2 stroke engine, help needed

[bawjaws]

yesterday on the ped disaster struck!, 60mph a big crunch and some grinding noises then the engine died, siezed, ive got the engine out today and all stripped, this is what happened:

pic 1+2 show the state of the piston, gudgeon pin clip somehow found its way out, snapped the piston rings and destroyed the whole top end

pic 3+4 show the flywheel end and the output end with everything removed, the problem is that i cant get the two casings apart, and i dont want to whack it with a hammer because its likely to break the cast, is there a special trick to doing this? or can anybody suggest if theres anything still in the way of it being taken off?

pic 5 shows the join with silicon stuff all the way round could it be this hats causing all the fuss?

all help welcome

 

[MrFluffy]

Firstly, 9 times out of 10, when you cant get crankcase halves to seperate, you've missed a fastener holding them together somewhere. Manufacturers do put them in daft places occasionally, so its worth triple checking...
Also, you can seperate crankcase halves by gently tapping near the joint to work it free. If you know where the locating spigots are in the cases, this is where it will be stuck. Gently tap around the spigot areas...
DO NOT try to get anything in the gap, most 2 strokes use crankcase primary compression and if you mark the surface it wont seal and will run like crap.
For drifting on the end of the crank, put the associated nut on the end so you don't damage the thread accidentally. If you look at the crank ends, they are centre drilled. You can usually rig up a puller (pusher) to push into the crank end via these, some of the manufacturers tools are this.
For the siliconed up joint, yes if its caused a air leak which has let the motor run lean with a excess of air...

 

[bawjaws]

wow that was quick! im absolutely sure that every bolt has been removed, when i was talking about the silicone i was asking if this is giving it a really strong bond and thats why its not coming off, or should it rip off easy?

im off to have another quick bash (possibly with a hammer)

 

[aero]

Heat the cases at the bearing journal and then you can lift the case off with the bearing on the crank.

it will be a bit of a fight still, but much easier then doing it cold.

Same when putting it back together, or you will get the crank out of alignment.


(ex motorcycle mechanic)

 

[oddball90]

Used to put bottom end's in a bucket of very hot water, then tap the end of the crank with a soft hammer. With the nut 0n the threads to protect the end of the crank. After splitting the cases the crank needs to be checked for trueness if you are not changing the big end.

 

[aero]

Normal blow lamp is usually enough.


be careful about bashing the crank as it is pressed together. hit it wrongand you will put it out. easy enough to sort though. Big copper hammer, vee blocks and a DTI.

 

[bawjaws]

For drifting on the end of the crank, put the associated nut on the end so you don't damage the thread accidentally

this method worked thanks, isnt the hammer the best invention of all time! "if your in doubt give it a clout"

theirs little metal fragments lying about everywhere, luckily the havnt been driven into the crank or the case though, the bearing and seals look ok too, it could have been worse so im quite lucky over that and that the back wheel didnt lockup at 60mph! the joys of belt drive and a centrifugal clutch!
its a good learning experience anyway, and arent 2 strokes soo simple? its just the way the manufacturers put them together thats a pain in the ar5e!

ill jetwash it all the soak the stuff in wd40 for a day or so until i get a replacement piston/barrel, thinking about a 70cc kit

 

[oddball90]

Wash the crank in petrol atleast cause the big end is usually a needle roller bearing, so will be full of all that crap, (spin the crank in a container of petrol) have got away with doing this without splitting the crank but it might be better to split the crank and replace the big end.

 

[gavuk]

If you have the funds available and are going big bore ,should look at racing crank as well ,because you have got the engine stripped right down

 

[bawjaws]

well, i dont even have enough money for the piston/barrel yet so i dont think ill get the race crank, i fitted a 70cc kit to my old scooter (same model) with all standard parts in it and it makes a whole world of difference in performance, and the guy i sold it to revs the baws off it, but mind you, it wouldbe nippy if i done all the work then the crank goes

ill see what i can sell

 

[madkayaker]

you only need one kidney

 

[bawjaws]

hehe yeah, and why do i need 2 ears?

 

[simon718]

having 2 lungs is over-rated as well

 

[madkayaker]

and two testicles

 

[simon718]

think i'd draw the line there mk

 

[madkayaker]

well there is the small matter of ten toes!

 

[simon718]

yeah, only really need your big ones dont ya

 

[madkayaker]

i star the bidding at £0.50

 

[simon718]

didnt really know there was a market for used toes mk, you misplaced one of yours? or do you just fancy a new mantlepiece ornament

 

[madkayaker]

some thing to hit students with on the end of a string