363 vs 370

[FerrinMotorsports]

Ferrin
I think Rupp was saying is that if he was on his 363 and u on a stock 250r ,depending on where u guys were riding ,u could beat him in certain places or vice versa
Bieng that Rupps bike is setup way more different then urs ,there's certain disadvantages and advantages on both ends

Truth be known I'm getting old and I think Rupp would probably kick my butt no matter what we raced....LOL

[Sand_Blaster]

I'm glad you made this thread. I do plan on a 370ESR build for a duner. Good info so far

[Jerry Hall]

I'm no expert but what I've been told is the rod angle on the 5mm crank is harder on the piston skirts than the 4mm crank, thats really the only differnece that I've heard of.

Yes the 5 mm stoker rod angle is harder on piston skirts than a 4 mm stroker. ................... but.................a 4 mm stoker rod angle is much much harder on piston skirts than a stock stroke crank.  One should not be worried about how hard something like rod angle is on piston skirts if you have the money to spend on any of the aftermarket cylinder kits and related components.  Before investing in one of these big bore kits one needs to be aware that any engine with big forged pistons require frequent piston and ring changes.  


The big bore kits are hard on everything, bearing pockets, transmissions, clutches, etc. not just pistons.  If we used a con rod a mile long it is not going to prevent these big bore pistons skirts and piston crowns collapsing.  The problems we have with these pistons is not because of the rod angle, it is because of the lousy design of the forged pistons being made for these kits.

[FerrinMotorsports]

Yes the 5 mm stoker rod angle is harder on piston skirts than a 4 mm stroker. ................... but.................a 4 mm stoker rod angle is much much harder on piston skirts than a stock stroke crank.  One should not be worried about how hard something like rod angle is on piston skirts if you have the money to spend on any of the aftermarket cylinder kits and related components.  Before investing in one of these big bore kits one needs to be aware that any engine with big forged pistons require frequent piston and ring changes.  


The big bore kits are hard on everything, bearing pockets, transmissions, clutches, etc. not just pistons.  If we used a con rod a mile long it is not going to prevent these big bore pistons skirts and piston crowns collapsing.  The problems we have with these pistons is not because of the rod angle, it is because of the lousy design of the forged pistons being made for these kits.

Jerry who in your opinion makes the best piston kit for a big bore??

[rk88r]

^Or some other oem piston?

[mandom250r]

which set-up would be best for a drag or duner?

[patman13mia]

jerry which of the cylinders do you think you could get the most hp and torque out of?? just wondering??

[Jerry Hall]

Jerry who in your opinion makes the best piston kit for a big bore??

There are only two that I know of,  Wiseco and Wossner.  I do not like the piston designs of either one.  I call the pistons that both of these companies make for the TRX big bores, "drag racing pistons".  Thin skits, thin parallel piston crowns are characteristic piston designs used in ultra high RPM engines that only need to run for seconds at a time and do not have to be designed to dissipate the heat from the crown at the same rate it is being created.  A well designed piston can be run wide open when tuned for max power for more that 15 to 20 seconds without the top caving in or blowing through.

[Jerry Hall]

jerry which of the cylinders do you think you could get the most hp and torque out of?? just wondering??

The only cylinder that I have done development on the is CP 330.  I have a ESR 330 that I am planning to develop this summer.

Getting the most HP or the most Torque out of an engine is not one of my goals.  The engine with the most peak HP will be good for the salt flats.  The engine with the most torque will be good for pulling stumps after logging.  Maximizing either the torque or power will not win drag races, super cross racing or be good for recreational riding.  

There are power curve shapes that are needed for each application.  Most dirt racing requires a power curve shape that will produce the most acceleration.  A power and torque curve shaped for acceleration needs to look more like a four stroke power and torque curve.

[patman13mia]

ahhh thats true. i didnt even think about that. like most ppl i find myself wondering how much hp or torque a quad has and then judge how fast it is from that. thats almost racial profileing now that i think about it. lol

[FerrinMotorsports]

There are only two that I know of,  Wiseco and Wossner.  I do not like the piston designs of either one.  I call the pistons that both of these companies make for the TRX big bores, "drag racing pistons".  Thin skits, thin parallel piston crowns are characteristic piston designs used in ultra high RPM engines that only need to run for seconds at a time and do not have to be designed to dissipate the heat from the crown at the same rate it is being created.  A well designed piston can be run wide open when tuned for max power for more that 15 to 20 seconds without the top caving in or blowing through.

I remember back in 1986 the oem pistons from Honda were better because of them being a cast piston. We had problems with Weisco pistons because the were forged ...  People would take them to their local machine shop and have their cylinder bored to the Honda manual specs and then bring them to us wondering why their piston seized.....They didn't know because after warm up a forged piston swells more than cast so it needed more clearance...If I remember ARTS pistons were good also for oem as if I remember right they were the one who made the pistons for Honda at the time...

[mandom250r]

ahhh thats true. i didnt even think about that. like most ppl i find myself wondering how much hp or torque a quad has and then judge how fast it is from that. thats almost racial profileing now that i think about it. lol

lol its funny cuz its true. i usually look at what pipe and paddles theyre running and judge them from there.

[Pumashine]

lol its funny cuz its true. i usually look at what pipe and paddles theyre running and judge them from there.

Exactly, if you are running a FMF I am most likely to go to the next post.

If you really want to know if a 363 is faster than a 370 you would have to have both bikes on the dyno with the same set up... pipe, carb, fuel. Just a little tuning on the dyno can give you another 10 HP.

The main reason we are running 4mil instead of 5 or 6 mil is that the hotrod 4mil has not had the pin moved where as the pin has been moved 1 or 2 mm on the 5 and 6 mil. Its the longevity of the crank and cost factor that guide us.

[mandom250r]

Exactly, if you are running a FMF I am most likely to go to the next post.

If you really want to know if a 363 is faster than a 370 you would have to have both bikes on the dyno with the same set up... pipe, carb, fuel. Just a little tuning on the dyno can give you another 10 HP.

The main reason we are running 4mil instead of 5 or 6 mil is that the hotrod 4mil has not had the pin moved where as the pin has been moved 1 or 2 mm on the 5 and 6 mil. Its the longevity of the crank and cost factor that guide us.

sounds good to me lol

yea i guess i would prefer an original plug-n-play part than one that has been machined or modified even though its new

[Pumashine]

sounds good to me lol

yea i guess i would prefer an original plug-n-play part than one that has been machined or modified even though its new

Excuse me I meant moved 5 or 6mm. The wedge that is welded in does not give 360 degrees support.