Malossi BBK for People 50 2T

[chaz35]

Blufx, below is link to Malossi piston at Scooterpartsco, supposted to fit the Malossi BBK for Kymco AC engines like People 50 2T Malossi pn 319987

https://scooterpartsco.com/malossi/malossi-master-part-list/malossi-piston-47mm

https://scooterpartsco.com/kymco-people-parts/kymco-people-50-2t/malossi-70cc-big-bore-kit-for-kymco-people-cobra-2t?zenid=visrslv6qikmjgj4icidn2hif2

[blufx]

Blufx, below is link to Malossi piston at Scooterpartsco, supposed to fit the Malossi BBK for Kymco AC engines like People 50 2T Malossi pn 319987

Thanks for the links, chaz but neither of pics show the port side of the piston. Malossi says that piston comes in 8 different sizes, but offers  no info on the sizes. I can guess the last two are  .4 and .8mm over size, but don't have a clue on the others. Meanwhile, the d_ckhead I ordered mine from is jerking me around. Presumably because I pointed out his was a d_ickhead.  LOL    One more day and it gets here.

[blufx]

OK. One more time. I finally got the correct piston today. I have the oil injector disconnected and plenty of pre-mixed gas  I'm putting in the fattest main jet I have while breaking in the rings. Wish me luck.

[mclark999]

Good luck

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[chaz35]

I gave up on my dellortodirect order, 30 days and nothing.  I sent them 2 requests for status on my order, no reply.  I notified paypal I want my $'s back.  I don't have the W17 needle I wanted to try with the AN bushing and atomizer.

So, what to do, guess it's time to install the AU bushing and atomizer which I got from treatland.  After some research and thinking about it for long time, I popped the bushing out using a 6mm bolt lightly screwed into the bushing.  The 6mm bolt threads were a little diff, so I didn't torque it much, just enough to take out the slack.   With the top off the carb, carb body facing down, and a light tap on the bolt head, the bushing popped out easy, no damage to the bushing or atomizer (in case I want to use it again).

I installed the AU bushing with the open side facing the engine.  I tapped it into the hole with 7mm socket, and pulled it snug by tightening the atomizer.  Swapping out the AN bushing for AU bushing turned out to be easy, but initially was scary, so I put it off for long time.

I verified Malossi 19mm carb has 4g float, 105 main jet, 38 idle jet, 50 starter jet, 30 barrel, AU bushing, 262 atomizer, and W6 needle.  I put it all back together, and was too rich.  pace already said it was going to be too rich, so I wasn't surprised.  I just wanted to see for myself.  Tomorrow I will try some leaner jets.

Also, I think I figured out can try different size atomizers in addition to trying different needles.  Instead of getting longer/ narrower W17 needle, can try larger atomizer  So, my plan if W6 needle is still to lean mid range with the AU bushing and atomizer installed, I will try 264 atomizer vs 262.  Cheers

[chaz35]

Carb now way too rich.  I installed my smallest main jet 96, changed needle to leaner W16, set 2nd notch from the top, and still way too rich, but idles nice with 35 idle jet.

I am going to order following:  main jets 94,92,90,88,86, W9 needle, and AU 260 atomizer.  pace, what do you think?  Cheers

[paceneedsstides]

need a W7 or W9 needle set 2nd from top a 38 idle jet and a 88-92 main jet. I'm running a 96 main on mine but it's rich and I got the opem Malossi PHBG filter from treatland.tv on there.

[chaz35]

pace, thanks Buddy.  I think will get W7 and W9 needles.  Will order tonight, treatland has fast service, very reasonable shipping rates, so I should have soon.  Cheers

[chaz35]

Got in some more carb parts and did some more testing, bad news, same issue.

This engine overheats even when so rich it cuts out.  The final carb settings were W9 needle, 3rd notch down, 86 main jet, 40 idle jet, AU 262 atomizer and bushing.  I have also started adding 3oz oil when I fill-up with gasoline and still have the oil pump connected.    I am pretty sure it's not the carb.  Have been racking my brain for solution.  I did some reading, was seriously thinking about lowering compression to detune engine (raising cylinder with extra base gasket(s), and/ or enlarging combustion chamber).

