Scooterotica

question gets asked quite often which yam rod

Big end to small end ctr 110mm (therefore 3mm pack plate require)
Small end 16mm bearing
Big end 22mm pin
Big end bearing 28x22x16
Width of big end 16mm (standard lam rods 15mm)
0.5mm washers

http://yambits.co.uk/rd250-conrod-kit-p-8938.html

might be useful

Thanks Gaz I've just ordered one, It will be the 3rd crank I've done with a Yam conversion, I use SIL webs. It's such a good cheap conversion I'd recommend people to save a lot of money and go along this great route.

totally agree

all my cranks on my bikes and those i build use sil webs and various rods - mainly yam

gaz

do you use the supplied crank pin?

Can you tell me too, which one of this RD400 conrods its ok for Lambretta conversion:
http://yambits.co.uk/advanced_search_re ... =1&x=0&y=0

Thanks!

regarding pins - if the split cranks are brand new then use the pin from the crank - but if not use the one supplied with the rod -the builder should check how it assembles - may need lock tight and welding

regarding the rd400 rod not sure just drop yambits a line and they will clarify - what you want it should be the same as the rd250 but longer 115mm

Big end to small end ctr 115mm
Small end 16mm bearing
Big end 22mm pin
Big end bearing 28x22x16
Width of big end 16mm - webs will need machining down to suit
0.5mm washers

i have done one and i used the supplied pin....but i had to shorten it as it was longer.....pretty sure the shims are 1mm and not 0.5mm...had to surface grind the inner webs to give it clearance as you said.
had a discussion with the guy who built it and must admit i had to agree that it was pointless using loctite as there is no clearance for the loctite to go in...ie it gets pushed out on assembly....so we welded it.i used slip guages between the webs to get a snug fit then used 2 g clamps to hold the crank to hopefully stop it twisting,was checked afterwards and still ran true,will be doing another one soon and going to try and build it myself this time

the last one i had done using a rd400 rod was built without shims, used the supplied pin and the webs ground back

rd 400 big end outer diameter is larger than the 250 so work needs to the rod and/or casing - Crank builder ground the big end down after discussion - he was comfortable with it as he used to do on other 2 stroke conversions

I've had mine done at Frontline, South Bank by Dave and he said you don't need to use the shims and loctite and welding isn't need.

had loads of stuff done at Frontline.. cranks/barrels/re-bores etc. if its good enough for dave , its good enough for me. proper old skool motorbike engineer. he tells crap jokes mind. mind.. he did set the boring machine to 72mm one time , when it was supposed to be 70.2 mm...........i collected the large washers the next day.......... but... fair play, he gave me a new Rapido 200 kit as recompence when he realised what had happened....