New chain for 39cc watercooled - where?

[CookMySock]

new chain for 39cc watercooled - where ?

Title says it all. We wrecked two chains running them in the wet with not enough lube. One thrown (low-sided the rider mid-corner lol) and the other one rather chewed.

$12-15 on trademe, better price or quality anywhere else? or do they all come from the same factory ?

Gee these bikes are high-geared. They take a lot of space to get fully wound up - prolly 50m or so before they stop slipping their clutch and start winding right out, and thats with the 45kg kids on them.


DB

[Gadgit]

Hay DB
The trade me ones are about the same as the ones you had and the price is about right.. You can get better chain if you take a smaple to someone like Total trade suplies (tradezone) or a bearing shop but works out a little more expensive... I'v run chinesse chain for years and never really had to many issues keep them lubed and the engine mounts tight...

[BigAl]

Hey DB, re. chains also check that you are not running them too tight, want about 10mm play.
I've seen some of the latest 'cheap' B1s where the rear wheel moves as the axle bolt alone doesn't seem to hold wheel in place and wheel moves back and stretches chain too tight.
What gear ratios have the bikes? if they are running a 6 tooth front and a 68 back then they should accelerate like stink from a standstill. Std racing gearing is 7/68 and that still motors from a standing start. The clutch will need setting and I'd advise going to an edgecumbe meet where those guys should help you out.
cheers.

[CookMySock]

Gadgit, ok thanks, will stick with the chink one.

BigAl, ok will count those teeth and get back to ya. They certainly don't accellerate like that, so maybe they extra high geared for some reason. Top end gets rather weird tho, ie fast!

Ah yeah, maybe its the clutch coz they rev real hard before engaging. Scary hard!

I thought next pocketbike day at Edgecumbe was this weekend, but its not, its next weekend so we will meet the crew then.

Does anyone have pics of what protective nylon is required on the bikes ? Hopefully I can have this sorted for next saturday.


thanks,
Steve

[BigAl]

Here's some picts DB, just a bit of nylon rod drilled and pushed onto foot peg bolts(profile to desired shape) and sparkling wine tops in the end of bars.

[Gadgit]

Hay DB Re clutch setting
If you can get your hands on a digital taco with a decent refresh rate it's the best way to set a clutch. Heres a bit of a run down if you haven't had a play with them yet.
Put the bike on it's stand with taco instaled, lightly apply the rear brake and rev the bike slowly till the clutch begins to engauge. The optium rev should be 8000rpm.
A good thing to check is the clutch springs are all set at the same lenght to begin with and then take them up evenly when adjusting them.
When adjusting the grub screws one flat of the hex is equal (or near to) to 200RPM.
By your discription I'm thinking your clutchs are set a bit low (below the powerband) and this is why it takes a while for them to come on.

[CookMySock]

BigAl, thanks for that. Hrm these grips already have some rubber doodad shoved up them.. with some plastic cap on it. One of the plastic caps fell off (?) and revealed the rubber wotsit. I'll ask at the track, but they look track-safe to me.

Pegs, hokay will find some nylon from somewhere and drill and cut to fit.

Gadgit, rpm, okays.. don't have a tacho, and broke-ass at the moment, so I'll get someone to have a listen at the track.

It sounded at one stage like a clutch was slipping as the revs slid up, but I think we got it a wee bit hot.


Looking forward to the weekend.

DB

[Gadgit]

I don't have a taco either lol I set mine by sensory method but have been doing it for a while and unless you know what they should sound like it'll be hard to do... but with a 45kg weight onboard the B1 should take off like a rocket

[racefactory]

mate you dont need a tach at all to get it good... a tach you could really fine tune it though.

really all you have to do is set the clutch so it KICKS YOU OFF the bike lol. bikes vary but 8000 rpm is good starter point.

tighten those screws to increase the biting rpm.. loosen to lower the biting rpm... trial and error is really the only way to get a great setting for your individual weight and bike.

what is also very important though... not only in order that your clutch engages with a bite...but for longetivity of clutch, is the spring length of each of the 3 springs...

my clutch at the moment is set at 20.2mm spring length... its very important you set these spring lengths to the same 10th of a mm using digital callipers.

i use standard chinese clutches and i am 86kg... i get 10 tanks of fuel through each 35 dollar chinese clutch because of this. found out the hard way. if you dont set them the same length... youll get pads engaging before other pads which will send your clutch to hell, overheat it, slip and burn.

a sympton you can use to help you on your way: if the bike launches.. then sits at one rpm for a good while... then suddenly kicks in and off you go - this means your clutch engaging too soon. these motors produce power only in high rpm.. they are piss poor at low rpms, piss poor. your clutch will be engaging and your motor not making enough power, result- slipping for ages till motor can free itself. thats sending your clutch to hell.

get yourself some digital callipers from repco... set that clutch so it bites hard and wants to throw you off... make sure you got same spring lengths

these bikes are ALL about the clutches... you can beat more powerful bikes easilly by having it set good.

my 39cc b1 kicks me off the back GOOD... and as i said im 86kg. i have been off the back once, it launches hard. need all the weight far forward to stop it rearing

hope that helps

[racefactory]

oh and about chains... a high quality one is DID chain. you can get it off of newmanz. DID is good. gearing- i use 7 68 gearing and bike is lifting the front wheel hard...

but a chinese one does me fine.. in my experience... the chain will not break as long as the sprocket and pinion are right inline with each other. also, that the chain has plenty of slack in it. in my experience... as long as your chain is straight and aligned properly, the chain will not come off no matter how loose it is. i have my chain pretty loose... at least a few cm play, makes your back wheel spin hell nicely.

also you want to use the right lube... wd40 or something thin like that will sling your chain off in a second. you want some thick stuff for these bikes... i use industrial chain saw lube, its thick and tacky like cow snot... works great... never had a chain off or break with it.

also you want to make sure your back wheel spins freely... that will free up power not to mention give your chain some life. my back wheel spins for 4- 5 seconds by my hand and im pretty pleased with that.

good luck.

[CookMySock]

many thanks trademe900. All good stuff. Looks like we have lots to learn.


DB