Speeding Up The CG125?

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Speeding Up The CG125?

I've got a 02 plate CG125 with L-plates.

I'm getting towards 1000 miles now, and am thoroughly fed up with it's quite low top speed.
The best i can hope for is 65mph, and up hills it can often sit at 50, making me feel like i'm crawling.

I've read websites, googled it, asked a couple of mechanics.. but it seems like no one can really suggest much, and i wondered if anyone here could help instead.

Ideally, i'd like it to be able to hold 70mph, so i can take it on the motorway without causing high blood pressure to other (car) drivers.
Obviouslly this is probably not going to happen, but i want to know if there's anything i could do to give it a further little boost.

I'm already aware of wind resistance, and make sure to wear a reflective jacket to keep it down. I'm also aware i can lean right down (looking like abit of a plank no doubt, but it will work).

Apparently i can replace the spark plug with a NGK DPR9EA-9 for "extended high speed riding", which sounds ideal because it will apparently disappate heat better than the NGK DPR8EA-9's used as stock (hence maybe a few more sustained mph top end).

I use Shell V Power petrol (just on the chance it helps me out).

I could also change the sprocket, but i'm told this will murder the acceleration so i'm not willing to touch this option.

Short of boring out the engine (which would be illegal for learner use), what can i do?
I'm not looking to spend alot on this, i just believe there's got to be something more i can do.

And before you suggest it, yes i'm aiming to pass my test, but i don't think i will be able to afford to buy another reliable bike. (at least not for the small amount the CG's sale will cough up, and even then, i must be bikeless for an unknown length of time, which is not attractive to me at all!)

Not a lot mate and if you take it on the motorway without passing your test then you'll get nicked, once you have passed your test your ok as trucks only do 56mph so where is the problem?if you want something faster buy an older aprilia rs125 or a cagiva mito sorry its not the answer you were looking for. 

When you want to go faster lie on the tank and put your feet up over the indicators, used to give me a couple of mph on my old 125 apart from that go for the RS125.You won,t get a lot more out of the motor as it is.

I got an indicated 73mph on my CG, once. Down a hill, with a tailwind. And a good long run-up. And I weighed well under 10 stone back then. And the baffles in the exhaust were knackered. Did I mention, that happened once in the ten months I owned that bike?Sorry mate, it's not going to happen for you. Go get a faster bike. 

Wearing a reflective jacket will do sod all. Lying down on the tank will help. Removing the mirrors will also help, but it's a pretty stupid thing to do.On an ancient (design) pushrod engine with low compression, changing the spark plug and running on higher octane fuel will also do sod all. Changing the rear sprocket down one tooth will make the engine rev slightly lower, but I'd be very surprised if this helps. The CG's power(10.5?) delivery isn't exactly peaky, so it's unlikely that with standard gearing you're leaving the power band at those speeds - it's simply that there isn't enough of it.To get more power you'll need to increase torque or revs. Increasing revs on a pushrod engine is expensive, so you're left with increasing torque by way of:free breathing exhaustfree breathing carbsover-bore.The first two won't be illegal for a learner as long as they don't take the power above 14hp. But they will invalidate your insurance, possibly fail an MOT, and will make it a pig to ride around town.The over-bore will make it illegal for learner use.All of them may risk lunching the crank or con-rod. But as size12 says, it's illegal to go on a motorway as a learner and you seem intent on doing that anyway.I'm not sure I'd want to make a CG any faster given the way they handle either - it's generally wise to improve a bike's suspension and brakes before increasing power. If you wanted something fast, why did you buy a CG? How much did you pay for it?Pass your test, sell the CG, and buy a stink wheel. You've got to have one while you're young (I assume you are)! If you want to use the motorways for any distance, you'll ideally need a 500 - there are millions of GS500Es going for sod all money. They can be made to handle well, cost naf all to run, and will sit on a motorway all day.

My burd has a cg, I got just over 70 on the clocks on it down a hill with the wind behind me and I was impressed!!! It will slow to 50 up a hill. At 60 it starts to wobble, it's not safe. It's funny, but I realise how dangerous it is.What you gotta do is wait pass your test and buy an old cb500 or knackered old fazer, then you can get past 70 on the motorway.

you could try fitting NOS?

Rolling on the floor laughing. I've got some rope.

Good point from coronajones tho' - Nitrous Oxide and supercharging (including turbo) would make it faster - albeit very briefly.

