Tanaka 21cc conversion ?
 

I believe this is a premium engine from a Tanaka AST7000, with 1,1hp

The rod piston pin bearing is a needle bearing

Is this engine made by Tanaka in Japan or is it another manufacturer ?

Like this but without the electic start
http://www.ereplacementparts.com/tan...906_34923.html
http://www.manualslib.com/manual/167...-Ast-7000.html

It needs a new carb and a prop adapter, and maybe more parts ?
Is this suitable to convert a to RC plane engine ?


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RE: Tanaka 21cc conversion ?
 

You need to change out the non resistor spark plug.

Most model engines had the NGK BPMR7F spark plug which is a taper seat spark plug much smaller than the one you have.

The tapered seat spark plug works perfectly in the hole originally made for a gasketed spark plug.

RE: Tanaka 21cc conversion ?
 

Thanks, i need all info i can get ....
( this is my first conversion )

How big prop for this one ?

I need a new carb, any tip ? the one on it have a 11mm hole

Ant tip for a prop adapter ? do it myself or buy where ?

RE: Tanaka 21cc conversion ?
 

It would help to know how many cc's displacement it has?  The horsepower figures are typically very inaccurate.

RE: Tanaka 21cc conversion ?
 

Tanaka AST7000
21cc
1,1hp ( factory info )

RE: Tanaka 21cc conversion ?
 

Sorry I missed the displacement in the title.

The engine is not big enough for a 18 X 8

Perhaps a 16 X 8 prop would be more to the engine's character?

RE: Tanaka 21cc conversion ?
 

Thanks w8ye

I need a new carb, any tip ? the one on it have a 11mm hole

Ant tip for a prop adapter ? do it myself or buy where ?

RE: Tanaka 21cc conversion ?
 

Some weed whacker engines are easier to convert than others. I've done a Homelite 25 cc and a Ryobi 31cc. Does that threaded shaft come off (you may have to use heat, I believe the factory lock-tights the shaft, it also may be left hand threads, is it metric)? Looks like the housing around the flywheel would have to be machined off (or it may simply unbolt). I just rebuilt a Sears air-cooled gamefisher outboard (50cc Tanaka engine), the rings and some carb part were available from Sears, I did get a piston for it from a Tanaka dealer, cylinder jugs were unavailable. I have a Bridgeport mill and lathe in my basement. Parts could be machined to convert it, but it may not be worthwhile.

Jeff

RE: Tanaka 21cc conversion ?
 

It sure looks like it could be an Echo / Kioritz 21.2, but the cooling fins are a bit different than mine.
Here is my engine:
http://www.rcuniverse.com/forum/m_91...tm.htm#9153860

I put an Rcexl ignition on it and it is a super engine. I have it on a 16lb. oldtimer for floating around with. I've tried many props from 13x8 up and am currently using an 18x8. The big prop only turns about 5500, but is more to scale on the plane and pulls it right along. It starts easy and runs so smooth. Here it is landing::D
http://www.youtube.com/watch?v=pEDqPsCNk30


http://www.rcuniverse.com/forum/m_82...tm.htm#8228949

Rod S

RE: Tanaka 21cc conversion ?
 

Yes it look the same in a fast look, but the engine block is also different

Nice vintage plane you have !
Here is my, but this is only 60" http://www.youtube.com/watch?v=b8lr_n_B8mg

Aha 18x8 for some low rpm, i maybe try it if i do a conversion on this Tanaka

Do you have a link to Rcexl ignition ?

RE: Tanaka 21cc conversion ?
 

I have not started on this engine yet, i maybe try to see if there is a ignition spark on it first ?

How much lash / space is it between the flywheel and the coil ?
( it have been off )

Yes of course i trim off some of the housing

RE: Tanaka 21cc conversion ?
 

0.5 mm (.020 inch) has worked well for me. Measure with a non-magnetic gauge right at the magnet part of the flywheel. Good luck.

RE: Tanaka 21cc conversion ?
 

The age old coil mounting and spacing method that has been discussed on here from the beginning and RCOnline before that is to get the magnet of the flywheel in the position of the coil mount.

Place a business card over the magnet and the coil on top of the business card. The coil will be held in place by the magnet.

