ooops

[a-teamlambretta]

dropped into inlet , might get away with just using top ring ??

image hosting site over 5mb

[Adam_Winstone]

What kit is this from?

[a-teamlambretta]

What kit is this from?

have a geuss lol

[Adam_Winstone]

Ah, if it is what your response makes me wonder about then please forget that I asked.

What's happened? Peg allowed ring to spin or was it simply a case of ring end being exposed by a port? Note that I ask this as a line directly up from the window cutout suggests that the peg and ring end might be in line with the port. Did the bottom ring get exposed by the inlet at BDC?

Adam

[a-teamlambretta]

bottom ring straight into port including peg

[Adam_Winstone]

Ah, that's the question that I went back to edit in whilst you quickly responded.

It may be that the kit was worked with a 58mm standard stroke in mind but that a longer stroke crank allowed it to then be exposed at BDC.

Adam

[a-teamlambretta]

images upload

free photo upload


piston at bdc , it was bound to happen . top ring should be ok as the peg is still in the cylinder and not lined up with any ports

[Adam_Winstone]

Was the piston the one supplied with the kit or has it been replaced at some stage? I'm not sure that I'm familiar with this piston type, as the 2 holes above the gudgeon pin do not look like those that I'm used to. I also note that there is more space between top ring and crown and more 'ring land' between the rings, placing the bottom ring pretty low on the piston... and more likely to be exposed by an inlet port.

Please feel free to respond by PM, if you wish, as I fully understand why you might not want to name product or dealers, especially when no conclusion has been reached as to why this failed.

Cheers,

Adam

[a-teamlambretta]

mystery over lol

free photo hosting

long rod fitted and 12mm packer under the cylinder

[a-teamlambretta]

its a wiseco piston and its all self inflicted lol

[Adam_Winstone]

From the photos, if bore is still in reasonable shape then run it on the top ring only and look into other piston options. NB: Single ring kits are very common but ring replacement tends to be needed at shorter intervals than 2 ring pistons.

A pal of mine was having issues with his kit breaking rings and when he nipped up and did in another ring/piston on the way to IOM, we had to decide whether we would fit his new piston (carry a spare) with 2 rings or fit it with just one, which would leave us a 'get out of jail' option if he somehow did another one on our trip (we were only about 30 miles out of Oxford at the time!). We opted to fit the top ring only and the bike ran without issue for the rest of the trip (choke on!) and then ran perfectly well on this top ring only for plenty of miles afterwards.

I'd figured out what the top end was after your previous photos

What is your bore and compression height of your piston? I ask as you may have other options.

[a-teamlambretta]

i had just rebuilt the motor and this was a new conversion to reedvale and rebuilt new crank with a rod from some kind of motor cross bike. varitronic ignition and lth reedvalve . exhaust modified by me to fit . i was just setting carb up when i heared it start clattereing and stopped it before any major distruction occured lol.

image post

[a-teamlambretta]

From the photos, if bore is still in reasonable shape then run it on the top ring only and look into other piston options. NB: Single ring kits are very common but ring replacement tends to be needed at shorter intervals than 2 ring pistons.

A pal of mine was having issues with his kit breaking rings and when he nipped up and did in another ring/piston on the way to IOM, we had to decide whether we would fit his new piston (carry a spare) with 2 rings or fit it with just one, which would leave us a 'get out of jail' option if he somehow did another one on our trip (we were only about 30 miles out of Oxford at the time!). We opted to fit the top ring only and the bike ran without issue for the rest of the trip (choke on!) and then ran perfectly well on this top ring only for plenty of miles afterwards.

I'd figured out what the top end was after your previous photos

What is your bore and compression height of your piston? I ask as you may have other options.

50.25mm on the piston . from little end centre to crown is 27mm. gudgeon pin is 12mm diameter. will have a look to see if any other pistons will fit. was running and sounding nice prior to the ring escaping , just needed carb setting up cant remeber what the rod is from length ect. had 1.2mm squish with a standard head gasket . no base gaskets where used. if i had then the top ring might have made a bid for freedom aswell lol. cheers simon

[mickey c]

Can I hijack your thread and ask what that exhaust is please? I'm doing a similar (ish) set up on a Vega but that exhaust looks ace, mine will restrict me. What is it a tricky modification?
Good luck with the top end.

[a-teamlambretta]

cant tell you yet, but it was a couple of cuts along the the welds rotate and re weld. so if you can use a grinder and welder its a peice of piss. i made a couple of brakets to mount . the reason i cant tell you is , 1 if it dosent work on my motor and 2 i havent asked the supplier if he wants it public knowledge yet. my vega when up and running will be going on a rolling road near the epicencentre of tuning ,to see how it performs . it might be scrap or it or good . cheers simon

[Adam_Winstone]

Hopefully someone with a little more experience of these motors will come along and give your some better advice than I can offer. I note that many of the conversions that we've discussed on Luna forums previously have been based on converting the larger capacity J components (J125, etc.)... like the link from this post (follow the link)...

http://www.scooterotica.org/forum/viewt ... 4&start=10

Here's hoping that you get it sorted.

Adam

[a-teamlambretta]

think it will be ok with this piston , will put it back together and see how it runs . cheers for the help . simon

[Warkton Tornado No.1]

That's a shame about your bottom ring letting go. No pun intended...

Your bike will run fine on one ring. There's minimal losses @ the lower rev range, but, ideally, two rings minimum for road bikes, IMHO.

I suspect the piston may have originated from the generic Suzuki type as they had several Ø50 mm nominal bores.

Recently, there has been Posts on here about the advocacy of the lower ring/peg entering the inlet port on other cylinder kits, & reading this makes me remain in the "Don't do it" camp.

Perhaps I'm naive, but having re-pegged on several occasions, I don't understand the fairly universal reluctance against it. Once upon a time, there was no alternative.

Good Luck though with this interesting project! It'd be great to see more of it in "Show your Ride"

[dscscotty]

Did you not notice the ring dropping into the port when jigging/building the top end?
Having tuned several vega's using reedvalve using and Tzr pistons, ring/peg location has never been an issue, Chiselspeed do excellent expansion pipes for vega's, the last one I did rolled nigh on 13bhp on chisels dyno with a good spread of power, not very high bhp figures but I can assure on a vega its enough!

[a-teamlambretta]

When using the tzr piston you need to use a j125 cylinder and starstream crank if you want to keep on a 4 speed box. I opted for what I had, a vega 75cc cylinder and reedvalved that. I'm expecting 12/13bhp from this once running again lol