Wildside:
Thanks for the compliments about this thread, and the success we've had converting these engines.

A plain bearing is a bushing, either bronze, brass, oil impregnated bronze, or even babbit (tin & lead), that is contained within a diameter at the end of the rod. That circle on the end of the rod is called a journal. From your description, you have a plain bearing. The alternative would be a ball or needle bearing cage.

The nipple on the crankcase to inject oil is probably not necessary. I've inspected my conversions' lower ends a few times, and there is always plenty of oil. Besides, the upper end of the valve train is more of a concern. There are some who have devised a check valve system to route oil to the cam gear to address that problem. I've not had to resort to that though. Never let the engine lean out. Even if your carb comes loose from vibration, causing an air leak, is enough to destroy the engine if you don't catch it quickly and throttle back. Besides, the crankcase on a 4 stoke needs to breath freely. It's not like a 2 stroke that has a sealed crankcase, using the pressure pulses to drive the gas-rich charge into the cylinder up through the bypass ports.

The lack of a lower support on the carb is one of the instigators of the vibration that can loosen the carb, by the way.

What is actel? What are it's thermal properties, such as Tg (glass transition temperature). Do you have any gaskets between? Do you have any performance numbers from this engine, running, yet?

yes I see what you mean by a plain bearing now, I've never had conrod issues in the past, mainly bearing corroison problems so fingers crossed with this new converison. I've just bench run the engine to see how it operates for now. I'm going to make a bracket to support the carburator, a piece of light aluminum should be ok as the cylinder will grow with heat, I quess 0.005" or so won't cause problems.

http://en.wikipedia.org/wiki/Polyoxymethylene "Acetal" spelt with a "e", my mistake. As far as thermal properties are concerned there are better plastics available. Acetal is very easy to cut and work with and the fact that I had some on hand. If I find my brass plate reaches high temperatures I will most likely make a new insulator.

I have no real gasket, just a thin layer of exhaust gasket sealant on the carb side, nothing on the brass plate side.

As far as RPM readings go, I have no tacho as of yet, but will sort one out.

.005" thick won't do the job of supporting the carb, IMO. Use 3/32 - 1/8 thick angle stock. Don't worry about the differential coefficient of thermal expansion between the carb, head, and the crankcase. From my measurements, the head will run around 300F (maybe a bit more right at the exhaust mani). The case will top out at around 150 degs F. So, aluminum's Tce is around 13.1 u"/inch/degF. This means that your engine's head will grow around .006" max. The bracket, since it's cantilevered, will easily flex this much. No worry.

As for the plastic, one cheap way to get better performance is to go to the grocery store and buy a small white teflon hot plate. They're cheap, and have very high temperature tolerance. Another material is cotton or glass impregnated phenolic. These are available at hot rod store or on Ebay as carb spacers for race cars. Kind of expensive. Also, you can buy phenolic stock right on Ebay much cheaper. Personally, I'd try the hot plate material teflon. Good luck.

my wording is always bad I mean I estimated a growth of 0.005" in the cylinders vertical high. you mention 0.006", so all in all very little. I'll make a bracket out of a some 2.5mm which is approx 3/32".

Well, duh. It never occurred to me your .005" was the head's growth! Now that I re-read your post, I can see that your meaning should have been understandable to me. I'm sometimes unable to generalize language.

Anyway, at least we arrived at the same growth independently. I also forgot to mention to use some silicon gasket sealer between the brass plate and the carb, at least. You'd be surprised how much air can leak by that interface. It could cause the engine to run lean.

For the bottom bracket I bought extruded aluminum 1/8'' from mcmaster and cut it to dimmension , then Igot it in to my mill and went to 2.4mm all around. For the plastic top part of the carb Iseal it with RTV , I cut in to the top part some grooves for the RTV to get better grip. Ihave couple more Zama on the way, seams like those are easy to adjust. I havs an OS 91 that I have and I will convert that one when I get back home.
You may run in a little issue with idle. Have the throttle screw out all the way and just bearly touching.
Idleneedle 1 1/2 to 1 3/4 turns
High 2 turnsas a start point.

