They say love is blind, and sometimes it’s blind and broke. This relationship might lead you to broke if you choose to rent a Suzuki GN125 to ride and backpack Vietnam. If you’re really looking for a quality bike, skip right to renting a quality Honda and save your money for mayhem, not mechanics. If you’ve already bought the GN125 read on and we’ll explain to you the best way to fix it.
Suzuki GN125 – Expensive, Troublesome, Beautiful, Crap!
The Suzuki GN125 hit a chord with the locals back in 1996, so much so it moved from an imported bike to a bike assembled in Vietnam shortly after. A bike with so much personality that’s truly fun to drive it’s no wonder the popularity of the bike soared. By 2001 the bubble burst, and now all that’s left are many great looking bikes often filled with Chinese parts and broken dreams.
Anyone who’s new to motorbikes might have come from something like the Yamaha Exciter, a bulletproof bike that only needs oil changes every 1000kms to maintain and otherwise flawless engine. After running around on this for a while and noticing the cruising eye candy that is the GN125, you might think you’re ready for something that looks a lot more sexy and a little less scooter.
Well, unless you’ve got some magic horseshoes up your ass that has allowed you to find one of these bikes in top condition, you’re very likely to spend a lot of time working on it or limping it around to mechanic shops. If your love of the bike is too strong to resist, not to worry, our very own Link feels your connection, and after years of taking his personal GN from shop to shop, he’s outlined some helpful tips and where to find the best GN mechanic shops and popular solutions.
As handy as it would be, the GN doesn’t have a kick-start. Unusual for this kind of motorcycle, but too bad, it doesn’t exist. The next problem is, the GN doesn’t generate its own power either, or if it does we’ve never tracked down the source of this power. Instead, it relies entirely on the battery.
Electrical tip #1. If you’ve just bought the bike, immediately check or switch to 9A+ batteries and make sure to use a proper charger that will stop sending power once the battery is fully charged. This will save further electrical problems down the road.
Link learned the hard way that not just any back-alley mechanic can work on the intimacies of the CN electrical system, and after trial and error have found an excellent Ho Chi Minh City mechanic in the list below.
Electrical tip #2. If you find your battery is dead or you need to push start the bike for any reason, turn on the key, pull in the clutch, drop the bike into 2nd or 3rd gear, then give it a good running start before releasing the clutch. As you hear the engine start to engage, pull the clutch back in and rev it up. Why not 1st gear? First is too low and you’re more likely to kiss the handlebars with your face when you drop the clutch opposed to the low transition into 2nd or 3rd. This system should work well to push start any motorcycle.
Cam Chain Tensioner
Little annoyances become big annoyances on motorcycle trips. If your bike has the familiar clicking noise coming from what seems like the engine. It’s likely the cam chain asking for maintenance. Over time the cam chain will gain slack and need to be tightened again, or the slack will begin to cause this slapping or ticking noise.
The annoying engine clicking noise is one of the most common problems that Suzuki GN125’s develop. If you know how to deal with it, then it’s not too bad! All part of Vietnam motorcycling.
Cam chain fix #1 is going to be using one of our recommended mechanics to manually adjust the chain tension, then have him explain to you in detail how to adjust it yourself in the future.
Cam chain fix #2 is going to be to purchase an automatic tension kit from the same reputable mechanic, and the problem will forever fix itself.
Cam chain fix #3 will be to buy a cam noise terminating kit to get rid of the sound. This last fix, however, is more like muting a problem, so you don’t have to deal with it rather than actually fixing it. Expect to come home and see your bike leaving you one day if this is how you plan to deal with the problem.
Typically an oil leak is a faulty seal, gasket or something loose. You’ll need to make your personal diagnosis to see if the leak is getting bigger and requires a fix or if you can live with it. Hell, sometimes just tightening the bolts around the problem area (gently so as not to strip any aluminum) can solve the problem. If this doesn’t fix it, continually pouring the cheapest oil you can buy into in the engine and watching it slowly chip away at your pocket money like the rest of the bikes problems are also a rational way to deal with it a leak.
CDI, or “IC” as the Vietnamese call it
Generally referred to as the CDI, you might hear it referred to as “IC” by the Vietnamese. Your CDI (Capacitor Discharge Ignition) is used along with the battery to build up a quick charge then send it to your spark and start the motorcycle. If you’re like Link and replaced the quality battery with a Chinese battery, you probably fried your CDI. Instead of saving yourself money on the battery, you now need to replace the battery and the CDI.
Good luck finding a quality CDI for your GN125. However, if anyone can do it, our specialty mechanic below can probably do it. The drama of finding parts for a dying breed of GN’s helped put it on The 40 best and worst motorcycles in Vietnam list.
