Rebuilding a Peewee 50 engine

[86mud]

Hi All

I am going to have a crack at rebuilding my sons Peewee 50 engine. I purchased the bike last Christmas off ebay and it has horrible piston slap and is down on power. I cleaned out the carby and that made a bit of difference, but I think the rings are stuffed. Also, where the exhaust bolts onto the block is cracked, so I can never tighten up the exhaust and therefore it is noisy.

Any tricks to rebuilding a small 2 stroke engine? I have ordered a new block, head, piston, rings, head gasket, studs etc..comes in a complete kit.

Cheers
Andrew

[460cixy]

No tricks very straight forward if it's a two banger just check and make sure there's no play in the big end or gugion they can die in this area

[91ramjet]

Hi there

When removing and replacing main bearings a trick i use is to have new bearings in the freezer and to heat up crankcase in oven then its just a matter of dropping bearings in to their housing. works a treat and wont distort bearings in anyway.

[Tank]

Hi All

I am going to have a crack at rebuilding my sons Peewee 50 engine. I purchased the bike last Christmas off ebay and it has horrible piston slap and is down on power. I cleaned out the carby and that made a bit of difference, but I think the rings are stuffed. Also, where the exhaust bolts onto the block is cracked, so I can never tighten up the exhaust and therefore it is noisy.

Any tricks to rebuilding a small 2 stroke engine? I have ordered a new block, head, piston, rings, head gasket, studs etc..comes in a complete kit.

Cheers
Andrew
It is general practice when rebuilding an engine is to check the piston ring gap before fitting to piston, if applicable here.
Place a compression ring in the bore about halfway down and square ring in bore (with piston) and measure the gap in the ring with a feeler guage, any gap is better than NO gap, check that the gap is within manufacturers specs. and repeat for other rings (if any), as a rough guide 0.005" (5 thou)/1" (25.4mm) of bore size, Regards Frank.

[85 county]

is nthis a real pee wee or a chinese thing?
if its a chinese thing just get a new motor of flea bay

ring Gap is very important, also it will have a locating pin on the piston which located on the ring gap, note one side or end of the rings will have a step.

botom end you shoulint need to tuch as a rule only if its been run with out oil in which case it would have meleted the piston to the bore first.

the bolting of the chamber to the baral is a big deal, could or probably will be losing a lot of power there

[isuzurover]

Paging Uninformed and Rick 130...

Uninformed is the guru of small 2st (chainsaw) engine rebuilds. He can get your 50cc engine producing more power than a 125 :D

[LandyAndy]

There is a puoduct that you coat the underside of the piston and the crankcase to increase the comp ratio;);););)
Unsure of the name of it,it decrases the volume of the crankcase incraesing the comp ratio.
Andrew

[d2dave]

It is general practice when rebuilding an engine is to check the piston ring gap before fitting to piston, if applicable here.
Place a compression ring in the bore about halfway down and square ring in bore (with piston) and measure the gap in the ring with a feeler guage, any gap is better than NO gap, check that the gap is within manufacturers specs. and repeat for other rings (if any), as a rough guide 0.005" (5 thou)/1" (25.4mm) of bore size, Regards Frank.

I was taught for ring gap .003 thou per inch of bore.

[jakeslouw]

is nthis a real pee wee or a chinese thing?
if its a chinese thing just get a new motor of flea bay

ring Gap is very important, also it will have a locating pin on the piston which located on the ring gap, note one side or end of the rings will have a step.

botom end you shoulint need to tuch as a rule only if its been run with out oil in which case it would have meleted the piston to the bore first.

the bolting of the chamber to the baral is a big deal, could or probably will be losing a lot of power there

I agree. You shouldn't have to touch the bottom end on the PeeWee.

In all my days I only had to do a bottom end once, and that was an IT175 that was comprehensively raped and heat-seized.
Once you have the head and barrel off, you can measure the big-end play by eyeball. Also just check the play on the flywheel / magneto side of the crank as that side runs dry and will have the most play of the two crank bearings.

Splitting the casings is quite an exercise that I wouldn't do without a comprehensive manual, if I was a first timer.

[Tank]

I was taught for ring gap .003 thou per inch of bore.
Different teachers, regards Frank.

[85 county]

I agree. You shouldn't have to touch the bottom end on the PeeWee.

In all my days I only had to do a bottom end once, and that was an IT175 that was comprehensively raped and heat-seized.
Once you have the head and barrel off, you can measure the big-end play by eyeball. Also just check the play on the flywheel / magneto side of the crank as that side runs dry and will have the most play of the two crank bearings.

Splitting the casings is quite an exercise that I wouldn't do without a comprehensive manual, if I was a first timer.

what he said, doint over think it, thay are basic motors with few rules. much easyer than a 4, but what rules there are are inportaint, like ring gap and location the pin in the pistion bore pistion sizes is also important.

doint muck about filling the pistion , it is good at speeing up the gas to the chamber but there isw a down side to this, real 70s thinking and not the sort of thing for a kids bike. a larg amout of the 2 strokes power comes from the chamber so geting this mouted hard to the barrel is important.