Adrian

I finally got some running time on my OS FT160. I used the updated Reichmuth ignition, now being manufactured by Ridge Machine Company. The system uses two pickups set 23 degrees apart. The low speed pickup handles things up to 2000 rpm and the second one then advances the timing between 2000 rpm and 4000rpm where it reaches full advance. The system was chosen because it has very small plastic spark plug caps instead of the huge metal ones common to the Chinese systems. With the engine mounted on my 1/4 scale Cub those Chinese cap looked ridiculous.
The results using 93 octane gas 20:1 with Avenger oil and a 18-6 prop are 1400 idle and 7500 WOT. The most interesting part of this is Initial engine timing is low speed pickup set at 37 degrees BTC and the high speed pickup at 60 Degrees BTC. If I set the high speed pickup at the normal 28 degrees BTC and the low speed pickup at 5 degrees BTC the idle can be dropped to 1100 rpm but the best WOT speed is 5000 rpm. As an experiment I install a Chinese ignition system and found that I had to set the pickup at 60 degrees BTC to get the WOT rpm up to 7500. I've been talking to Ridge Machine about this and even spent 3 hours at their shop working with them and we could not figure out what was happening to cause the requirement for the large timing advance setting. Any ideas anyone?
By the way I found that the OS carb performs more than adequately.

Interesting. The only thing that could cause it is a delay in the ignition itself. A timing light would confirm.

I'm putting together an OS FS-120 for gasoline. Have to make a backplate and intake manifold for the Walbro.

I have a Reichmuth ECDI on my G23. It runs great, but, how would I check the timing with an automotive timing light? I have a way old Sears timing light that is powered by 12 volt and has a flashtube instead of the way older neon light. It has an inductive pickup for the spark impulse. The shielding on the high voltage plug lead would prevent the spark from being picked up, right? So, can I insert a short non-shielded piece of spark plug lead into the ECDI spark plug wire , making sure I still connect it to the spark plug? Thanks.

Sincerely, Richard/Club Saito #635

I've made myself just such a short lead for exactly that purpose Richard. Works great.

Fsheplavy,

Something seems seriously wrong. Regardless of what that Reichmuth ignition is doing (and that seems strange too...), setting up the engine from scratch with an ignition (Chinese) such as an RCExl should get good results with the standard 28-30 degs BTDC on an OS Gemini Twin.

I don't mean to question your skills, but this is worth asking. Are you using a good, large diameter accurate degree wheel when setting the sensor locations? Do you have a good, steady mounted index pointer aimed at the degree wheel? Are you verifying the sensor location statically after the initial positioning? Some sensors fire before, some in the middle, and some just as the magnet is leaving the sensor area. There's lots of variation here. Usually, one must install the sensor close to the correct angle, then verify it statically by seeing the spark occur during a slow, hand rotation. Usually, at that point, one finds a second adjustment is needed. Also, halls are sensitive to magnet N-S orientation. Usually it will fire better one of the two available orientations. You have to try both ways to determine which orientation is best. (sorry if this is starting to sound like a Dr Phil show....!)

Beyond that, I'm wondering about the technology behind the Reichmuth. With a microcontroller governed throttle curve (like in an RCEXL or a CHEXL), there seems no reason to have the extra weight and complexity of a dedicated idle hall effect sensor. The microcontroller can easily detect RPM and adjust the "advance" accordingly from just one sensor. Thus, I wonder if there even is a microcontroller in the Reichmuth. Perhaps their approach is from "way back then" and has never been updated? Either that, or they're so smart and advanced (no pun intended) that we mortals cannot perceive the design intent.

