Help I have a twin port 1300 and decided to change to 1641 when I stripped engine I noticed it had two barrel gaskets input new pistons in and torqued everything down I turned engine over by hand but it stops at top dead center any help please

Do you mean gaskets or shims under the cylinders? Did you measure the deck heights, ie how far the piston crowns are below or (maybe in your case above) the tops of the cylinders at TDC?

If the piston crowns are above the tops of the cylinders you'll need shims underneath the barrels. The case may have been surface ground or flycut at sometime in the past.

They were like metal gaskets between barrel and block about 3mm each

Did you put them back?

No I used paper gasket can I get away with putting them back on

You really need to strip it back down and check your deck heights across all pistons then adjust each one with shims to the correct height.

Silly question but can I not use the oldones

set ur deck heights or when it gets hot you will get piston slap and wreck your engine simple as, new shims are cheap enough. personally i wouldnt of changed to 1641 and just gone to 1600 using german quality barrels as the 1641's are cheaper quality and thinner walled.
have you upgraded the heads to 1600?

Yes changed heads as well

If pistons and barrels are same size in height can I not use old shims

You can use your old ones. Check their sizes with a micrometer and use where required, placing them between the case and the barrels will raise your deck height.

Do you think I will get away with the push rod tubes as they are new but obviously I torqued it all down

All I used to do was pull the ends of the tubes to stretch them a bit before refitting. Worked for me. 

Make sure that the welded seam is at the top too as you can get the odd porous weld.

Quote from: Shaggy on February 28, 2014, 01:14:25 PM
All I used to do was pull the ends of the tubes to stretch them a bit before refitting. Worked for me. 

a gentle stretch works well. did the engine turn freely before fitting the heads.

3mm shims are spacers!  measure the throw of the crankshaft it should be 69mm ( heads off barrel on is easiest) as you can measure piston crown to barrel top edge at the ends of the stroke.