yamaha conrod questions

[tavspeed]

cheers will have a look at the ktm rod if i change to a 30mm deck height piston.
the ke 175d rod has a 15mm wide big end so can be used in standard width crank webs without machining them,and no shims,although not sure about what bearings are available in that width,
my rb crank webs measure 12.1mm each +16mm for the rod =40.2mm +.3mm for clearance +40.5mm,which is what it measured before i split it,and i can get a rb spec bearing to suit
this set up us with a dt125ypvs rod,

[Warkton Tornado No.1]

The overall width of the crankshaft can vary, obviously for the better in the case of wider webs with the resultant chance of less twisting. Special wider webs are available from one or two places. To accommodate that, allied to the fact that I can be an outspoken gobsh1te about the disadvantages of HPC, I had a batch of laser cut mag housing spacers produced in about 2012. I think I have one left, so they worked well & are re-useable. The program for production has been paid for, so any widths of standard gauge aluminium can be produced. Food for thought

Dependent upon the source of supply, some specialist retailers of anything relative to the top end should be prepared to mix & match the components required. Understandably, if you can get them 'on side' & even open an account whereby they may attract more business from you, they can be a flexible asset in that sense. TBH I almost feel embarrassed @ how infrequently I use an account that I have with Grampian Motors, but they are my immediate first choice for referencing any requirements & their components are excellent quality.

You can only ask, but hopefully, it can work out well. They know their stuff & have experience gained from not being tied just to, say, Lambrettas, where the relatively recent higher power (& often revs!) have necessitated the improvement of components.

In the case of pistons, I avoid Lambretta specific products because my belief is that the production of them is often an excuse for a hefty price tag, not that I question the quality of the likes of Wossner, for example. It's just that, if an engine geometry can accommodate an OEM or good pattern Polaris, Suzuki, Yamaha etc piston, then that is my personal preference, even if the component is forged rather than cast. (IMHO the theorists can argue all day about the advantages of the two types of piston, but any motorcycle derived piston is likely to be thicker & stronger than one intended for a Lambretta!)

I am not particuarly ashamed that I have to penny pinch & endeavour to source an eBay Wiseco NOS piston from the USA for example, but decades ago, racing on a shoestring budget necessitated finding OEM PE 250 pistons @ a reasonable cost, which was a fraction of what UK suppliers wanted.

My apologies for the ramble, but there are very, very few tradesman that make a living via Lambrettas do it for the love of the machine. It may have started out that way for them, but money has a way of corrupting that ethos......

[storkfoot]

cheers will have a look at the ktm rod if i change to a 30mm deck height piston.
the ke 175d rod has a 15mm wide big end so can be used in standard width crank webs without machining them,and no shims,although not sure about what bearings are available in that width,
my rb crank webs measure 12.1mm each +16mm for the rod =40.2mm +.3mm for clearance +40.5mm,which is what it measured before i split it,and i can get a rb spec bearing to suit
this set up us with a dt125ypvs rod,

According to my notes, yes, no machining required but I do have 0.5mm thrust washers which still produced a 40.5mm overall thickness. The Pin needed shortening. This was done at Grampians who are great if you can get to speak to the top man, less so otherwise.

[tavspeed]

did you run the ke175 rod with the supplied bearing with your ts1,a rb spec flat cage bearing at af is £12.50,but is 16mm wide,so possibly run that with .5mm shims,if the i/d will fit over the needle cage,cheers

[tavspeed]

have looked at various rods,and i think i am going to use the dt125ypvs rod as the big end bearing is 28mm o/d and i can get a rb spec bearing from af that is suitable,could'nt get conformation on what size big end bearings are on the other rods and didn't want to mess about sending them back.
the yamaha 110mm rod is ideal as i am going to try it with 2mm packer thus lowering the ts1 barrel 1mm,similar to what mb did with there touring tune,but they machined 1mm off the base.
this should suit my taffspeed exhaust and sx200 gearing better
ideally when funds permit i will try a 115mm rod,probaly a rd 400, with a casa 30mm deck height piston,as seen on steel weasels you tube channel(worth a watch by the way) as this gives a smoother engine and the piston doesnt rock as much due to the position of the gudgeon pin,cheers all

Other two stroke enthusiast's have proven the measurable increase in output of an engine modified by only fitting a longer rod.

Anyway, your choice, but the KTM is 118 mm centres.

hi warkton,just trying to get my head round these.measurement,
so with a 118mm rod and 30mm comp,height piston you would have a total length of 148mm,
standard lambretta length is 146mm

so to get piston level with top of barrel you would need a 2mm packer ??

if you used a 1mm packer this would drop the port timings 1mm ?? hope this make sense,cheers all

[Warkton Tornado No.1]

have looked at various rods,and i think i am going to use the dt125ypvs rod as the big end bearing is 28mm o/d and i can get a rb spec bearing from af that is suitable,could'nt get conformation on what size big end bearings are on the other rods and didn't want to mess about sending them back.
the yamaha 110mm rod is ideal as i am going to try it with 2mm packer thus lowering the ts1 barrel 1mm,similar to what mb did with there touring tune,but they machined 1mm off the base.
this should suit my taffspeed exhaust and sx200 gearing better
ideally when funds permit i will try a 115mm rod,probaly a rd 400, with a casa 30mm deck height piston,as seen on steel weasels you tube channel(worth a watch by the way) as this gives a smoother engine and the piston doesnt rock as much due to the position of the gudgeon pin,cheers all

Other two stroke enthusiast's have proven the measurable increase in output of an engine modified by only fitting a longer rod.

Anyway, your choice, but the KTM is 118 mm centres.

hi warkton,just trying to get my head round these.measurement,
so with a 118mm rod and 30mm comp,height piston you would have a total length of 148mm,
standard lambretta length is 146mm

so to get piston level with top of barrel you would need a 2mm packer ??

if you used a 1mm packer this would drop the port timings 1mm ?? hope this make sense,cheers all

I haven't checked your maths, but yes, that would make sense.

I have several thicknesses of base packers that I use to check the geometry that I seek with any engine build, but you can also 'trial' the whole set up by packing the base with the closed cell neoprene strip which acts as a spring to see what you get. Once a good squish, port timings etc is reached as far as the best compromise, then feelers can be used to assess what the best packer thickness should be. I hope that makes sense. The M8 fasteners are 1.25 pitch so quarter turn of each is about 12-1/2 thou in old money.

Beware though. Some packers are oversized in the transfer area, though the seller was trying too hard to be helpful, I guess.

I used to make my own but TBH I think AFR have a large range @ affordable prices.

(I hope you will consider spigotting the head & barrel as that not only centralises but is the best seal you can get IMHO)

[tavspeed]

cheers,good tip about the neoprene strips