Malossi BBK for People 50 2T

[chaz35]

Yes, I am glad I tried my 1st BBK on the People 50 rather than Super 9.  When I do Super 9, will have some experience, should get better results.  Cheers

[chaz35]

I pulled the crank seals and that was a job, stressed me out, looked like I was going to ruin something for sure.  I didn't know what I was doing, but had idea to drill small hole in seal, screw in a wood screw, and pull it out with screw anchored into the seal.  Execution was sloppy, but was good idea and worked very well after some miss-steps. 

I had trouble drilling the hole, drill bit wasn't long enough to clear the crank, and then the screws I used weren't long enough to get leverage on the head to lift them.  I used some safety wire to wrap around the screw head, the anchored the other end of the safety wire to a lever and the seal pooped out easy, it was great.  Next time, I will use a micro drill mandrel to extend the drill bit, should go better next time.

I messed up the seal pocket and crank journal just a little and need to dress it with some wet/ dry sand paper.  I plan to wrap the sand paper around end of electrical conduit to get into the pocket so I can dress up the scratched areas.  Would be easier if case was split, but too much trouble to split case just to clean up the scratched areas a little.

Bearings were probably OK, but there was some bad stuff in there.  I will do one more cleaning with the water hose and compressed air, then start putting it all back together.  Fortunately, having some nice weather, so if I can get some time could have it running soon.  Cheers

[chaz35]

Cylinder very difficult to get clean, I realized now what a bad job of cleaning I did the 1st time, my bad.  I think bore is pretty easy to clean, but the ports which have a rough casting surface still have some bad stuff in there.  I ordered nice spirel wire brush to clean out ports before I put it back together.  Looking good, I think it's going to run well.  Cheers

http://www.amazon.com/gp/product/B004FTPR32?psc=1&redirect=true&ref_=od_aui_detailpages00

[chaz35]

I got in spiral wire brush and worked very well, cleaned out a lot of grime.  I wore out the 1/4" brush and ordered 2 more 1/4" and 1/2" to clean out exhaust port.  This engine is getting really clean, should not have any issues with it being dirty this time.  Maybe bore a little loose now, but looks fantastic, ports appear to be properly chamfered, and nice cross hatching.  I measured new rings, piston in bore right side up and upside down like I read to do somewhere and still pretty close to specs I originally measured when I 1st got the kit.  It seemed a little loose then, so is even more loose now.

Hold up now is 7mm-1.0 tap to chase the cylinder bolts holes.  They are a little messed up, and just wanted to clean them up a little before putting it back together.  I didn't measure and assumed they were 8mm, was surprised 7mm, so had to order again, so waiting now.

Also ordered Malossi final gear kit and got it in.  I have kit for Super 9 too (Malossi 6711802) and received the Malossi 6711055 for the People 50 2T.  The round gear appears to be the same for both kits, but the shafts are different.  I hope they fit.  I plan to install after I get the BBK running right, think it will add approx 5mph top end, I am thinking this puppy may cruise at over 60mph, we will see.  Will be hassle to find shop to press the gears.  Cheers

[chaz35]

Another catastrophic failure, discouraging, but oh well.

I got it all back together well enough, actually I am getting good at taking Kymco People 50 scooters apart.  Was a little hard to start, so I put some oil/ gas mix down the spark plug hole and it started right up.  Made some ugly sounds for just a second, then settled down, maybe rings a little loud, I don't know.  Hindsight, I should have pulled the cylinder to see if OK.  I let it idle for awhile a couple of times, seemed OK, so I took it for an easy test run.  Was running well, and then something let go, I thought it was the rod, the way it sounded.  It coasted for a ways making a clanking sound until the clutch disengaged.  Engine turned over easy, no compression.  I was 3 miles from home and walked it back, a pain.

Best I can tell, piston failed at exhaust port side.  I guess too much trauma from the 1st mess-up, plus I was maybe too rough on the ring lands cleaning off the carbon?  At 1st when I saw the piston, I thought was lean condition, but I couldn't find any air leaks, carb was jetted rich at 45 slow, 108 main jets, and appeared to be working OK.  Just shortly before failing, I could tell the idle was stepping up, and bogged a little before it failed, but I don't think it was lean.  After 1st failure, I thought piston was OK, cleaned it up, and installed new rings.  I could tell it had good compression from kick starting, it ran crisp, felt great, was going to be really good, but not to be.

Here's a pic of Malossi BBK piston, after it failed.



