Stripping down the B1 Rep Engine

Hello

On Sat the 20th at Mt Wellington my bike just stopped. At first I thought it was the coil... then upon inspection I found that somehow the crank got bent?? no idea how.. Anyway, I have photos of the stripping down of the engine all accept for the flywheel :) I did that another day before I got the bright idea of taking photos for everyone else's amusement :)


Disclaimer : I have
never rebuilt a 2 stroke engine before, Infact it makes me quite a n00b. But hopefully I can help those more n00bish then I am :)

Removing the clutch

As you can see here the nut held up a mighty protest!, My first attempt was the impact wrench well hehe.. that just rounded the nut in 1 second. (A real nut is on back order). Note : Make sure you cover your intake port so no metal objects get inside.

Not giving too much care for the already bent crank the chissle came out :), I had to be carefull not to damage the housing. I also was planning on replacing the bearings also so no real loss there. Anyways, After some wacking and some grinding I was able to split the nut and unscrew it. I made a hell of a mess of the crank but thats ok.. as long as it could get past the bearings no the way out I did not care... I left the keys on also as a place to store them :)

Removing the barrel from the crank case

It may pay to apply some penitration oil like umm crc to the top and backside of the bolts that hold this on. Also note it is full of locktite in the threads. Be very carefull when removing the bolts. Applying a small amount of heat helps, be carefull not to apply too much uneven heat or burn up the gasket, OR ignite the resident fumes in the engine :) For example.. I used a pentorch to heat up the nut. Work the nuts out 1/4 of a turn out then 1/2 in. This is so any of the crank thread does not ball up and strip out the casing. Be sure to clean this all out before you put it all back togeather... tapping it out will clean it :)

You can see the underside of the bolt here. Spray some CRC up it :)

Poor mans allen key rench, does the trick :)

If you have gotten this far.. I am not going to bother explaining how to remove the reed block or anything like that :) But basicly now you are starting to begin to take out all bolts that hold the crank togeather.

It is not nessasary but you might want to remove the nut and pully from the pump at this stage so you can just slide the whole pump and impella out once the crank case is apart.

So why was my crank bent ?

Perhaps this is a clue :)

What I have discovered...

This is what was left oft he bearing in the piston :) It has seen better days. (And no I did not hit it with a hammer it was just that bad!) :)

For the most part the broken bits had just been spat out the exhaust but one chip had come off and scored the bore and piston, and also imbedded itself into the head.

Whilst I still could dress up the bore and head, I am not going to for this engine. It will become my spare motor. I have already got parts on order, I will most likely not acually end up using them streight away but I have fairly much decided to buy a whole new motor and swap over the clutch. That way I fix quite a few problems!. Also the motors come with a radiator, They are good for spare, And also a tail pipe :) Around $300 bucks they are. Quite expensive at this time of year. Also either way I would have been looking at a running in period for this bike even if I was to rebuild it. So it fairly much has killed some performance for this year from a bike that was doing easy 3rds last year (Different rider) and was quite happy to pass people on the streights.

This is what one looks like in bits!

Bashing out the bearings

Make sure you have a level and soft service for the crank to sit flush and flat on. There is a locator stub on one side of the crank case, drill a little recess for that to sit into on the wood. Lucky for me I just had to flick out a knot in the wood that was about the same size :)

Find yourself something that will locate itself into the bearing, You want to bash them out very squarely as to not damage the housing.

Flick out those crank seals first! Flick them out from the inside, do not lever against the crank casing when doing it or damaging any surfaces the seal comes in contact with. This is your fuel mixture we are messing with here :) Important! hehe we want all the crank seal we can get.

This is from the flywheel side, the other bearing is a bit more obvious.

Replace that water pump seal while you are at it too! Splitting the crank case open to replace the seal = money spent on more gaskets to seal it back up :)

See you all at Taumranui 2009 :)