I am down to the final decision of engines to put into my GP .40 size extra 300s. Either a 50 sx or 61 FX. I used the rcu engine comparing thing and it shows that both have a bore of .866" but the 50sx has a longer stroke of .85" when the 61fx has a stroke of only .77". how can that be? the 61 has more displacement, if they have the same bore, then the 61 needs to have a longer stroke, am i right or wrong?? i dont know. maybe its just a typo. anyone have any input? kinda confusing me.

sean

I'd also look at the Irvine 53 if I were you.

thanks, i'll look into that

sean

Ah, come on...spring the big bucks & buy the JETT Signature Series Barstock .76L, which weighs LESS than an OS .46FX yet has the same crankcase size AND will beat the pants off anything in it's range! All for the low, low price of just $325.00!!!

They're both oversquare designs. Either you have simply misread or the engine comparing tool has erred.

The 61FX has a stroke of .866in (22mm) whereas the 50SX has a bore of .866 (22mm) is possibly how the confusion arose? The bore of the 61 is larger at .946 in (24mm) as one would expect. Though both are short stroke designs, the SX is closer to square with a stroke of .847in (21.5mm).

Sean,

It is obviously a typographical error.

A .61 engine differs dramatically in size and weight, from a .40-.53.
You are likely to need more tail weight, if your model was designed for a .40-.53.

The majority of the added power will go to waste, just carrying all the extra weight.

Your model will also lose much of its agility and will land at higher speeds.

It will be quite a bit more cumbersome...

Are you sure this is what you want?
If not, just stay with a .40-.53 and I am not so sure if the OS is your best choice.

thanks for the input everyone. i think the RCU engine comparing thing has an error, because thats what it says. I am going to look into the irvine 53. I also have been told this model flies exceptionally well with the 61FX. As for the jett, no thanks. if i was going to spend that much i would spring for a YS 4 stroke to put on my funtana and then throw the OS .70 from the funtana onto the nose of the extra. As for being sure whether i want os or not, I have never had a problem with that brand. always reliable and fairly easy to tune in. Lets not start a engine bashing war here though.

sean

See following site for Irvine engines.

http://www.justengines.unseen.org/