holed piston :( so angry (now with pics)

[Donnie]

Good to know that the head was at least retorqued, lots of people cant be bothered and wonder why something goes wrong later down the road.

whether your locals have a thing for your dyno guy or not, you shouldn't rule out jetting being an issue.

I know that it's looking like a cast iron case that it was the going on reserve at full pelt that holed it, but I'm running a 186 muggy and I've had this happen a few times where im going along on full throttle, gone on reserve etc and there's no hole in my piston :-/

It's been said elsewhere, dynos are a great tool but they are not the be all and end all by any means. It's good you've learnt to do the chops too, most people don't.

As for what your scooter has cost you so far? You cant get despondent about that, mine's a shitter but probably owes me £1000 more than I'd get for it, but I don't care. I don't care what it owes me. The value for me is the scootering itself including all the great people Ive met and made friends from directly due to it.

Piston wise you'll need to go for the camlam / mike phoenix muggy one I'd think. you can't just pop in an escort / mahle as it wont match up. I don't know enough about the MB ones i have to admit but you may want to double check if the head would need to be reprofiled to suit.
Theyre supposed to be great pistons though. However, if theres an underlying reason that you don't resolve that caused this one to hole, then so will any other piston you put in.

Have you stripped the top end yet at all?

[tonydevon]

thanks, just spoke with cam lam, very helpful.

heads off, hopefully have barrel and piston off tonight

hole is right in the middle of the piston, plug is ashen grey colour, nothing like the colour it was when last checked about 7 miles previous.

if the barrel has survived then I will try to hold out and put new piston in, then go over everything else to double check it all, will look at that ignition timing too

I get so confused with 2 strokes, having been a 4 stroke man all my life, mines now 17 degrees, the suggested 19 degrees confuses my brain as I thought it would get hotter due to firing earlier? but I obviously need to read up on 2 strokes and learn. hence the reason whay when 17 was suggested to me originally, I went with that and didnt change it as I dont fully understand the effects

[servetakid]

Tony, you have my sympathy. I have had everything concievable go wrong scootering wise this year for me, but I am having some fun again so am well happy I didnt jack it in! So hopefully you wont as well.

While we are on the subject of ignition timing, I am having my rapido 230 set up on the dyno and an M-Tech fitted on saturday. What Igintion timing would people suggest as "safe" with fast touring in mind. I have always run 17' on static timing, but now I will have more flexibility would it be best to go back as far as say 14' at full throttle?

Cheers

[tonydevon]

yeah just bad timing (no pun intended) I sold another toy I had cheap to a mate so that I could buy and build the lambretta, my first one ever. sunk everything into it and suffered my first engine failure/breakdown in 20 years of riding, its just a matter of do I borrow money to fix it, or just cut losses and get rid of it, think my love affair may have just come to an abrupt halt LOL

need to just step away, put the hammer down and breathe LOL

Im glad that your back at it and enjoying it

[Adam_Winstone]

You are right that going to 19 would make things hotter, not cooler. Indeed, the one issue that we had in our group's recent run to Avignon was as a direct result of a shop 'correcting' a reliable motor's 17 degrees to 19 degrees... because that was what they deemed to be correct! All motors are different and any suggested starting points should be considered as exactly that, a starting point!

I don't think that I've been able to set any motor to 19 degrees in recent years, other than 100% standard motors with standard small carb and standard (non-clubman or expansion) pipe, without them running into heat issues when used on straight open roads. I have one of my reliable Euro motors set to 15 degrees static timing (with low compression and low rev porting/gearing) and know of people with auto advance/retard ignitions going to 14 degrees or less (where revvy pipe allows).

Don't get me wrong, I like to run as advanced an ignition timing as the motor allows but you need to let your motor determine that, not what the suggested starting point is or what anyone (including me) tells you it should be. A holed piston means that your motor is not only telling you that something is wrong... it is shouting it at you! If you run into overheating issues on a motor the first things to do are richen it up slightly at the throttle position that you were running at when things went wrong and knock the timing down a degree or two (16 or 15 in your case). When this has sorted out the overheating issue then you can, if you choose to, start to work back and monitor results.

Good luck.

Adam

[ArmandTanzarian]

Probably not the problem but I'll throw it out there anyway. A few years ago I set up Mugello and it worked great. Then blew a hole through the top of the piston after about 100 miles. As far as I could tell, the choke was sticking very slightly open so all of the jetting was off when I set it up. After a while the choke closed properly, leaned everything off and it went bang.

[a.j]

As for what your scooter has cost you so far? You cant get despondent about that, mine's a shitter but probably owes me £1000 more than I'd get for it, but I don't care. I don't care what it owes me. The value for me is the scootering itself including all the great people Ive met and made friends from directly due to it.

Amen to that. Have a breather Tony & get it sorted. You know it makes sense!

[WINTERMODEL150]

Make sure you pressure test it Tony when its been rebuilt to check for air leaks

[nelson pk]

Make sure you pressure test it Tony when its been rebuilt to check for air leaks

Good call. Leak down test is a very simple/ cheap test compared to what damage even a small air leak can cause.

[tonydevon]

well the barrel is only very very minor marked, piston is holed, and rings stuck in by the exhaust port, run finger nail up and down all the barrel, nothing that can be felt.

one very tiny nick in one of the ports, that will stone out no problems. plenty of debris fell out of the exhaust.

going to try and borrow the money for gaskets and piston, start stripping crank out this weekend.

have checked fuel flow from tap and all good, filter is clean, carb main jet is clean.

head was tight with no sign at all of any leaking, slight leak from exhaust manifold.

Im wondering if I have weakened it over the miles due to my riding style? Im used to big 4 strokes and rolling off the throttle a lot.