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Scooter Elements head (all the ones he sells look like this including the NCY one)

My 60mm high compression piston and cylinder showed up today from Scooter Elements, I'm stoked to get this thing installed but I don't have a head yet to pair with it.

Couple questions.

1. Could I just use the stock 57.5mm head? Don't want to but just curious.

2. Non of the heads Scooter elements sells will work with my valve cover. I can either find a non-egr head or buy an egr valve cover. His heads don't have the EGR port but they do have the EGR style gasket seating area and the part that sticks off the head for the EGR pipe.

3. What head would you use? Feel free to provide links.

I thought that your first bullet point might be the issue and I appreciate your response, this is the first one I've seen yet that is more then just "my cam works fine, it's not your cam dummy."

After I put in my a9 cam the bike ran well up until a couple weeks ago when I got stranded. I was out on a ride and after making several stops the scooter simply would not start anymore. I had spark, I had fuel, it just didn't make sense. I got it home and checked my valves and they were still in spec. That's when I did the compression reading and got 105 with the cam. The book for my scooter says 130psi is the min in spec and anything lower could have no start / hard start issues.

I honestly haven't rode the scooter yet since putting the stock cam back in. My wife and I are going to do a ride this evening and I'll find out if my hard start problem is now resolved or if it's caused by something else entirely.

glad you're ok,

I use blue lock-tite on everything except internal engine nuts and bolts. I use red lock-tite on my exhaust bolts, varator and clutch nuts. If it doesn't have lock-tite on it, it somehow always rattles loose... (in my experience) :-(

Harbor Freight sells several types for only $3 a bottle and a bottle lasts quite a long time. I use these three but I rarely use the low strength. Go easy on the red, it can take heat or special tools like an impact gun to remove. On my exhaust studs I only put it on the first two threads and so far I haven't had any struggles removing it.

Low = Purple = www.harborfreight.com/threadlocker-no-22-10-ml-low-strength-65193.html

Medium = Blue = www.harborfreight.com/threadlocker-no-42-10-ml-medium-strength-65192.html

High = Red = www.harborfreight.com/threadlocker-no-71-10-ml-high-strength-65191.html

Well I'm looking at the NCY 61mm cylinder and head. These are reportedly drop ins and will bolt up without machining the case. I called the dealer and they measured the OD bore of the cylinder at 62.5 and mine is 62.49 I'm sure it will fit I might just hit it with a light grit sand paper to get that hundredth of a mm flush.

I dug around since my last response and I'm nearly 99% positive I have standard GY6 top end parts. Head height, valves, cylinder, cylinder bolt spacing, everything is a match so far. I'm going to buy from reputable "None eBay" dealers who offer refunds if for some reason it wont fit. Wish me luck.

So I've been on the phone with scrappydawgs and they are telling me my options are very limited. They said based off the numbers I told them I can buy virtually any GY6 BB cylinder but I really can only get their 4-valve head. Basically, he said that the BN157QMJ has a taller head then standard GY6 scooters and longer valves.

He directed me to a link on their site, here is an excerpt:
"GY6 Scooter Version B - This engine is found in alot of higher priced quality scooters like Zhen, Lance, Fly, etc. The engine number will be BN157QMJ, and will have a 16" rear wheel ( although some Lance Duke Tourings have the smaller wheel BN engines, which are standard parts, with some other exceptions). This engine is made by BenNeng of the Zhongneng Industry Group. This engine has alot of non-interchangable parts, like the variator, head, stator, etc. The head on these is taller than a standard GY6 head, and has longer valve stems. The stators are 12pole DC types. The belts are longer than standard, and are often 906. The cylinders however will fit from standard parts. Our big bore kits will fit -B models. The performance 4 valve head will fit these without use of the longer chain and retention studs, as this engine already has them."

My motor is stamped 157QMJ-3 (no BN prefix) I DO have 16" wheels, the much taller intake manifold, an oversized variator (122mm if I remember correctly) and run a 906 belt. However I do know that my CDI is AC so I'm not sure if I have the 12-pole DC stator. I may have a sorta hybrid 157QMJ that's not entirely a BN model.

So anyway, I went out to the garage and grabbed my calipers and started measuring.

Can someone possibly confirm measurements from a standard Gy6 (157QMJ)

Valves:
- Intake Valve length 65.87mm
- Intake Valve Stem width 5.08mm thick
- Intake Valve Seat width 27.81mm

- Exhaust Valve Length 65.39mm
- Exhaust Valve Stem width 4.96mm thick
- Exhaust Valve Seat width 22.93mm

- Overall head height is 59.98mm to 60.30mm (seems to be thicker on one side.)

See the attached picture for the bolt pattern measurements.

I've migrated over to this forum following the advice of a local friend who hangs here a lot. I have a 08' Gy6 BN157QMJ-3 (16" wheels.)

Last week I got stranded for the second time due to no start (first time was ebay racing CDI failure.) I got it home and once again checked the valves which were still in spec. Next I did a compression test.. 105psi.

I proceeded to get a leak down tester and definitely had a leak from my intake valve.

Long story short I lapped my valves it did not appear they were bent and no markings on the piston of a collision with the valve. I also put in new gaskets and valve seals. I put it all back together and compression raised 5psi to 110. This explains my hard starts as book says min spec is 130psi. I tested my wife's and her scoot is 155 so I know my compression gage is accurate.

Ok so now I'm looking at BBK's and I want to go as big as I can without having to bore the case. I heard there is a 61mm NCY kit that will fit in 90% of GY6 without a bore but haven't tracked one down yet. My bore ID is 62.49 I know I can do a 59mm kit without any issues. Reliability is of the up-most importance. I'll sacrifice a little power for longevity and not walking or paying for cab rides home after being stranded.

So the other issue is my BN157QMJ-3 motor. Scrappydawgs sells parts for them but I honestly think my top end is pretty GY6 standard. The intake boot is definitely different but I was able to use the stock GY6 157QMJ head and base gaskets on my scooter when I re-assembled my top end. Is there an easy way to tell which cylinder to buy or do I need to contact the seller directly and get measurements?

Is boring the case that big of a deal? I'd love to do a 63mm kit but I know that my crank is unique and to my knowledge no one makes an aftermarket stronger one for this specific engine. Doing the 63mm would be fantastic but if it would turn my stock crank or rod to mush I don't want to chance it.

Any advice would be great, Thanks!