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my buddy just smoked his mxz 800 and it got me thinkin ... all these pro-x jugs with the powervalves use what looks like a ski-doo powervalve... and everyone knows a powervalve motor will whoop a non-powervalve one ... anyways i got thinkin why couldn't you put a jug offa something else on a 250r, ftz offers a bunch of motor kits including a jug off a odisie but there all honda stuff... back to the ski-doo i figured out that the bore and stoke of the 800 is 82x75 .... +3mm stroke to a r crank and you could even go to 76mm..... making a 401.23cc or something, so i went over and roughly measured his cylinder-crankcase bolts... they looked pretty close to 4inch x 4 inch.... they look like the same as the 250r (other than one set of bolts are inside the waterjacket, gotta take head off to take em out)..... the next thing is piston crown height, and rod length..... i gotta wait and take his sled apart and measure everything , hopefully the rod/crown height is shorter on the 800 then i can make a spacer plate to work..... but if all is right then all i will have to do is run a stroker crank and bore out my cases and of course i would have to make my own custom head since the 800 head is a 1 piece/2 cylinder head but i could have a 400cc powervalve motor.... just wondering if anyone has any info/specs of 02 mxz 800 engs or if anyone has any sugestions
 

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a PV motor will woop a non PV? peak hp will be practical equal with everything being the same. as for sugestions, you can do anything with money and a lot of time but you'd be better off abandoning that idea^^^ due to complexity, cost, and possibly reliability.
 

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a PV motor will woop a non PV? peak hp will be practical equal with everything being the same. as for sugestions, you can do anything with money and a lot of time but you'd be better off abandoning that idea^^^ due to complexity, cost, and possibly reliability.
^ now thats a hell of reply !! :eek:
 

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a PV motor will woop a non PV? peak hp will be practical equal with everything being the same. as for sugestions, you can do anything with money and a lot of time but you'd be better off abandoning that idea^^^ due to complexity, cost, and possibly reliability.
I got to agree with this, seams like I remember it taking that guy 2 or 3 years to finish that thang.
Neil
 

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i am pretty familiar with the rotax honda motors. when done right they rip....BUT....there is a ton of case work that needs t be redone, and you do have to move the studs... with all the new cylinders out these days, saber, puma, sphinx etc, you would be time and money ahead by abandoning your idea.....and the comment a PV motor will always make more power then a non...you should do some re search on that.... ;)
 

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ya...... a non-pv motor may make same peak hp.... but a pv motor is gunna have a way broader powerband it will have bottom end torque.... then still have lots of topend scream ... where a non-pv will depending on the porting either have bottom end snap and not scream out as much or lag in bottom....and then have a good hit of power and scream out ........ think of it this way what would give you better power for all around riding.. woods,tight trails, open fields, roads, ? iv rode both 85cr250 with the shity style powervalve that was made to not work... and then the 88/89 with the powervalve and i found the powervavle eng to have far more usable power......sure in a drag race they may be equal because your wide open the whole time ... but try and take one of your cali sand dragers to the woods in canada and ride , any roads/fields you hit would be awsome but the bush would suck i want something that can still lug a little but when you do wanna race some banshee you can still kick some ass
 

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i am pretty familiar with the rotax honda motors. when done right they rip....BUT....there is a ton of case work that needs t be redone, and you do have to move the studs... with all the new cylinders out these days, saber, puma, sphinx etc, you would be time and money ahead by abandoning your idea.....and the comment a PV motor will always make more power then a non...you should do some re search on that.... ;)
hey right on ... someone did do one eh ... you say they had to move the studs?... do you know what jug they used...see thge 440s are a rotary valve , same with 583 and i think the 670.... i think 700 is reed valve and i know 800 is reeds on this 02 i gotta rip the jugs off but they look like they may bolt on?...see i know nwere i can get this 800 jug for free, i have a milling machione at my disposal and mig or tig welder.....whats the max bore they go to on these aftermarket jugs before they move the studs?...... and whats length of stock r rod, what could ya get to have a smallend to fit a 20mm pin+ bearing?
 

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i'm not dicouraging you but their right with all the cylinders out there it seems to be not worth it. some guy on the web built a working pv hpp atc motor but it took alot of custom welding & machining. but if you have the means and the know how and the cash theres nothing better than building one badass motor and being able to say i built it. just do it to a spare motor b/c there will be alot of down time
 

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how do ya like the ct330 cylinder? .... im just checking out this settup.... i need specs on everything more that anything... ... im busy at home in the shop right now so i dont have time to go rip my buddies sled apart ... but when i do il know everything .. i got a piston and the crown height is less so the rod on a mxz must be longer and tyhe wrist pin is like 20mm instead of like 17mm or 16mm ( dropped my calipers after measuring the 800 piston , they were scrood up anyways)
 

