Is a gear up kit worth it for me?

Hi,

I'm running the following:

Aprillia Area 51 50cc water cooled
Standard rebuilt engine new standard crank / bearings / seals / piston / cylinder
Performance reed valve
Performance inlet manifold
Leo Vince TT exhaust
Performance variator / rollers / spring
17.5mm Dellorto PHVA (standard is 12mm)
Kelvar performance belt
Performance air filter in standard box
Standard clutch ... but racing adjustable clutch waiting to go on

I'm a big bloke ... 6 ft+ & god knows how many stone now... maybe 17.
Acceleration is not good 0-12/13 (clutch should sort that out hopefully), bike then takes off & accelerates really well from 12/13-40, then gradually picks up more speed depending on slope/ wind, etc.
It will top out at 55 on a long straight flat & up to 65 on a long slight downhill run.
It doesn't like hills... a smallish short hill will see my speed drop from 45 to 35-38.
All speeds from the bikes speedo, which I think seems quite accurate up to 35-40, judging by how I keep up with the traffic, but not so at higher speeds.
At no point does the engine feel stressed, it's only just run in & is easing up & giving more all the time.

There definitely seems to be more power available at any point than is reaching the road.
I think I will have to experiment with roller weights to sort things, maybe go a big heavier?

Anyhow, the question is, if I fitted a gear up kit to the above, am I likely to benefit from higher top speed? Will I lose anything in acceleration or hill climbing? Ideally, I would like to get another 5-10 mph out of it, as my main use is short trips including runs on dual carriageways / A roads, so any alternative ideas welcome.

Cheers,
Steve

 

if you do, you might get a bit more on a long downhill, on the flat will probably be slower, uphill will be chronic. It's a good engine, but needs at least a 70cc sport cylinder kit to exploit a gear up kit .......... in my opinion.

 

50cc - OEM gears
70cc - gear up

I did post up a while back that you might be able to swap over other OEM gears from different models that might allow for a 'gear up' but at a fraction of the cost.

 

Ok thanks chaps, just about what I suspected. I will concentrate on fine tuning what I've got at the moment... mainly fiddling with the rollers & clutch.

I have fitted stronger springs, It's just I've got this adjustable race clutch hanging about & a strong urge to play with it somewhere.

I had the race clutch fitted up to spring ,etc, ready to go so I just tried it (medium springs, medium contra spring).

The result was horrendous, had to rev the nuts off it before the bike started to move, then it only crept forward & died on me unless I sent the revs into overdrive. Some adjusting needed there I think!

Gone back to the standard clutch for now.

Regards,

Steve

 

m1tch... Swapping gearing from other bikes sounds good ... I suppose as long as you know what you are doing with ratios & can count teeth, etc. The other thing that puts me off the gear up kits is they all seem to be straight cut gears which are noisy & harsh... so gears from another bike would win on that score as well.

 

GUNS ... out of interest, how do you rate the 70cc iron head kits?
I'm thinking they might be better to live with in the real world & cheaper.

 

for some reason, the top performance gear-ups seem a little quieter than the rest, but they all whine at 40 plus. I love it, as it sounds like a super charger spooling up. Bear in mind that I only use the 70 local.

The Malossi iron kit is for me the best value for money, given their quality control standards, and as far as I would advise on a standard crank, the stage six street race is cheaper but it is a crank wrecker as it revs much higher. The Polini never gave me any problems in a year and a half of every day use, but given its price, I would go Malossi.

of course there is another half dozen cheaper contenders, that do the job, and on a budget, I am sure they work fine. But I guess you are like me, an extra £40 is worth the thought, of not being stuck at the side of the road, on a dark cold winters night, because your piston was cast on a Monday morning or Friday night.

people say the iron kits are more durable, but to me the selling point, is that they can be rebored, where as the alu/nikasil bores are so expensive to get replated, on 70cc sport kits, might as well be throw away. At the sport level of tune, cast is the best option, above that, cast retains too much heat for my liking, even though the Polini Corsa is cast iron, and they know a lot more than me about thermodynamics, wouldn't touch it.

