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General Discussion / Changing cylinders - anyone done it?
« on: March 25, 2021, 06:49:25 PM »
Hi everyone,

Has anyone tried swapping cylinders/pistons from the different SYM engine sizes? How about using different piston rings? I might have to 'cos of a parts availability issue so if anyone has looked into this, or done it themselves, please let me know. As far as I can see, swapping the 249cc and 263cc parts is straightforward, albeit time-consuming, but the 278cc might need major modifications.

So why do I ask? My 12 year old Citycom is just shy of 50,000 miles and is using oil (300ml extra needed between changes), has low compression, 10kg/cm2, and makes a knock noise when the engine is cold. It all points to worn piston rings/cylinder.

At the moment, it's looking like I'm going to have to fit a new piston, cylinder, etc from the 249cc engine, not the current 263cc, because that's all that's available at reasonable prices. It's no more expensive to convert than it is to repair, and the conversion would include a new cylinder too, so it might last longer/seal better than a repair. I don't think the 278cc cylinder will fit the engine block, although I'm in the process of checking for sure.

My problem is that I cannot get new piston rings locally - part no 13010-LEA-000 (the numbers denote a piston ring set, the letters denote the model) - the dealer doesn't stock them and won't order them. I can only get a complete cylinder and top end build and the dealer wants to charge me big bucks for this. Ebay is a similar story with 500% overpriced parts; however, I can buy a piston, cylinder, rings and gaskets for both the 249cc and 278cc engines, and for US$150 for either set - by far the best value. I've also reached out to family in Taiwan to see if they can get the 263cc parts but since these models are export, it's unlikely.

All the 249/263/278 engines have the same stroke but 2mm bigger bores - 71/73/75. The Citycom is 263cc - 73mm bore x 63mm stroke, and the cylinder/engine block gasket is the exact same part as the 249cc engine - both HMA. This means the smaller cylinder and its piston and rings should be fine. The piston will probably be lighter, which will reduce the load on the rod and big end. The issue will be whether the head from the 263 works efficiently with the 249 piston. I'm guessing they used the same design and sleeved the cylinder an extra 2mm for the smaller piston, with only a slightly different head shape. For example, the inlet pipe assembly, the camshaft, the valves... all the exact same parts for both. I've not been able to check exhaust, except for the gasket, which is the same. However, the head gasket is different - LEA for the 263cc and HMA for the 249cc. I will need to disassemble and measure to see which gasket would work best for the smaller diameter piston, assuming everything else mates up, as I think it will. Probably the bigger one, the LEA, is better to create a seal.

The 278cc is 75mm bore, same stroke - it has a different engine block/cylinder gasket part code (RFA not HMA) so the 278 cylinder might not fit the 263/249 engine block. The 278cc engines appear to be all RFA code parts for all gaskets and either L3A (GTS300i) or L9L (Z300) for piston rings/cylinder - 2 codes 'cos the latest 278cc cylinder is ceramic not steel lined.

Parts numbers are here:

The other option is to look into rings from a machine with a 73mm bore (Honda GX240 for example).

Here's some pics of the 2 troublesome parts that are specific to the 263cc engine - the rings and the head gasket. The other parts I need are the same (HMA) as the 249cc engine.

I can get this gasket for US$35 locally - the price in Taiwan is around US$10. The piston rings are on Ebay and they are about 5x the Taiwan price.



General Discussion / New-ish SYM scooters?
« on: January 30, 2021, 07:26:25 PM »

SYM have updated the design of the Joymax Z 300 to give it dual LED headlights and traction control. Behold, the Z+ which looks somewhat like the Kawasaki Ninja 400?

It has a page here.

I also saw the new (?) Cruisym α (alpha) which has LED lights, a new dash and traction control. Is this a slightly new version?

I have inserted SYM's images into this post but they don't seem to be displayed for some reason.


I've noticed my Citycom scooter is more prone to a rear loss of grip than the front. In fact, the front feels so unloaded it never feels anywhere near losing grip, but I can get the back to move around with some deliberately aggressive control. I wonder if this is true for scooters generally? It certainly feels quite different to a motorcycle in this regard.

