Valvetrain upgrade

[SAFETYpin]

Currently running 18lb springs 1.3 stamped rocker, gx200 head gasket on a genuine gx160. I already have the billet flywheel and rod, I am now looking for more rpm. My thought is start with valve train before major hp stuff. That way the valvetrain should match the capabilities of the rotating assembly.

I was think stainless valves, split keepers and aluminum retainers, 30-36# springs, billet steel 1.3 rockers, cro-mo push rods and guide plate.

I am trying to deiced If I should go larger valve or not? and possibly mill the head while its off. I have no clue how much that machine work might cost?

My goal would be for a 7500-8k reliable motor. I am not sure if the stock cam will get me there with the long throw 1.3 rockers, but it seems it currently wants to rev harder than the 18# springs can manage. And the agk site recommends not going higher than 18# with the stamped rockers. Without a tach I am not sure what its reving out to but I try pretty hard to keep the valves from floating.

So what would you do? I want more power on the most effective budget for a fun, fast, and reliable minibike.

 

[jesse8931]

I would say get a new cam and be done with it.

 

[SAFETYpin]

Is the cam going to get me more power below 6500rpm, because I think that's all my valvetrain is currently capable of?

I start wincing a bit when I think about my current OEM Honda valve spring retainers and valves flying around at near twice there intended purpose.

Upon further review, 6500rpm is probably optimisitc for the current setup. It still wants to make power beyond the capability of the valve train, maybe more like 5500-6000rpm with the #18 springs.

I figure the cam, port work and compression to match could all be added later. I currently can't spin any faster with what I have and am worried about breaking parts if I just throw 26# springs at it.

 

[Oldschool]

stainless valves, split keepers and aluminum retainers are not expensive and will give your peace of mind.
Your also going to want to use LASH CAPS.

New push rods are a must at high spring presure.

I am not a fan of conventional rockers.

I got my first set of Champion rockers and although the ratio a little wanting and they are heavy they need no guide plates.
I think they are better than OEM Honda to be honest with small lift cams.

I can't sugest much else....

 

[SAFETYpin]

Upon further reading its looking like I shouldn't exceed 26# springs on the factory cam, due to hardness of the cam and possibly flattening a lobe. Can anyone confirm that one?

I already have dual lash caps and the exhaust retainer on the intake.

Also looking to build a 8k rpm motor is probably silly, I really should just keep it mild. I'll still probably step up the valvetrain. Are the NR racing valvetrain packages a good deal, I can't seem to piece it together cheaper.

I guess I really need a tach to determine what kind of RPMs I am currently spinning...

 

[125ccCrazy]

Upon further reading its looking like I shouldn't exceed 26# springs on the factory cam, due to hardness of the cam and possibly flattening a lobe. Can anyone confirm that one?

no more than 18lbs on a stock cam..... going with a better cam will do more for your quest than heavier springs and bigger valves at this point...

 

[SAFETYpin]

no more than 18lbs on a stock cam..... going with a better cam will do more for your quest than heavier springs and bigger valves at this point...

So given that info, which rockers should I buy? I am pretty sure I can't run the 1.3 rockers with the 18# springs and a non stock cam due to coil spring bind.

Should I just get the 1.2 billet steel rockers, does that open up my cam choice to something intresting while still running the 18# springs? Or just a simple reinforced stocker 1:1, if I am not planning on spinning to the moon? Are the long throw rockers inhibiting my rpm by trying to open the valve too quickly and inducing float that way?

I am still planning on stainless valves, aluminum retainers and split keepers.

Its just a GX160 with just <9:1 compression with a bored gx200 carb from NR. I guess I am looking for the voice of experience to step in and guide me a bit so I don't throw away money, or end up with a poor combination of parts.

I am off to purchase a Tach of some sort, I can't diagnose the damn thing If I can't confirm engine speed. It sputters and doesn't want to rev past a specific RPM, I was under the impression that was valve float. BAH!

 

[novaracer]

So given that info, which rockers should I buy? I am pretty sure I can't run the 1.3 rockers with the 18# springs and a non stock cam due to coil spring bind.

Should I just get the 1.2 billet steel rockers, does that open up my cam choice to something intresting while still running the 18# springs? Or just a simple reinforced stocker 1:1, if I am not planning on spinning to the moon? Are the long throw rockers inhibiting my rpm by trying to open the valve toO quickly and inducing float that way?

I am still planning on stainless valves, aluminum retainers and split keepers.