Was also thinking about running hotter plug to deal with plug fouling.  Then I saw a couple of posts where guys use cooler plug for 70cc BBKs.  Josh/ Areomyst at ScooterInvasion recommends NGK BR9HS for 70cc kits, and I have very high regard for him.  Guy on that forum was having similar overheating issues and cooler plug solved it for him, amazing.  Maybe I have pre-ignition and never realized it?  I have never had problem with pre ignition before, so I don't have a feel for it, but my symptoms seem like that's what it could be.  Pre ignition would definitely cause high temps.

I have been using the standard NGK BR8HSA, and maybe all I need is NGK BR9HS?

So, I ordered some NGK BR9HS plugs and will wait until they come in.  Good chance this will fix my problem, I am hopeful.  Cheers

[paceneedsstides]

bro you are running lean if you are adding 3 OZ in gas tank and an 86 main jet. when you premix you got to factor that in as it leans your gas try a 90 I know you're in TX and all but you shouldn't be having that much trouble dialing it in. with a 96 main on mine and an open filter on there not premixing just relying on the pump I barely ever get to 350 here running around in 90+ weather at WOT all the time.

[chaz35]

hello pace, what plug you running?

[chaz35]

Hopefully, cooler sparkplug will be the answer, should have some by middle next week, have to be patient.  I am really enjoying my S9 LC, running very well.

I did see where one post stated many engine builders detune these engines.  Based upon my experience, I can see why.    Meanwhile, I did some checking on effect of adding an additional cylinder base gasket to decrease compression ratio, which should help engine run cooler.

The base gasket is approx .020" thick or approx .5mm.  The Malossi BBK is approx 72cc, combustion chamber is approx 6cc, so compression ratio is approx 12 to 1.  I measured the combustion chamber volume with burette tube accurate to .01cc and came in pretty close to 6cc.  The OEM compression ratio is 10.3 to 1 +/- .02.

I computed the cylinder volume of 47ml bore and .5mm stroke (diameter of BBK piston and thickness of additional cylinder base gasket) and came to approx .9cc additional combustion chamber volume.  72cc/ 6.9cc equals compression ratio of approx 10.4 to 1, or approx stock compression.

So, it appears I could add 1 additional cylinder base gasket and decrease compression ratio to approx stock.  I am not a mechanists, so if you see any erroneous assumptions, please let me know.  If cooler sparkplug doesn't work, I will probably add 1 additional cylinder base gasket.  Cheers

[paceneedsstides]

lol you're way over my head with all that I'm a put it in it runs better take it out it runs worse type guy lol. I'm running the 8 at one point was thinking bout running a 7 plug but never did I just blew my kit again with 5K miles on it but I got about 3K miles more than I thought I would out of it. I had oil pump cable snap one night at WOT 9600RPM and screaming down a hill and the engine siezed hard ever since then it had been running good but noticeably not as strong or fast so I knew I had damaged it. Was hoping to make it through the summer but oh well I will tear it apart today to check but I believe it just gave up the ghost slowly yesterday but not catastophic like last time so should be just an easy swap out. Plug looked good and just a tad rich when I pulled it lol.

[chaz35]

Sorry to hear, but I must admit Malossi BBK can take a lot of abuse and keep running.  I love the power, am pretty close to getting it perfect, just not there yet.  I also really like the Malossi 19mm Dellorto kit, very tempted to buy another one, try on 49cc S9.

Thanks for plug info.  I was leaning for hotter plug (7) until I saw a couple of posts suggesting cooler (9), so I will try that.  My NGK BR8HSA plug looked good too, maybe a little rich.  If this thing runs better with cooler plug, it will be amazing lol's.  Cheers

[paceneedsstides]

I would get the 21mm Dellorto carb kit if I had to do it again in fact once all is said and done I will most likely get a 21mm dellorto or clone. pulled engine out of scoot and yeah talk about thermal meltdown lol will post pics later.