Malossi BBK for People 50 2T

[chaz35]

Yes, I think balking is bad for engine, puts it under a lot of stress.  Good luck on your new BBK.  Cheers

[paceneedsstides]

25 miles on one hour heat cycle yesterday 40 miles on a lil bit over one hour heat cycle today but higher rpms. I also changed belt at same time and definitely notice the difference but now at 8K which is what I'm trying to stay at or under during break in at half throttle or under I'm running hot I did change jet to 94 and take off the dust/rain cover of open filter maybe tomorrow I will tryt o run with cover back on if thats not it will need to raise needle a notch. I am definitely loving the power and pull though ran so long on a damaged kit the new kit seems like a rocket.

[chaz35]

Yes, a worn out engine will run nice and cool.  Hope you don't have same issue as me, but mine is definitely a rocket when it's not too rich, but still gets hot.  Mine turned 10100 revs yesterday.

I am still messing with carb, seems to be very fine line between too rich and too lean, and several thousand different combinations to try.  Next I am going to try different throttle barrel, have 30 installed, and have 40 and 50 to try.  As I understand it, 40 will run a little leaner, and 50 leaner still 1/8 to 1/2 throttle.  I am going to try W7 needle too, and maybe W9 (don't have yet).

245luigi had link to cool 2 cycle tuning book and I read some of it.  One take away I got from book was you want to tune carb to be very close to being too rich.  Book encouraged me to keep trying with the carb, might eventually get it just right.  I got it pretty close with OEM carb, but didn't have different needles, etc to try.  Got real close with 19mm carb with AN nozzle, but then couldn't get the needle I wanted W16.  So I switched over the AU nozzle and had to start over.  Have learned a ton about Dellorto carbs, ask me anything, I can tell you lol's.

I have also been reading about squish.  Next, I am going to check squish in my engine, check combustion chamber cc's, and maybe try adding a cylinder base gasket.  I remember a kart engine I used to run Rotax FR125 that had different thichness cylinder base gaskets you could try.  Thinner gave more compression, more low to mid torque, thicker more top end power.  One thing I remember, engine with thinner base gasket had more compression and was harder to tune carb.  I think parallel to what I have now, too much compression, very hard to tune carb.  That engine was LC, I think AC harder to tune cause quicker to get too hot, LC can take more abuse.

I never actually worked on that engine, was before I started working on 4 cycle engines.  That engine made 28hp and if anything was wrong, it would blow for sure, so I was afraid to work on it.  Expensive too, $3000 for engine, $700 to rebuild, etc.

245luigi also linked ParaIndiana Like 50 BBK build, lots of good info, cool vid of him at the drag races with Like 50, looks like ran great.  But I will tell you, BBK tuned to run at drags would run too hot cruising 50mph on country road, I am prettty sure of that.

Cheers

[paceneedsstides]

yeah I talk with ParaIndiana all the time on Facebook he found me through my road rage news story on one of the pages I posted it to. I've got about 150 miles on new Kit so going harder with it I put dust cover back on air filter didn't make a difference with heat and the plug is definitely showing lean or hot so I changed 94 main for a 98 will be going for a ride in a sec to see how that does. Triesandluth is coming into town for 3 days and will have a loaner scooter for him and his gf from locals so we'll get some ride time in. I just talked with him about squish...I feel like the Malossi kit doesn't use it as it is an oring on head and a paper base gasket instead of the thicker and thinner metal base gaskets for other kits to change squish but then again I'm still learning bout these things. I also ported and polished exhaust port really good this time to help scavenge gasses and help to keep from 4 stroking from being rich and this time used a new metal and paper gasket and tyhe Malossi crush gasket on exhaust and I think it's sealed better than ever before for the moment. I'm also running pump zip tied to a lil past thre hash mark for stock oil and adding a tad to fuel to help rings seal better it smokes nice lol but seems to be working as this kit is definitely strong.

[chaz35]

Malossi has squish, just like others, 245luigi incorrect IMO.

O-ring head gasket makes it non-adjustable on head, unless you have head machined, which I probably wouldn't do.  I think o-ring head is pretty standard.  I think they use o-ring because probably required on LC heads, do AC the same way, so don't have to retool.   I looked some for flat head gasket that would fit, but didn't find anything.  I may check web for how to make one out of copper sheets, probably fairly easy to do, but maybe expensive after you buy the copper sheets, tools to cut it, etc.

