Crankcase dimensions

[Eoin70]

whats the maximum sized crankshaft you can fit into the minarelli horizontal enigne
i was interested in fitting a 47mm stroke crankshaft into it
but im unsure if it will fit even after heavy re working of the crankcases

 

[Mexicano]

Are you talking about 50 c.c. cases?, I think is possible, but check by your self if you can machine some 5 m.m. from your cases.

 

[Eoin70]

ill need to remove i think 4mm from the cases
but what is the clearnace between the crankshaft and the crankcases??

does the stroke mean the it is the crankshaft radius or dimaeter

i assume there needs to be some 1mm of room left between crankshaft and the crankcases to allow it rotate and wobble

 

[Mart]

I think you have to remove so much material that your crankcases wont seal anymore. But where do you find a 47mm stroke crankshaft?

 

[lilplaya_bm]

does the stroke mean the it is the crankshaft radius or dimaeter

stroke simply means the place on the crankshaft that the conection rod and big end bearing fits...if it is has 5mm longer stroke then the place on the crankshaft is moved 2,5mm high then stock...since there is two strokes to the crankshaft the difference in milameters moved is doubled(i.e. 2.5mm = 5mm stroker crank)...

strokers kits give more low end power but no speed...u can achieve way better speed from a stock stroked crank...the short the stroke the more power u get at a higher rpm, so the taller the stroke the more power at lower rpms...hope this helped!!!!

 

[lilplaya_bm]

eion-----go to msn, now

 

[Eoin70]

i want to fit a yz80 cylinder into my minarelli enigne
its stroke is 46,8mm
and ill use the crankshaft for the yz 80 itself

 

[Mexicano]

Eoin:

When I machined my case to fit a 48 m.m. crank I only needed to do it in one half case, and machined 2 m.m. only to keep 0.030" of tolerance between crank lobe and case, you may want to keep the most pressure inside the cases, so don't machine too much.

Another issue was to install a so much bigger cylinder (57.5 m.m.) BIG LABOR!!!, it is not simple but can be done.

Hope this helps you,

 

[lilplaya_bm]

very very very possible to put yz80 cilinder on minarelli but u should use a 90cc jog crank and get a different connecting rod or piston to fit the cilinder...yz80 crank cant work because(i think) it has grooves for the gears to run off of it...and a 90cc jog crank will be easier to install...

 

[Mexicano]

My advise is to look for used cheap parts from e-bay to do all the "paper work", this way you will have phisically all the stuff in you hands and can figure out what it takes to do and if it is possible.

I have seen complete YZ80 engines in $150.00Usd. or so....give it a try!

 

[emo]

whats the maximum sized crankshaft you can fit into the minarelli horizontal enigne
i was interested in fitting a 47mm stroke crankshaft into it
but im unsure if it will fit even after heavy re working of the crankcases

yes you can fit in a 47mm stroker crank on your 50cc Mina. engine.. it is popular conversion in our country & infact that is one of the most hottest topic in our local motorcycle forum..

 

[Mexicano]

[/QUOTE]strokers kits give more low end power but no speed...u can achieve way better speed from a stock stroked crank...the short the stroke the more power u get at a higher rpm, so the taller the stroke the more power at lower rpms...hope this helped!!!!

Lilplaya: I disagree a little with you....

From a theoretical standpoint, the displacement increase of an stroker engine should have one fundamental advantage, that is, increased torque output through out the entire rpm range. This theoretically happens because of a larger volume of gases being involved with each power stroke, as well as a slightly longer power stroke. Understand that with regards to a two cycle engine, the "actual power stroke" refers only to the distance from top dead center to the opening of the exhaust port.

 

[brookespeed]

the 47 leaves very little case left for sealing. I just used a grinder to make room for a 42 mm stroke and it's ok. I don't know where I'd get another 2mm from. I think the casting from Mexicanos engine are different than most minarellis so he may have had some more aluminum to play with. You could add some metal and then have it machined to be sure. If it's for a short case mina you can try and find cases from a jog90 and use them. Those will even require some work to get a 47mm stroke into. It can be done but I'd find a machinist to do it for one that big as there is no room for error with even a small slip of the wrist if you do it by hand.

 

[Mexicano]

EOIN 70: Brookespeed is right, my cases are very different from yours, sorry!, you should listen to him about the cases.

 

[lilplaya_bm]

strokers kits give more low end power but no speed...u can achieve way better speed from a stock stroked crank...the short the stroke the more power u get at a higher rpm, so the taller the stroke the more power at lower rpms...hope this helped!!!!

Lilplaya: I disagree a little with you....

From a theoretical standpoint, the displacement increase of an stroker engine should have one fundamental advantage, that is, increased torque output through out the entire rpm range. This theoretically happens because of a larger volume of gases being involved with each power stroke, as well as a slightly longer power stroke. Understand that with regards to a two cycle engine, the "actual power stroke" refers only to the distance from top dead center to the opening of the exhaust port.[/QUOTE]


i know for a fact that any engine with a shorter stroke will have more power at higher rpms and a longer stroke will have more power at lower rpms...not to say it will be slow but it is about tuning your engine to what u want...if u dont want to loose to much speed out of your engine then u can use a shorter stroke and larger conrod or a taller piston to make the port durations correct...it is a fact that was printed in a two-stroke tuning book(forgot which one)...it is true...