Increasing Your CC’s
Why ride a 125cc, when the same bike can magically become a 250cc? A common upgrade on motorbikes in Vietnam is to take the GN125 above its 125cc size up a level or two. Most mechanics can bore out the engine for you to a 250cc on the theory that the cylinder wall on the 125 is thicker than average. This is more wishful thinking than facts though, and if you’re looking for more power, you’re better off getting an upgrade kit.
Other options include picking up an upgrade kit that consists of a cylinder head, piston, and camshaft. These kits can easily bring you up to 150cc for around 1.5million vnd. They are also less risky and 100% easier to reverse than boring out the engine hoping to double its size. If you’re still thinking 250cc, remember that you need to adjust more than the bikes cylinder circumference. You’ll still need to change the carb, air, CDI, some jetting, and on and on. The bikes probably already a money pit, no point and digging it any deeper.
A simple fix that might give a touch more power and some piece of mind. Swap out the bikes crappy carb. If you can find a quality Honda Sonic 150 or Centa 150, replace it with one of those and you’ll notice a big difference at a small price.
Mechanics, Parts, and Help
Mr. Thanh in Go Vap district. He is an excellent source for parts.
He’s an excellent mechanic who’s turned his home into a mechanic shop into the place to get work done on GN125’s and other classic vintage bikes.
Contact: 0938998148. It’s easier to drop him messages on Facebook
Address: 710/2 Phan Van Tri, Go Vap District
Mr. Hưng at 117/13 Bàn Cờ, D3.
A skillful mechanic with the GN, SYM Bonus, Honda CD125. He also takes customization jobs.
Final Thoughts From Link
“Despite all the headache and money spent, this motorbike is actually fun for those who love the classic look! Just be aware that it requires some pushing the motorbike around when it inevitably breaks down. After all, is this not the point of a classic old school motorbike? It is supposed to be an ongoing classic project!”
Check out our motorbike tips page for more great info on motorcycling Vietnam.
29 Replies to “Tips To Maintain A Suzuki GN125 And Other Long Shots”
Hey, so I don’t inevitably get ripped off, how much should those carbs be?
Thanks for the article, really helped.
Thanx for all ideas ,my bike have got a shot in ages sensor so it continuously burn the fuse l checked all the shots l only found that one chore coming from sensor have got internal short inside the gear sensor
My 92 suzuki gn125 won’t go pass 40mph in 5th gear
A quick question about the air filter: the “cone” type works well with the electronic injection? it does compensate the mixture leaning? which model are you using^
I jumped back and forth from the K&N reusable type filter, to the orgignal one, and found no difference. Are you having fuel injection on your GN?
Hey thank’s for all those good information about the GN!
I just buy a GN from 1995 and I have big problems to go up to 50-55kh/h do you have any idea why my bike is so slow?
Can check again with the engine.
Thanks for the advice! Do you have any idea of where can I go in Hanoi to have a guy who know well the GN?
You can try this store.
Hoang Tien’s motorcycle repair shop
35 Hương Viên, Đống Mác, Hai Bà Trưng, Hà Nội
Thank you mate! And thank’s again for all the information in this topic!
I am so happy that I found this article. This was the topic that I need to learn.
Glad it helped someone
I just bought a GN125 in Hanoi not long ago, had the engine rebuilt, but it seems to run quite hot, even just riding around town the engine gets really warm quite quickly. It did this before and after the rebuild. Also is the another way to check the oil level? The oil window is dirty on the inside so I can’t check the level? Is it easy to replace/clean it?
In my experience all GN125s are likely very hot.
Cleaning the oil window is easy I guess. Replacing, only if you can find the replacement part.
Thank you very much
Welcome to phutungmotosuzuki.com
Thanks for your article but I think your being a little severe calling it a piece of crap! The CDI problem was caused as you admit by putting in a crap battery and it leaks a little oil but other than that whats makes it crap? There is apparently an issue with the rings going and unfortunately I was caught out by it (I think I have the bike Peter posted about earlier). I did an overnight run from Ho Chi Minh City to Siem Reap and it burnt most of the oil, there was about 200ml in it. Was making an awful racket up the top end. Had the rockers replaced there (couldn’t source new cams there) and by the time I got to Hue via Laos it was making a horrible noise again, very stressful waiting for it to give up but it just kept going and going (I was two up by the way…). Had the rockers, cams and rings replaced by Kim Thien in Hue, good bloke, recommended. Now its rattling, I pretty sure the big end bearings are on the way out. I’ve done about 4000kms since it ran out of oil and have about another 2000kms before I get back to Ho Chi Minh . I’ll see what Mr. Thanh (who I’d already met) can do for me, another good bloke, super helpful, was prepared to send me cams etc to Cambodia and let me pay when I got back to Ho Chi Minh but shipping was ridiculous… I love my GN125, the engine appears to be very strong and I believe she’ll get me there! She really hasn’t missed a beat (my stupidity for not checking the oil on my run and ignoring someone mentioning it was blowing some smoke at some point). BTW I replaced the carb soon after I bought it with a GY6 150cc (its what the mechanic in Vung Tau turned up with after I showed him a picture of a Centra 150, it was the same he had in his GN) after reading this article and it made a great improvement to the power and general running…
Thanks for your great story!
