FAQ and general information

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FAQ and general information

Post by bourney on Sun Jul 26, 2009 7:49 am

Carburettors, air filters and plug chops.


-What the jets/screws do and how to find them

Most carbs fitted to the RS50 and GPR50 have 3 jets. An idle jet, main jet and choke jet. Ach basically do what thy say on the tin, the idle jet controls the mixture at idle, the main jet controls the mixture at anything above ¾ throttle and the choke jet basically richens up the mixture to make cold starting easier.
On the outside of the carb are 2 screws, one is in the centre on one side of the carb with a spring covering the thread of the screw. This is your idle speed screw. It’s basically a screw with a tapered end, it screws in just below the barrel inside the carb, the further you screw the screw in the higher the barrel will sit, increasing the idle speed.
The other screw is on one side of the air intake on the carb. This is your idle mixture screw, it’s to adjust the air/fuel mixture at idle, it does absolutely nothing for the mixture at anything above idle.


To get at these jets is very simple. At the bottom of your carb you will see a piece of black plastic, this is called a float bowl. Un-screw the float bowl and the jets are staring you in the face. The one in the centre is the main jet, the very small one to the left of it is the idle jet and the other to the right is the choke jet.




How to know what size jet to put in

Whenever you change anything which adjusts the breathing and/or capacity of the engine you need to re-jet the carburettor. These changes include performance exhaust systems, open air filters, big bore kits, carburettor venture size (bigger carb) etc.

You need to change the main jet. To do this you need to do plug chops and re-jet accordingly until the plug comes out a chocolate brown colour.

There 2 types of jets for the dellorto carbs fitted to RS50’s. These are 5mm and 6mm thread diameter, so make sure you know the thread diameter size of the jet you need for your carb




How to do a plug chop

First get a shiny new plug, you could clean an old one but for the sake of a couple of quid it’s not worth the effort in my opinion.

-Now, warm the engine up on an old plug.
-Once it’s warm whack your shiny new plug in and go off down the road with the throttle pinned open.
-Now simultaneously pull in the clutch and switch off the ignition, do not allow the revs to drop/engine braking to kick in etc, just roll the bike to a stop.
-Change the plugs back over and ride home (or push it if you aren’t far away).
-Look at the electrode on what used to be your shiny new plug. It will either be black and oily, chocolate brown or white have a few deposits about.

Dark and oily = rich mixture, reduce the size of the main jet
Chocolate brown = Perfect, the mixture doesn’t need adjusting anymore
White and deposits = Lean, increase the size of the main jet.



Open air filters

These are foam and K&N style filters, basically any air filter that isn’t the standard air
box.
These air filters do absolutely nothing for the performance of the bike, they simply increase induction noise.
Like I said earlier, when you adjust the breathing and/or capacity of the engine you need to re-jet the carburettor. Fitting one of these air filters adjusts the breathing of the engine so the carburettor has to be up-jetted.



Bigger carburettors

When people say they have a 14mm carb or a 21mm carb etc they are reffering to the size of the carburettors venturi.
The biggest difference you will notice from fitting a bigger carb will be bottom end power, but it will add a very slight amount of top end.

Generally the biggest carb you want to be fitting to a 50cc is 19mm and if you add a big bore kit to your engine then fit a 21mm carb. However some have fitted 21mm’s to 50cc’s and up to a massive 28mm to big bore kits.
The problem with fitting huge carbs to small capacity engines is they get quite tricky to set-up, that’s why it’s generally suggested that you fit a maximum of 21mm carb to a big bore kit as it’s not too difficult to set-up properly.

You will need to set-up the jetting when fitting this carb.





Cylinders


What is a big bore kit?

A big bore kit is a larger capacity cylinder than the standard one. The capacity is increased by making the diameter of the cylinder and piston larger.
Generally the biggest big bore kit you can buy without having to modify the crankcases is 80cc. 80cc refers to the amount of air the cylinder can take in but it will never actually take in 80cc’s of air as volumetric efficiency is never 100%


What is porting?

Porting is adjusting the port timing. A 2-stroke engine has ports, to bring in air/fuel and chuck out waste gasses, not valves like a 4-strokes does, this is why the revs don’t drop back down as quickly on a 2-stroke as they do on a 4.
Adjusting the port timing is a great way of improving the performance of your engine. However, it’s a specialist job and I wouldn’t recommend doing it yourself because if you get it wrong or accidently scrape the cylinder lining you will need a new top end.