I know it isn't the tyres - front and rear match so they have the same grip, and pressures are correct, both warmed up, running on the same surface (of course). It is, of course, harder to get the Pirelli Angel to slide compared to Maxxis but that's the coefficient of friction, nothing else. There's a discussion of why contact patch is largely irrelevant and it is weight that offers traction on this page

My Citycom seems typical for a scooter with a strong rear weight bias - 77kg front 107kg rear is roughly 40/60 distribution. So the rear should have more grip, yet it feels the opposite, with the front being more secure. Maybe it's the huge sprung weight of the engine assembly at the rear that has an effect?

Has anyone else had this experience? Is it a thing?

I've been riding for 30+ years - learned to do stoppies and get my knee down on sports 600s, wheelie and slide on a supermoto, so I find it hard to believe I'm imagining it.

The CC is my first scooter - just hit 70,000kms, 66,000 of which are my use, and she's still running well, although not as well as 40,000 ago. Top speed is much lower and fuel consumption is higher.

Citycom 300 / Citycom 300 running costs in Hong Kong over 5 years.
« on: February 08, 2020, 09:11:04 PM »

I thought I'd share this with y'all since I think my CC is one of the best ways to commute and I'm willing to argue that with any takers :-)

Here’s a record of the averaged running costs over 24,000kms (2 years for me), in US$. I've done over 64,000 in 5 years so far, and although the LCD display is almost dead (burned out in the middle, like an old Gameboy), the rest of the scoot is fine. I bought the CC with 4,000kms on the clock, 4 years old, for $3,000. As you can see, the biggest costs are fuel, depreciation, and paying the man. It’s in order of expense, highest to lowest.

1. Fuel: on my regular commute I get 32km/l. That’s  $1,235 for 24,000kms. It’s mostly highway at 100km/h plus some lane sharing through jams and a little city riding. Compared to my Kawasaki Ninja 650R, this is a saving of about $600.

2. Depreciation = $1,200, 2 yrs – the machine cost $3,000 and I assume I’ll never sell it so it’s a total loss from purchase. As a result, depreciation loss per year keeps decreasing the longer the machine is in constant use and it’s had 5 years of this so far. The Ninja cost $5,000 and I’ve had it 10 years, and it’s still worth something, so they’re about the same. The CC would be impossible to sell here - the old age and the relatively high seat means no-one would buy it. It's fairly obvious that the more often you buy/sell vehicles, the higher this cost is, and it can easily be the most expensive.

3. The man - government mandated costs – insurance ($200 for 2 years), and road tax ($325 in 2 years) = $525 in 2 years / 24,000kms. Again, the insurance is 30% cheaper than the Ninja.

4. Tires – $120 – Maxxis lasted 18,000kms, would cost $100 to replace, but typically scooter tires cost around $200-$300 for 24,000kms it seems? For me, the actual cost of Seyoun NJK is US$60 for 12,000. Compare to my Kawasaki Ninja, which is $250 for 8,000kms, the Ninja is over 6x the price of the CC.

5. Belt – $50 – replaced at 21,870kms when the revs started rising a little – not fully worn – $80 for the SYM part: Mitsuboshi is $55 on Amazon. The second belt had worn to 23.1mm at 49,460km. The service limit is 22.5mm. I replaced it after 40,000kms of use (62k on the ODO) when it was 22.8mm and looking a little cracked between the grooves. Say $50 for 24,000kms.

6. Oil changes every 3,000kms and gear oil every 6,000kms is 11 litres of 10W40 engine oil and half a litre of gear oil (Castrol GL-5 85W-140) for 24,000kms = $45

7. Air filter – switched to K&N = $150 for the filter, cleaner and oil = a lifetime, so it’s hard to say, but call it $40 for 24,000kms.

8. Transmission – clutch, variator, rollers, etc. – still working fine at 62,000km. Clutch pads at 5.5mm – wear limit is 3mm – so clutch life is 120,000kms or so. Again, hard to say, but call it $40 in 24,000kms.

