Surfriding Stock stroke big bore power valve motors...love it or list it?

[masterblaster]

Ive test ridden and experimented with quite a few of these on "pump" gas from a few diff manufactures and builders.Many seem to be soft on bottom and throttle response. Some not as bad as others... but pull throttle wide open and count.. somewhere between 1. 1000 and 2.1000 then hold the heck on when it starts to hit. Is there anything short of major compression and race fuel or changing port timing to get low end power and response outa these? The mid range power seems good,so much so many are proping up to keep from spinning,and just learning to deal with it? just seems to make throttle response even worse.

Total loss,bigger 48 and 49 carbs,reverse jetting,higher timing,more or less water in head pipe,dryer waterbox,softer reeds,steeper/shorter prop,bigger reduction nozzle,smaller pump cone,softer/stiffer Pv springs,pining pv open or shut...none make a substantial diff on this issue? workin on a mechanical water injection valve,sim to a reverse jetworks valve to try and get water in to the bpipe in a better spot for low end and cut off fast to keep the rpms higher up top.What else besides race fuel or a stroker crank and riser plate will make a rec motor like these respond as fast as the throttle lever moves?

 

[orangefinger]

I noticed a difference between B-pipe and PFP, and for my personal preferences I almost like the B- pipe more it appears that the punch comes bottom to mid and then flattens out, the PFP comes way late mid-top and then hits way hard....but we could have also just set it up wrong...

 

[Tyrant1919]

Opposite for me. B-pipe is garbage compared to PFP on my pump gas 850.

 

[masterblaster]

the pfp on these type motors makes the issue even more apparent.Most are constant water injecting the pfp even with the large CC race gas stroker motors. Gettin the sound wave to move with water injection may well help with the b pipe and these type motors as well. The port timing ive seen in most them is pretty high,alot of extra piston weight to get movin also,even more so than the race setups use to have even using 220 lbs plus comp and race fuels

tyrant..what comp you runnin,are you using the pfp as a wet or dry pipe?

 

[Pablo]

Why not the normal mods u listed (compression, timing, carbs, reverse jetting, dry pipe) and make sure the pump can unload super easily off the bottom. Use a super low initial pitched prop with a steep progressive tail end to take advantage of the top end pull. I used a 87 redux nozzle with a stubby cone but never got down to a customs prop but wanted a 7-8 leading edge pitch and a 15-17 trailing edge. I tried playing with power valves too...spring rates and stenting them open as well.

 

[Freakrider]

Good thread, aren't the power valves suppose to give initial exhaust port timing similar to a snappy 61x cylinder or is it still higher like a 760 cylinder because how they are ported by design ? Theoretically it should have the best of both worlds unless it's ported too high to start with.

 

[Pablo]

I'm surely no expert, but yeah that's the thought on PV's. however I was getting better throttle response with them opening earlier.

 

[sjetrider]

IMO it takes advanced timing (like 30 degree min ) when running PV motors with PFP and it takes higher compression as well. The PV setups do take some messing with to get bottom end and I am with whoever said WTF arent they supposed to offer the best of both worlds? What is the point if they do not offer more snap at bottom like the 61X but more pull at mid like a 62T?
Keep in mind though that mid is where most pro Freestyle guy need their hit for multiple stunts. They want the pump to load down low and the motor to explode at mid.
Its something that takes getting used to when we have all been screaming low end brap for 15 years LOL

PV BB stock stroke motors do not hit any better to me than the non PV stroker motors of the same CC. Less on bottom i think but they pull a little longer. Pick your poison. I personally think if your on pump gas your going to struggle with the PV motors more than the non PV. It would be nice to have different valves to swap out the would change the port heights on low end 1mm at a pop and see where you can take it from there.

 

[MADMAT]

Good thread! I have ridden huge CC big dollar skis that don't snap as hard as my non ported 718cc 195psi 13/16-3mm Solas >85mm nozzle. I was like WTF!?

 

[KTM434]

I've ridden SS billet setups that left me feeling the same way. My big bore 61x cylinder layout works well enough for me in small sloppy FL surf. I do like most power down low

 

[Berky]

Yea some non PV 61x hit crazy down low like the jetmaniac/Blue , but the SS PVs can be so linear and pull to the moon if propped right . Pump tuning is very important and gets over looked often . The reduction nozzle diameter is super crucial and needs to go up to get them to spin quicker not just a smaller pitched prop. 1mm is a big difference in total reduction nozzle area so use caution , to big and it will shoot it's wad to soon and fall flat mid to top .

