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Discussion Starter #1
ok so im split between needing to get heavy duty valve springs or not. i have one person telling me i need them and another saying stock one will work just find. Im putting JE drop in pistons in my 2008 zx10r and my compression is going from 12.9:1 to 13.7:1. so ive been told i need heavy duty springs by one person and i dont need them by another. i dont want to spend the money if i dont have too. can you guys help me out with this plz
 

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I thought that heavy duty valve springs were required to eliminate valve float when increasing rev limits or changing a cam lobe profile?

How would increased compression cause the valves to stay open?
 
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I thought that heavy duty valve springs were required to eliminate valve float when increasing rev limits or changing a cam lob profile?

How would increased compression cause the valves to stay open?
:+1:

The springs are used to close the valves. The compression force will try to close the valves. So increased the combustion pressure will cause the valves to close tighter. Putting heavier springs in there to do the same thing is pretty useless if that's the only change. If the cams are modified, revs are increase, or forced air induction is used then the springs might be needed. Valve float is your enemy there.
 

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i've yet to see a drop in piston zx10 run any faster than a stk piston with compression mods. i've had 2 customers bikes, not my choice, not impressed. no need for hd valve springs as carpenters unless radical cam profile, forced induction, or nitrous.
 

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Needlessly using HD springs will Zap a Horse Power or 2. Carpenter will sell you anything, As stated unless radical changes to cam profile ie, where valves close faster due to increased lift or longer duration HD springs just make it harder to turn the engine.
 

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my experience with drop in pistons is they are a waste of money. cost of pistons, engine has to be pulled, broken completley down, rods removed from crank, reinstalled(which is a whole new process),
cylinders honed, engine reassembled and reinstalled, figure about $1500+ besides the rod/crank issues created. not aware of any 13.7 je pistons, just 13.5. can easily achieve that with mill and adjusted squish for about $150. if ur a street rider, be aware any compression mods increase engine temps so how and where u ride should be a primary consideration. thin hg, good performance valve job, int. cam or degreed stk. cams, good exhaust, and tune, that gen 3 will be streetable and a handful.
 

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Discussion Starter #8
Well gaz this is my plan, i was trying to do a budget build with my gen3 and this is what me and my buddy came up with

-Lighten & balanced crank, 13:7.1 wossner drop-in pistons (NOT JE MY MISTAKE), Complete valve job, gen3 racing intake cam and gen2 stock exhaust cam degreed with a retune.

ive only spent about $1100 just from that list but i was at 166rwhp with just bolt-on parts, im hoping to be close to 175- 180. My biggest problem is i cant find any solid degree number for that cam combination. and now that you say that i should have gained my compression the head with
milling and thinner head gasket.
 

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not knocking ur build, just trying to help. have'nt delt with wossners in a zx10, but have worked with je's and wiseco. check ur deck height closley, the je and wiseco pistons both have raised compression height tightening up the squish, so u have to measure and determine which thickness hg will work to provide minimium squish without piston to head contact. gen 3 race int, stk gen 1-gen 2 ex cam is a potent combo. my cam combo and used on a couple of other builds. degreed those cams to several different lobe centers, by far 110-111 int and 108 ex. made best power/strogest powerband. well prepped head, those cams, good tune i make 189-193 rwhp on mr12, so figure about 180-185 on pump gas. your goals are in line. good luck with build.
 

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Discussion Starter #10
Ya i previously had a .45mm HG on there but with the 13.7:1 pistons that are going in, im alittle worried about putting the .45mm HG back in. (if it even fits). I dont want to have to run race gas because of too much compression. But all in all we are going to double/triple check the piston to valve clearance, cuz i would hate to spend all this money just to blow it up when i start it. And thanks for the cam numbers, ive been wrecking my brain trying to find a starting point. thanks for the info keep it coming.
 

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Following along with this thread, I have a Gen3 and would like to see a bit more performance out of it. Engine is completely stock, has typical electronics and setup for drag racing. The bike doesn't see the street at all. Reading through this, it looks like quite a bit of power is left on the table with cam profiles and getting the head decked?
A few questions here:
What cam setup would be a step forward from stock for drag racing?
Are the OE cam gears adjustable or will I need to buy aftermarket adjustable gears?

Not trying to thread jack here, this just seems like an appropriate place to ask these questions.

Thanks,
MedicB
 

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be careful with cams on that gen 3, unless i could find a used gen 3 race int i would look elsewhere for more power, easy to overcam these stk piston engines for strip use. there is more to be had. .45mm hg to tighten squish, .020-.025 mill race only motor for more hp/torque, good cnc or serdi valve seat recut to to open seats and increase valve area, and redegree cams 110-111/108 using the stock degreeable cam sprockets. this is what works, most cams alone dont. little bowl porting add a few hp. got a gen 1 on the bench now adjusting valves with listed mods and stk gen 3 int replacing the stk gen 1 cam. got a call last night from customer in alabama due to rain finally got to run a similiar combo i did for him, ran 5.62/127 foot shifting his gen 1 on oxy fuel/well tuned bike with 91 degree track temp, bike go high 8.70's in 1/4. that's hauling ass in the heat. can set u up with proven combo if needed.
 

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GAZ-
You're the best man. You've always been a big help for me. In fact, I think you're the one who gave me a busa rear shock after I put my extended swingarm on.
Anyway, Yeah now that the race season is done, i've got plenty of time to figure out what I want to do with the bike during the off season. Low budget works best for me as i'm planning to buy a new truck and cargo trailer next spring.
One problem I have is I live on the west coast where motorcycle drag racing isn't nearly as big as it is on the east side.
My main goal is to pick up a bit more in ET but not take the reliability out of the bike. I was considering a small squirt of nitrous but if I can pick up some power with working with what is already there, i'd rather go that route.
 

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I was thinking about nitrous but was a little worried concerned after reading the bad things that happen, even with a small shot.
I’ll probably start with a sidewinder exhaust, if I can find one.
Looks like Brocks doesn’t make them anymore for the gen 3’s so they’re kinda tough to find.
 

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I've never had an issue with nitrous, but I never ran more than a .032 jet... though that did make about 7 more MPH even when I was only spraying it from 2nd gear and up (no chassis for it). If you keep it under 10hp per cylinder it should be fine on the motor. With really tiny shots like that you don't want to rely on a wet shot... do it dry and use the ECU for enrichment. The amount of extra fuel you need for < .032" nitrous jet is very tiny, and more often then not a fuel jet that size will clog up and cause problems. 36hp worth of nitrous only brought up my AFR's about half a point; real easy to tune for it with just about any software/hardware.

With how well you 1/8th mile, a 30 shot should get you close to 7-9 mph, I'd bet.
 

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05 stk motor gsxr 1000, good rider, 71 in chassis. bike running 6.15-6.10 113 mph as came to me. no tps signal to power commander, that fixed, inj's flowed/new fuel pump bike tuned made 168/78 ft lbs torque. ran high 5.70's/122 mph. 32 shot added 200 hp/100 ft lbs torque. throttle locked nitrous spraying on the hit runs 5.42/132.
 

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I'm currently running a pc5 with a wideband commander which data logs. The map i'm using has my afr right around 13.5:1 with MR12. This last weekend I played with the map a little and added more fuel to it. Apparently 13.5 is the happy spot. Got it down to 13 and started slowing down.

If I went with nitrous i'd probably use a progressive controller. I also have a 2-step on the bike so I leave the line at 100% throttle and don't really want the nitrous spraying while i'm sitting on the 2 step at 5k rpm.

Not sure as of now which direction I wanna go, but, it's good to know that I run a small shot and not hurt anything.
 
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