My plan is to put it back the way it originally was, and see how it runs.  I am afraid to try another BBK with this engine without a fresh crankshaft and rod assembly.  Cheers

[BettinANDlosing]

Interesting, a blown piston like that usually comes from wayyyyyyyy too advanced ignition timing. Did you get the key in where the flywheel mates with the crank? Could have fell out and you had mystery timing.

[chaz35]

Thanks for reply.  As I recall, woodruff key was stuck in keyway and I used pliers to remove it, so don't think timing was off.  I used kick starter to start engine and was easy to start.

[Stig / Major Tom]

Thanks for reply.  As I recall, woodruff key was stuck in keyway and I used pliers to remove it, so don't think timing was off.  I used kick starter to start engine and was easy to start.

Chaz, I know this is no help to your project - but wanted to give you a big thanks for sharing your experiences with us as you work through this hop-up kit.
Your descriptions of how you are going about things - including sharing the mistakes you made - is going to be really helpful to those following behind you.
FYI- this is fascinating stuff to read - though I'd never dare try anything like this due to my limited mechanical skills!
Good luck - hang in there - we're pulling for you!
Think I'll go change the oil in my Burgman....since it's blowing & practically snowing outside. When I can't ride - I want to wrench on a scooter - somewhere simple!
Stig

[chaz35]

Hello Stig, thanks for kind words.  Happy New Year to all!

[Triesandluth]

I definitely agree with @bettinandlosing, looks a lot like some wicked predetonation.  And really off timing would be a first guess. 
I've been really reading up on how may variables affect our little engines,  I think that too high of compression can also cause predetonation.  Just a bit from Graham Bell 's book on 2 stroke tuning.  A very good read,  but beware, it could put you into areas of modifications that you never dreamed of!

[chaz35]

Only thing is, engine wasn't under load, was just loafing along.  I think it was too much rod side play.  I am afraid to assemble engine, think will get bad outcome again.  So, I am going all out to fix this puppy, have ordered case splitting tool, new crank assembly, and new BBK.

I am going to fix it or bust trying.  Cheers

[Triesandluth]

Can't give up on it! Keep trying!

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[chaz35]

Got in cool crankcase splitter tool today and split the case.  Wasn't too bad, had right tool for the job.  Got crankshaft out without  the bearings, the bearings stayed in the case halves.  I think the bearing on one side was supposed to stay on the crankshaft, but didn't, shouldn't be an issue though.  I think the new crankshaft is without bearings.  The crankcase had no gasket which is what I expected.  I plan to use Hondabond or Yamabond when I put it back together.

The bearing on one side is binding, apparently has some debris from the piston failure.  The other bearing looks great, which is amazing after all the trauma.  These bearings look huge, this engine is really built, but bearings are not the best quality.  The other bearing I will work on a little and see if I can get it to loosen up, or will replace it.  If I need to take it out, I will heat the case and the bearing should drop out.  I have Ford mechanic friend and that's what he says to do.  There are lots of youtube vids showing guys using barbecue grills, kitchen stoves, propane torches, hot plates, etc to remove bearings from cases, if you need instructions lols.

Waiting on crankshaft now.  When that comes in will be time to start putting it back together, unless I have to order some more parts.  The crankshaft has a tight interference fit into the bearings, and I plan to loosen it by sanding down the crank journals.  It's a common technique to loosen up the crankshaft in the bearings in racing engines to lessen any binding, which reduces friction, and makes more HP.  You just put the crankshaft in a vice to hold it, cut a strip of maybe 1500 grit sandpaper approx 1/2" x 11" and wrap it around the crank journal.  Apply a little oil and work it back and forth to take off just enough OD so it slips into the bearing ID, not loose, but not tight either.  No guarantees, but that's what I plan to do.

That's all for now.  Cheers

[Triesandluth]

I've heard of the sanding too,more of a polishing ,  and a bit of a certain lock tight.  Can't remember,  606 maybe?
If you can find the bearings easily you might sound just replace them so you know everything is brand spanking new,  no room for failure.  When I do mine I'm going to try the freezer and heat gun combo. 
Would you mind taking some pictures of all of that,  especially by the reed block hole?  Maybe with the intake and reed block mocked up in there? I'm trying to decide if a small reed block spacer would be beneficial to reduce any air flow interference.  Some bikes they produce deeper than necessary. 
Also,  what kind of crank did you get? Just a stock replacement,  or something better?

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[paceneedsstides]

Tries is gonna scoot down to Charlotte and help me out when its time to do my Malossi BBK.........he doesn't know that yet though......