palezu's Benelli 49: to the unknown and beyond

[palezu]

Hello everyone. I haven't posted on this forum a lot but some of you might remember me. I decided to post my build here since it seems to me that here are many people who are interested in technical modding of 2-stroke scooters. On a Finnish forum where I also have a thread about this build, the people are mainly interested about external looks modding and not very much about the engine, so I thought I would get more interest from here.

On to the build:

It's a Benelli Quattronove 49 scooter, equipped with the popular 1E40QMB engine. My plan is, shortly spoken:

-make it go as fast as possible with the least amount of money
-try to make it go 100kph (about 62mph) with 50cc cylinder, and in acceleration it must outrun my friends 110cc 4-stroke pitbike (should be quite easy as it's a very low state of tune chinese engine )
-with 70cc cylinder the goal is at least 110kph (about 68mph) and in acceleration it must wheelie easily
-I make pipes myself and try to keep the stock air cooling, at some point I might convert it to LC, however.

As the project goes on, it might turn out that the goals are way too much, but we'll see

My inspiration to these crazy plans comes from some of my countrymen who have achieved 63 mph with an aircooled suzuki 50cc moped engine and 75 mph with the same engine but with a 75cc cylinder.

So here are some pics:

Here is the thing as it came to me



The power machine, quite dirty



Mileage was about 11 500km (7000 miles)



Fairings ditched, also try to remove all unnecessary things. Notice this model has a middle-frame fuel tank, thus it has a vacuum fuel pump to move the fuel to the carb. The previous owner said that the scooter had been stolen from him but he got it back, but the thieves had broken most of the fairings and they also broke the fuel tank cap, which is quite annoying.



Oil pump was leaking but I would have removed it anyway





Made a simple "crankshaft-out-pusher" to save the crank and cases from hammer marks





The pistonrings had snapped and piston seized. I found a couple of possible causes for that: carburetor needle clip was detached so it was probably quite lean, there was a small hole in the airbox which had been tried to cover with ductape and finally the oilpump also leaked. Dunno which of these caused it after all.



Cylinder looked quite bad but useable after honing. There is a scratch above one transfer port though which is bad, but should not be too bad.



Got the engine atomized and cleaned all parts



Did a portmap of the stock 50cc cylinder. It looks it has some potential, the transfers are quite tall and will have 132 degrees of duration if the cylinder is raised couple of mm's with a base spacer, to make the ports open fully. Without a spacer it will be quite mild, having about 165/112 durations.



Played a bit with a program called "Portmap Analyzer". Cylinder raised to 173/120 durations, the program says that transfers should breath well in as high as 13000rpm, and exhaust port would be good at 10000. These seem a bit over-estimated but you never know.. Exhaust port requires raising to make blowdown time-area good and make it play well with the transfers.



Used a poor mans hone to hone the cylinder ( 220 grit wet sand paper with a bit of oil ) and it started to look a little better. Also chamfered the exhaust port edges, they were really sharp as stock.



Couple of days later got enough money to buy parts. Visited local moped parts store with my friend, it rained and was quite a storm and we went with our mopeds (my road use scooter is a Keeway F-act by the way). The ride really sucked but I got my parts and some holy drink which keeps going



Piston is the cheapest I could find, it's a "Step Two" piston for a Piaggio scooter, but will fit to this with minor modification (needs only shortening of both skirts). In the Finnish scooter forum there was a huge doubt that the piston will fail instantly. These "Step Two" pistons have very bad reputation around here, but personally I think that the fault is 90% of the time not in the piston, but in the user. Lean carburetor settings, too little oil and sloppy installation always make it fail. I'm pretty sure it will last long enough if I don't make a stupid mistake.



Bearings are NTN, surprisingly they were with C4-type radial clearance although they should have been C3. C3 is good for stock engines which don't heat the bearings much. C4 has more radial clearance to cope with more rpm and temperature. I don't think C4 bearings are necessary in this project but doesn't hurt.



