or make a double throw crank and case

To do that will I need a lathe or some other expensive tool because I only have a drill press.

How do you think the Fuji Imvac BT-86EI Gas Twin works?

How would one seal the crankcase between the 2 cylinders?

I have a problem with my engine. I start It and it runs fine but the second time I try to start it it won't start so I took the back plate off to find out it was flooded. What's causing that I can't figer it out how is it flooding it self?

I picked up a 28cc gas engine conversion last week here on RCU, and the seller insists it's a great engine. Well, I've got a 40cc version also that appears identical to this 28cc engine. The 40cc has twice the compression of the 28cc. I took the engine to an experienced guy I fly with and had him look it over. He mounted it to a 2X6 stand he made, and only got 6900 rpm leaning it out with a 16X6 prop. We are replacing the ring confirming the performance isn't up to expectations. I'm curious about the specifications here and to get help as the seller disputes the fact the engine is weak. From reading this post he pointed out to me, it only seems to support the 28cc again is weak. Wouldn't a 16X8 or 18X6 prop exceed 6900rpm, while we used a very light 16X6 prop with a MAX of 6900 rpm? Also we had no problem spinning the engine over with a standard electric starter for .40 size glow, and after a long spin, it fired. I'd think it would have more compression than an electric starter could spin. When you take the starter off, the engine still spins on it's own another 4 or 5 revolutions. I'm a nitro 2 stroke kind of RC guy and nothing I've experienced would ever do these things. So, would someone give an opinion on what I'm to expect with this engine? Thanks. I'm thinking after a rebuild, we'll get into the 8000 rpm range. Correct me if I'm wrong.

What kind of promoses did he make as far as prop size and RPM?
What numbers have others posted with this engine?

What was the ring gap of the old rings?

Some don't believe in porting engines some do.
Some raise the compresssion then raise the ports to offset lowering the cylinder to raise the compression
some don't.

I just had a Toro done for me by Brillelli and here is what they said after they ran it.

" I just got done running it and it had a good idle at 1750 and a top of 7800 on a Mejzlik 16x8. It will go higher with break in."

This engine had the compression raised, ported, new carb and manifold and exhaust.

I have about $270.00 all together in this engine. It only turns 1000rpm more than yours.
How often will you use that last 1000rpm?

Motorcycles use labyrinth seals.

Bill

So do snowmobiles...in some designs. Capt,n

I had better luck with mine.

http://www.rcuniverse.com/forum/m_38...tm.htm#3855475

I've got a 32 that turned 6900 with a 18-8 while completely stock except for the muffler. I changed to a 1/2" venturi (32) Walbro carb and got 7500.

I had a 28 Mac and converted it to a 32 with a cut down 32 jug. Set up the same as the other 32 it was doing a little over 7600 with a 18-8.

At one time I had a Homelite 25 completely stock except for the muffler and it would turn a 16-10 at 7000 even.

I guess then my question should be is this ring OK and is soft compression acceptable on a gas engine, when otherwise on a 2 stroke nitro engine, you'd reject it even on a .40 size displacement? I intended to use the engine to fly a Giant Super Sportster. They rate it with a 32cc engine so I thought I'd be fine. 5 lb engines though seem ridiculously heavy compared to a 1.60 2 stroke. This is new ground for me so any experience in this area would be appreciated.

A decent 28cc engine should turn a 16 x 8 prop at 7500 or more, and a 16 x 6 more yet. A bad ring will easily knock 1000 rpms off. Stock spec ring gap is around .003" which is very, very tiny. Most, if not all used engines I take apart have a wider than optimum ring gap, often by quite a lot. Frank Bowman rings work great, and he can make a ring for just about any engine. He specifies ZERO ring gap for his rings.

I think Frank Bowman has a new e-mail address and I don't have it, so you will have to ask the other members for it. He doesn't have a website. His rings are the best!

As a reference, my mildly modified Homelite 25cc engines turn a 16 x 8 APC prop at well over 8000 rpms. My Echo 23.6cc engines are more powerful yet.

I did a Homelite 25cc for a friend of mine. Slightly larger carb, free flowing muffler, the exhaust port bridge ground out, base gasket left out to raise the compression ratio a bit, and a Frank Bowman ring. Stock ignition, no porting, no other mods. It turns an APC 15 x 8 prop at 9400 rpms. He likes the higher speed so runs that particular prop. I've recommended a 16 x 10 prop, but he likes it as is and doesn't want to change. The engine should be fine though, as the boat guys run them over 10,000 rpms, and I have a 30cc Homelite that is surviving fine at similar rpms....

Also be aware that it takes a couple of hours running to seat the ring in well, and the engine will gain power during that time.

AV8TOR