Honda CHF50 Metropolitan Jazz   

I'm publishing this resource page as a result of several enquiries from owners of the new generation of Honda scooters. None of the aftermarket parts from previous models apply to this new range and a number of owners have raised questions concerning performance and other accessories for their Honda scooters. The Metropolitan, Ruckus and Jazz scooters all use a four stroke motor unlike all ( but one) previous 50cc scooters which used a two stroke motor.

I would normally have waited before publishing a page until I had some first hand experience but  Brad, the owner of a restricted Metropilitan II,  volunteered to write an article about transforming his scooter with stock Honda OEM parts.   Thank you, Brad, for contributing the first information rich website about the Metropolitan! Links to other sites of interest are at the end of this page. If you know of any information that would interest please feel free to write.  

Doug, June/2003

February 2009

After reading this page, I'd suggest visiting the UrbanScooting forum for additional information on Metropolitan upgrade advice, modification results and current parts availabilty.  Lots of Met/ Jazz owners there to talk with.

Thanks for the intro Doug! And thanks for hosting this info!

This is for all of you folks out there that may have 'accidently'(or fooled by the dealer) bought a Honda Metropolitan 2(CHF50P). For those of you who don't know, the Metropolitan II comes heavily restricted from Honda to meet the moped regulations in some markets. What this amounts to is having a modern brand-new scooter with a wonderful engine that only goes 25 mph, while the Metropolitan 1 goes about 40(I hear, but not actually tested by me). After I came into a great deal on a used and slightly abused MET 2 scooter, I started to do what just about anyone else would do; figure out how to go faster. It was fairly obvious just from riding the MET 2 that it was restricted, so I set out to figure out what was restricting it. Much unlike the rest of the two-stroke scooters here on Doug's site, the MET 2 ended up having very thorough restrictions that are not cheaply or easily rectified. As honda appears to be going to more and more of a 4stroke lineup even for the under 50cc cycles, hopefully this is a good starting point for uunderstanding how honda engineers the 4 strokes and what we can do to make them go faster in the future. Read on to see what you can do to make your MET 2 more like a MET 1:

First off, a couple of tips:

Before trying to do any of the fixes listed below, I would highly recommend getting yourself a copy of the service manual here Thanks again for the link Doug!

Be very careful removing the plastic body panel clips or make sure and get some extras, they are quite fragile.

I am a big guy(6' 230), so remember that when looking at my speed numbers. My MET 2 before I made any changes would take me 25mph. I think the person who had it before me may have removed a washer in the exhaust already. I need info for this page from someone out there who is willing to take off their exhaust and see if there is any washer or plate or excess metal there, and/or maybe a MET 1 owner who can accurately measure the diameter of the exhaust pipe for that model.

I am not an expert at anything. Though I have tinkered pretty well with this scooter and have a decent general knowledge of things that go, it is very possible that I am way wrong on any of it. In other words, venture forth at your own risk, and don't expect anything from me if you screw up your scooter or yourself.