Exhausts


Will an arrow end can improve the performance of my bike?

No. The end can makes no difference to the performance of the bike; it’s just there to keep the noise down.
The part of the exhaust system that makes the difference to the engines performance is the expansion chamber. Each expansion chamber from each different company will be a different shape. The expansion chamber creates back pressures among others creating the powerband.


Will a newshape rs50 exhaust system fit the oldshape rs50?

It may be possible with a lot of modification but in short…. no. The newshape rs50’s have an underseat exhaust, meaning exactly what it says on the tin, the end can comes out underneath the pillion seat. So for this reason the newshape exhaust system won’t fit an oldshape rs50 without serious modification.



CDI

Will a ‘performance’ CDI make much difference?

Not as far as I can see. I’m not 100% sure what these so called performance CDI’s do but the only thing I can see them doing to increase performance is advance the ignition timing slightly. This can be done for free by rotating the stator plate slightly.

I spoke to someone who bought one of these and they said they can’t tell the difference between the standard and performance one




Crank


I’ve fitted a big bore kit do I need to change my crank?

Ideally yes. The big bore kit puts more strain on the crank which don’t forget was only designed to be used on a restricted 50cc bike. So for this reason most people replace the crank with a strengthened one when fitting a big bore kit.


What advantages are there to fitting a performance crank?

Aside from it being stronger than the standard crank there is no other advantage, they may be better balanced than the standard crank, I’m not sure.

The only other time you would replace the crank is if the big end bearing gives way or the crank/con-rod breaks. Splitting the crank is a specialist job and requires specialist hydraulic tools to do as it is essential that the crank goes back together perfectly as if it doesn’t the balance will be upset and it will vibrate like made and eventually just snap.
As it’s a specialist job it often costs just as much to buy a big end bearing and have it fitted than it would to buy a whole new crank so most people just fit a new crank.




Reeds


What do performance reeds do?

Performance reeds are just stiffer than the standard reeds, as they are stiffer they do not ‘flutter’ as much at high RPM.





Gearing ratios


There are 2 types of gearing ratio, internal ratio and external ratio. The internal gearing ratio is the gearing ratio of the gears in the gearbox and the external is the gearing ratio of the front and rear sprocket.
The problem with changing the external ratio is it effects the ratio in each gear but it’s a hell of a lot cheaper and easier than changing the internal ratio.

The higher the ratio the slower the acceleration but higher the top speed and visa versa.
Thinking you can just whack the gearing ratio up really high, have piss poor acceleration but decent top end is all well and good until you get to a hill, which you will be crawling up. You can only go so high on the gearing ratio before the bike isn’t able to pull it.

If you only use your bike to run around town and to do short trips on winding roads then gear the bike for acceleration, but if you use long straight roads a lot then gear it quite high so you can cruise at lower rpm and save your engine.

-Increasing the teeth on the FRONT sprocket INCREASES the gearing ratio and visa versa.
-Increasing the teeth on the REAR sprocket DECREASES the gearing ratio and visa versa




Clutch

There are 2 types of clutch a dry clutch and a wet clutch (multi-plate clutches can be either dry or wet but the single plate clutches are generally dry and used in cars.) The most common type of clutch used on a bike is the wet clutch, meaning the clutch runs immersed in oil. Pretty much the only bikes that use a dry clutch are ducati’s, this is what gives them the legendary ducati rattle.
A multi-plate clutch means it has multiple friction plates. This type of clutch is used in engines that need to transmit high amounts of torque.


The clutch in the RS50 is a wet, multi-plate clutch. So when you change the gearbox oil make sure you replace it with oil that is for use with a wet clutch.

When you fit a big bore kit replace the standard clutch wit a stronger one.














M.O.T requirments

You need a working:

-Dipped beam (and the aim and kick off have to be right)
-Main beam
-Rear sidelight
-Brake light for the hand and foot brake
-indicators (they have to flash at a specific rate)
-Horn
-Speedometer

The brake pads have to have at least 1mm of material on them and the disc must not be warped and must meet a minimum thickness.


The headstock bearings must have no play in them and when turning the handle bars lock to lock it must be a smooth movement, no clicking or cables etc preventing movement.

The front and rear wheel bearings must have no play and when spun up spin smoothly, not making a growling noise. You are allowed a slight amount of play in the bearings, it will just be put down as an advisory but I recommend that you do them anyway.

The exhaust must not be blowing.