Just to clear up a few things:1) I have no intention of going on the motorway with the L-plates (my apologies for phrasing my post in a way that caused that confusion). I'm thinking of the period after i've passed my test and before i've managed to obtain a more powerful bike (which could be actually a few years, which is a reason for the original question).2) I would highly recommend a read of this site to anyone that disagrees with the wind resistance concept. The fuel and spark plug are also mentioned there. Now i'm not a mechanic, and i know next to nothing about bikes, but i did do one test to check this guy's info: i did the same route with reflective jacket, and then with textile coat (the two opposites of wind resistance according to the webby), and i noticed i was pulling an extra 5mph top speed with the reflective jacket (something like 67 vs 62). So i'm going to take it that the guy was right . 3) I'm not actually crazy, the rope idea just isn't happening, amusing though the thought is ^^ . My (main) reasons for the CG were it's ultra-reliability, and fuel consumption. Very useful for a broke student with no mechanical ability!

Reflective jacket bends light to increase speed by creating a sencondary magnetic impulse field.Not effective below 50mph as a plasma trail will not ignite below this speed.Theory of phisiobullsyntheticsyntheshite by Dr Whom

why not just factor the average speed into your journey plans.leave 20 mins earlier. or, even better, fit an electrogravity drive / polarized hull, just like on the b-2 stealth bomber. 

Air resistance is caused by two things. The first is form drag. This causes turbulence, vortex shedding, stagnation points - all of which generate areas of low pressure behind the object, causing a rearwards, or decelerating force on the object. The second is skin friction. This is a thickening of boundary layer due to general pressure gradient. As the the Reynold's number increases, the boundary leyar thickens - it gradually moves from thin (laminar flow), to transitional (damped eddies) through to unstable (vortex shedding).  Now, think about it. Your helmet is already smooth. Yet it still suffers buffet. If you covered your helmet with textile it might actually help - the reason being that you can trip the boundary layer from laminar, to turbulent, before it goes through the lossy transitional phase. This is the same principle as the "golf ball effect", and also they way that swing bowlers make a cricket ball move by polishing one side and picking the seam on the other. The polished side doesn't trip the boundary layer and actually undergoes MORE drag!In terms of aerodynamics motorcycles are a short, and therefore relatively blunt, or "bluff" bodies. Most of the drag is form drag - you can feel this from the buffeting on your helmet. Bikes with panniers feel this as shimmy, etc, etc.SO. It is more likely that leathers will suffer less drag than textiles because they're tight and don't billow, so they don't create extra "form" drag. The effect of them being smooth could - depending on reynolds number - actually be more damaging than them being a bit rough, but this will pale into nothing compared to the form drag effects. It seems like sticking a Hi-viz over the top of a bulky textile jacket will do little unless the jacket is actually letting air through..The guy you quote is right to say that fitting lower bars won't help much, but that's simply because they only drop you by a couple of inches. If you laid with your arse on the pillion seat and your chin on the top yoke, it would help a lot more - look at the way GP racers tuck in. The bar position is more about allowing them the space to tuck in OR sit upright for braking, than actually dropping  their body down. As for the spark plug issue, it seems that the main reason for the change in plug rating will be the changes in carburation. Newer models will run leaner for lower emissions. Ths will make them run hotter, so need a spark plug that dissipates more heat. This leaner running and cooler running plug will also make it harder to start - probably why there are so many more people struggling to start CG125s these days.In all honesty, if you're a skint student and want something faster, your best bet is to get friendly with someone very mechanically minded. That way you can pick up half decent bikes for not a lot of money, sort the problems out, and have a good bike at the end of it. Spending any money on making a CG125 faster is not going to be well spent - "there ain't no substitute for cubes" is an old truism. You could do SO many things from freer breathing pipes, filters, carbs etc all the way through to serious engine work. All that would happen is a decrease in reliability, increase in fuel consumption, and at a cost that would enable you to buy something faster and still have petrol money left.

250 superdreams go for peanuts on ebay and they will hit 90 just


just wear the right streamline gear this man rides a CG (among other things)

hungry (not verified)

size12 wrote (see)

just wear the right streamline gear this man rides a CG (among other things)

Where did you get that picture of DAVEMAX. does he know you have put it on here, thats not on mate.

He said i could use any pic i wanted aslong as i didnt show him on his CG

Isn't that just a police biker without his top leathers on???

