zen 260 wont't fire.

[Mike Larson]

Terry, I'm going with the general consensus on the ring theory, if the motor is "pulling hard" , i'm betting you have a stuck ring, if not a failed one.... replacing the rings, at least on the motors ( not boat Zens) I've rebuilt, whether it be a new p/rod etc, the cylinder needs to be honed/crosshatched to a degree to allow the new rings to seat/seal correctly, or you run the chance of the ring sticking in the old cylinder race...... basically you have a nominal "square edge" on the new ring(s) rising in the cylinder prone to catching on any out of normal wear area in the old cylinder.... though it takes little time to seat/wear in to the cylinder, it will happen, and is critical to the sealing of the cylinder (compression) Take the motor to a small engine repair shop, and ask for a comp test, ( free, more than likely) if you cant find one, while not familiar with the poundage, I thought my modified 30 cc homelight was supposed to be around 130 pounds.... if you have low or little, the motor will not compress the fuel/air mixture and make the explosive mixture needed to create combustion...... seemingly, if you have fuel, spark, and air, you should have a running motor. Stated, I'm not a professional sm eng repair mechanic, and my thoughts methods are back yard, I like to work on them, and diagnosing problems/fixing two strokes usually mostly narrows down to what youve done........ I would possibly look at the gasket/case seal, and the carb isolater block gasket/seal for a compression leak, too....... throwin in my 2 cents, good luck.... mike

 

[tmunn]

I was able to get on the dock and I have the same thread going in 2 places.

Here is what the problem is......

I bought the boat used and the first time out the flywheel came loose and damaged the flywheel and pulley and cut off the key and wore a spot on the crank in the keyway slot.

The flywheel cleaned up nicely so i bought a new key and pulley and put it back together using BLUE loctite.Well guess what.

I found the problem .It was another sheared flywheel key,and more flywheel damage.

I decided to remove the cylinder inspect it and it all looks fine and all the gaskets look fine as well.

The middle of keyway where the key sits is slightly worn a couple thousands on each side of the slot and would be in the middle of the key way.

The pulley is still good.

The slot in the flywheel is now wider on the side that goes toward the engine than the side that goes outward.

1)Should the crank be repaired or replaced?I was thinking a bit of j-b welb on one side at a time then removed with a dremel.It is worn very slightly but noticable.It looks fine at the beginning and end of the slot.

2)Should the slot in the flywheel be the same width all the way through the flywheel and no taper?

3)Do you guys think I could get away with another flywheel and key.

4)Does anyone have a good used flywheel and new key.

We have have had open water for a couple months now and i cannot even get the first tank of fuel burnt out due to one problem after another.

These are supposed to be easier than nitro

Thanks a lot for your help guys.

Terry

 

[Krusty 181]

I was able to get on the dock and I have the same thread going in 2 places.
Here is what the problem is......

I bought the boat used and the first time out the flywheel came loose and damaged the flywheel and pulley and cut off the key and wore a spot on the crank in the keyway slot.

Terry ,this small bit of info would of been very useful at the begginning of the thread ........

you need to figure out why you are breaking the keys , if its because parts are worn then you need to replace them all

you may not be getting the flywheel all the way home when your installing it ..

BTW some( all?) quickdraws dont use keys at all , just the taper of the crank holds it in place

Andrew

 

[Mike Larson]

Terry, The timing when the coil hits is off from the key/crank being sheared, whatever the firing is, I'm not familiar with zen, at all, will be so many degrees before TDC, or after, whatever, if the crank is egged out bad, where the key fits, you may be in for it, it may run, but poorly, because the timing is advanced/retarded enough to create an out of phase combustion sequence......if, you deem the crank salvagable i'd get a new flywheel ( if yours was damaged enough this could be dangerous, they are just cast low yield aluminum) and a key, and have at it, I dont know if zen has the taper on the crank, or in the flywheel, or both, the keyway in the crank and the positioning of the flywheel have to be aligned with the index in the crank for the coil to pick up and fire at the precise moment it's designed to. I always set mine with the "card" method someone wrote, after torqing the flywheel nut down. use your judgement on the parts, it's should be a fairly easy fix...... Get with the dock guys in chat, they'll have a flywheel to you in short order, and more than likely give you better advice technically than I can..... they live zenoahs....... hang tight man, i'm getting ready to throw some thomas spt 20 questions at ya, like, whose turn fin ya usin, and how deep off the sponson edge is yours set? good luck mike

 

[tmunn]

Guys

I do not know why the key broke in the first place.The nut/pulley may not have been tight.

The second time was probably my fault for trying to use the worn flywheel and perhaps not getting the pulley(which is actually the nut with the ears on it for the starter dogs to catch on for the person that was asking) tight enough.

There was aluminum in the threads of the crank from the nut,possibly giving me a false sense of tightness.

I noticed last night while trying the pulley on the crank that it went fairy hard and not to the end of the threads at first.I turned it back and forth and have it going on the crank right up to the shoulder now.

I stopped by a reputable small engine repair shop and had them look at the keyway or groove in the crank.

He said that it was still fine.

This time I would like to ask what the proper procedure for installing the key,flywheel and pulley would be.

Should there be any type of lock washer in there somewhere?

There was not.

 

[impba3548]

When I had the problem, I just cleaned it up, installed a new key, then put the nut back on with some blue loctite and made sure it was good and tight! No more problems with that engine. Some of those engines were not torqued down properly I think was the problem, my son builds motors and he said that some of those nuts were so loose they could almost be unscrewed by hand. The flywheel fits on a taper and if properly tightened the key isnt even needed to hold it in position. We have run taperlock sheaves at work for years without a key. The secret is to get it properly tightened.

A stuck ring will give the same symptoms as well but your compression will be down.

mike sr

 

[tmunn]

I am pretty sure I can fix it myself if I had the parts on hand it is not very complicated once a person can see or is explained how things should look and work.

When I put it back together i was told that the keyway was not the same width all the way through but was tapered.

Now i am told it should be the same width for the keyway front to back or through the flywheel.

When I reinstalled the flywheel after the first incident it was taperd at the back and it looked made that way.looking back and knowing what i know now ,,,the flywheel was worn and should not have been re-used.

I am sure once i get the parts or get it back from being repaired i will see the difference.

I have an offer form the other forum to send it back for free repair so i sent the person a PM.we'll see what happens

Thanks for all your help everyone and if i need halp again i will try not to leave anything out..

Terry

 

[riph]

The crack is tapered and the flywheel has a tapered hole. Check service manual at:

www.zenoah.net/products/hobby/download/G260G231_408.pdf

Rip

I am pretty sure I can fix it myself if I had the parts on hand it is not very complicated once a person can see or is explained how things should look and work.
When I put it back together i was told that the keyway was not the same width all the way through but was tapered.

Now i am told it should be the same width for the keyway front to back or through the flywheel.

When I reinstalled the flywheel after the first incident it was taperd at the back and it looked made that way.looking back and knowing what i know now ,,,the flywheel was worn and should not have been re-used.

I am sure once i get the parts or get it back from being repaired i will see the difference.

I have an offer form the other forum to send it back for free repair so i sent the person a PM.we'll see what happens

Thanks for all your help everyone and if i need halp again i will try not to leave anything out..

Terry