Blown piston (post pics!)

[sickboy]

hi well to be honest i never go as far as you if its gone then i just buy replacement parts but with the fs i just didnt want to go out and buy parts for something that is not up to speck from the start but i have 2x fs engines laying here and my zen is in bits
so you said the fs is the same size as the zen piston well that will save me some time ill just take the piston ring of that and place it in my zen hope it works
will let you know

ps great work you got going there keep it up we all need to know

[sickboy]

Hi all so i thought i would try and get to the bottom of the poor fs motor well i found out that the fs con rod has way to much play from side to side as i have a 2 new ones here and thought lets compare them to the zen well i made a vid for all to see

zen motor on the left fs on the right of course ;D

PS rallyfinne you are right about the piston size they are the same i used the piston ring for my zen as my zen was not up to much any more

here's the video
www.youtube.com/watch?v=Hl_PY0OiQeY

[rallyfinnen]

sickboy: Yeah, I figured that was the case.. not sure it's the reason for the piston cracking though, but it's definitely a factor that makes me degrade the FS engine to s..t

After checking various engines (chainsaws, trimmers, mini-moto, rc boat engines etc) I decided to stick with the proved concept for now.
There was always some problem with the alternatives, price or technical.. The mini-moto engines were cheap, but all those had the carb connected to the crank case opposite the cylinder (reed), and that makes it (almost) impossible to fit on our cars.
These are however available at nice prices and typically around 40cc. Don't know about the quality though..
Trimmers mostly have the flywheel on the same side as the clutch, and then the flywheel will collide with the center drive shaft. (crank is only a 'half crank' like on nitro engines)

Well, looking at replacing the piston with ring and washers, it would cost around 40Eur, and then I still don't know how long the engine would last.
I ended up ordering a new CY 23cc without carb and exhaust, and that cost me abt 100Eur with shipping from Germany. I think(hope) that's a good quality/price ratio.
I'm still waiting for the warranty parts for the FS engine, so I guess i can have that as a spare.
I also ordered two Carbon Fighters, one as a 'spare parts car', and the second one for a friend.

I have some thoughts of using the drive line from the CF spare parts car to convert mine to 4wd..
I know I have to shorten the center drive shaft, and hopefully the rear drive shafts and cups will work in the front (without popping out).

[sickboy]

Hi so after all the reading i got thinking i have to fs engines here laying about doing nothing so with all the info here on our forum I have replaced the fs crank shaft+rod for the zen crank shaft+rod as i was doing the rebuild i noticed straight away the difference in the con rod there was much much less play. so carrying on with the build using the fs carb man that was a bad mistake the thing would not even idle i had to screw the idle all the way in and still it would not idle properly so i binned that also replaced it with my walbro 813 with no choke man what a difference one pull and this baby was singing so now for the test i will take the engine out that's in my fs now and put this rebuilt one in its place and give it a bash soon

ps when i do the it will be with the stock pipe

[rallyfinnen]

So, basically you now have a FS engine shell filled with Zen internals? :-)

[rallyfinnen]

I want to encourage everybody to post pics of their blown FS engines (I think there are quite a few of them..?)
Maybe we could come to a conclusion on the reason for the blown engines with a broader base of information.
I'm planning to do some experiments and see if i can get the FS engine to last. (yeah, changed my mind, I'm too curious! )

My plan at the moment is:

Step1
-Replace piston and cylinder on the blown engine (warranty parts). Also replace the washers on the piston pin with Zen washers. I should have all these parts in the end of the week.
-Possibly file a little on the piston & round off the lower edge of the intake port, I have a theory about the piston skirt catching on the edge of the intake port.. but more background & pics would help!
-Run the engine and see how long it lasts, and check what fails first.

Step2

-I will be getting a Carbon Fighter spare parts car sooner or (probably) later.. Order is in, but delivery will take time.. conrad.de is waiting for delivery from the FS factory.
-Replace the piston with a Zen 26 piston before i even start it.
-Maybe some other mods too based on what I learned during that time.
-Give it hell and see how it lasts..

So, please get your cameras, take some pics of that broken FS engine lying in a box and post them! Piston, cylinder, piston pin washers.. whatever is broken/damaged!
Maybe we can learn something!

[sickboy]

Hi Rallyfinne
well not exactly i have only placed the zen bottom end that's the crank shaft +con rod the rest is original fs ;D.
so im going to do a test with this engine when i have rebuilt my fg mt.My fg mt has been neglected for the past few months so thought i would give that a new breed of life with the modified fs engine ::)fingers crossed hope all goes well

[rallyfinnen]

Ok, sounds like an interesting mix :-)
Got any pics of blown engines you could post?
I have seen one more somewhere with the same type of damage to the piston. I'm curious if it's the same on all engines, and if the washers are broken on all of them etc

[rallyfinnen]

Engine is now assembled again and running..
This time I chamfered all the sharp edges on the piston and in the ports of the cylinder, especially on the skirt of the piston. I also put the Zen washers on the piston pin.
Removed the cylinder gasket for higher compression, squish is now abt. 0,7.
Having some thoughts on running it on E85 too (commonly available in Sweden), makes the engine run cooler and might gve some extra power.
It could damage the membranes in the carb, but what the heck, I've got three more :-)
Have been doing some running in today. I believe the running in should be done loading the engine but with a rich mixture, and keeping an eye on it so it's not overheating.
I think this helps everythin set better than just idling and not loading it much.

[sickboy]

Hi all just a quick one
So took the fg 1:5 home made fg out for a bash with the fs modded engine all went well but time will tell i need to get about 3 to 4 tanks threw it then i know it has solved the problem fingers crossed

[rallyfinnen]

For me the first engine lasted maybe 8 tanks, so maybe I'm askin too much when i want it to last longer? :-D

[rallyfinnen]

Was running it on E85 yesterday, and all was fine. Just had to adjust the carb a bit to give it more fuel.Seems to run a bit cooler on E85 too, Can't notice any increase in power though.

[338lapua]

well it finally blew after almost a year .
my piston washer on clutch side ,broke same as rallyfinnen's piston looks the same .
I was running those proline excavators and stock gearing a couple hours when it let loose.
I guess I can't complain compaired to everyone elses .

[rallyfinnen]

I'm now preparing step 2 in my 'plan' above

I replaced the piston in the CF engine with a Zenoah, and did some mild porting of the transfers.



Stone-protection on this one too:



Also weighed the FS and Zen pistons, the Zen was 1,1grams heavier. Seems there is a little less piston/cylinder clearance with the zen piston too.

[rallyfinnen]

The CF engine is now in the car, because I noticed that both main bearings have play in 'the old engine'.
I'm planning to replace the bearings and keep the engine as a spare. Still runs ok, and with new bearings is should probably rev a little bit better too.
I did some running of the CF engine yesterday afternoon. I also experimented a little with the running in.. Instead of adding some extra 2-stroke oil to the fuel, I added PTFE-oil (teflon lubricant). I was running the engine rich and also sprayed some PTFE in the carb while reving the engine.
I always put PTFE in the engines since i have noticed that they seem to run better after. I also read an independent dyno test where they improved the power output of a stock Zenoah 10% with PTFE.
I never used it while running in before, so I thought I would give that a try