 

Thanks for some interesting insights there guys.

What effect do you think a decent big bore kit would have on my acceleration & top speed with my set up as above & with a gear up?

 

different bike, end of.

 

Just spoke to a mate... he's got a 70cc cast cylinder kit unused that would do the job... I've got an old Suzuki CP80 I'm going to fix up as a "rat bike" ... he wants some of the panels for a modded scooter project, so a swap could be in order.... Doesn't appear to be any make on the kit, so probably a cheapo one, but why not if it's free. That would leave me enough in my scooter playing budget to invest in a gear up kit.

It's confusing as some sites selling them give a tooth count / ratio & others sell them as "+22%" , "+33%" , etc kits.... any advice welcome, as I've never looked into gear ratios before.

I've done loads of bike / scooter / car stuff over the last 40 odd years, but this is my first foray into tuning... I've always been happy enough just to fix them!

Cheers,
Steve

 

on a Piaggio 13/39 is about +20%, and that is the choice ratio for sport kits, get the lowest you can, around this figure. You want to buy the primary gear-up, not the secondary that needs a machine press to prepare. The primary gear-up change, is less than a hour, taking your time.

 

Good stuff, ta. How about something like this? :

http://www.donotlink-pedstop.co.uk/...it_3_parts_for_Yamaha_Aerox_etc__21-3921.aspx

They do a 33% one as well. Think I will check my current set up ... i.e. number of teeth on intermediate shaft, as they suggest, to be sure before ordering.

I'm assuming pop the exhaust & brake caliper, back wheel, drain transmission, pull casing & then the gears will just pull out of it? No gotchas with this job?

 

transmission cover off, clutch bell retaining nut, pull off the clutch/torque driver/belt, drain the gearbox, undo the gearbox cover bolts, might need a tap with the mallet ..................... take cover off*, bit of gentle heat on the inside of case, tap out old shaft, bit more heat, tap in new shaft with mallet, you will know when it is home.. Replace gear, put the cover on, bolt up, refill oil ......................... any surplus oil, clean up as will find its way on belt or pulleys.

The only thing I didn't mention is some will replace the bearing, some might replace the seal, others do neither. Remember if you use heat, easy to damage/warp the seal. Observe the seal position, and tap the new one in, before topping up with oil.

* there might be washer(s) between the gears and casings, notice their position as these shims are important.

 

Aha, thanks, should of thought the clutch, etc would have to go ... would be a bit tricky pulling the shaft otherwise

I generally replace seals whenever I dive into a job .. they are cheap enough ,,, but leave bearings alone unless they need doing.

Your advice is very much appreciated once again Guns. My next job is working on my mate to get the big bore kit off him.

 

just to expand on the 70cc kit, as you asked.

It is incredible how much difference a 40% increase in capacity makes with this size of engine. Admittedly it might include better timings than the stock cylinder, an increased compression ratio, better larger ports etc etc,

It won't give you a blistering, frame twisting 1/4 of a mile, but it will be the difference at the lights, between cars up your backside to 40 or with the 70 kit, staying ahead of them. Where it is extremely noticeable, is standing starts on an incline. So the Sport 70s are more about everyday commuting, the real world of 0-50mph.

Mid race kits are fun, but a nuisance in heavy traffic, stop and starting every five seconds, as they are gutless down the bottom end and the clutch biting point is so high, you really have to rev them to pull away, don't get me wrong, once in motion, they are poetry. When I take my SP70 around the twisty country lanes, on a dry day, very little compares to the experience, if you exploited the revs on a big bike in the same way, you could be dead in the same day.

 

Great insights thanks Guns. One thing I have though of is the exhaust... Leo Vince TT fitted is I believe tuned for 50cc engines, so I might get more out of it with one tuned for 70cc.

It's frighteningly easy to spend money on these little scooters & quite addictive!