Just redid my calcs. The 160 wants a .28 orifice and the 120 wants a .24 orifice.

The uneven distribution was caused by the carb barrel moving sideways as it opens which biased one side of the engine to receive more fuel than the other side. If your barrel doesn't move out as it opens, which it won't, you won't have the uneven distribution problem.

Insert came out with glow plug
 

Yep, the insert unscrewed with the glow plug during the CDI conversion. Truth be told I spec'd the length of the insert wrong. The glow plug hole on Saitos is canted with respect to the roof of the combustion chamber, which I knew ahead of time, but somehow spec'd the insert length 2 threads too long anyway. The swaged portion of the insert only engages the cylinder threading around 60% of it's perimeter. Perhaps that explains why the swaging of the 2 bottom threads was so easy. In addition I used JBweld only on the top 2 threads of the insert, none on the insert flange, and didn't ham fist tighten the insert during installation. It was tight enough to remove the glow plug with uncured JBweld, so I figured good enough. Wrong.

This time I used JBweld on the top 3 threads as well as on the insert flange and tightened the crimeny out of it. Might hold now.:eek:

I took the choke off and just used my finger (pinky) through the front hole in the cowl... Don't know how well that rubber button will hold up to gasoline... the boxers spit a lot of fuel out the carb when run on glow fuel, on gas that should be reduced quite a bit... I don't know what that button is made of, but its not silicone, possibly soft vinyl.

On the Gauil I replaced the carb 5mm steel socket head mounting screws with 5mm nylon screws, and a 1/4" silicone rubber insulator between the mounting flange and carb base.

If I were to run the os boxer on gasoline, I'd make a modification to the intake runners... I would cut the runners off about 5/16" - 3/8" behind the tube nut... leaving a stub and then use a rubber coupler to re-join the intake runners back onto the end of the stub... leaving a small gap between the ends of the of the cut tube... to thermally isolate the intake runners completely from the cylinder head.

My experience with JB weld, is it doesn't bond well to waxy metals like brass... I think you would have been better off with the hi temp red loc-tite, on the entire threaded portion ( well decreased threads ) and let it setup for 48 hours... if you have to remove the insert, just use heat to soften the loc-tite.

That's the next thing I'll try. All I have is the High Strength/High Temp 272 Red. Are you talking about 2422? High dollar stuff!

272 is good to 450f. If it gets that hot you've got bigger problems

JBweld is spec'd at 450 as well. Epoxies like JBweld can be removed easily after a soak in lacquer thinner for a few hours. How does one remove a part that's been locked with high strength 272?

The same way you remove case bearings: Heat it, but you're not likely to need to remove this part once properly installed.

...in fact, this part was designed to be installed and never removed again.

That's too quick a thought: If the barrel does not move sideways, you still CAN have uneven distribution if the fuel is biased left or right. The air will distribute evenly, but liquid has different inertia and might not distribute evenly at the T-junction.

Basically, a change in "relative tune" throughout the throttle range. On my twin, the both cylinders would show a different progression in temperature throughout the throttle range. For example, at idle the left hand cylinder would basically cool down due excessive rich mixture, at mid throttle both would run "about equal, and at full throttle the right hand cylinder would run the coolest because the rich condition changed from one cylinder to the other throughout the throttle range...

A barrel NOT moving sideways, does NOT automatically mean both cylinders will run equal, but at the very least I would expect the difference to remain more or less constant.

One thing that is very important, is that both temp probes are located as precisely the same as you can get them, because measurements vary with location. Get that right first, otherwise you are only chasing your tail.

Is that metric?

The OS and ASP choke seem to hold up well with gasoline use.
In fact, on my twin the ONLY rubber part I replaced was the HS needle O ring. everything else ((carb neck seal, LS needle O-ring, and the branch seals that seal the intake runners to the T-junction are still original and hold up well.

67 Runhours now...

The runners remain near completely cold,, despite the metallic contact where they connect to the head.
Also very little heat soaking after a hot engine stop. No explanation why, just an observation.

