Project 90 : Phase 3Since I partially melted the piston crown testing the 50-70cc MRP exhaust at the end of Phase 2, I replaced the piston and checked everything over. I have noticed that the compression is down to 175psi from 180psi when setup exactly as it was before. That's not bad for a cylinder with 2,000 miles on it in this project that has suffered multiple soft seizes, circlip failures, and again the piston crown melting a little.
I went over the CVT as well, checking belt width and cleaning things up to ensure everything is working properly. I went with 2,000RPM clutch springs instead of 1,500RPM clutch springs that I used in Phase 2. Either works well.
Phase 2 was all about exhausts with a ported cylinder. I believed that the small stock carburetor was holding back some of the exhausts in Phase 2. Naturally, Phase 3 is going to be all about carburetors with a ported cylinder. My plan is to test a range of carburetors from the stock 14mm all the way up to a 28mm DellOrto carb. Hopefully we will see what size or range of sizes works best at this point.
I wish to keep things as even as I can for all tests, but I will have to use a different intake for the largest of the carburetors. There isn't much I can do about needing the larger intakes. You just aren't going to fit a big 28mm carburetor in a stock intake. If you could, it would be a major restrictor.
The images below show that the stock intake manifold has a sort of ring cast in that reduces it's inside diameter. The stock intakes have a marking which says they are 20mm. I measured 19.5mm ID at the ring.
I used a dremel with a drum sanding bit and ground away this ring to make the intake path a uniform size. This creates a 22mm ID. Motoforce, and probably others, make a 22mm stock style intake. I own one and as far as I can tell it's just a stock intake made without the ring inside. Save yourself a little money if you need a slightly larger intake and do this yourself if you feel comfortable with it. Now the intake for the carburetor up to my 21mm can be the same. Here's a look at the intake after the mod.
The other thing that simply won't work with some of the larger carburetors is the stock airbox. I know a lot of people would probably opt for an open air filter, like a UNI or K&N, but I am not a big fan of these for street scooters. I plan to use s modified stock airbox that I currently use on a 103cc setup with a 24mm carb for the largest carburetors in Phase 3. It has a larger inlet and outlet. I also added three UNI filter vents to farther increase it's ability to draw in as much air as it needs.
If you would like more info about that airbox, have a look at the links below.
49ccscoot.proboards.com/index.cgi?board=carb&action=display&thread=134649ccscoot.proboards.com/index.cgi?board=carb&action=display&thread=2387&page=1In order to keep things as fair as I can when using the stock airbox on the smaller carburetors, I did the same mods, just leaving the stock carburetor connection in place. These first images show the stock inlet vs the newly modified inlet. This can be cut away with a razor knife or filed or ground away easily.
Next, I moved on to installing three UNI filter vents just like the other modified airbox has.
I suggest plotting your locations from the inside so you can avoid all of the internals easier. UNI suggests installing these pre-filter. That means they would be installed on the opposite side of this airbox, facing engine heat. I don't like that idea too much. This is exactly how they are installed on the other airbox and it has been working well for me, so I kept it the same. The vents require 1" holes.
It's probably not necessary, but I opted to add a little hot glue around each vent since they are at the bottom of the airbox to keep them in place on those rough roads. The blue filter elements can be removed without removing the whole vent, so it's still possible to clean them when you clean your stock air filter.
Unless you are sitting or kneeling, you really don't notice the vents. There is just a little more sound from the airbox now, but it's not much different than just removing the snorkel. The plain, stock, appearance and the low volume levels should help to keep this one under the RADAR.
With carburetor mounting and air supply figured out (hopefully), I moved farther down the intake path to the reed valves. I don't believe that the stock reed block will do a large carburetor any justice. A well-flowing airbox, large venturi, and big intake will do no good without more area to flow through the airbox IMO. I replaced the stock reed block with a Stage 6 VForce 3.
Here you can see the stuffer included, which helps to smooth airflow into the reeds. It has a 28mm opening.
This reed block is actually manufactured by a company called Moto Tassinari, which is fairly obvious from all of the markings on the reed block. It has been brought to my attention that there are different versions of this block. Apparently there are the versions that they manufacture for Stage 6 and Top Performance and then there is a version that they sell themselves. I am told that the version they sell has a little different construction and better carbon fiber reeds, but you can expect to pay a little more for it.
