Engine rebuild

DieselTech

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I'm curious? Are you using this engine on a bicycle? Or you building it for a vintage moped? Also is the Laura M48 a belt drive engine. Thanks.
 

heyhi

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It's a batavus hs50. The moped is around 40 years old or so. It was given to me from a family friend and it's been sitting there for years in good shape. I got it running, drove it around for a few weeks but it was pretty slow like very slow. Kind of turned into a little hobby. Since I'm going to be replacing the crank seals and bearings I figured I would get some more speed out of it. Hence the big bore kit. https://www.treatland.tv/ProductDet...XSprune7DD44jE8SWR749EhIJaCQFRdwaAibGEALw_wcB

It is a belt drive engine which I'm also going to replace the driven sprocket from 13-11 tooth. Get a little more low end
 

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DieselTech

Well-Known Member
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It's a batavus hs50. The moped is around 40 years old or so. It was given to me from a family friend and it's been sitting there for years in good shape. I got it running, drove it around for a few weeks but it was pretty slow like very slow. Kind of turned into a little hobby. Since I'm going to be replacing the crank seals and bearings I figured I would get some more speed out of it. Hence the big bore kit. https://www.treatland.tv/ProductDet...XSprune7DD44jE8SWR749EhIJaCQFRdwaAibGEALw_wcB

It is a belt drive engine which I'm also going to replace the driven sprocket from 13-11 tooth. Get a little more low end
Slick old ride there!!! Thanks for sharing some pics.
 

DieselTech

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Bad thing about using a stone on aluminum is, it will clog up rendering stone unusable. You would be better off with a double cut straight burr bit.
 

heyhi

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Back at it again. I found a machine shop literally 100 feet from my house that I didn't know was there. He's going to bore the case out.
Ended up buying a used crankcase for pretty cheap. My old case has screwed up stud threads that I pretty much made 100,000 times worse so I'm not going to be using that.

20221025_220249.jpg
Split the case, threw it in the oven and got it nice and hot and tapped it with a mallet and it opened up pretty easy.
When I open the case I found some scoring inside.

Should I go over this with some sandpaper?


The other question I have is how do I prep The mating surfaces so when I put everything together with the gasket it's not going to leak.

Is there any prepping I have to do before dropping the new seals and bearings

I plan on doing a leak down test, and taking some Port measurements just for the hell of it before I throw everything together. I'll keep you guys updated hopefully you can guide me through some of the stuff. I have a open thread on moped army but I'm pretty much not getting any help or suggestions there
 

heyhi

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Is there any prep work that has to be done to the mating surfaces where the gasket goes
 

weefek

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Is there any prep work that has to be done to the mating surfaces where the gasket goes
also more pictures will help. i have a good feeling most of us aren't familiar with this engine. take pics of both sides of the case. sometimes the case can be decked other times it can't be , depending.

like @Wrench said make sure the surfaces are clean. the bit of scoring or weirdness within the chamber itself doesn't mean much and I wouldn't worry about it. More than likely it's casting defects, which affect pretty much every one here. They're from China, there's a reason they are cheap. On my new replacement engine i ground as much of it as i could down but it probably doesn't amount to much.

Check the bearings both crank bearings and clutch bearings. I've had them be bad from the factory before. It's worth checking.
 

weefek

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Of course, clean it up, make sure all the old gasket material is removed,
maybe im alone here but i add a tiny amount of black rtv liquid gasket to all the seals such as these. also to the intake. i decked the intake port and also to the intake 'manifold' and just added a tiny bit of it to there and haven't had a problem. if it's an issue for other people please chime in.

I'm not using an intake gasket i just put a minute (VERY SMALL) amount of black rtv on the mated surfaces
 
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