The chain and sprocket should be in good condition and the chain correctly tensioned.

The tyres (on a moped) only have to have visible tread.

Swingarm bearings can’t have any play in them.

The brakes have to meet a certain braking force.

The brake levers can’t be too ‘spongy’, ideally not spongy at all

No splits/leaks from the brake pipes/cylinders/calliper etc

The accelerator must move freely and return freely, it can’t stick open, it must spring back on it’s own.

The seals on the forks and rear shock must be good


You don’t need wing mirrors for the MOT. If you have a pillion seat then you must have pillion footpegs or fit a single seat unit.




Some common problems


My bike is juddering near the top of the rev range, struggles to rev and doesn’t idle.
This is caused by a mis-fire. A mis-fire is when the spark plug sparks intermittently. This is often a simply the spark plug needs replacing, it’s common on a 2-stroke they eat through plugs, especially if the A/F mixture is rich.


My starter motor won’t turn the engine over, it just makes a clicking noise.
In this case the starter motor (or wiring from the relay to the start motor) is at fault. The clicking noise you are hearing is the relay clicking. You could either buy a new starter motor or take yours apart. The most likely cause of the starter motor fault is either the armature or the brushes. Inspect both and replace what needs be.






It's not finished yet. Any suggestions then send them to me and i'll chuck them in.


Last edited by bourney on Sun Jul 26, 2009 8:28 am; edited 2 times in total
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Re: FAQ and general information

Post by CraigB on Sun Jul 26, 2009 10:34 am

Brill page, havnt read throught it all, but i saw a bit saying "rs50" Is this based on them or just a general 50cc thing you'v wrote?

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Re: FAQ and general information

Post by bourney on Sun Jul 26, 2009 11:05 am

CraigB wrote:Brill page, havnt read throught it all, but i saw a bit saying "rs50" Is this based on them or just a general 50cc thing you'v wrote?


It's mainly based on them as there a broad range of mopeds using different carbs and whatever but generally it can be applied to any scooter. there's no properly specific thing in there for the RS50.
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Re: FAQ and general information

Post by CraigB on Sun Jul 26, 2009 11:10 am

ye gdgd, very usefull Smile

and i see you figured out how to make a stickey? haha

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Re: FAQ and general information

Post by bourney on Thu Jul 30, 2009 11:20 am

CraigB wrote:ye gdgd, very usefull Smile

and i see you figured out how to make a stickey? haha


Yeah finally figured it haha
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Re: FAQ and general information

Post by Matt_151 on Thu Jul 30, 2009 12:18 pm

if i put a 19mm carb on a rs50 , how much better would the bottom end be ? does anything significan need doing? thanks
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Re: FAQ and general information

Post by DanHam on Thu Jul 30, 2009 2:25 pm

nice one bourney, bet that took time to write out

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Re: FAQ and general information

Post by bourney on Sat Aug 01, 2009 6:01 am

Yeah too fuckign ages dan hahaha.

As for the bottom end with a new carb, you won't see a huge difference. Most people are disappointed when they do these mods to a 50 and the acceleration dosn't pull your face off.
Yeah you may notice a slight amount of difference but nothign earth shattering.

You need to set-up carb when you fit it.
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Re: FAQ and general information

Post by Bluecollarlove on Sat Aug 01, 2009 10:46 am

Very useful for noobs and the non-technically minded!

I was thinking of installing a K&N filter and dynojetting my bike, but to be honest, it goes fast enough. Unless I'm looking to whip about 0.2seconds off circuit times, it's really not worthwhile going overboard....!

The only bit I don't get is the bit on 'Exhausts'. Maybe it's different for smaller cc. bikes than larger ones? The manufacturers have to follow noise emissions standards and their standard cans restrict power more than some aftermarket ones. I dunno about Arrow though? On every bike I've had, adding an aftermarket exhaust, like Renegades on a SV650S, really makes a huge difference to the flat spot in the power curve....
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Re: FAQ and general information

Post by DanHam on Sat Aug 01, 2009 11:02 am

the performance exhausts do come with a restrictor but we all take them out, this improving performance and making it louder, your only meant to add them legally onto your bike for track days and if you have a full licence

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Re: FAQ and general information

Post by Bluecollarlove on Sat Aug 01, 2009 11:09 am

Ahhh........

Looks like there's room in the market for removable baffles? My Akrapovics are actually road legal with removable baffles....like...permanently removed!