I haven't measured squish yet, but will report back when I do.  I think fairly easy to measure, may do it tonight.  Earlier I didn't want to mess with it, but I am ready to look at now.  I am thinking I want the 20mm intake mainifold now, may help with temp?  At 1st I thought too expensive for what you get, but looking better to me now.  Did you know is Kymco part?, maybe can get cheaper somewhere else, racingplanet is not the cheapest place, but has a lot of cool stuff. 

Yesterday, I ran 84 main jet and was too rich, next I am trying 83.

I think best tuning tool is CHT we have been using.  A lot easier/ better than plug chops IMO.  If you read a lot of BBK kits install threads, they almost always will stick them at some point, and don't know what happened.  With CHT, you can at least monitor head temp and see if something is wrong.

I am getting close, mine keeps running better incrementally.  I keep coming up with new ideas to try.  A lot of work, but has been fun.  Cheers

[chaz35]

Tried 40 throttle barrel, appears to help a lot, leaned it out just enough.  I was for the 1st time cruising at approx 9000 rev's with CHT at good temp, 350 to 370F, amazing.  Carb specs: 83 main jet, 40 idle jet, throttle barrel 40, needle W9 set at 3rd notch down from the top.  Max CHT 415F, but was at very little throttle, going down slope.  Accelerating, or cruising under a load was good.  Maybe needs larger idle jet, might try 42 next.  Maybe need to change driving style and get out of gas all the way to reduce speed, engine doesn't like very little throttle position.

I did figure out the ring clatter sound, happens when engine is too hot.  For one tank of gas, I added an extra 1 oz oil, but really didn't make any difference.  I finally figured it out when I kept going to leaner jetting, and didn't have the noise, hear it when engine is really hot, rev's are high, but engine is under very little load.  I am running oil pump normal, and adding 2 oz oil per fillup, usually 1.3 gallons.  Based upon my records, I am burning approx 3 oz per gallon gas, or approx 43 to 1.

Tomorrow I plan to check squish.  Cheers

[chaz35]

I checked squish and came up with .060" or approx 1.5mm on both sides of the piston at the wrist pin.  That's pretty conservative IMO.  I have never seen the actual spec and don't know what it should be.

I do know if set-up for racing, it would probably be less.  I checked the Rotax Max FR125 I am familiar with and the spec is .9mm to 1.1mm for a racing engine, so 1.5mm is not totally out of the realm of possibility for a sport engine.  With 2 cylinder base gaskets, I could increase squish to .080" or approx 2mm, which I hope will keep the engine cooler.

I just got back from a long ride and ran great, but still gets too hot.  To keep engine cool, I have to run it too rich.  From time to time depending upon the slope of the road, wind direction/ speed, how long I have been cruising, etc the engine will get a little leaner and really take off and run like it's supposed to.  However, it will soon get too hot and I have to slow way down to cool it off.  If someone was riding my Super 9 LC with me, my People 50 2T with Malossi 70cc BBK would get left behind by a 49cc LC.  My Malossi BBK is definitely a jack rabbit, but has to take breaks from time to time, so where/ how I ride, it is coming in last.

I am tried of tuning the carb for now and ready to try something new.  Next, I will add the additional base gasket and see how that goes.

I have also been looking at Airsal 70cc Sport kit, which is advertised to run cooler, and may try one of those?  Cheers

[paceneedsstides]

Airsol is meant more for race or someone who will tear down engine more often and is only 1 ring design I have heard good things about the Athena/Stage 6 kit (Stage 6 is a repackaged Athena) and the Polini Corsa kit. I am almost where I want to be I thin I'll drop jet tomorrow to 96 and possibly play with needle afterwards if needed but she's flying good now and only getting hot when it starts missing cuz of too rich and 4 stroking because

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[chaz35]

I pulled cylinder tonight and added another cylinder base gasket.  Exhaust, cylinder looked really good, color dark approx 1" into header, then turns nice light color, no carbon.  Piston has some blow by from the balking I would imagine, but otherwise looks OK.  No rough spots on cylinder or piston best I could tell.  Would be easy to hone cylinder and change rings, but I just want to add a gasket and do my test.