Its just <9:1 compression with a bored gx200 carb from NR. I guess I am looking for the voice of experience to step in and guide me a bit so I don't throw away money, or end up with a poor combination of parts.

I am off to purchase a Tach of some sort, I can't diagnose the damn thing If I can't confirm engine speed. BAH!

for your goal you need the setup my son runs the nr 252-0607 26lb springs with the nr ss valve kit with the automotive style retainers and locks he is running nr ho welded rockers but champion rockers would be better because he has to run the billet guide plate. but its what i had. on his mini it is quick and fun to ride all day long.:thumbsup:

 

[SAFETYpin]

for your goal you need the setup my son runs the nr 252-0607 26lb springs with the nr ss valve kit:

No issue with the 26lb springs on a OEM Honda cam?

 

[mmisterbungl]

No issue with the 26lb springs on a OEM Honda cam?

he's talking about an after market cam when he said "nr 252-0607 26lb springs"

252-0607 is the cam

 

[jesse8931]

Just get the cam and call it a day

 

[rmm727]

I have that cam with 18lb springs and it pulls pretty hard after 3k rpm. It floats the valves at 6200 rpm. This is on a 5.5 clone.

 

[saychz316]

just keep in mind that 18lb springs coil bind really quickly. somewhere around .280" if i remember right. a .252" lift cam with 1.3 rockers will put you over that. if you run the 1.3 rockers like you said, you will need 26 lb springs over the 18's. and yeah, get the valve, locks, retainers, and lash caps first. like cranky oldschool said, they are worth the piece of mind.

 

[Oldschool]

just keep in mind that 18lb springs coil bind really quickly. somewhere around .280" if i remember right. a .252" lift cam with 1.3 rockers will put you over that. if you run the 1.3 rockers like you said, you will need 26 lb springs over the 18's. and yeah, get the valve, locks, retainers, and lash caps first. like cranky oldschool said, they are worth the piece of mind.

I am not cranky.

I don't like the sugestions I am seeing.

I think a less complicated valve train is a better place to start.

Stick with a smaller cam that has more durration. When you look at what you gain with high lift and the strain it puts on parts then sometimes its not worthwhile.

Also you head realy needs to flow well and you need a decent size carb to get the advantages.

Right now Tim Iskedarian has these black Momba cams he is grinding.
Its a parkerized cam with modest lift at 275.
Use stock ratio rockers and 18 pound springs.
Nothing there likely to wear out fast or bind up.

Dyno 265 with 236 intake is also a good little cam.
Not so much lift but the durration is what is important.
A smaller cam with a stock size carb will perform better with more durration.

Save the big stuff for a bigger engine build.

 

[graygoose420]

My motor is barley mild . 26springs with ret. & Locks, black mamba isky cam, valves one size up ,1:2 rockers, jetted up mikuni . I hit 8k every week. On 100 octane. It's been running since Feb. Of this year . I've also hit 30+ mile rides a couple of times

 

[graygoose420]

Black mamba is 270 lift 246 duration . Great cam . I should know I used the first one at our spot . I think I got the second one he made. . I currently own two.

 

[SAFETYpin]

Black mamba is 270 lift 246 duration . Great cam . I should know I used the first one at our spot . I think I got the second one he made. . I currently own two.

Any block clearance required for that Black Mamba and does it still have a compression release?

I just shot off an email to Smallenginecams to see if that cam/package is still avalable....

 

[graygoose420]

Any block clearance required for that Black Mamba and does it still have a compression release?

I just shot off an email to Smallenginecams to see if that cam/package is still avalable....

clearance might be needed .Not sure. Solocali put my cam in . Cam has release. Their not on the site anymore but I'm sure he has them or could make one real quick. Cam works great and is pull start . :thumbsup:

 

[SMALLENGINECAMS]

Any block clearance required for that Black Mamba and does it still have a compression release?

I just shot off an email to Smallenginecams to see if that cam/package is still avalable....

Hi guys,
The "black mamba" cam deal is still available. You get the cam, 26lb springs, Brad Penn oil, std. flat top piston, and rings for $85 shipped. There is no clearancing needed.
Tim

 

[SAFETYpin]

Hi guys,
The "black mamba" cam deal is still available. You get the cam, 26lb springs, Brad Penn oil, std. flat top piston, and rings for $85 shipped. There is no clearancing needed.
Tim

Any deal minus the piston as I have a GX160 and don't need the piston?