Yfm350 serious power build!!

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duneracerweston said:
a stock stroke warrior has alot of torque but a stroke would build more if you want to try it go for it but bump the comp up and put a wed .390 in and you will have more torque with stock gearing then you know what to do with

do as you please im just not a fan of strokes because of the way i ride
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You prolly stay in the revs for longer periods of time, I'd really have to try a good stock stroke setup just to see what it feels like man but I really don't know, heck my junk aint even runnin right near stock right now:( Anyway, I just kinda like the idea of some additional stroke b/c I'm 230lbs. Right now I'm geared 14/40 with Holeshot XC's all around(20x11x9's out back). It's just a dog right now man but the engine is worn pretty bad, I haven't done much with it the past 2 weeks b/c I wanna try to get a new timing chain & guides so I can get it timed right & then go from there. It just spits & sputters & runs like ass right now, kinda sucks.
 
Mine is stock right now am sure is getting worn, and it runs good, most times 1st gear for me is too low I can take off in 2nd without flogging it at all. My dad weight is close to yours and it get up and go with him on it. Yours just maybe worn out rings could be pretty worn. Do a compression check see what it has left, if the cylinder is ovaled out, might be able to do a rering, hone put a lighter aftermarket piston in it and bet it be better than what you think. My uncle swears by wiseco, he put one in a 250x 3wheeler and would stay or out run the 350x's all day.
 
I basically wanted to do this thread to gather wintertime ideas for a rebuild. All I know is that it smoked & used about a 1/2 qt every 3 rides or so & I'm pretty hard on it sometimes while riding but it was running ok, not missing or anything but the valves did need adjustment. Anyway, I had a spare head that I cleaned up the ports in & lapped the valves. I wanted to give it a shot just to see if I could get a lil more power out of it for the time being. I also just used one of the 3 headgasket layers to try & bump compression some but it don't run as good as before. Timing won't line up so I know that's one problem, I also don't know if I pissed the carb off somehow when I had the engine torn apart Or not, I may try cleaning it once more before I give up on it.
 
I weight the same as you and am for the most part stock other then a filter and pipe, and it's definitely not a dog by any means. Before the warrior I had only ridden my cousins Honda and Kawasaki 250's. This thing is MUCH faster then those and way more agile.
 
If its going through that much oil more than likely its burning it, the plug should look black and kinda tar like. If you want to do a refresh do a rering, and hone, the timeing chain maybe be stretched why its not lined up. Get a lighter aftermarket piston, bump the compression up a tad will wake it up. Then go for a filter and pipe setup.
 
I guess I shoulda said it already & I need to make myself a sig but I have a Trapp & K&N filter as well as modded air box. I also have a 45pilot & have tried 3 different main jets, 150, 152.5 & 155, it ran best with the 152.5. Sorry I didn't include that. It definitely burns oil guys, no doubt, I have a spare engine & i atleast wanna bore that jug & put a new piston in it. I've read some posts online where guys say leave the Wiseco pistons to the pingers & go with JE. i had kinda hoped to scratch up the cash for a 366 JE. I have even cleaned up the original head that was on it & am thinking of putting it back on just to see if it changes it back to the way it was before, heck maybed the head I put on it has some issues, I really don't know right now.
 
I don't know, seems like people here prefer Wiseco, I know the JE's are heavier which will have an effect on power. Probably really can't go wrong either way though.
 
Hdale85 said:
I don't know, seems like people here prefer Wiseco, I know the JE's are heavier which will have an effect on power. Probably really can't go wrong either way though.
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Haha, that's what I heard about the Wiseco, that it's heavier than the JE, LOL, WOW! Anywho, I also read that the Wiseco piston needed warmup time in order to properly expand & the JE didn't, however, my opinion is that all engines should have some warm up time before flgging. The JE does advertise a tad more compression though, which is nice.
 
Always alow 5-10 min of warm up time at a idle and it will last longer the reason it feels tired is probably needs bored JE is lighter then Wiseco idk were you got your info from but its only like 2-3 ounces
 
I always let mine warm up be it cold or hot outside, it lets the oil flow through first before blasting off. Even with my truck I let it idle a few seconds before taking off.
 
Hmm I don't know you see so much information all over it's hard to keep things straight lol.
 
'00 WO-YA! said:
Haha, that's what I heard about the Wiseco, that it's heavier than the JE, LOL, WOW! Anywho, I also read that the Wiseco piston needed warmup time in order to properly expand & the JE didn't, however, my opinion is that all engines should have some warm up time before flgging. The JE does advertise a tad more compression though, which is nice.
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The problem for me with JE is that unless you wanna do a stock bore, higher compression or the 366, thats the only ones I see in the high compression. Even on thier site they dont have anything else. I need an 84mm and want higher compression, my only choice is Wiesco.

On the warm up I always give it a few minutes to warm up before I take off. I beat on them hard enough riding, so with the warm up it also makes sure the oil is flowing good. Of coarse not everyone is running 15w40 Rotella either.
 
elwood said:
JE list the weight of thier pistons on there site, here is a link http://www.jepistons.com/Catalogs/Powersports/ATV-UTV/Yamaha/yfm_350_warrior-raptor_350.aspx

Wiseco didn't list thier weight on thier webpage
http://www.wiseco.com/ProductSearch.aspx
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Their both lighter than stock, so for me it comes down to who sells the bore size I need with bumped up compression. I still wish some one made 11:1 compression yet, big compression bump over stock but can still run pump gas.
 
1998yamahawarrior said:
Their both lighter than stock, so for me it comes down to who sells the bore size I need with bumped up compression. I still wish some one made 11:1 compression yet, big compression bump over stock but can still run pump gas.
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Thats alot of it anything that is lighter than stock to reduce weight, thus getting to spool up faster. Less rotating mass is going to give a boost. Anything I think in compression thats higher than stock would help, running a 11:1 on pump you would have to run a 90 or up octane wouldn't you to avoid pre detonation? Could you get away with running a higher 10.?:1 mill the head deck a tad thinner head gaskets and keep clearance for the valves? And reach a 11.1 or be close to it?
 
yes but no one knows the head volume to work out howmuch needs shaved to make it work right ive heard you can run 12.5:1 on pump but ive never confirmed that i know imma run race fuel if i run 12:1 or higher
 
I agree with the fuss about JE not offering enough options, it would be nice to have an offering for every .5mm but I guess JE figures that the bore doesn't need to be serviced as Often as a 2 stroke so they don't bother with as many offerings. I would imagine that someone could get close to that 11:1 marke fairly easily by seperating the head gasket, although a new timing chain might be a good idea at that point.
 
[ this thread has tons of motor mod info cand it be a sticky? just thinkin aloud here ]

ok im going to try and measure the oem head volume this week with dans head and see what i get
 
duneracerweston said:
[ this thread has tons of motor mod info cand it be a sticky? just thinkin aloud here ]

ok im going to try and measure the oem head volume this week with dans head and see what i get
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Hmm, makes me wish I had a combustion chamber ccing kit. I guess it's simple really, a piece of clear plexiglass with a hole to add some sort of colored water & some petroleum jelly to seal it, heck, you could prolly even use an old sringe for the volume as long as ya kept track of it, it'd just take more time. Oh....yeah, this has turned out to be a good thread, I'm proud to be a part:)
 
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