9. Brake pads – the front and rear use the same pads and I’ve used 6 sets in 60,000km – the originals, 1 pair of EBC sintered ($20), another EBC organic ($10) in the front and some very cheap unbranded pads in the rear ($2.50). Brake fluid was replaced at 30,000kms for $15. Overall that is $20 in 24,000kms. The rear brake is so powerful, every pad I've tried has made little difference. The same can't be said for the front, where only the EBC are good enough, and the SFA264HH sintered pads make it a decent brake.

10. Spark plug – Iridium CR8EIX or CR9EIX (tuned) every 30,000kms or so is $10

And that's it for running costs.

For repairs, I needed new fork seals and ATF fluid ($50), a new main stand bump rubber ($10), a new left brake light switch (a standard part used widely on a huge number of machines, $5), and some rear axle nuts and thread lock ($10). I might say I need a new display but not yet. It's bad but the ODO and fuel level are still readable. The clock can barely be made out, which means it's useless on the go when I need it.

The total running costs are $3,285, and it means $0.137 per km or $9.58 for my 70km commute. In Hong Kong, it means about HK$1.07 per km, or HK$75 a day, which is about 35% more expensive than the cheapest public transport but it's less than half the time, and is so much more enjoyable and convenient. It’s also about $600 a year cheaper than the Ninja, mostly because of lower tire, fuel and insurance costs. 🙂

I've got my eye on an X-Max 300 and a MT-09 as replacements/upgrades, but as long as the CC and Ninja keep doing what they do, I am holding off on the new machines.

Well done SYM - you made a mighty fine scooter.

General Discussion / Clutch pad thickness - how thick when new?
« on: November 13, 2019, 07:34:21 PM »

Does anyone know how thick clutch pads are when they are new for the SYM 250/300 models?

I have a Citycom 300 and the service manual says the wear limit for the pad "lining" is 3mm, and the pads measure 3.5mm thick after 62,000kms. If I know how thick they are when new, I can work out how much longer they should last.

The manual p.143 also says the thickness of the clutch "weight" is between 6mm and 3mm. Does it mean the weight is the lining? Anyone confirm the pads are 6mm thick when new? If so, it's 25,000kms per mm of wear for my commute, so another 12,500 or so left before I need new "clutch weights/lining".

I just changed the belt - lasted 40,000kms - so if I can avoid taking that section apart again for a while, that'd be great.

There were no other problems when I did the job yesterday - lots of black dust of course, and some minor wear on surfaces, but nothing problematic with clutch, variator, etc. The new belt has dropped the revs by about 10-15% for a given speed and the machine seems to be a little smoother, with noticeably less mechanical noise at idle. After 40k, the retired belt was 22.7mm wide, with the service limit being 22.5mm, and it was also showing some lateral cracking in the grooves.

Thanks for any help on the pad thickness :-)

General Discussion / GTS300 is no more... Joymax Z replaces it
« on: January 30, 2019, 09:26:05 PM »

Just seen a report on a Hong Kong site saying the GTS300 (RV300?) is discontinued and the new Joymax Z replaces it, alongside the Cruisym as the premium version of the 300.

Hong Kong has a 35% tax on new scoots so the price is much higher than elsewhere. It is 12kg lighter and I'd be interested except for the low seat.

Citycom 300 / Cut and modify the stock Citycom exhaust muffler?
« on: April 17, 2016, 07:39:52 PM »

Has anyone tried to cut and modify the stock Citycom exhaust muffler, or a similar design? I have done a lot of Googling but not found any pictures of the innards to see the inside routing design. I only found this post by Doug Reid so far

I can see the exit pipe has a curve inside - so I can't see how long or how deep inside the muffler it goes. I put a very long cable tie down the pipe and then pulled the tie out until it caught on the end of the pipe. It seems it 27.5 cm long.

I can also see a mesh on the inlet pipe and measured that as 15cm from the front of the inlet. I assume that mesh is the start of the cat.

The whole muffler is 61cm. I'm guessing it is like the design of the Zuma or the Honda Faze 250 ?