I'll let the folks at Moto Tassinari explain the benefits they claim with the VForce3 design, since they do a better job of it than I will. Here's a quote from their website (
www.mototassinari.com ) :
"
The unique design of the VForce reed valve system features double the reed tip surface over a conventional reed valve design. This has two major benefits: 1) The reed petals only travel half the distance as a conventional reed valve design to get the same airflow. 2) Because the reed petals only need to travel half the distance of that on a conventional reed valve design, there is a greater chance of them being fully opened as well as a better chance of sealing when they are "closed". A reed petal never truly "closes" in a classic sense, as it is always in movement. Consider this, an engine operating at 8,000 RPM results in a reed petal opening and closing 133 times in one second. This fact, sheds light on another VForce advantage. Since the petals are only traveling half the distance, they generally last longer are they receive less wear than the reed petals on a conventional reed valve design."
Sounds good to me. Just as in Phase 2, I installed a 5mm reed spacer under the block.
I wanted to add a little more data to this phase of the project. I was curious what, if any, effects larger carburetors may have on engine temperature. There's really only one simple way to find this out, so I picked up an Auto Meter cylinder head temperature gauge and a mounting cup to assure a clean install.
This gauge reads from 140°F to 340°F. I wasn't exactly sure what to expect, but I thought this would cover it.
One of the reasons for selecting this gauge is the sending unit. It uses a probe that threads into the cylinder head. You have to drill and tap the head to accept a 1/8" NPT fitting (and hopefully you'll drill a little more straight than I did). I have used this style of fitting as well as thermocouple rings that go under the spark plug before. Both options seemed to read the same, as far as I could tell, but I find the screw in style easier to work with. It requires a little more effort to install, but you don't have to deal with it every time you remove or install the spark plug.
There are gauges out there that are more compact and easier to install, but I am a fan of Auto Meter instruments and especially the Ultra-Lite series' styling. A big advantage over some gauges intended for 2-wheelers and ATVs is that the Auto Meter has it's own back lighting. My rides are primarily at night, so this is very important. Auto Meter includes a red bulb cover, but that provides a sort of pink glow with a yellow tint as shown below. If you want true red (or other color) illumination, I suggest picking up colored LED bulbs. I have these in my Mustang and they look much more manly with the red LED bulbs. ;D
With all of that tied up, I was ready to fire up the engine and get Phase 3 in tune. I plan to tune exactly as I have before. I will not be looking to the CHT gauge to aid my tuning. I will be tuning for the best performance and using spark plug readings if necessary.
Upon starting the engine and tuning the idle mixture, it became apparent than the engine was operating more smoothly than it has before. In the past it seemed that anywhere much below 1,400RPM the engine would struggle to run and want to stall out. Now I'm seeing that it will chug along happily down to about 1,050RPM. I have done a few modifications at once to begin this phase (Stage 6 VForce3 reed block, enlarged intake, airbox mods), but I believe this is largely from the new reed assembly. I still set the idle higher, to help keep the charging and lighting system working, but it's interesting to see the change. Here's a very brief video of the low idle.
www.youtube.com/watch?v=33bxgID97CoI proceeded to check the jetting and adjustments, and was a little surprised to see that not much changed. I thought I would have needed to go a step up on the main jet after the airbox alterations, but the same 90 main as I used before the mods works well. The needle clip is set in the center position.
While tuning, I noticed cylinder head temperatures higher than I was hoping to see. So high that they were maxing out the gauge on wide-open runs.
I was hoping to see temperatures within the gauge's operating range, both to attain useful information, and because I felt it would be safer. The engine has likely been operating at these temperatures throughout the project, so I guess they are alright, but I at least needed to find a way to get the temperatures back on the gauge.
I looked to different cooling fan and shroud setups to accomplish this task. Project 90 uses the cooling fan that it came with. It's a typical minarelli cooling fan, found on 49cc and 90cc engines. There is a larger version that moves more air, and I happen to have one. I've only seen these on 90cc minarelli engines. The size difference is obvious.
I don't think these will fit under all cooling fan shrouds. Both of my long case Vento Tritons appear to have extra room under their stock cooling shrouds with the smaller fan in place. The larger fan fits perfectly. My other 2T scooter, the Keeway Venus, does not have this extra space under the fan shroud. Before you consider picking up a larger fan, have a look at your shroud.
I also decided to try out a cooling fan air scoop that I made a long time ago. The idea is that it "scoops" up air when riding at speed and helps to move it across the engine. I should also note, my "stock" fan shroud has had the grill removed to create the maximum open space.
You can find more info about the cooling fan shrouds at the links below.
49ccscoot.proboards.com/index.cgi?board=gentech&action=display&thread=39449ccscoot.proboards.com/index.cgi?board=gentech&action=display&thread=393I evaluated each setup with three bits of information. I began with idle temperature. I let the engine idle at 1,300RPM until the gauge reached it's minimum mark at 140 degrees. Once it was at 140°F, I let it idle for exactly 10 more minutes and noted the temperature.