Without them, it just cuts the grade for track day rules <99dB. I've no idea what they sound like with them on actually.
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Re: FAQ and general information

Post by DanHam on Sat Aug 01, 2009 11:18 am

Well Morgan you are a bad influence on me haha, your tempting me to remove my baffles and get a small number plate haha Smile

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Re: FAQ and general information

Post by Bluecollarlove on Sat Aug 01, 2009 11:23 am

i never owned anything as small as a 50cc! But aren't the police in North Wales (under Brunstrom) and the provinces rather picky about bikers? If you're on a 50cc with anything illegal, including visor, they'd have a field day. Some of them seem to make a habit of hammering 16 year olds for any minor infraction.

Whereas here in the city....as long as you're riding respectfully (i.e. no sparks from the titanium sliders coursing across expensive Mercs and Jaguars with knee out antics whilst filtering), they tend to leave you alone. I have seen a number of scooter kids get pulled over. Well he was riding on the pavement at 30mph!! Very Happy
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Re: FAQ and general information

Post by DanHam on Sat Aug 01, 2009 11:27 am

Ohh right, I had thought that they were quite strict in North Wales, I was out riding one day doing about 50 and there was a copper in the distance with a speed gun, a handheld one, soo I dropped to 35 mph he just looked at me and smiled haha, I think he new deep down

Then there was another copper pulling bikes on the other side of the road and from what I could see was he was going over that Factory and 2 other bikes with a tooth pick

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Re: FAQ and general information

Post by Bluecollarlove on Sat Aug 01, 2009 12:01 pm

Yes...that's what scares me about north Wales (besides the human size pot holes on the B roads).

There are a few biker groups that go riding out in North Wales and only ever have whinges and complaints to feedback after weekend rides.

I guess the traffic copper couldn't get an accurate estimate of your speed since you're such a small target compared to his car. I must say, it makes me cross when the police behave like that. I don't mind if they do it to Japanese 4-in-lines, but on an Italian v-twin. Have respect man!! Lol.
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Re: FAQ and general information

Post by bourney on Sun Aug 02, 2009 3:12 am

Bluecollarlove wrote:Very useful for noobs and the non-technically minded!

I was thinking of installing a K&N filter and dynojetting my bike, but to be honest, it goes fast enough. Unless I'm looking to whip about 0.2seconds off circuit times, it's really not worthwhile going overboard....!

The only bit I don't get is the bit on 'Exhausts'. Maybe it's different for smaller cc. bikes than larger ones? The manufacturers have to follow noise emissions standards and their standard cans restrict power more than some aftermarket ones. I dunno about Arrow though? On every bike I've had, adding an aftermarket exhaust, like Renegades on a SV650S, really makes a huge difference to the flat spot in the power curve....

The exhaust restricts these little strokers.

They have a washer tack welded into the end of the expansion chamber (where it meets the end can), it restricts gas flow so restricts the power of the bike.
The new RS50 also have a wire meshing in a section of the exhaust which is restrictive (like a cat is on cars and new bikes). I'm not sure if this meshing on the RS is a sort of cat to meet euro 3 regs or if it is just a restriction thats harder to remove.. Anyway, this section of the exhaust has to be cut out (grinder is now your friend lol), the meshing removed and then the section welded back in place.

K&N stylee filters on these bikes do shit all other than make more inducation noise. On 4-stroke bikes (more so cars though) they make a fair bit of difference as the standard air boxes have resonance chambers, these chambers reduce induction noise, but in doing so restrict air flow, so fitting a K&N provides free-flowing air but increases induction noise.


Last edited by bourney on Sun Aug 16, 2009 2:14 am; edited 1 time in total
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Re: FAQ and general information

Post by DanHam on Sun Aug 02, 2009 8:58 am

Bluecollarlove wrote:Yes...that's what scares me about north Wales (besides the human size pot holes on the B roads).

There are a few biker groups that go riding out in North Wales and only ever have whinges and complaints to feedback after weekend rides.

I guess the traffic copper couldn't get an accurate estimate of your speed since you're such a small target compared to his car. I must say, it makes me cross when the police behave like that. I don't mind if they do it to Japanese 4-in-lines, but on an Italian v-twin. Have respect man!! Lol.

Tell me about it, but alot of the roads near me are being re tarmacd I hope, well they are quite slow, they have removed all the white lines and cats eyes and then stopped :/

Hope fully they will have it done soon lol the road is a mess, they are also re tarmacing a part near the horse shoe pass to
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