I had a small problem before I could rebuild the engine. The other bearing was stuck in the crank and I didn't have a puller. I was in a hurry so I did a bad thing, broke out the angle grinder and ground the bearing off. I tried to be as careful as possible but accident was inevitable and I hit the crank axle with the grinder. That's not so bad as long as you don't hit the crank oil seal sealing surface. Fortunately I didn't hit it but it was really close: (the rightmost blueish line is the oil seal sealing point)



It does not cause problems but was a stupid mistake and pisses me off Better use a puller next time

Piaggio and stock 1E40QMB piston comparison:



Shortened both skirts about 4mm and intake side skirt another 4mm to lose some weight. Did a groove for the boost transfer and rounded all edges. Rounding the edges is also a very good trick to make these cheap pistons last better.



Got the bearings installed using hot and cold method. (vari side failed, had to hammer the bearing in )



After a long sweaty time got the bottom end together. Cases are badly mismatched to the cylinder but will take care of that later.



Used 2 base gaskets. Deck height was about 0,5mm and timings ridiculous 168/113. Mild at first.



Head will be in stock form at first. Did not measure the compression ratio but will do that later when I lower the head.



Got the thing to roll and put my self made exhaust on (isn't it pretty )



A bad running video without drive belt in place: (way too much oil in the fuel and sputtering a bit due to broken spark plug cap)



Got it moving eventually but did not pull well full throttle. Sputtered and sounded like it was lean and too rich at the same time. Tried smaller main jet but no help. Replaced spark plug cap and it worked.

For some reason the pipe does not fit perfectly to this scooter. It goes too close the fan shrouds so it's impossible to put the shrouds in place, have to weld the pipe a bit. I made the pipe to my Keeway scooter and it fits it without any problem although the engine is same, only cylinder is different (a TNT 50cc cyl in the keeway).

Rode it a bit to get the carb and vari dialed in a bit and decided to move on in the tuning. Pulled the top end and piston was still fine although I ran it without the fan shrouds in place. Took pictures for my country mates who were sure that the piston will seize within first 5 kilometers of riding. At this point the piston has not seen probably even 2 kilometers though but it didn't look too bad. Only on the exhaust side the rings looked a bit worn but that might be because of the old seizure mark in the cylinder above the ex port which might make the lubrication worse on that area. I think I should get the cylinder honed properly.





On to tuning, made a base plate from 1mm aluminium



Deck height about 1,5mm and timings 171/121, still not very much but I proceed gradually.

Put it together and tested. Acceleration was noticeably better but still not very amazing. CVT spring heat fade problem is huge, but have not done much tuning yet. Tested top speed which was mind blowing 69 kph (42 mph) which is ridiculously little. Still did not have the fan shrouds in place. Did not seize but cylinder was hot as a grill. Not very smart I will check the piston tomorrow if it now has some bad marks. If it doesn't, I guess I can say the Step Two piston is good enough.

The front vari pulley is badly worn and belt is worn too. I have to buy a better variator and a new belt. I think if it already had those parts, it would have gone about 46 mph but still not very much.

I don't have a tacho but it sounded like about 9000rpm at top speed. Need to make it rev more to break even 85 kph (53 mph). I might need a better pipe, the current pipe is very thin and shallow cones which is good for broad torque curve but not very powerful and high revving. Before making a new pipe I will raise the exhaust port to about 182 degrees and lower the head quite a bit to have some kind of compression.

Also these Euro models usually have restricted CDI units which are limited to about 10000rpm. This one has a strange DC CDI which I have not seen before. Also has a different 8-pole stator which is probably a DC model for DC CDI. I don't know if this version has limiter or not. I planned to buy a "racing cdi" from ebay which should be unrestricted, but I'm a bit afraid it does not work on this because this has different stator..

Also these models have a bit short about 13:1 (if I remember right) final drive ratio which might also cause some headache..

We'll see where this goes. Hope to receive some comments.

[90GTVert]

Great post/thread. Once you start really getting into it, you should consider upgrading the crank. Stock cranks aren't good much past 10,000RPM for extended use. Those deep gears prob won't serve you well later. They may be an advantage for now though.

Apr 20, 2013 17:33:04 GMT -5 palezu said:

in acceleration it must outrun my friends 110cc 4-stroke pitbike (should be quite easy as it's a very low state of tune chinese engine )

I have had a few of those. When compression was increased they really woke up. If you start beating your friend so bad that it's getting boring to race, then tell him this. lol

[teddy554]

Nice work cant wait for more

[palezu]

Got something done today. Checked the piston from yesterdays abuse but it looked still fine, except on the exhaust side a scratch was developing worse.



Cylinder doesn't look too good too



The old seizure mark above the exhaust port probably caused the scratch in the piston. I sanded the cylinder again, this time little more thoroughly. Still couldn't get rid of the seizure mark, I guess I have to live with that or get the cylinder bored over, or buy 70cc straight away.. :D

Then I changed the dampening wool from the silencer. Old wool was quite oily.



It made the sound of the exhaust a little bit smaller, but now I really started to notice how loud the air filter is. I think I have forgotten to mention, carb setup is stock 16mm "Leader" and legendary "Pipercross" open air filter.



It's so annoyingly loud that I thought about putting the stock air box on, but there is a small crack in it, and I also would have to readjust the jetting, so I left the open filter on. By the way now it has a 105 main jet and needle clip at the richest position.

I'm wondering if the e-choke works or not. When the engine is stone cold, it doesn't start until I spray some brakecleaner into the air filter, and I have to keep spraying for some time before the engine warms up and stays running on its own fuel. So that kinda tells that the choke is stuck in the off position. But it seems that it sputters on half throttle when cold but when the engine is warmed it doesn't so that tells the opposite that the e-choke might be working. Also the choke thing warms up significantly when the scooter is running.

I had planned to lower the head next and even got it done. First I drilled some holes to remove material faster and also the holes serve as a guide for grinding.



Next I took the "part-destroyer" angle grinder and ground the head to about right spec



Then sanded it flat with wet sand paper on a flat surface. Turned out decent



Volume was 3,2cc. With the volume between the piston dome and cylinder deck and piston dome displacement taken into the calculation, uncorrected compression ratio seemed to be about 13,3:1. I guess that's about good for the current pipe as it doesn't produce a whole lot of back pressure (at least I think so).

Fired it up and immediately could notice better throttle response. On the other hand, it seems that now the idle mixture went rich because it won't start without pulling on the throttle at the same time and mixture screw seems to work best at the leanest position. Some time ago I lowered my Keeway's head too and it has the same problem. Stock idle jet was 22.5, tried 17.5 but still too rich. I haven't bought more jets because they are too friggin expensive, 8 euros a piece

Takeoff felt little better, it felt it had more torque. But once it got moving it felt that the rollers are now too light. It seemed to rev above powerband and acceleration was worse. I think it might be because the powerband is now moved to lower revs, or the power difference has somehow affected the variator settings. I have to try a bit heavier rollers..

Next I prob should buy some carbide cutters for my dremel from ebay so I can start porting (ruining) the cylinder. Also should weld the pipe to a different position to be able to put the fan shrouds on before I overheat and seize it. I also thought that I could make a new pipe straight away and use the header from the current pipe but currently I don't have any sheet steel, should get that somewhere..

[190mech]

Are you riding it without a fan and cooling shroud?
I have built many pipes from old washing machines,etc!

[aznatama]

Palezu, nice!! I have a 2008 x49, and so does another member here. We both have 70cc kits on ours though, so I'm wondering why not get a 70cc kit?

I'll be following this, since I like how you removed some weight off the cylinder. I'm wondering how much this would affect things, and how much can be safely taken off.

For the exhasust seize marking, is the stock cylinder steel? if so, did you make sure all the aluminum was removed by using a chemical dip? I've been reading about using NaOH to remove aluminum and carbon from iron parts.

Lastly, are you keeping stock gauges? have you looked at the newer x49 digital guage w/ tach? I wonder if you know how that cluster works and if it's easy to swap into our model x49's.

[palezu]

I will get a 70cc kit at some point, but first I want to see how much power I can push out of the stock 50cc. Of course would be easier to buy a 70cc kit straight away to get more power more easily but I like challenges and it's kinda cool to test how fast you can go with the "legal" stock cylinder.

You mean I removed weight off the cylinder head, not the cylinder? I haven't probably removed even a gram worth of metal from the cylinder..yet

Lowering the cylinder head, thus raising the compression ratio, has many good advantages. It rises engine thermal efficiency(lowers consumption), rises power and especially bottom end torque.

You calculate compression ratio by measuring the volume above the piston when it is at TDC. That is your combustion chamber volume. Then calculate cylinder volume + comb chamber volume and divide by comb chamber volume and you get your compression ratio. That is the uncorrected compression ratio. Corrected compression ratio is calculated by using only the volume above exhaust port as the cylinder volume. I use uncorrected compression ratio, because exhaust pipe back pressure and couple of other things affect cylinder pressure so corrected ratio doesn't tell very much because those other things must also be taken into consideration when thinking if the ratio is too high or not. And uncorrected ratio can be calculated easier because you don't have to know how high the ex port is.

Well then you want to know how high compression ratio is safe. If you have a mild exhaust pipe which doesn't produce much back pressure, or doesn't produce any back pressure like stock pipe(usually), then I'd say you can go for a 13-15:1 ratio. Provided that you can use good fuel, I'd say at least 90 octane. But if you have a peaky and powerful exhaust pipe, compression ratio cannot be made very high because when the pipe starts to work at certain revs, cylinder charge pressure rises so much that it will start to detonate if the compression ratio is too high. For a such pipe, I'd try something like 11-12:1 ratio.

I'm not an expert and this is an extremely complicated thing, as everything in 2-strokes. I guess the best way is just trial and error But you do not have to aim for max performance. Measure stock ratio and see if it seems lowish and raise to about 12:1. That should be at least safe.

Also the shape of the combustion chamber affects the compression ratio. With a "squish" chamber, you can have higher ratio, but in a squish chamber, some of the mixture is left unburned which prob is not good if you want low consumption. A normal spherical chamber is a good for if you aim to lower consumption, but not the best for high power. Depends what you want. But it's so complicated that I suggest studying on the subject. A.G. Bell's 2-stroke tuners handbook is good for starters, should be found with google.

For the exhasust seize marking, is the stock cylinder steel? if so, did you make sure all the aluminum was removed by using a chemical dip? I've been reading about using NaOH to remove aluminum and carbon from iron parts.

Lastly, are you keeping stock gauges? have you looked at the newer x49 digital guage w/ tach? I wonder if you know how that cluster works and if it's easy to swap into our model x49's.

The cylinder is cast iron. Chinese cast iron, though No I didn't try chemical removing. I've read about it too, I guess it works. I just sanded it mostly out, couldn't get all of it out but it looked useable. I do believe that the cyl will work well enough and not seize, I just have to make sure I don't do stupid mistakes, like I have already done, rode it without the shrouds

I'm not using any gauges at the moment. I will get a cheap digital speedo somewhere and prob also a tachometer. I don't really know about the newer model digital gauges.

Are you riding it without a fan and cooling shroud?
I have built many pipes from old washing machines,etc!

Yeah but I have done only short accelerations, except one time when I tested the top speed, but will not try it again until I have the shrouds on place

Good tip I have also thought about reusing my old computer case to make pipe from it. Have to look around junkyards for old washing machines

Once you start really getting into it, you should consider upgrading the crank. Stock cranks aren't good much past 10,000RPM for extended use. Those deep gears prob won't serve you well later. They may be an advantage for now though.

I have had a few of those. When compression was increased they really woke up. If you start beating your friend so bad that it's getting boring to race, then tell him this. lol

You might be right, I remember from your project when the wrist pin bearing failed when you revved it a bit more.. I have planned to drill a oiling hole to the conrod for the bearing when I have got the thing to scream above 10000. Also will use good quality oil with about 4% ratio.

I have a 110 pitbike too. They're tons of fun to drive around forest, but they're a bit lazy. I have tried to make it faster. Ported the head and tried a 22mm carb but it didn't help much. Head porting helped a little bit but not enough. Then I tried to weld the camshaft to have more lift and duration, but didn't help by any means, only bottom end torque suffered I think it was because I welded a bit too much to the intake lobe and some time after I found out that now the intake valve is closing about 25 degrees later than stock, so that might explain it. I should do some more research on it and try different things but the pitbike has stood in the corner of the garage since I bought this scooter..

How did you increase the compression of the pitbike? I have a spare head for it and I tried to lower it with my DIY method, but it seems that it's one **** of a job. It's now half way done but it's so big that it takes an year to sand flat by hand... High compression piston would be much easier but I don't know who sells them.

By the way, my road use keeway scooter seized today when I was going to school. Was going uphill full steam and then it lost power and locked the rear wheel. Skid for couple of seconds, then it started again. I was kinda surprised but didn't want to stop and push it to the top of the hill so I gently drove it to the top and shut it down to investigate what the heck happened. Then it wouldn't start any more, had to push it one kilometer to school. I found out how hard it is to push and how much work the 50cc piston has to do to move the thing forward

An hour later I tried to start it and it started and seemed normal. I was kinda surprised by the seizure because it has worked almost like a charm for 6000km's now. It's probably because I now have a tuned pipe in it but because our stupid law, I have to have a restrictor washer in the vari and also have restricted throttle, and oil mixed to fuel (pump leaked). What happens is I have to drive 55km/h with about 9000rpm and only 1/3 throttle. It doesn't get much fuel in so it doesn't get much oil in too. I think oil starvation caused it. It had worked well before because it was colder, today it was the first warm day of the spring so it heated more and now seized.

I had forgotten my 2 stroke oil home so had to buy a new bottle, put a bit more oil to the tank and drove home after school and it worked fine, except acceleration was noticeably slower.. Darn, I think the cyl needs to be honed and needs a new piston..

[aeroxbud]

Cool project

[2strokd]

Good read! I like your "do it myself" and "get the most out of it" approach

[palezu]

I have done something. Pulled the clutch apart and changed the springs to malossi yellow ones. They're not very stiff, so I lightened the clutch shoes a bit by drilling two 8mm holes to them.



Clutch engages now at about 6000rpm. It's good for now at least.

Then I got and cut the pipe and welded it into different angle with my grand fathers trustworthy crappy ESAB stick welder. Weld was of course ugly as hell, as is the whole pipe. But it was good enough so I could install the cooling shrouds finally.



Previous owner had tried to paint the fan shroud silver but obviously he hadn't done any prep work so the paint surface looked like it was first dipped in bird crap and then dipped in sand. I was again in a hurry so I just lightly sanded the old paint and then painted it with base black. But I hurried and the paint was still a bit wet so there are some silvery finger marks. Have to paint the thing again, a bit more carefully, when I have time.

I also drilled some holes to the top of the cylinder shroud to let the heat escape more freely. I think the stock air outlet opening looks really small? A cylinder head temp gauge would be very handy, have to look for one..

I got some gas and went to forest to test it out. Launch acceleration is reasonably good but then it feels it revs too much and loses power. Adjustments needed.. Suspension is horrifying in bumpy forest roads, my pit bike is way better there. Rode around the forest for probably 2 kilometers and then it started to sound louder and louder. I'm very used to the exhaust bolts loosening and pipe joint starting to leak so I thought that is again the problem and drove home. Header bolts had loosened, but also more:





One thing I have noticed about exhausts. If something can go loose or break, it will. Constant vibration and heat does wonders. The support bracket had also cracked. An exhaust needs double heavy duty fastenings to prevent failures. It's off to the welder again.. It might be that I can get some sheet metal soon. If I can I will use the header pipe from that pipe and make a new expansion chamber. Shorter and beefier. More rpm and peak powerrrr. I hope to break at least 50mph then.

Carburetor needs some checking. Cold start is almost impossible without starting fluid spray. Kinda odd because the e-choke seems to be working.

[aznatama]

Nice! good idea about venting the head cover. I never though about that, and the stock exit is feeding hot air directly into my intake vents.

Have you adjusted the jets at all?

[palezu]

I have only played with the main jet. Currently it's a #105. Seems good, it doesn't sputter and hasn't seized But I have to get some more jets, can't risk seizure by running lean.

Forgot to mention that I cleaned the stock airbox, fixed the crack with hot glue, removed the intake "restrictor" and replaced the open filter with it. Much better sound.

I got started with the exhaust work. Cut the old pipe and saved the header. Got the new pipe dimensions dialed in and made an ugly paper model. Test fit.



Here are specs of the new pipe, calculated with a excel sheet which is made by some of my countrymen who are crazy 2-stroke tuners.



Let's hope it even moves with that pipe.

[palezu]

Something has happened.

We were doing some pit bike riding in forest and I found a sheet of rusty metal. It didn't look too bad so I took it home and started pounding metal.



I was supposed to weld it with my neighbors good MAG welder, but his dad had taken the welder away to somewhere. I had no choice but to try to weld it with my old ESAB stick burner. At first it seemed virtually impossible, but after burning many holes and many bad words, it gradually started to look like something. Welds are ugly as hell as is the whole pipe but as surprised I was, I finally got the pipe ready. Behold, here is my Braaap Kit 2.0 Rust edition:





It can not rust because it has already rusted. Perfect. Still have to do fastening brackets and mount for silencer.

I tested it a bit by revving again without drive belt in place. 105 main jet was way too big for this pipe. Changed to 92, still too rich. Took the air box out, still a bit rich but now it revved to somewhere.



At 0:14 in the video, if you look closely, you can see a small puff of white smoke coming out of the carb. I didn't notice this until I watched the video myself. I think that means that the reeds are floating! I was pretty surprised. It could cause some amount of power loss, have to get carbon reeds from somewhere.

I ordered a carbide burr for my dremel from china some time ago. Have to wait for it and then I can start to port the cylinder. I have to raise the exhaust port a bit, to 185 degrees so it will work well with the pipe, at least I hope so. Then it should move somewhere..

[90GTVert]

Very cool to see how much you did with an piece of scrap and a welder you didn't wanna use.

[palezu]

Hello again, sorry for the long delay.

Not much has happened because I haven't had time nor money, but I'll post something so the topic won't fall so much down.



Carbide cutter for dremel arrived from China. Turned out to be real good quality, I have ground a lot of things with it and it still keeps going.



Got the ex port ready. Actually after taking the picture I filed it a little bit more up. Timings are now 188/120 if I remember right. Theoretically, according to the time-area figures, the cylinder should now give plenty of power at high revs, about 11-12 000 rpm, but on 2-strokes, theory calculations usually always fail, so I don't know..

Then, a other crazy plan: Old Naraku 50cc cylinder which suffered a circlip failure. Plan:



How the exhaust side looks now: (I had previously tried to make it a triple part exhaust port. I had drilled the auxiliary exhaust ports already, but I was not satisfied with them, and thought that a two-part port would be easier to make so I welded the auxiliary ports full and ground and weld and ground...that's why it looks so rough right now)



Comparison with a stock Yamaha Aerox cylinder:



I have to weld the bridge on the port, ground and file and sand a heck a lot and then take the cylinder to be bored over. We'll see if it will scream like a 50cc Kreidler or if it will be a complete failure.

At this point, I had swapped the piston from the Benelli to my Keeway scooter because the pistonring of my Keeways piston had snapped and I didn't have time to buy a new one. Soon after I bought a new piston for the Benelli. But, I made an awful error when I was preparing the piston. I was supposed to grind a groove in the intake side for the boost transfer, but I accidentally ground the exhaust skirt of the Shining New Piston, which ruined it because now it did not cover the exhaust port any more at TDC.

So, I was quite pissed and didn't want to buy a new piston again because lack of money. So I thought what if...and took my Keeways old piston, which was otherwise good, but the snapped pistonring had dug a small dent in it. I ground the new pistonrings from the ruined new piston to fit in the old piston and put it into use. It seemed to work.

But not for long, jetting apparently was a bit too lean:



Cylinder was ok after some sanding(again). The cyl is prob very out of round, but never mind :D Soon I will get some money so I will buy a new pistonkit, a better clutch and some other stuff so stay tuned..

About the performance of the scooter so far. Not good. The highest speed I have achieved so far, is 80km/h (49,7mph). And that was with a commercial Gianelli Extra exhaustpipe, not with my homemade rust can. A pity. Top speed with my DIY pipe was 79km/h, so it's practically the same. But something doesn't work because it should go a lot faster with my DIY pipe. The Gianelli is some amount longer and it's power peak is well over 1000rpm lower than with my DIY pipe so it's not good. With my pipe, it screams like mad in acceleration, but doesn't have any more power. But there are still things to try before I have to admit that my ugly diy pipe is bad and have to design a new one:

-jetting (was apparently too lean with the 105 main because it seized)
-fiberglass reeds
-fit the diy pipe better to the cylinder(they're a bit mismatched now)

To be continued some day.. I hope to receive comments.