ARG, wrist pin pullers?

[Mr. Peanut]

http://www.dreamgate.ne.jp/NSR/technical/mc28topend_rebuild.html

Can someone please explain the process of removing the top end in english? any tips would be appreciated. Im going to rebuild my NSR250 engine. :D

[Ixion]

The article seems quite self explanatory? Are you confused by the term "wrist pin"? It is what the Yanks call a gudgeon pin. They have this thing about not calling stuff by its proper name. Like their spelling.

Normally the gudgeon pin pushes out quite freely in a circlip located gudgeon. At most a gentle tapping, or gentle warming of the piston. The article specified that the engine being worked upon had seized and jammed the gudgeon.

It seems a nice simple motor. Basically pull of in the way stuff, remove cylinder head bolts , cylinder head, remove cylinder retaining nuts, remove cylinder. Flick out one of the circlips (don't drop the bastard into the crankcase!), push out the gudgeon pin.If it does need a press tool, you can make one, or buy them cheaply from (I guess) Repco or Supercheap. All standard two smoker top end stuff.

Reverse the proccess for reassembly, usual two smoker warnings about ring pegging etc.

It's all in the (very well written) article.

[Motu]

The Yanks call it a wrist pin,proper English word is gudgeon pin.I've never used a gudgeon pin puller in my life,even tight ones can be knocked out with care.When fitting the piston,heat it up with hot water and the pin will slip in - when I was working on trucks we would put all the pistons in the shower upside down and turn it on hot,and fit them one by one,don't worry about the water,it'll evaporate with the heat.You can heat the rings to make them less brittle too - I used to know a proffessional engine builder who kept a table lamp with no shade on his bench,he put the rings on the hot bulb before fitting to the pistons....different sized bulbs to match piston size.

That looks like a good article,easy to follow - good luck....

[Mr. Peanut]

:first: Thanks for the help, not confused anymore :rockon:

[Paul in NZ]

If you do 'tap' them out, make sure you support the piston / rod with one had against the hammer blows (taps). Obviously, you don't want to be whacking the piston and rod sideways.

Some old crappers I've had needed a puller but we always made them up as described with a length of threaded rod (or long bolt) and bit's of pipe etc. Simple and easy way to get them out.

Don't rush it....

[Mr. Peanut]

I think what ill try and achieve is a zen like state of ultimate patience and infinite organisation. Thus leaving nothing for fate to latch on to :yes:

If it doesn't budge ill go have a cup of tea, think about it then try again :rockon: (NSR engines don't exist anymore :bye: )

[F5 Dave]

Good luck that the powervalves haven’t rattled their way through the exhaust ports. I imagine that a few of the top replating companies will be able to repair most damage like cracks around ports etc if it is a bit sad.

Don’t be afraid to give the piston a decent (takes a while) warm with the fan heater if it is reluctant, but the pins should be easy to remove. Whent eh barrels don't want to come off a few gentle taps with rubber mallet or plastic faced hammer in the upwards direction. Then check for the last bolts holding it on. . .Like the PV connections etc

[Mr. Peanut]

Oh my engine isn't broke, I just want to freshen it up while i've got the money :D

This is one reason why the NSR250 is the best of the two-stroke race reps. It uses reed valves, it does have an exhaust valve but I can't see how that could interfere with the exhaust port.

[F5 Dave]

Erm, not sure of your reasoning, the last real 2 stroke (bar aprillia GP bikes) to use anything OTHER than reed valves was the KR250 (like the 1st tandem twin) or the RG500, both of the mid 80s.

Don't get me wrong I love 2 strokes, but at this age most have had or are having powervalve problems. If yours is low mileage then just make sure you inspect it well & replace parts if they are sloppy or stripped. Rebuiding before the break is a sensible thing to do, this should save you grief.

[Mr. Peanut]

Oh dear, I need a new crank. You're right I was confused, the NSR just has a superior powervalve system which wont fall into the cyclinders when it wears. :rockon: