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. ;-)up
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. ;-)up
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.
Yes engine turned over fine and also ran perfectly before hand
So wot you're saying is stop back put old shimms on then put back together should be fine
You should really check the deck height, the old shims may be too thick for the new pistons, you may need thinner ones. Too great a deck height can lead to low compresion ratio and poor performance.
Took heads of at tdc piston is flush with top of barrel please help
You need to add shim(s) under the cylinders until you get a minimum of 1mm (.040") gap (but idealy not much more) between the top of the piston and the top of the cylinder at TDC making sure that the tops of the cylinders are level with each other.
I do have four 1 mm shims that came from the 1300 barrels there were two on each barrel can use these
I'm sorry but you've lost me a bit. At first you say there were 3mm shims under the original cylinders than you say there were two x 1mm shims under each cylinder and you've got four of these in all, wouldn't 4 cylinders x 2 make eight shims in all?
If you're sure that your deck height is exactly zero and that you've got 4 shims exactly 1mm thick then sure, you can clean them up, give them a smear of Blue Hylomar ane re-use them. Discard any paper garkets. Re-check the deck height accurately with a straight edge and feelers before you re-fit the heads.
Quote from: Tone on February 27, 2014, 09:04:53 PM
They were like metal gaskets between barrel and block about 3mm each
Yes sorry I was guesstimating 3mm but there was 2 x 1 mm shims under each barrel so I have 8 shims in total sorry for confusion I'm just stressed lol but I must admit the gap from piston top to top of barrel on 1300 was a massive 15mm
Just be very careful as if you dont have enough gap between the piston and top of cylinder then it may well idle but when you rev it there could be contact between the pistons and head.
Too big a gap and you lose compression and some power.
I would have thought you need to fit the shims, sealed as ManxDavid says, make sure there is a gap with the barrels pushed fully home, dont forget to check all cylinders.
Loosely tighten the heads to ensure barrels are fully home, remove and check gaps again.
Torque 1 head and remove and check again, then do the other. This just in case a barrel moves while turning the engine over
This may seem really overcautious but (IMHO) better to check several times rather than blow your engine up
Good luck
dave
Quote from: Tone on February 28, 2014, 06:11:07 PM
Yes sorry I was guesstimating 3mm but there was 2 x 1 mm shims under each barrel so I have 8 shims in total sorry for confusion I'm just stressed lol but I must admit the gap from piston top to top of barrel on 1300 was a massive 15mm
That needs invesigating. 15mm?
Quote from: parrothead on February 28, 2014, 06:38:14 PM
Quote from: Tone on February 28, 2014, 06:11:07 PM
Yes sorry I was guesstimating 3mm but there was 2 x 1 mm shims under each barrel so I have 8 shims in total sorry for confusion I'm just stressed lol but I must admit the gap from piston top to top of barrel on 1300 was a massive 15mm
That needs invesigating. 15mm? That would be a bent rod or 4 very unusual unless it has some incorrect pistons measure pin to piston top height and full length top to skirt.
Was this a 1200 engine that someone put 1300 barrels on and now it is not a case of the pistons hitting the top and locking it but the pistons fowling on the crank? It certainly needs the stroke measuring.
Rob
But he says the piston crowns are level with cyl tops, weird.
All sorted now mate came round measured 1300 like a tw.t I was looking at piston ring mark that showed 15mm ended up being 2mm so worked same with shims as 1641 is now thanks for all your help
Cool, well done!!!
Did you end up putting just one shim back under each cylinder or two?
Two piston ended up at 1.5 mm below barrel
Cool, good luck with the rest of the build!