GY6 Cylinder Rebuild Kits Trkimal 47mm 80cc Big Bore Upgrade Kits for 49cc 50cc 139QMB Engines 64mm Valve scooter moped parts, GY6 Engine parts for Chinese Scooter(64mm Valve Length)

Great as it (almost) has everything needed in one kit for a good price. After watching Roush's video, I got this installed in around 5 hours.Important note #1: keep in mind this kit includes no carb jets, which I did end up needing for reliability and performance reasons. I live at sea level, and an 85 main jet ended up being perfect for me. This is with a stock exhaust, and a stock carb/intake. If you have aftermarket items there, you will need more fuel.Important note #2: I ordered a 64mm valve kit as 64 vs 69 has little to nothing to do with impacting performance unless you will be porting. This ended up making a little more work for me, as my original motor came with 69mm valves (the gy6 uses both 64 & 69mm in different scooters). This was no big deal as the kit came with rockers for the 64mm setup, but required a bit more hassle in disassembling the rocker assembly and changing them out. This is something only a few tutorials show/go over, and can be tricky. Try to find out your valve length before ordering to save the hassle.The 8.5 gram rollers included with this kit were definitely a bit too heavy, and were not allowing the bike to get into its power band. I switched those out for a set of 6.5 gram rollers, and she now rides like a dream. This cost me a few mph in top speed, but the hill climbing and responsiveness improvements are well worth it.Overall I'd say this current setup feels about 1.8-2x the power over stock, and is well worth it. Next I'm going to be doing a few transmission upgrades as the stock definitely feels like it's sluggish/underperforming. This will include a new variator, clutch, and contra spring for rpm control. I made these upgrades on another scooter of mine and saw huge improvements. After will be a new exhaust and possibly a carb. Good luck and have fun!

Put this part on my scooter and when the mechanic told me it was ready in a day I was shocked. The acceleration dramatically increased from 7.5 seconds to 2.8seconds. I went 32 mph in 2.4seconds last night. However the parts need to be worn some more so for the next two weeks I will keep top speed of 18mph even tho i can go faster.Note: this 80cc kit works best only if you upgrade 5/5 performance parts : racing Muffler, carburator filter, racing clutch kit (sliding rollers sold separate), racing secondary gear transmission, and 80cc kit or bigger bore to your motorcycle this method applies to all motorcycle, scooters, mopeds, atv , and dirt bikesAll together you should spend about $290 in all 5 parts including its assembly and a good mechanic about $250If you're looking to upgrade and go up the hill 35mph you can do all this and save money and timeI will leave an update for the future on this bigger bore upgrade for 49/50cc scooters

I'm a mechanic, and I did the swap in my shop. I consulted the Roush's Garage video on youtube (helpful reference guide) and knocked it out in about two hours. It's easier if you elevate the scooter to a good working height. When you do your break-in procedure, make sure the engine is hot and has just been running for your first and second oil changes. Makes a difference in how much contaminant debris is suspended in the oil. If the engine is cold and hasn't been running, a lot of that debris settles and doesn't come out when you drain the oil.The power increase: what can I say? Given that 80cc kits are actually 72cc, it's only a 45% increase in displacement from a 49.5cc bore. But it FEELS like a full doubling in power, if not more. The torque curve is definitely better for take-off and accelerating up to 25mph than the stock engine. I can easily get up to 40, hills are no longer a nightmare, and I don't feel like I'm holding up traffic on my commute. Top speed with 5g sliders, a 2000RPM clutch and yellow contra spring, and stock final drive gears is 45 or so.70 miles on the upgrade so far, and no problems or complaints. All the extra parts thrown in the box are a nice convenience too.

Moped ran for 2 weeks the started having problems cranking. Got low compression. The intake valve guide was oversized, allowed the valve guide to wear and begin kicking the valve sideways losing compression. Also shims under valve springs were never installed. Tappet adjusting screw had defective threads also.

This was the way to go. Get a complete kit so everything matches. The cam I received got banged around during shipping so I ordered a A9 cam to replace it with from glial off amazon as well it was perfect upon arrival. Everything went together well not a single fitment issue. And it made a big difference in the power. I am doing all this to a brand new scooter. Let’s say it left a bit to be desired. Most of which really was carburetor issues. Put a Japanese carburetor on it and with a little more jetting work and patience I should see a massive improvement.For the money you just can’t go wrong.This is why I bought the scooter to begin with. It’s just a project to prove it can be made into something fun and reliableKeep in mind the Chinese scooters are not so bad , they are just mass produced on assembly lines. And this kit is the beginningPoint.Don’t hesitate it’s worth the money.

Item was exactly what the description said. Fast shipping and reasonably priced for what all came in the kit. Bore out kit for a scooter. Excellent and honest seller. Would definitely buy from them again. A+++

This is great if you feel the need to refresh/revitalize/upgrade your scooter. The rebuild components come in handy as spare parts or just improving reliability of the moped. I will purchase this again in the future.

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