Top end Tuning 70cc Project

IHey guys. I have a Suzuki Zillion 2005 (ish) Here's my setup for what I know so far:

70cc BBK (Not sure the piston diameter I did not fit this)
Gianelli Sports Exhaust
Standard Airbox
Keihin PWS Carb w/0.75mm Main Jet
Clutch Rollers ??? *guessing around 4-5G

So here's the problem. I have amazing acceleration, when at slow speeds (~5mph) it can accelerate to about 35mph in around 6 seconds *roughly*. But then it will just top out at that speed, it will even pull up hills at 35mph, I've taken people on the back at around 30-35mph depending on gradient of road/hill etc.But when I accelerate from stopped, at lights or a give way or something, it stutters foward for a second or two and then all of a sudden a huge jump in acceleration...

The other thing is I *THINK* its running a little lean. I haven't had chance to check the spark plug yet but I intend to tomorrow, but when I start the bike up I have a little white smoke coming out of the exhaust while warming up, but after that there is no smoke at all, not visible anyway, just a sort of air. Now my friend has an SR 50 and that smokes quite a bit constantly.

Now I've just bought a bigger jet, because a friend of mine knows a little about bikes and said that the engine requires more fuel to reach its top end better.

Downhill speed is around 40-45MPH, after that there feels like theres something stopping me go any faster like a gear, but I have plenty more hill to go down to pick up more speed but it just doesn't.

I Only want to get it upto about 45-50MPH on straights so I can keep up with the traffic on the way to work! It's so annoying/dangerous when people over take in bends, but I understand that they are in a rush

Any suggestions would be great and I will try them as long as I can afford them !

Thanks dudes!

 

Hi there,

Check out this thread that I started - basically the CVT will only go up to a certain speed, once its maxxed thats the top speed, perhaps look at getting a 'gear up' kit as you have more power

http://www.scootershack.co.uk/threads/stock-variator-speed-limit.23670/

 

with the 70cc kit, you would imagine it has had the variator restrictor removed, but has it ??

I would be first checking that the belt is getting up to the top of the variator/top gear and low in the torque drive.

your mate and you might be using different oils, some smoke more than others. White smoke is water going through the exhaust as steam, the water is a by-product of combustion, all engines make it, as the engine and exhaust gets hot it stops being visible, as all engines heat up at different speeds, combined with different oils, they will smoke differently, and that doesn't take in to account, the oil-pumps spitting out slightly different ratios.

White smoke at other times, is normally a sign of blown headgasket/crack in the engine.

 

Hey guys, I have checked if it is restricted in the variator before, and for what I could see it wasn't restricted.

I'll look at that gear thread now.. Will get back

 

Ok I had a look, I really don't think thats the problem, I thought my CVT should have enough gear ratio to pull me quicker than that? People I know with mopeds tuned simiarily to mine can get like 50MPH and they haven't changed their CVT only the clutch rollers & springs...

 

even the wrong belt can dramatically reduce the top speed,....... not unknown, for some one not to check, they have the right one.

 

How do you mean wrong belt? Isn't a belt just a belt? What sort of belt should I get ??

 

Another quick question, I was looking at the carb earlier, and i noticed a cable coming off the top of the carb, its just a basic 1 core wire which has a pop connecter on it, is it a temprature probe?

 

on some peds, it is quite common to be sent belts of varying lengths, and only one length is ideal to see the right gearing. Belts also stretch. So that is why I would check the operation of the belt, going through the gears. You can put thick marker pen down the pulleys, run it, then examine where the belt has been, by the ink erased by the belt friction .......

the wiring is probably for the electric/automatic choke.

 

So you think upjetting will not make a difference? I'll do what you said tomorrow if its dry weather

No the electric choke has seperate wiring, it's just one standalone cable not a DC connection, just one wire, like a probe would have so I'm guessing its that.

 

the only wires I can think of, are the electric choke or possibly an electric carb heater.

 

Oh, probably a carb heater then... I have never upjetted before and I have a sports exhaust, air filter and a 70cc kit, should I got for around #95 jet? I'm on #75 now..

 

and now this;

you are lucky you have a piston left. All air filters flow air differently, so start large and work your way down. read the jetting guides.

 

Sorry but I am not very clever with this stuff! by airbox I meant air filter, they're the same thing right? I can take some pictures tomorrow anyway...

The guy I bought if off I'm still friends with and that's all the info that I was able to get off him..

I can get a #98 jet tomorrow I'll try that and work my way down, using the spark plug as a sign of lean/rich mixtures? (I've been doing quite a lot of reading up on this, I'm not actually that technical experienced )

 

I never run open air filters, they look good but that doesn't cut it with me, when I am 100 miles away from home, and in a down-pour where the filter is soaking wet and the bike is conking out. Also thet are noisy, and my exhausts tend to be loud as it is ................ as for jetting, there is a mile of difference in jetting, up to around 20 sizes, depending on make of filter.

I did see a test recently, on extra fuel consumption, and strange enough, they don't use that much more fuel, which was contary to my beliefs.

 

Mine is pretty loud. I've never had problems with the rain, living in Wales too with the rain almost every other day, I think its because the air filter is kinda sheltered on my bike by the fairings. If you like I can make a video of what I mean with the acceleration problems etc tomorrow, again if it's dry. Maybe that would help people understand my problem, Thanks for your help guns btw!

Well that doesn't actually surprise me, 0.**mm is a very small amount of fuel flow so I'm guessing it would be hard to notice a massive fuel economy difference, I'm not really bothered about fuel though I'd rather be paying extra in fuel and being able to keep up on dual-carridge ways than being over taken 24/7!

 

I've had a play around today with the bike, I put the #98 jet in and it's way to rich, to rich to even ride, a lot of white oil smoke coming out of the exhaust. So I'm going to drop it down to #85 and try that... Also I'm going to have a look at the variator again later, because last time I didn't actually take the variator plate of and only the front cover.. maybe I just didn't see the washer from there?

 

The stock air box is part of the tuned intake btw, much like the exhaust, there are intake pulses coming back out the carb when the reeds shut, which is why you see 'boost bottles' for sale between the carb and intake to gather the extra fuel and then reintroduce it in the next intake:​

​

http://www.scootershack.co.uk/threads/open-filters.11964/​

 

So shall I leave the airbox on there or leave the K&N thing on there?

 

the standard air box won't rob you of any power, save you a bit of fuel, safer in the inclement weather, and much easier to set up the carb with, so in a word yes. Especially to get it running right.