Two stroke rebuild! (bottom end)

[mr jamez]

Started yesterday, all I need to do now is get the fly wheel off and I will be ready to seperate the crank cases.

At this point the only damaged part is the left centre crank case, not sure what I will find once I get them open. I have a spare one, but the engine has done a lot of miles and I bet the bearings are fairly worn, so a good opportunity to do a rebuild.

Now, the manual states that a puller is not needed for the cases unless they are really hard to get apart. I am thinking a rubber/plastic mallet along with heat will do it. Or if I can get a universal tool cheap then that is cool any tips?

Also from reading various articles the right case slips off the crank and leaves the gearbox in one piece, the next step is to seperate the crank from the left hand case, can this be done without a hydraulic press?

As for bearings, I read that you can put the crankcase halves in the oven and the bearings will drop out/be easy to push out. When it comes to installing, heating the case and freezing the bearings will be the best way to get them in, can I use sockets on the outer race to help drive them in? not sure about the crankshaft bearings though.

Not too sure what bearings/seals need to be replaced really

The honda manual also states that there is a tool for putting the halves back together? If I really do have to buy all these tools, then a replacement engine will be a hell of a lot cheaper.

A brief guide would be good, I could probably do a small write up or something for future referance?

Oh and one a side note, how was she running? when it comes to putting it back in how the hell do you tell which way it goes round, the markings are gone and I was too stupid to take not There seems to be some brown stains down the side also (shiny bit is where I rubbed it with my finger). It is fully run in and was going really well

https://img200.echo.cx/img200/1595/rebuild28qn.jpg

[J.K.R]

On the two smoke bottom ends ive done (cagiva wmx 250 multiple times, honda cr125 and 250, loads of others), just a bit of faffing about, make sure youve taken all the screws out tap the cases with a mallet to ease them apart, usually crank either comes out one side or the other, and may come from both if your lucky! and yes putting the cases in an oven to take them out but you can get them out normally (sometimes) its better to put the new bearings in the freezer as saves tapping them. Be careful of what youre doing (make sure the gearbox doesnt fall out ) Never used a tool for putting the cases together just line everything up.

best tip : take your time!
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www.oldskoolsuzuki.info

[J.K.R]

Keep rubbing over the piston (its just carbon build up) and all of your marks should reappear with the arrow pointing towards the exhaust port (front of the engine) and std or the oversize number (say 0.25 etc)

hth
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www.oldskoolsuzuki.info

[mr jamez]

Cheers. Just got to wait till my mum goes out now so I can use her oven

Looking forward to getting started now

[swampy]

The easy way to tell if you are putting the piston on the right way round is to see where the locating pegs for the rings are. These are nearly always on the carb side of the piston (because the rings never make it as far as the inlet port, and therefore cannot snag on it). This is definitely the case on the NSR (I know 'cos I've just rebuilt the top end on mine )

HTH
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"I hate to advocate drugs, alcohol, violence or insanity to anyone, but they've always worked for me." Hunter S Thompson
"Faster, faster, faster, until the thrill of speed overcomes the fear of death..." Hunter S Thompson

[stinkwheel]

I usually use a big socket on the outer race of a bearing to drive them in, either that or use the old bearing as a drift. The heat/cold thing works well.

Slowly, gentle tapping with a good nylon/hide hammer, plenty of tea breaks. Draw pictures. Draw on parts with marker pen to show orientation.

If a bit is solid, find that hidden bolt!

I like to draw an outline of the various bits of the bike (eg crankcases) on a sheet of wood then drill holes where the bolts came from. This means I can put the bolts in the holes as I remove them. Similar thing with nuts using panel pins. Makes reassembly a doddle compared to throwing everything in a box, keep the boards for if you ever have to do it again.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[mr jamez]

I started yesterday, I had to drop the engines round to MTC on friday to get the flywheels off, I think they must have found the puller at the end of a rainbow or something because I'll be damned if I could, cost me a tenner for both so to MTC.

Engine is now in bits, am in the process of cleaning it all up, will probably take a few pics.

One of the main bearings seems to be shagged, rough as a badgers arse. The engine was rattling so perhaps that was the cause, I just thought it sounded like that.

One question, where do I get the crank rebuilt? one of the main bearings needs to be removed and I might as well get a new big end put on. Is this something any engineering place could do or am I going to have to send it off?

[cagiva gezzer]

Just sent mine off to stan stephens and its £25 plus VAT + parts.

PJ engineering also does it, so does SEP.
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"because one stroke isnt enough and four strokes waste two"

[mr jamez]

Will get it sent off to stan stephens soon then.

Another question ( )

How do I draw the crankshaft through the bearings? because from taking it apart I can see the crank is wedged on there pretty firmly. I guess if I had a collar or something then used the thread on the end of the crank to pull it through Only part I am wondering about really as I have all the rest figured out.

/secretly glad about the engine destroying itself

[cagiva gezzer]

Stanstephens are on their summer holidays now / soon, so if you're in a hurry you might be better trying elsewhere.

Bottom end reassembly. I'm putting mine together using the oven and the freezer. Putting the crank and mains in the freezer and the cases in the oven at (someone else will say) degrees. The heat expands the bearing seats and the main bearings (slightly smaller due to being cold) just fall straight in. Put the cases and bearings back in the oven then drop the crank into one bearing, then place the case onto the other end of the crank. Couple of taps of the ends of the crank and its sorted.

That method works on cagiva / derbi engines, however honda might need special puller tools like rotax engines as mentioned here.
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"because one stroke isnt enough and four strokes waste two"