high lift cam (a9) for 139qmb gy6 50cc

ive found the cam I want to pair with the #sa88 52mm big bore kit. I've been referring to it as high lift but have been told by others that this is incorrect. What do you think?

[JeffreyDjRTBEdwards]

So i have the 50 mm bbk 69mm valves. Ive only used a9 in previous builds, is there something better? Right now I'm using stock cam and rockers, but I'm topping out at 30mph at 8k rpm. I know i need a variator and weights to help the rpms. Just doesn't feel strong as previous builds last build cruised 45 anywhere and hit 53 topped out. I'm only a 120 soaking wet tho. But 30 after bbk! Bring the power guys. Please and thanks😅

[michaelgrimley]

I came across a few people posting about the A9 cam causing the piston to slam into the valves because of the high lift and the added duration. They were discussing an Airsol 50mm cylinder and piston kit specifically. Also the exhaust valve being the one being the one getting most hits and eventually breaking and dropping into the cylinder. You can imagine the damage done to everything after that. Has anybody out there experienced this before? Any ideas how to mitigate? One post mentioned using 2 or 3 base gaskets and that does sound like it could work.

[ORIGINALCONCEPTGARAGE]

More lift can increase power, and increased lift without changing duration increases power without affecting the point of peak power on the rpm band.

So im thinking as long as lift doesn't affect the turn around or duration as high lift can cause problems if say ment for race being used on the street because those higher speeds ment to take place the whole run over normal usage could then make the engine not run as good on street use unless the duration for more street performance is used in the high lift profile with duration if that makes sence i dont know im guessing honesty

[robertjames]

That's a cam for the 69mm head it has a higher left for the longer rocker arms and will give you a higher left for the 64 mm head

[dobby]

Is I left you're right I can see it myself

[ORIGINALCONCEPTGARAGE]

I actually might have a cam for you to research if you want to check it out. It came with a roller roker Kit But Heres The Weird Thing It Says Its For A 50 But Being Sold As A 150 Cam If Youd Like To Looks At It I Donts Minds Sir

[obgyscooterdr]

Idk but my Glixal ATKS A9 cam is pretty good

[ORIGINALCONCEPTGARAGE]

I'm sorry for spam commenting I didn't mean too. But on youtube it really does help. As it counts as engagement.

[thundercatt]

Try a big valve head with the 23 mm intake and 20 mm exhaust valves and larger intake and exhaust ports, to go with the high lift camshaft.. 3.5 rollers on a 1500 lbs clutch spring.. using a 81 cc cylinder kit, not the 72 cc one and adjustable carb .. use a y spliter on the vacuum lines running to the fuel pump instead of plugging the egr side and using just one line....

[seanmayo]

Maybe high lift is best for 69mm valves. Idk really

[jacken]

Have you been able to measure the extra amount of lift the cam has?

[kingdasouf]

Duration and overlap actually make more a difference in these gy6 motors
The Hoca A9 cam is a beast
It is higher lift and has an advanced love timing for high rpm
The Hoca A11 has almost the same lift but is retarded instead and it makes power everywhere and continues to make power beyond the A9

[seanmayo]

Maybe ask yourself. Why 64mm or 69mm . My stock 50 maddog had 69. Bought rolling wrench 81cc kit an it was with 64mm. I do know that it's easier to check valve clearance on 69mm in a Maddog. Mine hasn't run in awhile
It's cursed.