Malossi BBK for People 50 2T

[chaz35]

I feel like carb a little too lean less throttle and too rich lots of throttle.  So, I changed idle jet from 40 to 42, turned out the mixture adjustment screw 1/2 turn to 2 turns out, and went for long ride.  Definitely helped some, spot where engine wants to race at approx 8500 to 9000 revs and get too hot cleared up, ran cooler, high temp for ride 394F.  Engine was pretty happy to cruise at approx 7800 to 8200 revs, could do that all day now.

Since I now recognize detonation and apparently pre-ignition, I am wondering if main jet is rich?  I already associated detonation with too much heat.  Was surprising that have detonation when you reduce throttle.  I always thought it happened when engine was under a load, so learned something new.  Will have to do some more testing, but I am starting to notice doesn't have pre-ignition unless engine maybe hotter than 370, then it will balk if go WOT for long.  pace has described the same symptom, engine balks at WOT, and we thought engine was too rich.  I not so sure now.  I think cooler plug helped, so that indicates pre-ignition to me.

I may try larger main jet, but 1st I'll try larger idle jet, the next size is 45 as I recall.  I have them all from 35 to 48, and ordered 50 and 52.  I also ordered nozzle AU264, and needle W3 to try.  So I will have nozzles AU260, 262, and 264, and needles W3, W6, W7, W9, and  W16.  Needles W3 and W9 appear to be the best needles, have the same taper length.  W3 shaft diameter is a little smaller than W9.  So, I can try W3 and W9 with different nozzles and maybe get better results?  Needle W9 and nozzle AU262 is leaner than W3 and nozzle AU262, but W3 with nozzle AU260 compared with W9 with nozzle AU262 I don't know?

Another goal is to get engine to rev better, seems to labor at higher revs.  My Super 9 LC loves to rev, I want BBK to run same way.  Maybe getting close to time to try new Tecnigas Trek pipe.  Cheers

[chaz35]

Larger idle jet went the wrong way, ran too rich most of the time, generally ran cooler, high temp 392F.   Did show some flashes of brilliance between needle and main jet throttle positions, so I know there is serious HP in there.

Don't really have anything else to try until get some more carb parts in.  I may add another base gasket, still seems like too much compression.  2 most helpful changes have been cooler plug and 2nd cylinder base gasket.  Until then, tuning carb was hopeless IMO, it was too lean and too hot, or too rich and 4 cycles, no in between.  Another base gasket (3 total) may be the trick.  Cheers

[paceneedsstides]

just bought Stage 6 upgear kit hope that will lower my rpms no need to go WOT much I may try your plug theory out not gonna mess with gasket though

[chaz35]

Yes, the up gear is critical IMO.  Otherwise, you have tons of power, but can't shift out of 1st gear lols.  My Super 9 LC (after I did the CVT mods tha gives a little more top speed) is geared perfect for 49cc IMO, but would definitely need up gear with BBK.

I take it you didn't have up gear before, and this is 1st one?  Looking forward to your report.  As I recall, you will lose some low end acceleration, but should be able to compensate for that with CVT mods.

While I am waiting for more carb parts, think I will try 50 throttle barrel, should lean it out a little up to 1/2 throttle.  May also lower needle 1 notch from 3 down to 2 down.

Actually, People 50 2T is running pretty well.  Yesterday, I passed a couple of Harleys and they didn't go around me again until we hit a long straight, then they blew by me going maybe 70mph in 50mph zone, it was fun.

The other cool aspect with the base gaskets is you maybe can get more duration/ ports open longer.  I am new to all that, and definitely not ready to start grinding on the ports, but additional base gaskets may be a good mod for other reasons too.  What you are looking for is to have piston even with bottom of ports at BDC, which gives maximum duration/ time ports are open.  I think normally, piston is just a little above bottom of ports at BDC.  I will check mine and report back.  Cheers

[chaz35]

Changed throttle barrel to 50 from 40 and dropped needle to 2nd notch down from 3rd nothch down.  Both adjustments should have leaned it out a little.  I took for ride, and ran great, probably best it has ever run.  However, got too hot as usual, so returned pretty quick.  Took out my Super 9 LC for nice 2 hour ride, ran like a champ.

