Hello. I bought an LT80 yesterday and it is in need of a top end. The thing was bored and the guy cut it too big somehow. It appears that the piston is a weisco and is 50.60mm wide at the crown and 50.9mm wide at the skirt. The bore is 50.96mm wide near the deck, as measured with digital dial caliper. He says it ran but he could hear loud piston slap so he tore it down.
How many bore sizes are left and can I order a piston that will work with this bore size?
Also, I plan on getting an intake/ FMF Fatty and doing some port work. My plans are to run an extra base gasket and mod the piston crown to increase my transfer duration, widen my exhaust and increase its duration, as well as trim the piston skirt for some more intake duration.
It also looks like the boost port could be widened a good bit?
Question is how much should I cut and if the porting will work with my stock pipe until I get the FMF.

By the way I have a brand new weisco 673M05100 piston for sale if anyon's interested or maybe trades for a 51.5mm piston.

Thanks in advance!

 

Pics

 

Edit i just double checked with the dial calipers and I came up with 50.97 at the top of the bore and 51.18 at the bottom. Looks like I definately need an overbore.

Weisco piston for cheap! $40 shipped

 

Your bore is 51mm. Your piston is 51mm. You need a long feeler type gauge to do a accurate measurement. Even if your measurements are close, it's only 6-7 thousands and that within the operating range IMO.
Wiseco's demand more clearance. (.0035-.004) and they rattle till warm.You have the correct piston.
You have 51.5 and 52mm left for bores.
The stock pipe works very well w/mods. I use the Trinity Racing pipe.
Modding the piston...you have a blaster don't ya?! They do that stuff on them. LOL
Duration doesn't change unless 1) ports are raised (not widened) or 2) stroke the crankshaft.
You've not mentioned shaving the head to correct the ratios. Altho a extra base gasket won't change it much.
Tons of info in here or get a 2 stroke book by A. Grahm Bell. Might help with philosophies.

Edit: I see your edit.. I still think that you need to get it measured more correct. I use calipers but only for a "close not accurate" measurement.

 

So put the piston in the bore, set upright and stick a long feeler down there?
What would you say the cutoff is for the weiscos, .005"?

 

.008 or .009
I get motors in that run, and a next size piston fit's right in. They seem to run forever.

 

Is there a certain position the piston needs to be in the bore when measuring this, and a special feeler guage that I need?
he one I have is like a 3/8" wide blade and approx. 3" long.

Also, my 51mm weisco piston is missing a c-clip. Can I order an OEM one or will it be a special one from weisco?

Thanks

 

The piston can be in any position to measure. The 3" long feeler gauge is better than nothing. Should work.
A stock cir-clip will work.

 

OK. I can get a .009" feeler down in there without pushing too hard.
I'm going to go ahead and go out to 51.5mm on it; I was thinking about running the pro-X piston as it is a good bit cheaper than the wiseco....Has anyone ad problems with these?

 

51mm wiseco piston for sale practically new $40 shipped
Comes with rings, pin and circlips
No bearing
Piston has not been ran since I took the pics above
Willing to trade for a 51.5mm