I know this thread's been been put to sleep, so this is a bit of a long shot. Just wondering, when tappy says that a freer breathing exhaust would make it a pig around town what he means. also, how easy is it to take the baffles out of the exhaust, is it just a simple question of a long bit of metal and bashing them through?Also, tried taking the airbox cover off my '51 plate CG and found i got a HELL of a lot less power than with it on, any ideas/fixes?CheersBen

TJBeezer wrote (see)

I know this thread's been been put to sleep, so this is a bit of a long shot. Just wondering, when tappy says that a freer breathing exhaust would make it a pig around town what he means. also, how easy is it to take the baffles out of the exhaust, is it just a simple question of a long bit of metal and bashing them through?Also, tried taking the airbox cover off my '51 plate CG and found i got a HELL of a lot less power than with it on, any ideas/fixes?CheersBen

yes, put the bloody thing back on it. Look, it isn't going to happen. You're far better off spending a bit of time learning how to service it, clean it & ride it & not crash it. You do all know what chain lube is yes? Consider it his way-you all bought the CG for a reason. Same reasons as the buyer will when you come to sell it. So keep it standard, keep it shiny, keep it well maintained. It's that resale you want to aim for. I dunno what the brakes are like on these, but if they're not that hot then that's a mod that's acceptable. Essential even! If you want to do the lying on the tank thing, I use a tankbag & let that take the weight of my chest. Makes all the difference having a cushion. Perhaps consider a 2nd hand screen. Perhaps. Keep off the dual cariageways then. Play riding tuition games. Dare I mention countersteering? get some extra instruction. Go for a ride out with someone more experienced. Develop slow speed control of the Gods. This time is all about learning & confidence. And safety. It's one thing coming off at 60 (which you won't because you're all paying attention). It's quite another at 90 (which you well might because stuff happens a LOT quicker). There's a very good reason you're restricted to what you are & it's for your own good. not what you wanted to hear, but.. And if you get points for loud pipes, bad tyres (3 for each tyre) nicked for speeding, nicked for mods taking above the power, you're insurance will be bum clenching. Which would be such a shame because you're all trying to build up that NCD. Besides, consider it a right of passage. We've all been there & we only had 50ccs. You won't half love your next bigger bike & be able to fully use it. HTH

What does "Sorry, this thread has been deleted" mean exactly, and WHY? Since I can type here, I'll assume its still "open", in some way.If you REALLY want to put some effort into this, I'd say you are more likely to get payback (and less likely to break your bike) if you leave the engine alone and try and  improve the aerodynamics. Since standard naked bikes are so bad, significant improvements are possible with fairing, though the biggest have been achieved with a "feet-forward" configuration that won't be achievable with a CG125.DIY fairing could be low-tech and quite cheap. For temporary, experimental attempts you could use skin-on-frame techniques, or papier mache. If you get something useful you could do a more permanent job in glassfibre. As a bonus you might get some weather protection, and maybe some crash protection too. There are potential dangers, of course, like reduced steering lock, sidewinds, (see the controversy on "dustbin fairings") sharp edges, so you'd have to be careful, and regard it as an experiment, but if you survive your bike should be easily restorable to stock, and anything learned could be transferable to another bike,Checkout Craig Vetters sitehttp://www.craigvetter.com/pages/470MPG/470MPG%20Main.htmlOr this streamlined Honda Innova. A crude prototype increased top speed by over 10mph, with more to follow (though this is a feet-forward design, and the focus is on mpg) http://www.wired.com/autopia/2010/01/streamlined-honda-innova/http://www.gizmag.com/honda-areodynamic-scooter-conversion/14071/   

empty your pockets befor eyou get on the bike! loose some weight, go for a jog 3 times a week!!! leave it alone man, just ride it and sell it on when done and buy a faster bike later. its really not worth the effort How fast do you want a 125 to go? how much money have you got?!!! you could spend a few hundred quid having the cam reprofiled and maybe a re-jet, bigger carbs, high flow air filters blah blah blah, you could have the head skimmed blah blah blah.........but theres really no replacement for displacement on a road bike. bigger engine; more power to you.

it might touch 120mph if you threw it off a cliff

just thought i would tell you what ive done to my giantco 125 hunter (cg clone), changed the front sprocket from 15t to 17t,rear from 49t to 36t,fitted a 28mm delorto carb and fabricated a new manifold as well as ported the head,machined out the barrel and fitted a new liner,bored to 69mm using a honda g200 piston,also had to machine out the crankcase bore to take the new liner as well as fitting packing under the clutch springs to stop it slipping,the next step is to make a new single walled down pipe for it out of stainless steel,all these mods have taken the top speed from about 60mph to over 90mph,time will tell how long the bottom end will last!,fuel consumption has gone from 100mpg to about 60mpg!

Ha ha ha, brilliant. Completely silly, but sounds like fun You done any changes to the valves / pushrods / cams?