 

[d_moss]

well i wanna ride a stroker then because i feel my BB850 hits hard.

 

[KTM434]

I had an 85mm reduction nozzle on my ski and broke it on the sandbar. Put a stock one in just for strength. Definitely lost 1/2 a second of throttle response but I hate breaking parts in surf. 1/2 a second can be a long time. I'll probably run a stubby cone and dry out my waterbox a little to see where that gets me.

 

[River Rat]

well i wanna stroke my bb850 with a 5mill and see if it hits harder then

do it!

 

[masterblaster]

pablo..ive tried that as well,I found the bigger the spread in pitch the more water it had to move through the pump at once,it loaded even worse and hit even later.Im using a smaller pitch prop with leading edge and trailing edge closer together.Ill try anything other than race fuel and high comp,These motors are already pushing the envelope of long term reliability pushing those heavy huge pistons around on stock rods,race fuel defeats the whole purpose of a dual purpose rec motor imho.add high comp and the factor goes even higher.

615..im finding much of that to be true,the more of these i ride and compare. Id say i find non pv stroker motors with far less cc to hit even harder off bottom.not as much mid to top sure.. but is that what we are after with this type motor? Its certainly not a pro freestyle motor category. Just like you said it does take getting "use to"The only thing i wana get use to is the motor responding and hitting at the same presice level the throttle is pressed. That is what makes a motor linear to me,pulling the throttle and waiting a sec or 2 and gettin wip lash just isnt desirable for our kinda riding.

tem..very true with pump setup,problem is with these type motors,they develop so little low end power on low comp pump gas and so much mid to top,you have to set up prop,nozzle for mid to top hook up or they just cavitate through most their powerband. Im starting to think they have to be high comp race fuel,high timing to get really good response.defeats the whole purpose of a SS budget motor,youll pay for a stroker crank in fuel costs and headache gettin it in no time.Especially with todays much cheaper adr stroker cranks. We have had a couple blue motors in our group,they are very snappy,but with the comp setup well over 200 lbs longevity was a major issue with every single one of them,same thing im trying to avoid here .Ive ridden some pump gas strokers that ripped off bottom and lasted far longer,some were even stock cylinders with plate on the bottom.

 

[CARBONX2]

Smaller carbs give more low-end due to higher velocity,(better atomisation, signal, etc.), will help prevent the lag. Might lose some peak hp.
Something that no-one runs but I have found to work, is individual boost-bottles. I know there are a lot of nay-sayers out there but I have tried them and they work when designed correctly. The hassle comes in where to put them.
Pipe design can also do it, longer diffuser(more low-end torque) - some peak hp will be lost. Not many people building their own chambers for jetskis, quite easy to do with a b-pipe type header/manifold.
A shorter/straighter intake manifold will also help, better signal to carb. PHP make one that is reported to work. Mounting carbs on a flat plate directly to manifold should work very well(going to test this soon), problem is water ingestion on freestyle/freeride skis(thinking of building tubes from filters located high down to carbs for the manifold test)

 

[speedysprocket]

Just going from 46 Novis to 48 Novis made a big difference on my 70mm stroke, 950cc power valve engine and let me turn a larger prop. Bottom end got better, not worse. That was the difference that has gotten me all the way around doing flat water flips from a 180 slide.
I have none of this proverdial "snap" because my power doesn't turn on and then turn off. I have smooth power from idle to wide open throttle and I love it.

 

[Freakrider]

I want a motor that will 180 hop flip my Freak or cruise up to boat wake slow and rip it around for an easy flip. Also want it to last at least 2yrs of riding, summer and winter riding . Which motor someone tell me?

 

[bware52]

^^^ Yes please!

 

[Camaroz28850]

There are too many variables to generalize and say that ss aftermarket PV engines do not have good bottom end power. Hull weight, pump, and tuning play a huge part in how a ski "feels". If you ride a ported 61x in a 60 pound superfreak and then ride a blaster with an SS PV engine, its obvious which one will most likely feel like it has more bottom end. It wouldn't be a fair comparison.

I have ridden at least 3 skis with aftermarket PV cylinders / stroker cranks that felt like they had a lot less bottom end than my SS 865 Xscream. I have also ridden skis that had a SS dasa / SS TPE and neither of them felt like they were lacking bottom end power. I will say that the power felt a lot more linear in both of those setups when being compared to mine, but I would think that most would prefer linear power for surf riding.