One thing I have often wondered about, if my engine shroud is complete, maybe why I am running hot?  I'll take a pic tomorrow and post.  It has open area on carb side approx 1" wide and 3 or 4" long to let air out I assume, or maybe I am missing a piece that's supposed to be there, I don't know?

I rode maybe 2 hours, 40 miles or so, was hottest time of day, over 100F today, so good test for my engine overheating.  High temp 407F, max rev's 9950.  Was fun, except when had to slow for hot engine, can be dangerous in traffic, so I don't like it.  This thing is amazing when it hits the just right spot and takes off, very smooth and powerful.  Seems really strange my main jet is so small, I was too rich with 83 main jet.

Will do my 2 cylinder base gasket test tomorrow, and report back.  Cheers

This is Airsal BBK I was thinking about:    http://scootertuning.ca/en/cylinders/73003-cylinder-airsal-sport-70cc-kymco.html

[chaz35]

I added 2nd cylinder base gasket, put all back together and went for long ride, very hot day, over 100F.  Made fairly significant difference, ran a lot better and cooler.  I can tell carb needs some more tuning now, too lean low end, too rich top end.  Maybe need to replace plug, so will install new NGK BR9HS for next ride.

Piston in the hole approx .020", recessed lip on combustion chamber for squish approx .020" and cylinder base gasket approx .020" equals .060" squish I previously measured.  I added another gasket, so now squish should be approx .080" or 2mm.  I am thinking now would run better with larger combustion chamber, but don't want to increase squish anymore, 2mm probably too much as it is.  Will be looking for someone with lathe who knows something about cutting head for 2 cycle engine.

People 50 2T definitely faster than Super 9 LC now, except can still get too hot.  Now, appears only does it when very little throttle.  Engine seems to have nice powerband starting approx 8500 to 9000 revs, makes a lot of heat in this range with very little throttle, but runs cools if under load and lots of throttle.  If additional gasket didn't make difference, I was going to maybe check for air leak next, but don't think has air leak.

I am happy, feel like made a lot of progress, but still some to go.  I can tell this engine has some more speed, just need to keep tweaking.  Cheers

1st pic is blower housing, does cut out area look OK?



2nd pic is head, some carbon on exhaust port side.



3rd pic is piston, I guess doesn't look great, but engine has good compression.



4th pic is inside cylinder exhaust port side, showing some wear, but no deep scratches, looks OK to me, engine has had lots of abuse, and approx 2000 miles.

[chaz35]

I did some reading on 49ccscootproboards, a great info resource.  I found 2mm squish probably pretty good, maybe even go to 3 base gaskets, and ring chatter I am hearing is probably detonation.  I also think my Malossi BBK is running fantastic compared with others, maybe I have been too critical, expecting too much from it.

Now, I wonder if balking I am getting at WOT is really pre-ignition, and not rich condition?  I changed to new plug and seemed to help with balking some.  However, was cooler time of day so probably not the plug, probably cooler air temp that helped?

I was looking at Airsal 49cc kit too.  Looks pretty cool, has huge exhaust ports with bridge in the middle.  Some say it runs like 70cc kit, but didn't see builds, costs same as 70cc kit, so not many willing to try it.  I will probably order Airsal gasket set to try, has 2 base gaskets and 1 head gasket I could probably use to adjust squish on my Malossi BBK.  Cheers

[paceneedsstides]

Hey do you still have that Malossi Final Gear set?

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[paceneedsstides]

This is how yesterday went for me

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[chaz35]

What happened?, looks like shaft broke at clutch?  Is that OEM Kymco part or Malossi?  As I recall, final drive kit replaces shaft the clutch is mounted to.

Sorry, I haven't looked at my Super 9 LC to see if either of my final drives work on it or not.  Maybe will soon, I need to replace rear tire on one, would be a good time to check.  I need to keep my final drives until I can figure out what I have.  All I know, they don't work on my People 50 2T.  I will probably get rid of my People at some point, and only have S9's going forward.  Cheers

[paceneedsstides]

Yeah going WOT in 4 lane traffic needle buried hit a bump and snap. Well I guess I'll have to pay full price for it then they're aren't as cheap as they used to be

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