What I'd like to do is keep the cat for environmental reasons, but improve the gas flow by losing or widening some of the interior chambers/piping. I already have an aftermarket pipe so the stock muffler is not in use. Something like this:

Any thoughts anyone? Do you know anyone that has done a successful mod?

All the best,

EDIT - just seen a cheap after market exhaust on Ebay.
Looks interesting...

Citycom 300 / "Citycom" decals / stickers / font ?
« on: June 11, 2015, 12:26:39 AM »

Someone knocked my CC over when I was at work and damaged the near side. I can repair a lot of the damage myself but if I repaint the side panel, I will need to get the side decal that says "Citycom 300i".

Has anyone had the sticker made for their scoot ? Do you know if it is a standard font or if there is a scan of the lettering available somewhere to get a sticker laser cut ? Maybe a SYM catalogue/brochure has it ? I've hunted for one but so far they are very small and not clearly defined.



Citycom 300 / Replacing the headlight control unit
« on: May 25, 2015, 03:21:59 AM »

Anyone found a quick way to change the headlight bulbs ? There doesn't seem to be enough space behind the bulbs to do it without removing the front fairing - anyone found a way to avoid this ?

I wanted to run some LED H4 bulbs but the HCU won't let me - it seems it has a load detection circuit and the load is too low. So when one bulb goes, they both go off. That's just dumb. With LEDS, the bulbs come on briefly but then turn off.

So I got two relays on Ebay

and removed the hcu and cut the wires going into the connector. There are two thin wires, one blue, one white, that come from the switch. There are two thick wires blue (hi beam) and white (lo beam) that connect to the bulbs. The green is earth and the red/white is always live from a 20amp fuse - be careful not to short that.

The relays come with wiring harnesses - the yellow is the coil controlling the switch, the blue is the input voltage, and the black and the red are the switched output voltages.

To get at the hcu - remove six screws around the brake levers, and then lever down the black "handle front cover" on page 198 of the manual, then remove five screws to remove the windscreen, then unclip the coloured handguard. Then two screws to remove the black "front cover" centre piece, and lever that up. The rest is stripping wire, feeding on a piece of shrink wrap, twisting the wires together, soldering, heating the shrink wrap to insulate the join, then some electrical tape to insulate and keep the water out. Going slowly, doing it well, about two hours.

Changing the bulbs is a major pain - another hour - get the front fairing off (10 screws and 3 bolts), remove the rubber lamp protector, squeeze the lower retaining clip pins together at the bottom so they come off, remove the connector, fit a new bulb into the lamp, put the clip back on, then the electrical connector, then the rubber protector, repeat for the second bulb, then refit the fairing. I broke a bit of plastic holding the retaining pins at the top so I also had to repair that.

What a job.Hopefully the led bulbs will last forever so I never need to do that again.

Citycom 300 / BAW15D led tail/stop light bulbs ?
« on: April 07, 2015, 01:54:52 AM »
Hi all,

I'm in the process of upgrading the lighting to LEDs.

I already did the 3 T10 bulbs - front sidelights and rear number plate lamp. So next I'll get two LED 18W H4 led headlights - should be about the same lumens as two 90W incandescent bulb.

I'm also looking for LED tail light bulbs - the fitting is a Phillips 12495 which is the same as BAW15D but it's hard to find LEDs in that fitting. Has anyone done this? Did you manage to get LED bulbs? I can probably order some from China if needs be but that can be slow and a lot of hassle.

If I do have to order from China, is anyone interested in a group buy ?

Thanks !

EDIT - after a few days hunting, I haven't found anywhere, and I can't even find anyone selling the mounts either. I can get pretty much anything and everything except BAW15d. Thanks SYM. So either I change the sockets or I make my own bulbs. What would you do? Since I had a dead bulb, I made my own.

I've posted details on my blog about halfway down the page. Here are a few of the images if you're curious.

The tail light is brighter, the stop light about the same, but they use a lot less juice and should outlast my time with her. So hopefully, that's the last time I think about them.

Citycom 300 / AISV Air Injection Solenoid Valve
« on: March 18, 2015, 02:24:23 AM »
A bit of silliness, this one.  :o

If you don't know the AISV, you can look at my post about exhaust changes to read about the AISV location, routing, etc.