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the 330 is a monster its set up for xc so its all bottom but on top it still whines out harder than my old 250 cyl ported for top
 

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the 330 is a monster its set up for xc so its all bottom but on top it still whines out harder than my old 250 cyl ported for top
cool... ports are proly designed different in the 330? are they pv? do ya have to run stroker crank for it? and what kinda $ ya got into it , if ya dont mind me asking
 

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yes much different design, non pv, not to sure on the stroker mine is a stock length longrod with a spacer plate. i got prob about 1500 in that motor but that also includes the pc'd cases and totally re-doing the bottom end
 

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Discussion Starter #14
yes much different design, non pv, not to sure on the stroker mine is a stock length longrod with a spacer plate. i got prob about 1500 in that motor but that also includes the pc'd cases and totally re-doing the bottom end

was that buying everything new? every kit iv seen on the internet new is $1600 without crank.... my bike had a hotrod crank with short rod... i was gunna get a 295 sleeve put in mine get it ported or try to myself and get a hotrod crank with longer rod and run a spacer plate..... but i dont know if ill be happy with it and ill prolly have a grand into it at least then im worried if ill be happy with it...and ill have all this money into it when i coulda taken that money and put it into a really good settup .. i have a fmf fatty ,turbine core2, boysen reed valve( thinkin of boysen rad valve or cr cage) reed spacer wiseco 1.25mm oversize , coolhead with i think stock or 1cc smaller dome and stock 36mm kehein carb with k&n filter running all my stock airbox ,lid,snorkel because we get into mud riding sometimes i would also like to buy a programable cdi..... would like to run a cr ignition but i want my lights
 

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ya...... a non-pv motor may make same peak hp.... but a pv motor is gunna have a way broader powerband it will have bottom end torque.... then still have lots of topend scream ... where a non-pv will depending on the porting either have bottom end snap and not scream out as much or lag in bottom....and then have a good hit of power and scream out ........ think of it this way what would give you better power for all around riding.. woods,tight trails, open fields, roads, ? iv rode both 85cr250 with the shity style powervalve that was made to not work... and then the 88/89 with the powervalve and i found the powervavle eng to have far more usable power......sure in a drag race they may be equal because your wide open the whole time ... but try and take one of your cali sand dragers to the woods in canada and ride , any roads/fields you hit would be awsome but the bush would suck i want something that can still lug a little but when you do wanna race some banshee you can still kick some ass
the PV typically would make moe power over a broader rpm range, but what happens alot is people do not know how to tune there PV to make the PV work like its supposed to. i recently built a 370 PV for a friend of mine, originally was an esr cyl, and we blocked the PV off and re port the cylinder and cut another dome, and he said he cannot feel any loss of power in the lower rpm range and this is on drag race motor with quite a bit of exhaust timing. you do have to muve the studs using th 800 mxz cylinder. here is a pic of some of the case work that needs to be done.......
 

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Discussion Starter #16
it looks like they changed it alot... think the 295 kit like i explained would be close to a banshee on first bore with fmf pipes and reeds.... no porting done?
 

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the PV typically would make moe power over a broader rpm range, but what happens alot is people do not know how to tune there PV to make the PV work like its supposed to. i recently built a 370 PV for a friend of mine, originally was an esr cyl, and we blocked the PV off and re port the cylinder and cut another dome, and he said he cannot feel any loss of power in the lower rpm range and this is on drag race motor with quite a bit of exhaust timing.
I was thinking about blocking off the PV on my cylinder. It doesn't seem like it does much besides leak and make a mess. Mine is ported for low end so I thought it might not change much. Eventually, I would like to switch the PV to a CT or rotax. Neil says they work much better than the ESR.

iwem, consider the costs of a custom exhaust and intake for that Rotax hybrid. A custom in-frame pipe will be very expensive and it will be a pain to get the rotax intake to fit up to your 250r air box. It is much easier to do these conversions on drag motors with out of frame pipes and no air box.
 

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your PV cyl that is ported for low end power may ont actually be a low end motor with the PV removed. usually the exhaust is pretty high when removed...
 

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your PV cyl that is ported for low end power may ont actually be a low end motor with the PV removed. usually the exhaust is pretty high when removed...
You are probably right. It just seems like the PV opens so quickly that it isn't very effective. I have some spring spacers from ESR that I'm going to try. The spacers put more tension on the spring so that the valve will not open so quickly.
 

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The problem on the ESR valve, is where the pulse hole is located. The hole is right in the middle of the valve blade itself where it will see presure quicker than the other valves.
The Rotax & CT valves use the pulse hole that is located in the cylinder casting behind the valve blade out in the exhaust port. Those PVs will not see full presure untill the valve blade is almost completely open so in turn they work slower.
Neil
 
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