barrel bored to 175

[kennystag]

Hi All,
I can get my barrel bored to 175 on my GP 150. What piston would I use, would I be able to use the same con rod ,thinking will the small end fit, what other mods would I expect to have to do.
Cheers
Stag

[hullygully]

depends on if you have electronic fitted?
what carb do you have on it now?
what exhaust do you have on it now?
fast flow fuel tap?

[kennystag]

I will be fitting a Jetex 22 mm carb, and fitting this exhaust, ebay item number 171870912577. I do not see how the electronic ignition has much to do with it, but no i do not have it, very happy with points thanks.
Cheers
Stag

[drivera]

Yeah a rebore to 175 and a conversion piston of the same size will be fine , 22mm Jetex will be ok or a 20mm Dellorto if you can get one would be good , don't worry about the ignition points will be fine

[kennystag]

Thanks mate,
Could you please point me to a piston that would fit the 175 rebore.
cheers
Stag

[Adam_Winstone]

Often works out cheaper to send your barrel off to a dealership that will supply a suitable piston and carry out the rebore. You also benefit from being able to go back to the Lambretta dealer if they get it wrong, although their experience (providing they do their own rebores) should mean that they get it right.

I currently have a pal needing to get his barrel rebored, after having it rebored a month ago!! The local 'bike place' that did the rebore got it all wrong and bored it out SO BIG that it now slaps, hardly starts and runs like a bag of nails, with clearance enough to drive a bus down both sides of the piston at the same time!

Another pal has just had to go back to a tuner/dealer too as a local engineering shop did such a bad job on his GT kit rebore.

In both of these cases it then cost the owner all of the postage, the time and hassle, and then the price of another piston and starting all over again.

Adam

[Adam_Winstone]

FYI - AF will supply a good quality Mahle thin ring conversion piston and do the rebore for a VERY REASONABLE sum, and supply a new 175 head for less than it will cost you to have your 150 head machined to suit the increased bore size (needs to be addressed).

[drivera]

FYI - AF will supply a good quality Mahle thin ring conversion piston and do the rebore for a VERY REASONABLE sum, and supply a new 175 head for less than it will cost you to have your 150 head machined to suit the increased bore size (needs to be addressed).

Yup , give AF a try

[kennystag]

Many thanks to all who responded with the information regarding my top end. I will post what direction a take.
Cheers
Stag