Same thing on my 200Ti, drowning the front cylinder at idle and drowning the rear at mid range to just under wot. Worst disparity between cylinders I've experienced. It does use a rotary sliding throttle barrel. CDI will help with dropping cylinders but this engine may not be a good candidate for gas conversion using the factory carb. Ideal would be to use Chris's design or run two carbs on short intake runners, like the Saito 300T-TDP.

it's the same units that chris used when he said the .40 cid engine had a .2 orifice, probably millimeters since only america uses Inch-pound. all I did was scale the orifice area linearly with respect to engine displacement, remembering that on our twins, the displacement is twice the fuel flow rate since both intake cycles happen at different times.

Ya... the jet size is a simple metric id measurement in MM - Not an accepted jet measurement - Im using a short "choked Bore" of a 3D printing nozzle as the "blank" so they seem to react quite lineally in our application as Ratio of area = avalible fuel.

do you need any photos and measurements of my mounting plates or are you going to wing it? just let me know if you do. by the way, the magnum mount is slightly longer (or maybe it's shorter) than the os ft120 mount even though they are interchangeable. the cases on both engines are the same length though so i swapped mounting plates when i swapped the ft160 in for the ft120 on my rv8.

...it miight make sense to make a mounting plate that's a custom length to match your specific airframe so you don't need to mess with spacers too.

Just the 272 is good enough, that cylinder won't reach 400-450F, if it does, the engine won't run worth a bugger... the Gaui 50cc cylinder head temp reaches 280-290F... if I peak it to lean run rpm 320F... but I always run it 200rpm down from peak, slightly on the rich side... turns a 20-10 just a bit over 7400 rpm.

Yes, and when run on methanol, they run too cold, and the fuel condenses in the runners... No easy way to heat up the runners... its a common issue with glow 4 stroke engines to get the fuel to vaporize, they would be more fuel efficient.... I tried running the boxer on zero nitro and wasn't too impressed with the performance, so I run it with 8% nitro in the mix.... pulls the 21 pound J3 around with little more than scale like performance, not under powered by any means, but well balanced... not sure if I would attempt to do the gas conversion on that model. just due to the combination of the reduction in performance, and the complexity of re-plumbing the fuel system over to gas... there's a lot of work to get to the fuel lines buried in the wings and fuselage.

Your engines troubles are complicated by the fact that it basically is an odd firing twin, BUT drawing from 1 carb. That always messes things up.
Things should be a fair bit better with double carbs.

Its not an odd fire twin Bert, its an even fire twin... Clarence states that in his review... the crank journals are set at 30 degrees, cam timing is setup same as a even fire twin... if it was an odd fire, it would have had the Saito signature dual carb setup they use on all their odd firing twins... I would suspect the aggressive valve timing, and glow plug ign.

Ran the 200Ti with CDI on METHANOL today. Engine ran pretty hot and throttle response wasn't spectacular. Still tried to drop cylinders intermittently.Very sensitive on the lsn, more so than on glow ignition. The timing is set to 31 with no propensity to detonate, even when overly leaned. Seems to need more timing advance. I saw a solid 200 increase in peak rpm over glow ignition and the fuel economy is not only better but shockingly so.

BTW, Saito did make an odd fire twin with a single carb, the FA80T MKl. The MK2 of that engine had dual carbs.

Well they certainly did, must have been their first odd fire twin engine... The 130TD had dual carbs with the spit fence between the two carbs... was a menace inside the J3 cowling, I ended up extending the spit fence back to the firewall and up to the inside top of the cowl to stop each cylinder from ingesting the others standoff.... Clarence didn't go into to much detail with his review on the 80T.

Ign timing can be advanced when run on glow fuel, I run the boxer 34-36 degrees, but when you do that with the stock ign, you advance the idle timing as well... on gasoline with that compression ratio, you'll have to retard it some, around 28 degrees.

What oil content are you running?... what propeller?

Yep, I've run others at 34 degrees with no problem, however those engines didn't have a very high CR. The 200Ti is 13.7:1, thought I would start low and advance the timing 1 degree at a time until the engine no longer sees gains, then back off 1 degree.

I'm running 15% synth/2.5% castor. I could use a lower oil content, I know, but I like to run the same fuel in all my methanol engines, 4 stroke and 2 stroke/.55 to 2.2 cu in.