Big end crank pins?

[corrado]

Are all after market cranks, like MEC race cranks, using a 22 mm big end crank pin? Is it just SIL GP 200 ones that are 22.9 mm?
Was thinking of having yam 110 rods fitted to some spare cranks (MEC & SIL) that I've got.

[Knowledge]

Martin,

I think some of the SIL cranks are 22mm, and some are 22.9mm. Similarly, some aftermarket cranks come in either size. There don't seem to be any clear rules (I'm happy to be put right on this...)

John Howe at Jahspeed has new pins made to order for his cranks, and seems to be able to cope with most combinations. He presses them together with many tonnes of pressure and then trues them. He seems to get good results as he is very fussy about the tolerances and the engineering firm he uses in very understanding of this (and his next door neighbour).

Martin

[shocky]

Martin,

I think some of the SIL cranks are 22mm, and some are 22.9mm. Similarly, some aftermarket cranks come in either size. There don't seem to be any clear rules (I'm happy to be put right on this...)

John Howe at Jahspeed has new pins made to order for his cranks, and seems to be able to cope with most combinations. He presses them together with many tonnes of pressure and then trues them. He seems to get good results as he is very fussy about the tolerances and the engineering firm he uses in very understanding of this (and his next door neighbour).

Martin

just be aware that some 150 cranks have a 13mm oil seal shoulder on the flywheel side and cant be fitted with a nu2205 bearing only a nu205 and early 125/150 cranks can have a 19.9mm stepped crank pin as well

[corrado]

Martin,

I think some of the SIL cranks are 22mm, and some are 22.9mm. Similarly, some aftermarket cranks come in either size. There don't seem to be any clear rules (I'm happy to be put right on this...)


Martin

Thanks Martin, clear as mud then.

Steve, the SIL ones are all out of new SIL GP200 engines but I'll check that measurement to be safe.

[corrado]

A well known Lambretta tuner based in South Yorkshire (no not Tuner Tom) sent me this ..........

Bloody hell this old chestnut again.

Let me set the record straight. Im sure someone will correct me if Im wrong.

All Innocenti GP 150 and 200 type cranks had a straight 22.9mm pin, the exception was the GP125 (some were also fitted to 150s as well) these had 19.9mm stepped pins (I think) same as an Sx/Li pin using a big end bearing size the same as a Gp200 22.9mm.

All GP 200 types use a 10mm flywheel bearing shoulder with the wider 2205 bearing.
All 125 and 150 types used the thinner 205 bearing.
All Li, Sx, Tv cranks use the same pin 19.9/22.9/19.9mm with a 13mm shoulder.

Early SIL GP cranks used a 22.9mm straight pin, most crank shoulders were 10mm but some were 13mm (no set rule as per normal SIL cranks, to my knowledge SIL didnt use stepped Li type pins. Some SIL cranks used a 24mm straight crank pin! (very rare) Later type (mid 1980's) SIL cranks swapped to straight 22mm pins.

Early MEC, Teminei and Mazzucelli Gp cranks used 22.9mm, around mid 90's most swapped to straight 22mm pins.

All AF type cranks have used 22mm straight pins.

That should cover it clear as mud, does that help?



Helps me but I'll probably still use an Alpha crank if I ever finish my RB20 engine.

[shocky]

A well known Lambretta tuner based in South Yorkshire (no not Tuner Tom) sent me this ..........

Bloody hell this old chestnut again.

Let me set the record straight. Im sure someone will correct me if Im wrong.

All Innocenti GP 150 and 200 type cranks had a straight 22.9mm pin, the exception was the GP125 (some were also fitted to 150s as well) these had 19.9mm stepped pins (I think) same as an Sx/Li pin using a big end bearing size the same as a Gp200 22.9mm.

All GP 200 types use a 10mm flywheel bearing shoulder with the wider 2205 bearing.
All 125 and 150 types used the thinner 205 bearing.
All Li, Sx, Tv cranks use the same pin 19.9/22.9/19.9mm with a 13mm shoulder.

Early SIL GP cranks used a 22.9mm straight pin, most crank shoulders were 10mm but some were 13mm (no set rule as per normal SIL cranks, to my knowledge SIL didnt use stepped Li type pins. Some SIL cranks used a 24mm straight crank pin! (very rare) Later type (mid 1980's) SIL cranks swapped to straight 22mm pins.

Early MEC, Teminei and Mazzucelli Gp cranks used 22.9mm, around mid 90's most swapped to straight 22mm pins.

All AF type cranks have used 22mm straight pins.

That should cover it clear as mud, does that help?



Helps me but I'll probably still use an Alpha crank if I ever finish my RB20 engine.

did you thank ralph then :ninja:

[GPMatt]

no sure if its worth doing this? plenty shops are offering this conversion for next to nothing. sil webs take the 22mm pin