This is the whole system, not including the reed valve in the head. The AISV valve is in the bottom left corner, connected upside down in the photo. Oops.

I tested the AISV with a 5W bulb connected up instead of the AISV unit.

Below about 4,000 rpm (manual says 3,500 rpm, seems about right), air is sucked into the exhaust to help emissions and the bulb stayed off, so the AISV is open by default and gets no power. And this is also obvious because I can suck air through it when it is disconnected. Above 4,000 rpm, and with a steady or opening throttle, the bulb came on, meaning the AISV valve is closed. As soon as the throttle is closed above 4,000 rpm, the bulb went off. The bulb won't come on below 4,000 rpm regardless of the throttle.

On the move, I later found that the AISV will stay closed at high speed even when the throttle is closed, until the speed drops enough so the revs are below 3,500rpm.

If I disconnect the AISV and don't put a load there, the yellow warning light on the dash stays on telling me there is a fault - annoying. If I put a small load, say 1W, the warning light is still on. When I got to a little over 2W load, the warning light goes off, and this gets reliable around 4W. The AISV unit uses 6.5W (13V / 26R = 0.5A) and (13 x 0.5 = 6.5).

So for lack of a better idea, I decided to fit some under-tray lights to use the AISV power. Totally silly but hey, why not.

EDIT : I've now partly changed the use of the AISV - it also charges a 9V battery and this powers an underseat bucket light.

The charger uses a maximum of 2W of the 6.5W maximum available. The battery can power this light even when the ignition is off and it doesn't drain the main battery.

They are connected up using this circuit - the TP5100 charges the battery and the two diodes protect the circuit and battery.

I took the tray off and fitted the wiring and bulb holders. They were made out of some aftermarket indicators I had never used. The test bulbs here don't draw enough juice to turn off the warning light.

This is how they look installed and illuminated. They’re not bright enough to notice during the day because the light has to reflect off the road to be seen, and that’s fine. It's a bit of a chav idea to do this anyway, but here in Asia, pimping your scoot with colourful lights is very popular. So I'm trendy. Finally.  ;)

Nice of SYM to have created the perfect recess for these lamps. They are slightly recessed from the underside of the scooter so they won’t get damaged going over speed bumps, over kerbs, etc, and shouldn’t pick up tons of dirt either.

The light is more noticeable at night of course when the front area under the scoot is lit up. They don't extend to where the headlamp beams are visible. Just an under glow.

The ECU (orange/black wire = ground) grounds/sinks the supply voltage (red/yellow wire = positive 13V) up to 500mA, and the charger uses 150mA so the bulbs can be us to 350mA - about 2W each bulb. The connector here makes it easy to disconnect for removing the tray.

So, next up, a really big spoiler, stretched chassis, lowered suspension, and an airbrush of my favourite Korean girl band. ;-)

Yeah right. Oh, BTW, I also removed the last of the AISV stuff by removing the metal pipe and blanking off the ports. Removing the AISV stuff has taken about 350g off unsprung weight and another 150g (net) off the frame. Not anything significant but less unsprung weight is always a good thing.

cheers !  ;D


Hi all,

After commuting on a Citycom for a month, I decided to start modifying it. I've done this a lot on motorcycles.

I've been running the modifications for around 800kms and all is good so I thought I'd share. When I got the scoot, she had under 4,000kms, and she's now almost 6,000 ready for a big service.

I've put all this info and other stuff on my blog if you're curious.

I opened up the airbox and checked out the pipe connecting the airbox to the throttle body. It's long and twisty and has a much larger diameter (42mm) than the airbox air inlet tube (33mm). The pipe could do with a better flare into the airbox.

The inlet tube in the front of the airbox cover is removable so out it came. However, the circular hole this left was still much smaller than the 42mm pipe, so I trimmed out all the plastic and added some epoxy putty to smooth the new intake. This gave a similar intake area to the 42mm diameter pipe. Like this :

and the square ridges too

After that, I removed the tab of plastic on the inner half of the airbox, since this another way to restrict the air intake to less than the 42mm pipe.