I also used two different riding conditions to measure the performance of the fan setups. For each test, I rode for 2 miles at wide open throttle and noted the readings. I stopped at a landmark (driveway) to assure I traveled the same distance each time. I then turned around and cruised home at 40MPH and took note of that temperature. Here are the results.
Fan | Shroud | 10min Idle | 2mi 40MPH | 2mi WOT |
Stock | Stock | 185°F | 350°F | Max |
Large | Stock | 155°F | 290°F | 340°F |
Large | Scoop | 160°F | 280°F | 325°F |
As you can see, there is a sizable temperature drop with the larger cooling fan across the board. Riding temps continued to decrease with the addition of the air scoop, other than at idle. The idle temp increase with the shroud could be a very slight restriction from the length of the scoop or it could just be a fluke. None of the idle temperatures concerned me, so I opted to use the large fan and scooped shroud for the rest of the project.
The down side of the larger fan is that it should create more drag on the engine and could have a negative impact on throttle response. I didn't notice either of these effects. I'm sure it makes a difference, but for a street ridden scoot I feel that the temperature drops are well worth a loss in performance that you probably won't even notice.
I got my large-finned cooling fan from a stock 90cc Triton engine. If you wish to pick up your own, I would suggest searching eBay or retailers of 90cc ATV parts. I have heard that some do not fit. I'm not sure if it's merely a shroud clearance issue, as I showed you before, or if there is more to it. There are aftermarket fans made as well.
Parts For Scooters carries a Hoca "turbo" fan, part # 169-142, that appears to have a little larger fins and is available in different colors.
With the intake sorted out, the carburetor tuned, and the gauge and cooling covered, I could finally get out for the baseline ride of Phase 3. I rode for 32 miles and observed 56.95MPG, the best fuel economy thus far in Project 90. I will do my best to keep the same riding style for all of the tests in this phase, because I hope to see a good comparison of fuel consumption with various carburetors.
The idle, as mentioned earlier, is not the only thing that smoothed out. The entire rev range feels more smooth than it has before. Throttle response is very crisp. While neither of these give great gains in performance, they do make the ride more pleasant. I was thoroughly impressed with the results of the VForce3 reed block and smoothing/enlarging the stock intake.
WOT cruising speeds remained unchanged from the baseline of Phase 2, keeping me at 48-52MPH sitting up. Maximum speed increased by 1MPH, to 59MPH at just under 8,500RPM.
With outside temperature at 50°F, I observed 325-340°F cylinder head temperatures with long WOT cruising. Riding at 40MPH, I saw cylinder head temperatures of 275-285°F.
Overall, this seems like a good street setup to me. With a strict budget in mind, I would leave out the Stage 6 reed block, because it smooths everything out, but doesn't give any major gains. The large cooling fan is now one of my new favorite mods.
Project 90 : Phase 3 : Baseline SpecificationsBore : 52mm
Stroke : 45mm
Displacement : 96cc (95.56747199999998cc)
Cylinder : Stock Ported w/1.2mm Base Spacer
Exhaust Duration : 188°
Boost/Transfer Duration : 130°
Cranking Compression : 175psi
Squish Clearance : 1.1mm
Cylinder : Stock Ported w/1.2mm Base Spacer
Cases : Port Matched & Mildly Trenched
Carburetor : Stock 49cc/90cc
Main Jet : 90
Pilot Jet : 22.5
Needle : Stock. Clip in middle position.
Air Filter : Stock Airbox w/o snorkel. Inlet enlarged and UNI filter vents added.
Fuel System : Stock tank, 1/4" hose, 1/4" fuel filter, manual petcock.
Oil Delivery : Pre-mix. I removed the stock oil injection system in favor of pre-mix in order to provide consistent oiling with any modification. I am using AMSOil Sabre Professional 100:1 Premix, mixed at 50:1.
Intake : Stock, Enlarged To 22mm
Reed Block & Reeds : Stage 6 VForce3 w/5mm Reed Spacer
Exhaust : Stock 49cc
Ignition System : Stock CDI, stock stator/flywheel, Bando coil, NGK BR8HS spark plug.
CVT Belt : 788 17 28 Bando
Variator : Hoca Performance Variator w/Modified Fixed Drive Face
Roller Weights : Dr Pulley 6g Sliders
Clutch & Bell : Stock
Contra Spring : Stock 90cc
Clutch Springs : 2,000RPM
Final Drive Ratio : Approximately 10.125:1
Max Speed : 59MPH
Cruise Speed : 48-52MPH
Fuel Economy : 56.95MPG
CHT @ 40MPH Cruise : 275 - 285°F
CHT @ WOT Cruise : 325 - 340°F
Ambient Temperature : 50°F
Other Info For ReferenceElevation : ~40ft Above Sea Level
Rider Weight : 265lbs
Fuel : 91-93 Octane (Premium)