It seems you have answered your own question though.
You have visited several mechanics on your journey with difficult to solve problems.
At Tigit we like the GN, huge fans.
However a good motorbike does not breakdown :D.
The GN used to be a high quality bike that was used by the Police in Vietnam back in the day. The lack of support from Suzuki, replacement parts and well trained mechanics at the same time, made it a crap bike.
This is where backpackers get confused, the rental of a genuine and modern Honda, say a Honda Blade, will have a holiday of no issues.
Just like renting a car back home… A traveller should not expect to be visiting mechanic shops 🙂
For the same amount of money to buy a GN, I did get a second hand Honda Blade, which I know (not believe) that it’s capable of taking me everywhere I want to, and maintenance cost is minimized to an oil change every 3000km, plus smooth and quiet sound for the ride.
Yeah, point taken, I was aware of it while I was writing my story 🙂 But there is one BIG problem with the Blade (for me anyway), it’s a scooter 😉 I’m 6’1″ and the GN is comfortable to ride, I can sit on it all day!
Just an update on the bike. The noise from the bottom end got really bad but i must admit i wasn’t being very gentle with it, got a bit carried away on some of the deserted back roads 🙂 Put it on the train about 800kms from Saigon and took it to Mr Thanh. Excellent mechanic, really knows his stuff, very through. He’s working on bikes fulltime now, honest pricing, highly recommended. The engine required a rebuild top and bottom, clutch, cam chain etc. Plus I got him to put a 150cc piston in while he was at. Basically a new engine, it’s running great, I’ll be keeping it. And keeping a closer eye on the oil 🙂
I heard Mr Thanh began with pure passion towards the GN125, and wasn’t trained as a motorbike mechanic. He learnt everything about motorbike himself. He is skillful for sure, but always has a long list of waiting customers :).
I know there is a 150cc upgrade kit with 150cc piston and cylinder for the Gn125, which can be installed without any modification. Is it the one you’re getting?
No, not not the kit, cylinder bored and new piston. I was a little concerned about how much of a difference it would make but it’s been well worth it. Added 15kmh to the top speed (now ~110khm), gets there with much less effort and in the past you knew immediately when you started going uphill, now it just keeps pulling. Full consumption is up of course but not by much. I havn’t pushed it too hard yet, giving it some time to run in properly. Glad I’ve done it 🙂
Did you ever follow up with the oil leak problem?
Hi, thanks for spending time reading.
I haven’t had time to follow up with the oil leaking problem, however I believe that it is caused by certain broken rubber seals, and replacing the seals is the solution for this. It may sounds like a quick fix but actually the mechanic will have to open up the entire engine to do that and it is very time consuming.
The oil leaking problem on my GN isn’t too severe, and I haven’t really used the bike much except for going to work so I just choose to ignore it :D.
Thanks for taking the time to write the article. It was very informative. I wouldn’t be surprised if our bikes were leaking from the same spot. On my bike, there’s a rubber cap on the side of the rocker arm cover that slowly leaking oil. The oil drips down the cooling fin towards the front of the engine. I spoke to one of the mechanics you cited and received a quote for the repair. I haven’t decided if I want to get it fixed.
Hey Pete, would love to know the result of your effort so keep me updated.
Thank you for “Tips on push starting the bike when battery is dead”. It saved my life!!!!!!!!!!!
I’m glad it did!
Hey there mate, nice blog about your gn125. Where can i get the honda sonic 150/centa 150 carburetor? Is there anyway they can ship to singapore? I’m from Singapore by the way. Hope to hear from you.
Hello there! Thanks for spending time reading. Unfortunately I don’t know how to get a Honda Sonic / Centa 150 carburetor to Singapore. Maybe you can check with Honda Dealer in your area? If you can’t, it’s simply down to experimenting different type of carburetor to find out what works best for you. Something 150cc is considered good.