cmartins

what is your SPE?

Red Raider

My Feedback: (86)

I had a stock SPE 26. I put it on the test stand to begin the run-in and it ran fine for a couple of tanks. Then the problems started. To make a long story short, the only solution was to replace the ignition and the carburetor. BCMA did the mods for me and now the engine runs very nicely.

remote59

My Feedback: (2)

I have a spe 26 from bcma with ch ign 11 mil carb 16x6-10 prop.
can only get 6900 rpm,lousy idle until adjusted timing now I can
only get 6500 but it will idle ok and transistion pretty good 10.5 lbs
thrust,anybody got ideas was hoping to get in 7000 rpm range.

Red Raider

My Feedback: (86)

I don't have enough experience with engine yet to be able to make any suggestions. I've only run it on the test stand, but like "remote" I've been able to get about 6700 rpm. I'm using an 18-8 wood prop and thought that might be too much, thus holding down the rpm. The gas and oil mix does make a profound difference, however. Just a thought.

Magna

Throw it away..... really! After running one for couple of gallons, a stock SPE26 is no where near what a 26 should be. May be the carb need to be change as Poco mentioned.

Its a very light engine and should have much better potential. But even most of the nos posted here in RCU does not come close to other 26. My spe26 can only spin APC 17x8 at 7400. My G26 spin APC 18x8 at 7800. My G20 is spinning APC 16x8 at 8400. This will have more thrust than 17x8 at 7400. 26cc should spin 17x8 close to 8000 based on what I see when I was running in my G26.

So my SPE is not sitting on a bench. I prolly use it on something like Sopwith Camel....

pianori

My Feedback: (2)

There is more info on the SPE 40 in the thread below.
Some mods on the 40 and a video.

[link]http://www.rcuniverse.com/forum/m_3463908/anchors_5640973/mpage_2/key_/anchor/tm.htm#5640973[/link]

Kaoma

My Feedback: (4)

Interesting thred.
I have the Evolution 26GT motor with the original Walbo carb. Since this carb is not throttle/choke RC friendly, I wold like to swap it with a DA-50 carb that is identical to the original Evolution carb BUT the venturi number on the Evolution is 24 and the venturi number on the DA-50 is 34. Would it work or not? Performance good or bad? Please help. Thanks.

pianori

My Feedback: (2)

I have no idea about the DA 50 carb and the G26. The DA is a 50 cc engine and the 26GT is a 25.5cc engine... I do not know about the bolt pattern of both engines and if they match. It looks like the 26GT is the WT481 model. If I were you I would go to the walbro website and look for the specs of each carburetor to see if they match and take it form there.
Check out this site
http://wem.walbro.com/walbro/group2.asp?FamilyName=WT

Antique

My Feedback: (4)

The carbs have the same bolt pattern..The cast numbers are the size in 64ths of an inch...
The carbs need a crankcase pulse to pump fuel..
The DA carb has a fitting on the cover that connects to a fitting on the case for the pulse...
It will work on the GT if the engine has a fitting in the case, or if the mount on the GT has a pulse hole in it that matches the hole in the DA carb base...
Since the DA carb has a fitting in the cover the hole in the carb base might not be drilled all the way through for the crankcase pulse...

Kaoma

My Feedback: (4)

Is the venturi opening too much for the DA-50 carb to put it on the 26GT motor?

Antique

My Feedback: (4)

Nope. I tested a G46 with a WT76A carb, worked just fine, but no better than the smaller carb that comes with it....One of the big myths on this forum is larger carbs will make more power....If the engine has too small a carb on it in the first place, yes, larger might be better..An SDC 80, the largest carb with the same bolt pattern as the HDA48D, makes no difference on a G62....

pianori

My Feedback: (2)

If the throat of the carb that sits on the body of the engine has a smaller diameter than the maximum opening of the venture of the carburetor you will not get any increase in power. On the other hand if you can bore out the intake you might notice an increase in power. When I modify some of my engines I bore out the intake. In my case it added about 1000 rpm over what the engine use to run at before. I also replaced a 9mm diameter carb with a 14 mm diameter carb. I bored the intake from 10 mm to 14mm. that did it for me. In your case I believe that you have an aluminum intake so it is not that easy to bore it out (mine was plastic). Before you go crazy and buy a carburetor measure the diameter of the carburetor you have now on there and then measure the intake diameter where the carburetor sits on. If the intake diameter is larger than the carburetor venture intake you will experience a gain in rpm if you go with a larger diameter carb. Otherwise you might not. However, some carburetors work better than others in transition. I know the WT540 is an excellent carburetor as it has an extra spray bar for the fuel resulting in a much smother throttle response and transitions.
Any way that is just my opinion.

pe reivers

I thought this was a SPE26 thread????

The Chinese 26cc engine I tested had the same 25.4cc chain saw basic cylinder/crankshaft like the SPE, but rear reed valve intake. Gas would puddle in the engine, and cause a very low idle each time the engine altered attitude. So I removed the rear carb, modified the case, made a rear cover to take the rear bearing, changed the carb to piston induction, and tested again. After the mods it looks like the SPE engine.
MA 16x8 @ 7750 rpm , slightly unstable. Ran it for about half a gallon.
starting is reasonable, unless wet. Then Compression goes down the drain. (see later)
I checked Compression Ratio this afternoon. It only is 7:1 swept volume. This is very low.
Squish is 1.8mm, so I could drop the cylinder about 0.8mm to increase the CR. However, exhaust timing is only 146 degrees, and transfer a meagre 100 degrees. Both would suffer, and create a large mismatch between the intake of 130 degrees.
Lowering the cylinder, and raising the exhaust port to 150 degree timing seems the way to go, if the carb can be mounted on a longer intake duct.
At the moment, blowback is tremendous when I open the throttle. This will get worse if I lower the cylinder, so I contemplate a smaller carb to get good fuel consumption at around 7500 rpm. This would make the engine perfect for the medium power hungry planel like J3Cub etc.

The compression going down the drain was due to the ring bottom lands not being flat, so the rings do not seal well when the oil gets thinned by gas. Normally, rings are ground to flatness and final dimension after hardening. This seems not to be the case in chinese chain saws. That may be the reason that copperhead needs to motor the engines for a long time before they will start. It may also be the reason that dyno oil is needed for running in. Maybe even carbon deposits are needed for a good seal, so synthetics are out of the question. In that case I have a problem, because that type of oil is not available anymore [&o]. More initial wear will seat the ring bottom land faster, though I doubt that will happen fast enough at the low compression ratio that I measured.

Having said this, it seems a system that needs a long time to run in well. up to that time, the engine's performance will increase noticeably

pianori

My Feedback: (2)

I am not sure if this is an SPE 26 or 40 thread. The title of the thread reeds "stock SPE engines" so I assumed that it is for both. Some people asked some questions about the 40 so I answered the best way I knew how. I do not know anything about the 26 so I have no opinion on it. I assume that the metallurgy would be the same since they come out from the same factory. I like to attempt to make things better so in an effort to do so I worked on my SPE 40. I personally used a Klotz synthetic oil initially at a 30/1 ratio for the first gallon and then went up to 47/1. I have now about 2 gallons through it and it has picked up some more rpms on a static bench. I am putting in some custom rings specifically matched to this sleeve-head. I changed the muffler to one with slightly more volume in it and lowered the heat about 0.0008 inc. I assume that if I use a tuned canister I would get more performance out of the engine.

I have not run the engine with the new rigs yet as they are being installed. So I do not know if there will be a difference. I assume that I would pick up from 100 to 200 rpm. Now I upgraded to a larger diameter carburetor, went from 9mm to 14mm opening. I am running a Mejzlik 20X8 and so far it is spinning at 7400 rpm. I also heard that adding a velocity stack helps retain the spilled fuel inside the carburetor. Some have experienced some increase in rpm by using one. I have not used one yet.

I want more performance so that is why I am putting in the new custom rings. I might drop the head another 0.0002 inches if the clearance allows. I will see. The exhaust timing does not seem to affect the overall performance yet. I assume since the head is dropped the exhaust will occur a few degrees before than the original setup which will mean that the maximum horse power will be available at higher rpm. As I understand I can increase more the torque of the engine by running a little richer oil mixture in the gas, thus creating a better seal for the rings creating a higher compression, but that would leave a lot of carbon deposits in the combustion chamber as well as possibly foul the plug.

I must also say that I have changed the original ignition as the one that comes with it is not that good of a quality. I would say that I saw the biggest improvement by changing the carburetor and the ignition. I am using now the Chinese made rcexl ignition. In my opinion it is a much better ignition than the original Melody ignition. I left the melody ignition working continually for 3 hours and it failed to work after that. Now it does not work at all. There is a new ignition that Melody made that you can operate from 4.8 to 17 volts that is their new update. I have it but I have not tested it yet.
Any way that is all I know about this engine.

karolh

Can't buy a thirty cents engine and expect dollar type performance

Karol

pianori

My Feedback: (2)

For me is fun to tinker. I do not expect anything Karol and especially $0.30 for a $1. The engine is what it is. I just try to make it better. That is just me. If it was a ZDC or a MVVS I would be doing the same. Just trying to make it better...

karolh

Point taken, however unfortunately I think that you are in a small minority.

Karol