stroking :)

[tonydevon]

ok so this might seem like a stupid question to some, but can any 2 stroke engine be stroked subject to suitable conrod sourcing?

stock is 56mm bore x 50.6 stroke
CAGIVA MITO 125 CONROD
BE: 28
SE: 20
Center Distance: 110
BE Pin: 22x8.9x51.5
SE Pin: 16x10.8x45
BE Bearing: 28x22x16
SE Bearing: 20x16x22

also what characteristic does the engine gain through longer stroke as opposed to boring?

theres a big bore kit available for my engine (mito 125) takes it to 160 but over 500 quid and the reports that I hear arent very polite

I was just sat wondering about how else the engine could be improved and realised just how often I see and hear of lambrettas having longer rods fitted.

I have a spare set of engine cases, another set that are damaged but have good 7 speed gearbox in them, and a spare crank thats got tired big ends, so ideal for surgery

[shocky]

I guess anything can be but an air coo.ed lammyor vespa just needs a solid packer to compensate wouldnt you nedd something more techinical being water cooled and how does the cylinder bolt down is it long studs like a lammy or short bolts at the base of the cylinder ?

[tonydevon]

its short studs with nuts at base of cylinder, making a packer with o ring sealed water ways isnt that hard, have to look closer at the studs that secure the barrel down, they should come out easy and source replacements.

I think I need to look at space inside the crankcase etc for the BE of the rod in case a longer one has bigger OD

was more of a thinking out loud exercise and trying to work out if its even feasible.

recently learnt a lot about the head and CR CCR etc, really enjoyed learning new things and hopefully putting it into successful practice.

decided that I would like to learn more, never going to be an engine tuner, but I like to understand things

just done the maths, very small gains to be had in cc for a lot of work LOL

[shocky]

I looked online at cylinder kits and answered my own question

[Spanish Fly]

Tony.
I'm sure a surgeon of steel like yourself knows this.....but....your post reads as if fitting a longer rod will increase the stroke.
Obviously it won't. You need to increase the throw of the crank with an eccentric crank-pin or a different crank with a greater distance between crank centre and big end.
A significant increase in stroke may well require a longer rod to prevent the piston tw@77ing the crank webs at BDC but just fitting a longer rod will not increase cc but will affect port timing.

SF

[tonydevon]

[tw@7 mode on]DOH, I can build you frames or suspension, complete bikes trikes and custom cars, but still learning with regards to modifying engines

of course the crank needs modifying too.. I knew that LOL [tw@7 mode off]

think its time to just get the engine running as well as it can in stock setup, then move on, RGV250 motor next build

will stick to building them rather than trying to do engine work that I havent a clue about

[Darrell Taylor]

agree with last post ,not sure your seeing best from what you have ,a 6 or 7 speed motor with 26-28 bhp should go really well ,or you could big bore the original cylinder and mod head for less than the cost of a kit

[tonydevon]

boring it out is a problem with the way the powervalve works, I know that it currently has some obvious issues, they are being addressed after this weekend.

it does go well, hoping to do a 1/4 sprint with it one day for a giggle, but once you get it up beyond 8k you just keep shifting and 85mph comes up rather easy,
I have realised that a big part of the problem is me, never ridden low torque hi revving 2 strokes, my muggy GP was easier to ride although not as exciting, many years of big 4 stroke motors and in particular brit twins, means that my ears and brain start to get rather anxious at the sound of a 2 stroke motor up at 8k to 12k rpm, I went out and rode it like a teenager that had just stolen it last night LOL, it is great fun, just needs keeping on the boil and doing the riverdance on the gear lever

was just trying to learn and think ahead about options to improve it further, think I have discovered that the best way to improve it is leave it the hell alone and build another scooter from scratch with bigger engine