And then finally, to smooth the intake area as best as I could, I added some foam filler and a layer of epoxy putty to the cavity. Like this :

It's very subjective, but the throttle feels like it has a slightly better response. For sure, there is now some induction noise which makes the scoot sound more like it has an engine. It isn't loud at full throttle, and sounds good to my ears.

When the air filter is due for replacement, I may consider fabbing my own using a K+N filter.


I didn't want to pay big bucks for an exhaust because the engine clearly isn't going to deliver significantly more power and the CVT means that power would only be noticed on top speed runs. The main reasons to change the exhaust were the looks and the weight.

So I got an exhaust for a Honda CBX 250 (?) and an interface from Taobao, figuring that they were so cheap (US$40 plus US$20 shipping to here in Hong Kong) I could give them a go and not be unhappy if they turned out to be trash.

The interface with sizes :

The exhaust :

And the ad:

I was surprised to find they were good. The interface inner diameter was 1mm too tight so that got filed down to fit. The outer diameter was 2mm too small so I added some thin steel pipe split along its length for clamp tightening. The exhaust bolted on without interfering with the original exhaust mounts or sticking out from the side of the machine. It fitted very well in fact. I got very very lucky with that. :)

The exhaust sound is very deep but much too loud for me without the decibel killer fitted, and sounds kind of farty with it, and the exhaust didn't seem to make any change to the performance. That was really surprising - I'd expect that it would have less back pressure and that would either cock up the fuelling, or knock torque off the bottom end for a small gain at the top. But actually, no obvious fuelling change at all - just more noise.

However, the original with its bolts weighed around 8kgs and the replacement weighs 2.5kgs, so that's significant, especially since the 5.5kgs reduction is unsprung mass at at the back of an already back-heavy machine. It also looks much better to me, so it's a keeper.

I recently checked the spark plug, after about 750kms, to see if it was running too lean. Surprisingly, it's not. So that's great, although I'll wait until I've seen how a new plug colours to be sure. Fuel economy has averaged at a little over 32km per litre, which is a slight improvement, but I wouldn't assume that is only these changes.

Before :

After : 

I've also been slowly re-spraying the silver parts with either black or graphite paint. The first things I did were the grab handles and side panels, and I've also done the rear clamp, rear shocks, front forks and I did the wheels with black spokes and graphite rims. I'm very pleased with the look.  ;D

EDIT Forgot to say - I removed the AISV stuff -it adds air into the exhaust below 3,500rpm when slowing down on a closed throttle. That caused some pops and it affects emissions, not performance, so off it came. And the pops stopped.  ;D

Air comes from inside a low frame tube on the spark plug side of the engine, through a rubber tube into an air filter can, and through another rubber tube into the Air Injection Solenoid Valve. When the AISV is open, the air flows through another rubber tube into the head where there is a reed valve. The output from the valve flows out of the head and through a metal tube to the exhaust port. So I removed all the rubber tubing and filter can, plugged the frame tube, plugged the AISV but left it electrically connected, and plugged the head entry to the reed valve. This came off :

So overall, I'd definitely recommend the airbox mod but the exhaust hasn't made much difference.

Cheers !

Citycom 300 / Citycom turning radius?
« on: September 20, 2014, 06:49:59 AM »
Hello all,

I'm thinking about getting a Citycom and would like to know the turning radius?  I know the 300 GTS is 2.5m from the manual, but the Citycom manual doesn't say.

The other scoot I'm looking at is a Kymco People and that is 2.2m - can the Citycom do this?



EDIT : I bought one. The turning circle is 4.25m, so turning radius is just over 2.1 metres. That's pretty nimble - a Honda PCX150 is 2.0m.

First impressions. Comfy, very comfy. Power is adequate. Storage is awesome. I miss a clutch for pulling out of junctions. Front brake is very disappointing - glazed pads? She's only had one owner who did just 4,000kms in 4 years. There's a bit of minor rust - already fixed that with Jenolite and Hammerite. Chassis flex is something I'm gonna have to get used to I suppose, and combined with the light front end, the handling is "entertaining". But the comfort, wow. 

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