Simple Mods GY6 150cc, Stock Engine

[Goosey]

Well with the scooters getting landed on by a tree this spring it has taken me some time to get past the tree gremlins and move on to improvements. Roadrunner, Starting point 55mph-57mph, no tach so can't tell you if improved there.

The first things I added were a performance coil, and unrestricted CDI, and a new stock stator. These were done while troubleshooting a no spark issue.
No increase in speed, but it starts like, now,
and seems to feel smoother all around.

12gram Dr. Pulley Sliders, from 14gram rollers.
Much smoother take off. Less jump at the get go.

A9 CAM, so far not likeing the noise, but I will see tommorow how it does on a test drive performance wise. Maybe it'll make up for it :riding:

[190mech]

Its not the cam chain clicking is it?? :stumped:

[90GTVert]

I was just under the assumption that it's the typical big cam noise. Increasing lift and ramp angles tends to make more valvetrain noise. If it's much louder, you might wanna take another look.

[Fox]

I say make the clearances smaller by a thousandth at a time until it quiets down.

[stepthrutuner]

I'd say that's good advice from Fox. A more aggressive cam profile should generally be accompanied by stiffer valve springs and/or lighter valves and actuation components to control the added inertial effects from the steeper up and down ramps. :popcorn:

[Fox]

Make sure the cam chain guides are aligned properly. Shine a flashlight down in there and make sure the upper chain guide didn't get lodged along side the chain. That would definitely make a loud noise and affect the chain tension(er).

[Goosey]

The noise is a definite "clack". No grinding of any kind. I don't notice it so much at higher revs, though it does sound like a beast :twisted: When I back off it has a very loud valve clack. I think it's the valve clearance, but I will also check the chain out again. After I have a nap, kids, cat and a chipmunk messed with my good nights sleep. Need to get in my zen zone.

. A more aggressive cam profile should generally be accompanied by stiffer valve springs and/or lighter valves and actuation components to control the added inertial effects from the steeper up and down ramps. [quote/] Perhaps I will be pulling it till I can do something about that. I will have to dig for more information and see what parts if any are needed.

[190mech]

It isnt as easy just plopping in a cam and happiness forever comes..A longer duration cam lowers the compression,thus a higher compression piston takes care of that,then that higher lift will sometimes "coil bind" the stock springs,thus high lift springs are needed,OH! and how about when the valves bang into the top of the piston when the additional lift and duration ever so lightly bend the offending valve.In other words,Its a juggeling match!!When all of these problems are over come,then happiness will be with you!! ;D

[Fox]

What is the power like? Is it running good I mean other than the clacking?

[Goosey]

I havn't run it on the road. Don't want to put all the plastic back on if I can't solve the noise. But she fires right up and roars like a lion Runs fine, and fiesty. Throttles up and down good. But the actual power while riding I don't know. It just clacks, which my gut tells me is wrong. I've been wondering if it would help if I tried shifting the cam by a tooth either way if it would make a difference. Can I run it without the cover on it without hurting anything for testing purposes?

I have been trying to find a previous post in either forum where the guy first asked if it mattered if he installed the CAM top dead center, because of a noise? I believe he had figured something out. Can't find the post. I found several mentions of people who installed A9 cams as a plug and play along with standard transmission, and filter upgrades....

Ahh, gotta go to work. In my car today

[stepthrutuner]

There's a heck of a lot of physics and metallurgy engineered into finger-follower cam mechanisms. The wiper pads on the underside of the followers are contoured and set to length to accept the action of the cam. Longer (full open) duration means a shorter time to get there (and back). The sound you hear could be due to the follower slamming back down on the wider (longer?) cam surface that used to be already going down hill by then. A heavier oil could help a little but that increases splash and shear resistance elsewhere . Stiffer valve springs would limit the amount of hop of the follower away from the cam but want to slam the follower back into contact with the cam harder and increase wear pressure. Advancing or retarding a cam by a tooth is a very drastic timing change. Increasing thickness at the head gasket advances the cam and then necessitates a piston with a taller deck height to compensate for the drop in comp. ratio. Keep studying it and you'll get to a better point, Goosey!

[stepthrutuner]

If you want to try a heavier oil this is a good additive.

[90GTVert]

I forget the number, but I checked into moving the cam a tooth one way or another when i had a degree wheel on my 50cc GY6 and it's more of a hop than you'd wanna make. I don't think it'd matter anyway. Moving the cam one way or another is simply changing it's position relative to the crankshaft and flywheel. I'm guessing your noise is coming from the valvetrain, and that would still be operating the same way. You'd pretty much just be introducing the risk of improper timing causing a valve clearance issue or a non-starting/poor running engine IMO.

Any time you make a ramp angle steeper (common in aftermarket cams) the valves are going to open and close faster. Add more lift and they are traveling farther. Both cause more potential for valvetrain noise.

Worst case scenario, you have the same clack I heard on my GY6. It was the piston and valve making contact. I would call that noise fairly obvious though. I'm used to a clickity clack, this was kind of disturbing. If you are really worried, pull it apart and check your clearances. I don't think it would be an issue for you, mine was caused mostly by valves and valve reliefs not being properly aligned (parts mismatch that was my fault).

[Goosey]

Longer (full open) duration means a shorter time to get there (and back). The sound you hear could be due to the follower slamming back down on the wider (longer?) cam surface that used to be already going down hill by then.

Would that be why it sounds better at higher RPM's? Is this likely going to damage the valves? Do you think a different valve spring is needed?
Aren't I full of questions?
Let me rephrase that other thing, If I am off by a tooth, would it cause the extra noise, or would it just make it run like .

Moving on, I put in the stock cam for now. I may experiment with the cam adjustments at a later time on the Baron, as I don't need the bugger to get me to work. Don't tell the Baron I said that he's already temperamental.

I have a teflon coated variator and lighter weight ( so they advertise ) variator fan, 115mm. and a 1500 clutch, and spring, from Monster GY6, that I am going to combine with the Kidn'me performance clutch pulley...comes with and meant to be run with a longer belt, normal 743, comes with kevlar Bando 757.
Teehee, so one at a time? or throw the works in?

Found this on a different forum,

The engines that have a 'P' in them have a taller head and a different cam, bigger valves and flow etc. You can change
out the JUGs with a standard engine, but you must keep the head. There is only one 180cc BBK available for that
engine type...

Quess what? 1P157QMJ, on both scooters. I also found an A9 on ebay that stated the 1P157QMJ as not compatable, "heavy sigh" well, if I ever need to change out engines again. Anyone with a 150cc, GY6 with no P interested in a A9 ?

[stepthrutuner]

You probably could go as low as 0.002" on the exh. and 0.0015" on the int. A heavier oil will help. I say if you can get it quietened down a bit you might get used to it. Just check it after riding it for a couple of hundred miles as long as the noise remains acceptable. A lot of guys might want a little more bass from the exhaust to accompany the increased valve timbre. :popcorn: