ScottMcM

My Feedback: (66)

One of my flying buddies has a Webra Speed 120 that the compression is gone in. He has tried to disassemble it, but gets stopped at removing the piston. He can't seem to figure out how to pull the pin. He has asked me to see if I can find anyone that works on these engines, because he doesn't want to destroy it. If any of you guys can help, we would really appreciate it.

Hobbsy

My Feedback: (102)

Scott, you should be able to screw a 4mm screw into the wristpin pull it out. I'll check my .91 and see.

ScottMcM

My Feedback: (66)

Thanks. I'll call him right now and tell him.

ScottMcM

My Feedback: (66)

He has another question. Does the Speed 120 have a head gasket?

Sport_Pilot

I think Webra did not use a head gasket, but you might find a shim which can be reused. Has your friend located parts? I don't think you can buy Webra parts unless someone has some NOS somewhere. If it is a ringed engine you might be able to buy from Mr. Bowman, I am sure someone here will send the address. Gaskets can be made from thin gasket material.

ScottMcM

My Feedback: (66)

I don't think he has located any parts, and that may be what kills this project. I believe it is a ringed engine. He claims that it runs, but that the compression is low.

1QwkSport2.5r

As long as the piston and liner are in good shape, a new ring will have the engine running like new. Frank Bowman can be reached at [email protected] I believe.

ScottMcM

My Feedback: (66)

I just spoke with him. He got the engine disassembled(thanks for the advice). He says the piston and liner look good, but the piston moves"really easily" inside the liner. He says it looks as if the ring is a dykes(sp?) ring. Is that correct? If so, how hard is it to replace it, and can Frank Bowman supply them?

1QwkSport2.5r

I believe frank does make dykes rings, but I'd email him to verify.

The piston on a ringed engine will move easily in the liner, especially if it has a dykes ring or a worn out standard ring. Dykes ringed engines never feel like they have a lot of compression when turning over slowly. That's normal.

tiffitech

Yes Frank is makeng Dykes rings also, sent him a P&L Set for an 6,5ccm MVVS with broken Dykes Ring sometimes before and he made one for me. This MVVS is now on the List of Engines he makes Rings for. This is an incredible good Service from Frank and this for such a good price!

Regards,

Holm

ScottMcM

My Feedback: (66)

I have sent him an email. Thanks for all your help, guys.

Sport_Pilot

A broken in dykes ring will feel like a worn out normal ring. They use the compression pressure to expand out to fit the cylinder. Probably just need to put it back together.

Hobbsy

My Feedback: (102)

Scott, one thing to check and consider, if it is a Dykes ringed engine. it will have lousy compression at flipping speeds. It depends on combustion pressure to push the ring outward. The idea is to reduce friction losses. If it has bars across the exhaust port it is a ringed, the ring will be on the top edge of the piston and almost invisible if Dykes ring. If no bars on exhaust port it is an ABN engine.

ScottMcM

My Feedback: (66)

I have talked him into putting it back together, and running it. It may be ok. He said that it runs, but he didn't test it further.

captinjohn

My friend bought 2 of the1.20 Webra engines. One would hand start but the other one needed a electric starter to get it going. I put a Frank Bowman ring in it & it had good compression before starting. It hand started real easy from then on. Get Frank,s ring & don,t look back. Capt,n

earlwb

If the cylinder and piston aren't scored too much, I would just put a Bowman ring on it, and new bearings. It should be fine once the new ring seats in good. As the engines get larger and larger in displacement, they tend to have slightly more loose pistons in them. So a piston that seems a little loose may still be perfectly fine.

But new parts are going to be hard to find. When Webra went out of business, they closed up the factory. All the parts are there too. I don't know if anyone bought up the goods in a auction yet.  Most of the retailers didn't stock much in the way of parts for Webra engines, they would order the parts when a customer requested them. So the factory had all of the parts.

airraptor

My Feedback: (66)

That webra 120 on a Bisson pitts muffler should spin a 15X8 Apc at around 9,100-9,200

ScottMcM

My Feedback: (66)

He says the liner looks good. Wants to know if he should rough the liner up a tiny bit before installing the new ring, or just install the ring "as-is". Thanks again, guys, for the help. I was successful in getting a new ring ordered from Frank........I was wondering what to get the old guy(my friend) for Christmas.....I think this will do just fine.

1QwkSport2.5r

The new ring from frank will have instructions; you use 400-600grit sandpaper and lightly buff a cross-hatch pattern into the liner. Nothing crazy.

earlwb

I typically just use the ring without roughing up the cylinder with super fine grit sandpaper. It might take a little longer to seat the ring on a more smooth surface, but then I don't run the risk or adding more premature wear into the mix either. But it also depends on if the cylinder is hardened or not. Some engines use a hardened cylinder sleeve and the hardened surface is very thin, so roughing it up would wear through the hardened surface. Normally one would use a hone to hone the surface of the cylinder, but the special small Sunnen hones are quite expensive. You cannot use a brake cylinder hone as it is still too coarse for a model engine. A machinist person might make a homemade hone and use some lapping compound to hone a cylinder too. But in my opinion, just leave the cylinder alone and use the new ring.

blw

My Feedback: (3)

You won't go wrong if you let the ring do the work.

tiffitech

It's not really needed to rough up the cylinder in a 2cycle engine. On a normal 4cycle the roughness is good to hold the oil on the surface and to make a good oil seal.
Our model engines aren't needing this and F. Bownman means this also. (Wrote it to me sometimes before in a mail)

Regards,

Holm

1QwkSport2.5r

Frank included in all of the piston rings I have ordered from him a set of instructions. He suggests lightly buffing the inside of the liner with 400-600grit emery paper or sandpaper to seat the ring quicker. I'll go find those instructions and post them up later.

earlwb

Well unless someone knows what is meant by the "lightly buffing" the cylinder wall, they are well advised to not mess with it. Many people have ruined otherwise, what would be  useable cylinders, doing it.

proptop

My Feedback: (8)

My take on it is...(after a close up inspection w/ jewlers loupe ) if the engine doesn't have a whole lot of time on it, and there is no visable varnish present...no ridge at the top of the bore...factory cross hatch still obvious...then leave it alone.

If the cyl. wall looks like it has a glaze on it, then I will use 1000 grit wet/dry w/ light oil wrapped around my finger...just a few minutes to clean things up some....no metal removed, just varnish, crud, whateveryawannacallit...