Not at the moment,there isnt much that can be done with the cam as its a single lobe that operates both the inlet and exahaust,i may grind 20 thou of of the base circle of the cam to increase valve lift but thats about it as far as the cam goes,i have a spare bottom end that i may strip,im thinking of offsetting the crankpin about 4mm to give an 8mm longer stroke,this should strech it to about 238cc,but we will have to see when i can find the time to do it as its not a 5 min job.as it stands its about 197 cc at the moment.

Just thought i would explain the maddnes in doing this!,before i get thrown in a room with rubber wallpaper.the bike is a april 2010 model that i brought with a busted fairing for £200,so its pushbike money,and its only got 6000miles on the clock,im a self employed mechanic and have free reign of a decent machine shop,mills lathes etc,one of the things i forgot to say is,the piston kit for the honda g200 engine was £12 from ebay,the liner was from a 875cc hillman imp,the g200 piston is ideal as its flat toped which helps keep the c.r down a bit,it also has a 15mm gudgeon pin,the carb was scrounged from an italian nsr 125 honda with a homemade flange tig welded on,on the firt run it holed the piston but i tig welded it up and built up the piston under the crown to give it a bit more meat,after machining out the squish band in the head and fitting 2 head gaskets its runing ok at the moment,its only done 100miles since the work so its still running in,the whole lot stands me at about £250 and about a days work,its a small price for a bike which i imagine is putting out twice the power as standard and if it blows up it hasnt realy cost me a great deal,i wanted more umph from 40mph to 60 mph so i wasnt getting stuck behind lorrys without the guts to get by them,i dont think doing anything with the valves is an option as there isnt much room to fit bigger,i take it up to about 9000rpm with no valve bounce and max power seems to be at about 8000 so i dont see much point in lightening the rockers etc,hope this info is some use to folk trying to get more umph out of a cg!,cheers for now.Paul.

Not at the moment,there isnt much that can be done with the cam as its a single lobe that operates both the inlet and exahaust,i may grind 20 thou of of the base circle of the cam to increase valve lift but thats about it as far as the cam goes,i have a spare bottom end that i may strip,im thinking of offsetting the crankpin about 4mm to give an 8mm longer stroke,this should strech it to about 238cc,but we will have to see when i can find the time to do it as its not a 5 min job.as it stands its about 197 cc at the moment.

Yeah - guess you could put in lighter push-rods, heavier springs, and a slightly harder opening cam, but sounds like a pretty fun project anyway. Of course - there's always super-charging and nitrous

well time for an update,ive done 3000miles so far and made a few changes,first off i found another head off of a loncin off road bike with a 2mm larger inlet valve and a 1.5mm ex valve and fitted that along with an oil cooler,with this fitted it does 0-60 in about 7 secs,not sure of the top speed but the speedo and rev counter go off the clock (speedo goes up to 87mph) but i think about 95 at 12,000 revs,also forgot to say i ground 2mm off of the base circle of the cam,im running about 20 thou clearance on the valves and piston,not a lot but it seems ok up to yet!,well the problems so far are two blown head gaskets and a busted gearbox second motion shaft bearing!,firstly on the head gasket,well this was fixed by making one out of a piece of copper hot water cylinder and annealed and its been no trouble since,then on to the gearbox,this was a bit hairy as the bike locked up solid at about 65mph!,when the bearing broke up it let the shaft move sidwards about 3mm causing the kickstarter to engage,this shot the lever downwards at great speed denting the silencer,luckily it mist my leg which im sure it would have broken!!,the shaft was scrap as the bearing surface had bits of needle roller welded to it!,i ended up using one crankcase fron the loncin engine as the bearing was about 1mm bigger than the standard giantco crankcase,also the clutch end of the selector drum is supported by a needle roller as the original case it just runs in plain alloy,also the jet in the oilway that feeds the bearing has beed drilled out to 2mm to increase the oil supply to the bearing,was it all worth it?,well as the whole lot has cost me under £100 for all the mods and a few hours work i think so,it comes on cam at about 7500 rpm and pulls to 11000 plus,ive had a few old honda 250 twins from the 1970s and this would thrash them into the ground,so ive got a bike thats light goes like stink looks pretty standard and is fun to ride,so on the whole i think yes,the only downside is the fuel consumptiom,about 45mpg but you cant have it all ways lol.

