Gearing of a small bike for frequent pillion

[Mentacycle]

Should I get a bigger rear sprocket to compensate for the hills and extra weight?
My bike is a 4 stroke 125....

[Teflon-Mike]

Your CPI.. retro-thingy?..... I went looking for specs vis your "It don't start" thread..... It's NOT a good sign when the adverts devote more text to the 'classic' styling and mention the hey-day of the 'racing singles', and even more to how attractive the price and finance package is.... it really isn't.... and that's for one that works!

One spec that I did glean however was that it makes a heady 7Kw/10bhp!

I would hazard a guess that it has a chink derivative of the push-rod CG motor, given that blurb made no mention of Over-Head-Cam...

However... most Chink 125's are down-geared out the crate to comply with local legislation to only be capable of 55mph.... so if the gearing is as original, it probably doesn't need it... I think it's a 13/32 combo, OTMH, and usual mod for UK is to fit 14T front to up-gear for a 60mph road-speed... so check what you got before you start.

Meanwhile, it has a five cog box, of which top is pretty much redundant anyway... stick to the four lower gears, DO NOT short shift up them too early, max it in every one before shifting; even solo! Makes fair chunk of its lowly power, low down, and common newby trait on these things is to short shift all the way to 5th before 40, then wonder why it wont go any faster... needs two down-shifts and thrashing to the max to get at the small oomph it has, so use them lower cogs to the full.

FWIW, I have done a fair bit of 2-Up tiddling; biggest worry is the pillion themselves... "Sit down, sit still, Hold on tight....you are LUGGAGE! Luggage does NOT poke me in the ribs me grab me around the neck, or furiously smack me on the back of the head to look at an effing sheep in an effing field! LUGGAGE.. what are you again?.... right; make like a sack of spuds, and try not to scream!"

It is a lot more important on a lightweight; I weigh 90Kg, bikes only 125Kg or so, so the bike only has small weight advantage over me, solo. Add a pillion, and the weight advantage reverses, and any little wiggle is much more dramatic and if pillion is trying to hold the bike up as you tip in, and then dropping into the bend, things can get very out of shape very quick. Especially when lightweights tend to be short and rather more inherently wobbly to begin with.

Key to riding a tiddler anyway is ultra-smoothness. Key to pillioning, is ultra-smoothness, you have compound problems 2-uppig a tiddler.. you need be ultra-ultra-mega smooth.

On a heavyweight the mass damps so much more... Bikes likely twice the weight or more of rider; adding a pillion, ratio stays in favour of the bike, the extra is far less likely to upset them. On my old thou, I used to just give them my race hat with tinted visor so they couldn't see too much, and stick in ear-plugs... they could have been doing acrobatics on the bunny, DAT bike wasn't going to go anywhere but in a straight line in anything like a hurry! 750's a tad less planted; daughter's abut as heavy as a half eaten packet of crisps; she used to clamber all over the damn thing, USUALLY taking photo's with her bludy smart phone! And only became a problem when she tried shoving it m my face to show me a google map!

Snowie, my O/H is a little less of a lightweight... especially when there's beer around! More when its MY beer! She's a tad more of a handful on the bunny.... but then she's a rider! Riders make BAD pillions! They really do! She is usually trying to do my riding for me! B-U-T.. when she had her little Chinky Cruiserette 'Thing' we did a fair few longer 2-up runs on that, when she was looking for another bike; done a few on the 125 Super-Dreams too actually....

Smooth, slow, deliberate; plenty of braking time and space, plenty of acceleration time and space; thrash it through the gears and DON'T snatch changes, or brakes, be deliberate and positive setting it up for corners, lots of predictive riding, lots and lots and lots of smooth, don't try dong ANYTHING in a rush....

Gearing? Probably the last thing you need worry about, for 2-Up tiddling, really. As said, the Chinks are usually short cogged from the off, for local legislation, and will often top out at about 55 anyway; up gearing, wont often help them go very much faster very often anyway, and tends to make 5th even more of an over-drive. So use the revs, access all that 7Kw of powah! at peak revs; dont short shift, give yourself the rev-room to make slow deliberate and smooth changes, and not have to rush them, or make so many and expect not to be getting into top all too often, on all but NSL roads!

If you need to adjust anything for 2-Up, much higher up the list and about the only thing you likely can adjust, is tyre pressure! And ridng style.... SMOOTH SMOOTH SMOOTH!

And don't forget the pre-ride talk... "YOU is LUGGAGE!"

