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piston/head rebuild questions
Posted: Thu Apr 17, 2008 8:31 pm
by po89mm
howdy all,
i purchased a 86 spree (completely disassembled) with the head removed and the piston replaced. However the head was never bolted back on.
Im currently im in the process of putting it all back together with some additional parts i purchased in the lot.
But long story short is there anything i should know before i slap the head, gaskets, etc etc, on the block? Is it permissible just to take engine parts off another bike and just slap them together on another bike, or will there be custom fitting required?
im no mechanic so bear with me
Posted: Thu Apr 17, 2008 11:18 pm
by 85inwhite
You need a new head gasket. no way around that. The head bolts I believe torque to 7-9 foot pounds. you need to torque them properly too. dont over torque or under torque them.
also dowload a copy of the manual in the tech links here, its a life saver.
as far as parts inner changability. has the piston been run before or was it put in there and left? you need to make sure if the piston was put in that the cylinder walls were also addressed. The old piston may have scored the walls or done damage to the cylinder walls, if that is the case these must be corrected or the new piston will be shot quick.
The old piston and the cylinder was "mated" over time, so any imperfections were on both parts at the same spots. Its tough to explain. The new piston being true and hopefully not damaged should fit into the cylinder with no issues. However if the cylidner walls were damaged, it will be like putting a square peg into a round hole.
A lot of the other parts should transfer over, But things like gaskets, dont try to re use them if they are used.
What parts are you specifically looking to swap over. that would help out.
Posted: Fri Apr 18, 2008 1:39 am
by po89mm
forgive me im still learning the correct termonology..
the new piston was installed (with rings) and just alone with no cylinder jug around it. The replacement piston looks NIB and unfired , the part im looking to swap over is a used, but undamaged cylinder jug.
Posted: Fri Apr 18, 2008 10:04 am
by chevyguyjay
there shouldnt be a problem at all. just a couple of things to check and look for. make sure the piston is put on correctly, and not on backwards. make sure both wrist pin clips are in. make sure your piston rings are put on correctly, and not upside down. and, make sure u put the head on correctly. any one of these not done correctly, will result in a seized, or blown up engine. 
Posted: Fri Apr 18, 2008 4:48 pm
by Kenny_McCormic
does the jug have any scoring(black streaks)? if it even has a little have it honed, also while you have the head off have .020" shaved off at a machine shop, it will help performance.
Posted: Fri Apr 18, 2008 4:50 pm
by jstone
Was the scooter sitting for a long time without the jug on it?
Posted: Sat Apr 19, 2008 11:47 pm
by po89mm
i snapped a few pics for you guys, the registration tags expired in 1989 if thats an indication, i say its highly likely that the scooter has been sitting idle for a while.
piston in block
close up of side view
top view of piston
top view of jug i want to use
jug turned 180*
Posted: Sat Apr 19, 2008 11:53 pm
by po89mm
ok based closer inspection id say the piston isnt NIB
and that long * threaded rod you see is just to gauge how things fit up
Posted: Sat Apr 19, 2008 11:54 pm
by chevyguyjay
dont look to bad. give the cylinder a quick hone, and throw on some new piston rings. 