Ha ha ha - I SOOO need to see that some day

could easy get the 124cc pushrod engine doing 80-85mph but with you will have lost its reliabiltiy afew simple things to get it faster are for starters a bigger cylinder and piston go for 150cc then run it in properly!!!!! a free flowing air filter and bigger jets in carb then set up mixture screw and idle screw so set up for bigger cylinder and airfilter... then get a bigger front sproket maby 2teeth extra and smaller rear sprocket 2 teeth less... all of this is available online and will only cost around 150 if installed correctly will get it going alot faster!!!!!! if run in properly and not ragged for ATLEAST 500 miles then the bike will be pretty realiable my mate has a cg125 br and has it cruising happy at about 73 on straights and about 80-84mph top speed down hills and hes had like that for over 6000 miles with no ishues or signs of ishues! got to remember that with a bigger air filter and carb the cylinder will get very hot if carb not set up properly so make sure you have it running slightly lean as its air cooled and will keep it cool! also doing this to the cg125(150) will blow the baffels in the exhuast so no need for a race pipe and dw it isnt any loader so no need to worry... and he has a the old drum brakes and they are not made to stop you past 65 so brake shoes will get replaced more quickly and so will clutch plates and tyres take it account its gunna cost you more for tyres petrol brakes oil clutch plates if ragged!! if used just to get abit faster but not ragged then nothing should cost more not even petrol as bigger front sprocket and smaller rear sprocket means that the speed will be faster but engine wont be going as mad to make it go that speed!!! rant over!!! good luck if this helps!!!

Hello I have a cg125 2006 model and myn does 82mph and it's standard apart from havin a Pirelli front tyre and a Michelin rear tyre

In that case your speedo is over-reading by about 20mph. Even if you weighed 2 stone the engine wouldn't rev that hard with standard gearing.

A lot of these suggestions while helpful will probably not do much for your average CG 125 owner as they are unlikely to have access to a machine shop or indeed the know how to do extensive mods such as cam re profiling etc. My advice is to find someone who races or used to race a CG and tap in to their knowledge. There are many Honda c90 or nifty fifty racers out there, I know there was a CG race series ( not sure if it still exists) and as long as it is a four stroke small single the same principals will apply. 17 year olds who want to make their bikes go a little quicker will always exist, so lets try and help them with practical advice. If I were to try to gain a little more speed I would start with letting the engine breathe better, a slightly bigger carburettor, free flowing air filter (k&N with suitably uprated jetting), and a less restrictive exhaust would be a good start. My advice is to use only parts of a known good quality and do not expect miracles. A hundred pounds or so spent on performance parts may result in a couple of MPH gain and an almost un noticeable acceleration improvement, but the same money spent on decent tyres shocks and brake shoes will make your life a lot happier, safer, and make your bike appeal to a wider market when you come to move on to something bigger, as there is no substitute for cubic capacity when you want reliable power. So use your humble CG to gain riding experience for when you can move on to something bigger. When all is said and done all major manufacturers have massive development departments that test and develop products over many years to make sure they will be reliable and durable in (normal) use, so when you mess with the things that extremely experienced guys have spent years perfecting you are extremely unlikely to be improving anything and most likely to upset  what is usually a compromise over performance, economy, and longevity.    

Some bs in there I think, I am very dubious that a CG can be bored to 197cc having just built one at 172cc myself. And running weak will cause over heating not prevent it! My Engine build. The crank case mouth needed machining out which broke into 2 oil galleries requiring tig welding and rerouting of the oil feed to the gearbox. An HE30 ally liner was made, inserted and Nicasil plated, Forged 66.5mm Wiseco XR200 piston I could have gone to 70mm but would have been .1cc over 175 which is no good for my intended use!  bigger valves, 272 deg cam @ 1mm lift with 106 lobe centre and 64 deg of over lap. CRF15R0 32mm Keihin FCR flat slide carb. Combustion chamber and Valve seats cut deeper deeper into the head to gain more valve to valve clearance for the increased over lap and valve size. The cam was one made by a tuner in Thailand for the Australian bucket racing series which I have modified further with more lift and duration. Titanium tappet adjusters, lightened rockers and followers. Hopefully it will be on the dyno in April, looking forward to that! Pics here. http://s164.photobucket.com/user/tench8/slideshow/cg172  

is this all a dream 

Had mine on the dyno today, 20bhp at 10500 rpm, a totally flat torque curve from 7 to 10.5k and it over revs to beyond 13000 with no valve bounce and only a 1bhp drop! Well pleased with that. I should get the graphs sent to me tomorrow.  When you over bore a 2 valve engine they often produce peak power at lower revs because the porting and valves reach peak air flow at lower rpm so I am very happy to see the peak power up there, shows the bigger valves, increased lift and duration did more then just allow for the extra capacity.

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