The first place I wanted to correct the restriction was with the ignition system. I am not sure to what extent there may be differences in the programming for the two units, but the MET 2 definitely has a different Engine Control Module(ECM) than the MET 1. As you can see below, the units are the exact same physical dimensions but bear different numerical markings which I have typed in yellow for clarity. The unit is from Shindengen, so I'd love to hear from anyone out there with some knowledge of what these numbers may mean or if it is possible to reprogram these in any way. This was by far the most expensive part, so any info on altering its characteristics would likely save you and others some money. The service manual does list a procedure to reset the data in the unit if the throttle position sensor is moved or replaced, so that may be somewhere to start, just be careful expirementing as it is an electronic device.
After replacing the ECM, the scoot would not start at all, so at first I was worried that I had gotten a bad unit, but I investigated further and found that the wiring harness for the MET 1 had a different part number(by the way, a table of the parts used is at the bottom of the page), so I ordered one. I wish someone had already written this page, because there ended up being only one small difference in the two. As you can see below, the position of the Red w/green stripe wire on the large connector(which goes onto the left hand side of the ecm as pictured above) differed by one space. I didn't try moving the wire on the MET 2 connector, but that is the only difference I could see. If you try moving the wire to save the hundred something dollars on the wire harness, let me know how it works out. 
After getting the new wires in and hooked up, the scooter started right up, but what I immediately noticed was that now the idle speed was very high. It is my hunch that the timing map for the MET 1 ECM has more advance than the MET 2, but this is just a guess. I would welcome any other hypotheses. After getting the scooter back together somewhat, I went for a test spin and still no faster, although the motor did seem to rev higher at full throttle, so there must be more restrictions. Further investigation revealed another possible candidate, the movable drive face(as honda calls it, but is commonly known as the variator). Again the part for the MET 1 had a different part number than that for the MET 2, and so I ordered one. Although this part was not that expensive, you still might be able to save yourself some money if you think you might be particularly skilled with aluminum grinding. As you can see below, the difference is in the thickness of the area where the rollers will be at top speed. The MET 1 variator will allow the rollers to move further out and up, and being lighter may be a slight advantage as well, I am not sure. To understand why this is important and CVT in general, you might want to have a look here(see BASICS section):
Put the scoot back together and another test run, still not much difference, maybe a slight bit over 25 to maybe 26, but before the speedo would stay pegged on 25 even on downhills so I view this as progress. There still had to be something else holding me back though. The next part number I found different was the final drive gear. After removing many parts to get to it, sure enough they were significantly different. The MET 2 had two more teeth than the MET 1 final drive. Wow, honda sure isn't making this simple are they? This part, it seems, there is no other way around except for new as the sprocket part is from the same piece as that shaft. You can see below:
I put the scoot back together pretty fast as I thought I was really going to be going faster now, but still the same as before, slightly over 25. The engine just wouldn't put out enough power, so on to the carburetor. The service manual lists the carb for the MET 1 as NVK00E and the MET 2 as NVK00F. As I had already spent quite a bit of time and money on this already, I didn't order a whole new carb although I am still curious to know if there are any differences in the actual body of the carb. The jet sizes for both carbs were listed as the same(main jet #72, slow jet #35). I did however notice a difference in another part of the carb, the number for the Diaphragm Spring. After removing the top cover from the carb and the spring, the difference was obvious, the MET 1 spring was quite a bit shorter than that of the MET 2. I presume this is to allow more fuel flow with less vacuum from the engine. See below:
Since I was messing with the carb now, I decided to get the idle right once I put it back together. Idle is supposed to be 2000 +/- 100rpm. I didn't have a tach, so I just winged it. I did notice in the idle adjustment procedure that the manual states that the proper position for the pilot screw on the MET1 is 2 3/4 turns out while for the MET 1 it is 2 1/8 turns out, so I let out the pilot screw another 5/8 of a turn. I don't have a tool for the pilot screw, but found that a small flathead screwdriver with a blade-tip with approximately the same width as the straight edge of the pilot screw head, moved around the inside edge of the recess, worked well enough. Test ride and now I can get up to speed quicker, but top speed is only maybe up to 28. The only other different part number I could find was the camshaft and sure enough the manual lists the following specs for cam lobe height:
  MET 1 MET 2      
  intake 29.2365-29.3165mm intake 27.8909-27.9709mm      
  exhaust 29.2907-29.3707mm exhaust 27.9503-28.0303mm      
I bought the camshaft, but have not yet installed it, but I did find something else. At the mounting of the intake pipe to the cylinder head is a metal gasket that is restricting the the flow faily seriously. A gasket that is not present on a MET 1. See below:
This finally did it, I reassembled without the metal gasket and without the green paper gasket and wow, I am now up to about 37 mph. I get to about 25 even quicker than before and slowly creep up to 37mph! If I had it to do over again and I knew about this gasket before, I would have tried that first to see what effect it may have had, but I am not about to swap all of the old parts back in to see what would happen just by removing this. Someone please try it and let me know and we will get it on here. Given the specs for the cam, I am sure there is still a little bit more power to be had, but I am happy at 37mph until I can get around to tearing the engine apart to replace the camshaft. I'll be sure to update this as soon as I do though. Below is a list of the MET 1 parts used:  
Part Name Part Number
ECM 30400-GET-671
Wire Harness 32101-GET-671
Movable Drive Face 22110-GBC-000
Final Gear 23430-GET-000
Spring 16050-GET-671
Camshaft 14100-GET-000
Bikebandit is a good source for these parts if you don't have a Honda Motorcycle dealer nearby(the place that sells Honda motorcycles here actually uses BikeBandit, maybe they are not really a Honda dealer if they don't order straight from Honda, I don't know)  

Future plans

possibly using some parts from the new Honda Ruckus/Zoomer. The carb for this model is listed as NVK00C, so who knows what the difference may be. The engine code for the Ruckus is AF58 vs AF55 for the Metropolitan, so not sure what the differences there may be. Given the differences between the MET1 and 2, I would probably look at those areas first on the Ruckus if I could, anybody out there want to volunteer some data on the Ruckus?

I did find this page, and this which are both Japanese but list some aftermarket exhausts for the Ruckus and also appear about the general shape of the exhaust on the Metropolitan.

Malossi also lists a multivar for the Dio clean 4 which has the same engine code as the Metropolitan, so it may be possible that it would work.

Maybe if someone out there has the access and experience to make a camshaft with even higher lift, we could experiment with that, I will donate my MET 2 cam for modeling once I swap it out.

Maybe someone will come out with a big bore kit for this scoot :)

Good luck!

Questions, coments, suggestions, additions are welcomed.  

  Real World Results

    The following are e-mails I received from Metro II owners who have taken the plunge and  de-restricted their scooters. I've tried to include a variety of comments to show how  "upgrading"  your scooter will bring instant results. Remember that top speed isn't as important in urban traffic as acceleration. All e-mails so far have been  enthusiastic about the results they've had and quite a few appear to be from people who don't consider themselves "mechanics".