Next, will add another base gasket (3 total) and test.  I have had this engine apart so many times, I can add a base gasket pretty quick, not a big deal.  I did some more reading on 49ccscootproboards and appears I am going in the right direction, we will see.  Cheers

[chaz35]

Haven't changed anything, been reading a lot on 49ccscootproboards.  In "2 Stroke Performance" section, I started on last page 59, and went forward, up to page 10 or so now.  Read any threads that looked interesting, including words like:  set squish, tuning Dellorto, running hot, sticking, Airsal BBK, Malossi BBK, any Kymco 49cc scooter BBK install, BBK kit comparisons, 1 ring piston vs 2 ring piston, etc.  Take aways:  (1) my scooter is running pretty normal, probably just needs more narrow needle at this point, (2) Airsal BBK is cool, but not as forgiving as Malossi BBK, (4) common problem for engine to run lean with very little throttle and high revs (like going downhill), (6) I know when I have detonation and pre-ignition, (7) I know how to check squish, (eight) I know how to check port timing, (9) Dellorto 19mm probably best carb for what I am trying to do.

I was very temped to order Airsal BBK, probably will get one at some point.  I finally decided my Malossi is probably the best BBK for me, at this time.  Airsal makes several different kits with T6 being the racing kit.  I would not want the T6 kit for street riding, would get Sport kit.  Airsal Sport should make significant more HP over Malossi, but apparently doesn't like a lot of abuse like my Malossi has been getting.  Probably would have trashed several Airsal Sport kits by now.  After I get my Malossi BBK tuned better, maybe time for Airsal kit later.  I really like the Airsal kit:  (1) alum cylinder, maybe runs cooler? (2) single ring piston, revs higher, less friction/ maybe runs cooler too (3) comes with 2 base gaskets to adjust squish, (4) has head gasket instead of o-ring, I think head gasket is better for AC engine, and (5) low cost.

The Malossi's BBK strong points IMO:  very nice quality kit, makes good HP and torque, should last long time (cast iron cylinder and 2 rings), it's very durable, can take a lot of abuse and keep going.

I got my Eurocarb order, came in no problems, can recommend this Dellorto vender for any parts you can't get from Treatland.  I am waiting for more carb parts to come in from Treatland, then will try W3 needle and different nozzles.  I also ordered a couple of Airsal gaskets kits that include base gaskets and head gasket.  Probably won't add another base gasket until I test some more on carb, maybe add a head gasket from Airsal gasket kit to decrease compression, and may retard timing.

I think can retard timing a touch and help it run cooler and probably rev better.  Trade off is less low end torque.  I know how to tune the CVT, so I am not concerned about low end torque.  Kymco service manual says timing not adjustable, but I bet it is.  You have to take out the key, turn the flywheel the right direction (can be confusing, if go the wrong way you advance timing), torque flywheel back on in retarded position without key (probably need to lap the taper with grinding compound), and you are good to go.  Cheers

[paceneedsstides]

Getting way too into it for me lol my Stage 6 gears will be here Thursday the guy threw in a 20mm ported Kymco intake manifold to provide more flow from the carb. I was running pretty good when the shaft snapped 94 main and up around 50 at all times. Only time it would get warm is when it would start the hesitation then it would get up in 380s or higher at WOT. If I can cure the hesitation then maybe I can cure any overheating issues.

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[chaz35]

Will be interesting how your 20mm intake works.  I think about getting one, but haven't pulled the trigger yet.  Did you ever look at my pic of blower housing?  Does yours have rectangular opening like mine?  I might tape it off and go for a run, see it makes a difference.

I plan to get Malossi air filter, I guess you got yours from scooterpartsco?  Cheers

[paceneedsstides]

I got my filter from treatland I wanted the crhome cover and scooterpartsco didn't have it. as for the blower housing yeah mine has that also I don't think it affects much and atleast on mine. Like I said my overheating issues occurs with the hesitation other than then it runs cool and fast.

[chaz35]

I did some more reading regarding 2 cycle engines running at low throttle, like cruising/ or coasting down a hill.  Overheating in these conditions is a known problem.  Too much heat can build for 2 reasons:  (1) engine getting very little oil with low throttle position, and (2) engine runs leaner in these conditions.  I even saw explanations for why 2T engine runs hotter in a lean condition.  Apparently fuel burns slower in lean condition, so hot gases can linger longer and over heat engine.