But all rather previous.... you gotta fix the thing yet! Remember old adage; before looking for more than standard, make sure you got all you should have AS standard! Sod the mods; worry about making it work... then work reliably... and being a Chink, those two should keep you plenty busy, and if you have time left over to contemplate mods... DONT... just count blessings its working and you DON'T have to do anything else to it with spanners!
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My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?'

[Rogerborg]

[Kickstart]

Hiya

Might help with moving off from standstill. The rest of the time you can probably just use a lower gear

All the best

Katy
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[RhynoCZ]

OP, the top gear tends to be the overdrive, which is meant to sustain high speed with reduced engine rpm. The word sutain is very important here. In the real life it means, use all the gears to gain speed, then shift it in the top gear and leave it there, unless further acceleration is needed.

Now for the final drive gear ratio. Back in the day, I did some experiments with my NC27. When I bought it, there was 44teeth rear sprocket. The bike was very quick, did 190+km/h and was very fun to ride. But all that led to worse fuel economy and vast amounts of heat, as even when going 30mph in the 6th gear, the engine rpm was sky high. The Factory setup was meant to be 34 to 38 teeth. I did get 38 teeth, the bike got slower (165+km/h) and less fun, but I could do 20MPG more, with less heat.

So try more teeth on the back, if you've got the time and money, but I wouldn't bother. More teeth back = longer chain. Or you could get less teeth on the front sprocket. Loosing one tooth or two from the front you propably won't even need to shorten the chain.
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'87 Honda XBR 500, '96 Kawasaki ZX7R P1, '90 Honda CB-1, '88 Kawasaki GPz550, MZ 150 ETZ
'95 Mercedes-Benz w202 C200 CGI, '98 Mercedes-Benz w210 E200 Kompressor

[Mentacycle]

Great advise there folks, thank you all!

Here in hilly and laney Cornwall Its all about riding smooth, so I'll see how it goes.

My pillion is my 12 yr old lad, so i can train him to be luggage (excellent way of explaining it to him).

Its about time for his phone calll to me asking 'Dad is it fixed yet?'

Most go for now, and again thanks for you replies!

[WD Forte]

I'd try a smaller front sprocket and adjusting the chain too
that may give you more pick up but less top end speed.

It's still a 125 though so that limited power has to be managed via the gears especially in a hilly region like Cornwall, so no magic bullets I'm afraid.
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bikers smell of wee

[Rogerborg]

By the way: you do have a category A / A2 / A1 motorcycle licence, right?
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Biking is 1/20th as dangerous as horse riding.
GONE: HN125-8, LF-250B, GPz 305, GPZ 500S, Burgman 400 // RIDING: F650GS (800 twin), Royal Enfield Bullet Electra 500 AVL, Ninja 250R because racebike

[Tracer1234]

[WD Forte]

[Commuter_Tim]

[Mentacycle]

[Teflon-Mike]

[Mentacycle]

Deffo an strange time for bike tests, just after the CBT was first introduced, passed on a C90 of all things, was allowed because it was semi-auto.
Nevertheless I passed with 1 minor fault (very brief wheel locking during emergency stop) in the days when you could book your own test, my full licence cost a total of 54 quid!

Back on topic: I cant bloody wait to get this bike sorted!

[Pete.]

A wheel lock on the e-stop is insta-fail, not a minor.
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a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[Mentacycle]

[Teflon-Mike]

Honda Cubs are an anomaly; in the 90's folk passed tests without auto-restriction on them, cos they have gears, if no manual clutch. (Favorite of the London dispatcher / cabbie in training, doing the knowledge, ISTR.)
Verdict was out in the naughties! I recall asking the question a few times, and the best answer I got was "Redundant; they aren't 120cc!" Which was a little unhelpful, as student in Q wanted to do moped test on a C50!

They also 'lift' under braking curtacy of the monstrous torque reaction of that 3" brake drum on the leading link!
According to my instructor circa 1988, they actually sent out a memo to examiners, as a number had failed Cub-Riders on the e-stop, because they were watching for fork dive and didn't see it until after they had stopped.

As to the lock-up... ISTR that the stipulation of the day, was that the e-stop had to be performed under full control; a 'lock-up' wasn't instant fail, so long as it was corrected and bike didn't fish-tail. I am not sure that the current guidelines aren't similar and a lock-up, is an absolute insta-fail, I think they still have some discretion the check-list hasn't eradicated.

[Mentacycle]