Big Valve Head - Worthwhile or not?

[humanshield]

Been thinking about getting one of 02Starriders Big Valve heads.

One of the things that's held me back is info from other forums.

Some folks say that the ports behind the valves cannot be opened up so there really isnt much benefit gained from them.
They do have bigger valves, but  the ports behind the bigger valves do nothing to benefit from the larger valve.  So essentially
little if any gain.   So I read elsewhere.

Anyone have any additional info?

[90GTVert]

I think it'll help, especially with a big bore. I've only cut a stock head in half so I'm not sure how much different the aftermarket stuff is. I have some here, but I haven't got far enough along in my project to try anything or look over stuff much yet. The size of the valves should help. I can tell you the ports are larger. IIRC the way the intakes are setup the port ends up being enlarged mostly at the bottom of the port. I think it can help, though I believe ideally some material would be removed on the top... but that's where the really thin area is below the valve spring seats. If you open up the bottom of the port with how many of these heads are setup then the mixture comes in and is pushed toward the wall on the long side radius. If the port were able to be opened on the top side more then it could probably be aimed more directly at the valve and seat. Some porters will fill floors when raising the roof to keep whatever they feel is an ideal port cross sectional area and try to avoid dead zones. All of that said, I haven't tried a head on one of these in years now, but I did get an improvement when I used the Scrappy big valve head on my last 4T 50mm bore.

I have the 02 head, Hoca, Naraku, and Scrappy. Expect similar quality to a stock Chinese head with the 02 unit. Kinda hard to go wrong at their price though, significantly less than the other options. Mine has rough casting and poor finish on gasket/mating surfaces. Expect the Taiwan made stuff (Naraku, Hoca, NCY) to have better finishes and quality control. The Scrappy head had the best port work, and is the only one that has an actual human going into the ports. Their old head prepper is a member here and no longer does their heads as I understand it, so I'm not sure what they're like currently.

[blaq]

I ordered from 02starrider on ebay what 100 CC big bore kit for $199 and I had to get a replacement head because one of my valves was burnt I kept it to see if I can fix it or replace the valves which I've seen on videos that it can be done so I just kept it and now it's sitting outside hope it doesn't rust up or anything like that I got it covered a little. Also the air filter that comes with that big bore kit I think this is called the uni air filter and when you sit it on the carburetor your seat punctures the uni filter and it breaks up so I see that filter as being flawed for this Chinese scooter

[stevec]

best big valve head you can get IMO is from scrappydogscooters, they make them in the USA and are done to order so if you want one it could take a couple weeks to get it and the ports are done.
if you do get one with the ports done you will see an increase in power but most of the chinese big valve heads don't really do anything.

[humanshield]

Thanks guys.  Other than you, seems like very few people have any experience with Big Valve Heads.

Can't seem to find anyone who used the one from 02Starrider.

My scoots doing pretty darn good with just the 50mm BBK (easy cruise at 35mph even in strong headwinds and uphill). Maxes out about 42 to 43 top speed depending.

So not sure if I'll go the $140 for the SD Big Valve Head just to gain maybe 3 or 4 mph top end.
Then again it would probably increase gas mileage at the same time.

If there was even half the improvement from the cheaper Big Valve Head I would probably do it since it's about the same price as a stock head.  I just can't find any people who've used them or are willing to discuss their results.

What would REALLY help is seeing a really clear close up photo of the 02starrider Big Valve head without the valves so I could see what they did to fit the valves in.

Are they stock heads with the seats cut for the larger valve or different castings?

If the port underneath the valve seat too quickly narrows back to stock port size it could potentially actually result in a decrease in performance.

[jc33777]

I am putting a big valve head on my build its from Scooters To Go maybe they can comment on their heads

[dude]

Not sure if it'll help i cleaned it up a little. It's a different seller but 20/23 vavles.

[90GTVert]

I took the valves out of my Growsun head from 02starrider earlier to give you a look. Took me a bit because of cropping and resizing trying to get you some decent large pics without taking up so much space.






Exhaust





Large ridges under some seats. This is the intake side, present on exhaust in spots as well.



Growsun intake.




Poorly machined intake mounting surface.


Stock head.


Stock exhaust.


Stock intake.




The Growsun is way larger. Look through the pics and you can see there are issues to be dealt with, but it's not just a stock head with larger diameter valves and nothing else. Looks like a decent head for the price, but at least the one I have really could use some work. The intake sealing surface will likely require refacing or a lot of sealant just to avoid leaks. A lot of overhanging/rough bits should be addressed.

If you look at Taiwan made heads (Hoca, NCY, Naraku) it's not hard to see the difference between the made in China vs made it Taiwan stuff.

[dude]

I have a NCY head and the ports are larger than the Growsun head. But I haven't used either. Not sure what the vavle size is on the NCY.

[humanshield]

Awsome photos Brent !


It does look like that intake surface will need proper machining to get it flat.
Poor QC on that

[humanshield]

Great pic DUDE

But neither of your web links works