OEM 2T engines generally don't have this issue, they are detuned compared to sport or racing engines, so generally don't generate too much heat.  LC engines are better able to cope with heat than AC engines.  Racing engines don't cruise/ coast down hills, so don't generally have this issue.  Sport tune engines ridden on the street can definitely have problems.

Apparently, you can't fix the problem with carb jetting alone, and that has been my experience.  The cure?, retard timing, lower compression.  It's a compromise to still have some performance gain, but be able to ride without overheating.  I won't have head gaskets to install for awhile, so I may work on retarding timing today.

I will proably try more oil too, maybe a better oil?  I have oil pump connected like normal (using approx 1 oz per gallon with BBK), and was adding approx 1.5 oz per gallon at fillup, so approx 2.5 oz per gallon or 50 to 1.  I am going to try adding 2.5 oz per gallon at fillup,  approx 3.5 oz per gallon total with oil pump.  Will see if that makes any difference.  Cheers

[paceneedsstides]

Just zip tie your pump open like I did if you're worried about oil in low throttle and no throttle spots because the more oil you add to tank the leaner your fuel will be.

[chaz35]

Hello pace, thanks for checking your blower housing, eliminates that issue.  Good suggestion to zip tie oil pump open.  My speedo recently went out, so I can't check oil consumption, or I would try it.  Will have to wait until I get speedo fixed.

I did retard timing approx 3 degrees, and went on long ride today, 100F+, was very hot, but tolerable on scooter moving through the air.  Retarded timing seems to help some, but still needs some work.  I lost a little low end torque, but appears didn't loose any HP once revs get up to 7000 revs or so.  This thing has some really nice HP from time to time when it's happy.

Seemed to rev up better in 9000 range, seems to labor less.  Still getting hot, but improving incrementally.  Most of the time, ran around 350F, would cool down fast, if stopped.  Cruising, would slowly creap up to over 400F, but now would actually cool down, if I ran it WOT, so I thought getting close on carb.  There are only a few long runs where it gives up at the end and starts acting up with pre-ignition.  Detonation a lot less now, not much an issue any more.  The critical CHT reading seems to be approx 370F, when it get there I know it's going to balk/ have pre-ignition.

When treatland order comes in, can try W3 needle, may be the trick?, or 264 nozzle?, I don't know.  Cheers

[paceneedsstides]

They fit. . .
Stock. . .
Vrs Stage 6 . . .

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[chaz35]

I got in carb parts, what to try?, thinner W3 needle or larger 264 nozzle?  So, !st I changed AU262 nozzle to 264 and went for long ride.

Made fairly substantial difference.  Rode for nearly 4 hours, burned almost 5 gallons of gas, was fun.  Never had to back-off to cool engine.  High temp 397F, max revs 10080.  No balking/ pre-ignition, very little detonation.  Carb still not perfect, I think engine still needs a little more detuning.  Had good acceleration from stop, would cruise nice, but would lean out a little, make more HP and revs would climb.  Then could give it a little more throttle, would get richer again and settle back down.  So, doesn't just cruise steady, have to vary throttle slightly as you go.

Carb set-up:  idle jet 50, needle W9, nozzle AU264, main jet 83, throttle barrel 50.  I think I will change throttle barrel to 40 and try, should make up to 1/2 throttle a little richer.  When Airsal gasket kit comes in, will try head gasket to lower compression.

I have been reading Two Stroke Tuner's Handbook, by Gordon Jennings http://www.amrca.com/tech/tuners.pdf.  A lot is over my head, but does have some very good info, helps to understand how 2T engine works.  Definitely describes issues I have been having with carb.  Also, makes it pretty clear can set up engines differently for different uses, like drag racing compared to roadracing. 

Roadracing set-up is what I want.  I think Malossi kit comes set-up more for drag racing, that's why getting too hot when I go out for long ride, high speed cruising.  Cheers

[paceneedsstides]

Good info I may try that nozzle I got on the road again yesterday my CVT definitely has to be retuned for Stage 6 gears never got past 8700 rpm but needle is buried slightly after 8K. She ran warm but not hot. Will try lighter rollers but will probably also need lighter rear spring. I have been wondering if the problem at WOT is from an air leak the o ring head gasket to me seems the weak link on the Malossi BBK. That or maybe the oil pump as alot of people in 49cc has suggested doing the delete as it it a trouble spot for air leaks.

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