Hi Rick,

Ithink the 2 pickup sensors on the ignition is used also on the calculation for RPM and other stuff. You have to set them up at the degrees mentionated, the pic measure the time between the 2 sensors and figures the RPM and so on. I know Iread that some where, What is gets me is the 60 degree stuff to obtain the 7500 WOT.If it was with one ignition module ...can say that may be something wrong with the module, but 2 units and same result.....I can not comment in any way.

On another hand I just did another conversion on a FG 30 a friend of mine had the engine and he was not happy with that carb. I put my Zama carb and with any adjustment on the carb I give it a start. Start great, run great, Idle, transition to WOT. It spins a Vess prop 18x8 6800RPM's I did a fuel test and it burns 1 OZ in 2.6 min WOT.

On the FA180, same carb, prop I get only 6200. Diffrence is in the valves, FG30 are 1mm smaller , Intake 2.5mm smaller, exhaust 1mm bigger VS FA180. Iwill try to decrease the intake on the FA180 to see if I get better results.

<font color="#00265e" size="2">w8ye</font> , If I good remember you have a FG36? Iwill like to know if possible the ID on the intake mainafold, I will like to compare that with a FA220, that will be next project, then a FA130T, FA300Tand a Enya VT240.

My plate is full for the summer.


Thanks
Adrian

I missed this before. Do you have a photo of your setup?

Greg

The 60 deg situation with china ignition is completely illogical. As the other guy said, show a picture.

The only possible benefit to justify 2 halls is the pic could easily tell if the engine started backwards and then it could command a shut down. Otherwise there isn't anything you can do with two you can't do with one with clever firmware.

The difference in the valve diameters is probably rooted in the fuel originally intended for the engine. By the way, when you compared the valves on the 1.8 vs the FG, you made three comparisons two of which contradicted.

Anyone interested in seeing pictures of a scratch 1/4 scale Skybolt bipe in getting close to finishing , speak up. 50cc gas 2-stroke.

Hi Rick,

FG30intake 9.75mm( inlet mainafold), Exh port11mm,5x1 threads ,Valves both 14mm,0mm NKG, 3 CC comb chamber(10:1)
FA 180 intake11mm (Inlet mainafold), Exh port 11mm, 14x1 threads, Valves both 15mm , 1/4 32, 3 CC comb chamber(10:1) I


Adrian

Happened to come across this picture showing a RCEXL ignition sensor adaptation ala CH ignition style on a Saito 91. I'm thinking this is Earl's engine?

Nice Picture,

Iwill try to convert one of this , Ihave the engine but no Compression. Ihave to tear it down to find out why.
Ijust finish couple weeks ago a Saito FA120S, Runs Great! , I will move to a FA150S, Then FA220, Wt130 and WT300.

I update the post above , Imeasure the comb Chamber on the FA180 and seams to be the same with FG30.

Adrian

P.S. If any one needs a C&amp;H ignition, Ask me about, I make them under Bill Carpenter License.

Could be a broken valve spring.

What is the price of your ignition with no advance curve? Also do you have a website or photos of the ignition you make? Thanks John

John ,

Website will come , the parts, set-up and the upcomming wedding at the end of the month let my bank dry.
I PM you.

Thanks
Adrian

HI, guys, I need a little help here, I am trying to convert my saito 180 over to gas (petrol) can any one assist me n locateing a walbro carby for the project, in one thread it is mention a WT-456-1 carby, but cannot seem to locate one, is this the correct # or a typo????
Many thanks
Barry

Correct PN, but may be discontinued

Yes TKG is right,this carb is discontinued but still available , try ebay. carb works andI use it in many conversions.Is around $40.
If you do the mounting for sensor and you send me the intake , I can make the addaptor plate and put a zama C1qp8 carb that is the"sister of wt-456-1.

Adrian

Adrian,

Is the Zama as good as the Walbro? I still want to send you my FG-14 to convert..sorry it's been so long...a rough year...

Rick

YesRick it is and I like it better...It seams to be easyer to adjust....but that may be my personal feeling.
FA 14 did not made one ....but I will give a try when u decide .

Adrian