was the motor mount bolts, the 3-48's kept coming loose so I went to 5-40's with stainless washers. When I made the base the uprights were fitted into the runners and held in place with one 2-56 screw per side. These also came loose so I put two 3-48 screw per side.
While running the engine the other day at my buddies place it would start and run great for about 3 minutes then you could see the fuel being pushed back away from the carb. My buddy said it looks like it's vapor locking, I said it didn't seem like something this small would do that. While I was fiddling with the carb a rested my hand on the intake manifold and WOW, it was as hot as the head. What was happening was the carb was getting so hot that when the gas fed up to it it was boiling the gas and pushing it back away from the carb. We blew on the carb and manifold with an air gun till it cooled down, hit the starter and it fired right back up.
Last night I took the intake manifold off and machined .04 from the .125 flanges and made insulator pads. Today I ran the engine until I thought the cylinders were hot enough, about 4 minutes, and felt the manifold, it was barely warm. I shut the engine off and restarted it several times. I fired up and ran great. Another gremlin taken care of.
My buddy had a piece of steel plate .75 thick. He surface ground it for me and I'm going to make a base for the engine. It will be mounted on rubber bushings to try and isolate some of the shake. At home I can clamp it to my workbench but at a show I might not have that option so this should allow me to run it without it dancing off the table, as long as I don't rev it to high.
We put a tach on it for this morning's run and it will idle down to about 900 rpm. On the high end I've had it up to about 5000 rpm but at that speed it starts acting like the Tasmanian Devil.
All in all I'm thoroughly pleased with the outcome.
George

 

[Paulsv]

George- what material did you use for the insulator pads?

 

[bronson]

I just read this thread from beginning to the end what an amazing build to say the least and machining was unreal. The write up was very interesting very well done.

 

[gbritnell]

Hi Paul,
I had posted some pictures of my engine on a motorcycling forum. One of the responses was where did I get such small spark plugs. I explained that some fellows made their own from Teflon or Corian. The responder said he worked for a boat building company and he had all kinds of scrap Corian and would I like some. I said sure so after a week or so I got an email telling me that at that time he didn't have any Corian but had some similar material would I be interested in it. I looked at the specs for it and it had very good thermal properties so I said yes. He sent me a whole box of scrap pieces. Here is a link to what it is.
http://www.jjorly.com/g10_fr4_sheet_material_price.htm
George

 

[lee9966]

George,

This is a fantastic build, I read every page with fascination. ;D

Would you by any chance have plans for that carb or one like it?

Thanks for the wonderful lessons!


Lee
Long time lurker

 

[gbritnell]

Hi Lee,
I have plans for the carb but it would only work on an engine with about the same displacement. I also have it fancied up to look more like a motorcycle carb. I do have a drawing for the carb on my 4 cylinder OHV engine which has a smaller displacement and isn't so fancy.
George

 

[lee9966]

If you are willing to share I would love to take a look at either drawing. I am sure I will learn from it, and perhaps scale to a different size just for fun.

Thanks!

Lee

 

[gbritnell]

Hi Lee,
I sent you a message.
George

 

[mu38&Bg#]

That turned out very well. It sounds great.

 

[metalmad]

I just had to watch your vidio again and well I guess its all been said
just fantastic
love it
cheers Pete

 

[Orrin]

George, I've not been able to follow this thread until just now. I'm awestruck. Your workmanship is beyond superb. Then, when you posted your artwork my admiration for you and your skills more than doubled.

Best regards,

Orrin

 

[BenPeake]

That is one champion build and what a beautiful sound it produces! I'm very impressed with the ridiculously complex shapes you magically pull out of plain stock - it's like black magic. I think if I tried that, it wouldn't go so well. I can only imagine the satisfaction you experience when you run it. Congratulations and thank so much for posting all those pics! My hat goes off to you.

P.S. What is your next project?

 

[gbritnell]

Thanks Ben
I'm thinking of some sort of radial engine. I don't know if it will be of my own design or of one that's already out there.
George

 

[Drei]

What is the main difference in designing the v twin in a 90 or 45 deg angle? Does it effect the RPM or torque?...

Drei

 

[seagar]

Wonderfull result from a real craftsman.Thank you for the privalidge of allowing us to follow your build.Your an insperation to all that are new to this great hobby.

Best wishes,
Ian(seagar)

 

[gbritnell]

Thank you Ian.

Drei, supposedly a 90 degree engine balances better than a 45 degree engine. That's one of the reasons I built it this way. As far as rpm or torque I don't think the angle of the cylinders would have that much affect. As with a full sized engine the cam design and head porting would have more of an affect on the torque output.
gbritnell

 

[cncjay]

where did you get these plans,,,,,,? very cool engine i would love to have a set!

 

[stevehuckss396]

George designed this one himself.

 

[jwcnc1911]

I do believe if you contact him, you can have a set for a more than reasonable fee. You can see the work and talent involved - so you know what ever the cost, it will be less than it should!