Then attached and tighten the coil.

Remove the business card.

I have done them this way on magneto ignition engines for many years and never any trouble yet.

Business cards are generally in the .010" - .012" range

The standard dimension for weed whackers and chainsaws is .3mm or .012" in the service manuals

RE: Tanaka 21cc conversion ?
 

The definitive carb for these would be a Walbro WA-167 or a WT-499. They have a 11.11mm venturi, twin adjustment needles, but no choke.

At one time you could get these from Horizon but I don't know of a good source right at the moment. Horizon's search engine has been trashed by some "learned system" rather than a "key word system".

http://www.davesmotors.com/s.nl/it.A/id.4131/.f

It is said that the WT-499 is a alcohol carb which is true but you can turn the needles down enough to run gasoline too.

http://www.mowersoutlet.com/Carburet...67_p_4636.html

RE: Tanaka 21cc conversion ?
 

Thank you W8YE, I stand corrected. I remember the business card tool, and have done it that way, but I was thinking the cards were closer to 0.020 inch, i.e. 0.5 mm. My mic is still packed from my recent move. The closer, the better, as long as the coil is not rubbed by the flywheel.

Sincerely, Richard

RE: Tanaka 21cc conversion ?
 

I was taught in high school (based on a Briggs 3hp vertical shaft) to use a piece of notebook paper folded twice to get three thicknesses which is about .009" and set the magneto to this setting. I've always done this on my engines and its always worked. What is the max gap before spark quality starts to suffer?

RE: Tanaka 21cc conversion ?
 

Reading all the chain saw and weed whacker manuals on my hard drive, the magic magneto spacing number is .012"

RE: Tanaka 21cc conversion ?
 

FOR THE RECORD

I happened to see an appointment card in the trash so I put the calipers on it. 

The card measured .0115".  

You are going to see this number vary some if you go around measuring all the business and appointment cards in the house.

.010" - .015" and you should be OK? Too close and I'd worry about wobble and too far and the spark may be weak?

This distance does change the timing a minute amount but that is a minor factor.

RE: Tanaka 21cc conversion ?
 

Hi W8ye,

I think I've run across your comments on my thread about converting Saito (and other) nitro engines to gasoline usage. So, I received a free plane from a guy at our field who doesn't like to do repairs after a hard landing. It's a Great Planes Katana 50. The cowl will need some repair, sanding, and bondo to make it presentable. Unfortunately, it's yellow. Now, yellow fuel proof lustercote (Top Flight) is known to need 10 cans of spray to cover anything. And it doesn't react well to primer either. So, I'm going with a gasoline engine and rustoleum paint to get around that hassle.

I have a Tanaka 21cc gas engine, unconverted yet, just like the one shown in this thread. Should be a good candidate for this plane. HOWEVER, I noticed there is no reed valve for the intake. Does it have it's own porting and thus not need reed valves? How does it get around blowing air back out the intake from the crankcase? Or, is it just missing from the pictures?

Any insight will be helpful.

RE: Tanaka 21cc conversion ?
 

Many two stroke engines don't have reed valves. They are what's called piston ported, with the piston opening and closing the intake port, as well as the exhaust and transfer ports as in a reed valve engine. Works fine, and actually tend to make slightly more power than a reed valve two stroke at higher rpms.

AV8TOR

RE: Tanaka 21cc conversion ?
 

OK, thanks for the info. I suspected as so (piston-ported), just like a nitro 2 stroke really. At first glimpse, the output shaft looks way too long, but when I line it up in place on the Katana's firewall, and hold the cowl up to it, it becomes apparent the shaft is really just about the right length. I will machine my own prop hub, and convert this thing over to electronic ignition. Should be a screamer.

RE: Tanaka 21cc conversion ?
 

It looks like a nice engine to convert; somewhat like an Echo actually. I don't make a backplate mount for engines like these. I just put studs in the four crankcase holes, and mount the engine directly to the firewall. Sometimes it is a bit of a pain to get to the nuts inside the fuselage behind the firewall, but it does save some weight and the hassle of making a mounting plate with counterbored screws mounting the plate to the engine.

AV8TOR