I received an e-mail from Derek about his Metro II and his results from just removing the carburetor restriction His letter  follows:  

" I just bought a 2003 Met II and immediately wanted to see what I could do to speed it up.   I am not about to do all the things you did, but I figured I could handle moving the restrictor plate on the intake.  Piece of cake!!   I am now getting about 30-31 mph (I'm 6', 230lbs) and much more zip on "takeoff".  I may also tackle replacing the variator and the carb spring, but definately not the gear swap or the ECM swap. "

Cody wrote about modifications he did to his Mero II and had the following to say:

"I found Bradís information to be very helpful.My experience: after removing the restrictor plate on the intake, I achieved 25 mph much faster and the eventual creep up to 29 mph.Not satisfied, I followed the advice of Brad and replaced the MET 2 carburetor spring and the variator with MET 1 parts. I didnít notice any difference after I replaced the spring; however, I did notice a significant difference in the time it takes getting to 30 mph.My scoot no longer creeps!I have the same acceleration to 30 mph as I do to 15 mph.My scoot feels like it is less governed and the best thing about it is it only cost me $36.00.Another issue I face is drag.At 6í 2Ē, 215 lbs I form a scoop so I installed Hondaís recommended reflector shield for around $100.00 and I immediately noticed less drag as the shield is formed in a way that allows air to pass by me smoother. I now can accelerate to 31 mph."

Diane and Greg wrote me about their "metro modification results".
 "On our Metro II, we first took out the restrictor plate, and we got up toalmost 30mph right away. It still felt that we were being electronically restricted, so we replaced the ECM unit (~$300 at BikeBandit). We did not purchase a new wire harness-- instead, we put a small piece of solder tape that linked together pins 10 and 11 on the ECM. This closed the circuit to the ignition, and we are able to start the scooter without any problem. The new ECM allowed us to get up to 31-32mph. We thenreplaced the carburetor spring and variator plate, and now we can get to 35mph without much problem and almost 40mph on downhills. YAY! "

Glenn wrote with some details on switching variable pulleys and modifying the throttle spring.

".....Please note, I am about 185 lbs and 6'4"
Here's what I have done: Removal of the restrictor plate only helped me
get up to 25-27 with much more "pep". I was happy, but ordered a new
Met 1 spring from BB. Since they were out of stock, I just took the
liberty to clip the existing carb spring by about a half inch and bent
it so it would be flat on one end when I reinstalled. This made it
possible to get up to 30. Of course, not happy, I ordered a variator
plate and had it installed withing 25 minutes... Oh jOy! It was a
completely different ride 0-30 in ten seconds, and it can slowly creep
up to 35 if I lower my head and sholders to reduce drag. I also noticed
that since the new variator is lighter, the transmission does not slow
the bike down after backing off the throttle; this is good, but the
brakes need more stopping distance, especially down a hill." has set up a storefront offering aftermarket custom parts for the Ruckus as well as loads of info and links to other Zoomer/Ruckus sites for those interested in modifying their Metro.  The Ruckus shares a similiar engine to the Metro and there are links at to Japanese websites showing Ignition kits, aftermarket mufflers,high speed pulleys and custom airfilters. While it can be a chore reading a translation of a Japanese site, its worth seeing what parts are available in Japan for the 50cc Honda 4 stroke scooter motor.  The majority of Japanese "Zoomers" show an aftermarket muffler, airfilter and variable pulley as the most popular engine modifications which battlescooter is now offering for sale in North America. 

Clicking on any of the photos below will take you to the MyScoot Graphics shop for scootering merchandise.
Metropolitan T-shirt

Chf50 "tune-up" specifications from Honda service manual for 2002-2005
Where different, the ch50P specs are noted with a  "P" afterwards.

Engine oil type and quantity
10W-40  API "SG" or higher
0.6 litre (0.6 US qt)  at draining
0.7 litre  (0.7 US quart) at disassembly
Final reduction oil type
and capacity
Hypoid gear oil #90
0.1 litre (0.11 US quart)
Spark plug type(NGK)
 and Gap
Standard:                                            CR8EH-9
Cold Climate (below 5 C or 41 F) :  CR7EH-9
Extended high speed:                        CR9EH-9

GAP:  0.80- 0.90 mm  (0.0.031 - 0.035 in)
Tire Pressure
Front : 18 psi   (125 kPa,  1.25 kgf/cm2 )
Rear:   28 psi  ( 200 kPa,   2.00 kgf/cm2 )
Drive Belt width
(replace when below service limit)
New:              18.15 mm (0.715 inch)
Service limit: 17.15 mm (0.68 inch)
Roller weight
Outside Diameter
New:               16 mm
Service limit:   15.4 mm 
Valve clearance
Adjust with shims
Intake:      0.10 +/- 0.03 mm (0.004 +/- 0.001 in.)
Exhaust:   0.19 +/- 0.03 mm (0.007 +/- 0.001 in.)
Pilot screw opening
CHF50:         2 and 3/4 turns out
CHF50 "P" :  2 and 1/8 turns out
Clutch Lining thickness:             2.0 (0.08 in ) minimum

Clutch bell inner diameter :107.0 mm ( 4.21 in) standard
                                              107.5 mm(4.23 in) maximum