150cc Timing Chain Crankshaft Sprocket
 

Hi Gang! I see very little on this subject. Mostly I see action and removal guides for the OTHER side of the engine (the right side) with the starter clutch and oil pump. On the left side where the timing chain resides; WHICH sprocket on the crankshaft is the PROPER one that drives the Timing chain? A poster on another forum had mentioned the INNER one; that is the one closest to the counterweight on the crank. There is no info on this in the online manuals either. Word I get is, one sprocket is for the Timing Chain, and the other is an oil slinger.
Can anyone clear this up? I ask because my engine appears to be having timing issues again.
A sale on ebay shows this. It is new to me as I have not pulled the crank out of a GY6 engine yet.

https://tinyurl.com/y9uuldo4

It appears on my engine that one of these sprockets may be larger than the other. The inside one appears to have "cogged" teeth on it while the outside one has more defined and sharper teeth and looks smaller.

Maybe a better view...http://www.partsforscooters.com/164-111_GY6_Crankshaft
if you are changing that gear you better read up on it or youtube it. I might be a really tight on the crankshaft.

Hi Roscoe, I did not intend on changing the gear. I wished to know WHICH gear on the crank the cam timing chain rides on. I know the camshaft gear and Upper chain guide LINE UP with the outside crankshaft gear on MY engine and have seen plenty of crankshaft views (with no chain on).... But, another enthusiast stated the chain goes on the inside gear, not the outside one. I am fighting a constant miss and backfire with this engine. It has new rings and has about 150psi compression. I think the previous owner may have put new rings in it as well. The cylinder was honed also. I ringed it because it seemed to be pushing a LOT of oil up into the head although oddly, it was not smoking....but now it is.
Thanks for the link.

Are things apart to the point that you can count the sprocket teeth? The sprocket with exactly half of the number found on the cam sprocket, is the one to use....or do they both have the 17 teeth I counted in one of the links above. (Can only see 1 of the 2 sprockets well enough to count)

Hi rks How do you do? Thank you for your reply! No sir, I haven't split the case. I keep thinking the chain is bad. Nobody has been able to affirmatively answer my inquiry except you. Many folks must have seen what gear their chain is on when removing the head or adjusting the valves, doing BBK's etc. The noticeable engine miss has haunted me for quite some time and I thought...AHAAA!...I have the chain on the wrong crank sprocket! But no...just trying to alleviate splitting the case you know? I do know the crank gear with the sharper sprocket-like teeth on it is to the outside of the case behind the oil seal and seems to line up with the camshaft sprocket real well. The gear with the more blunt looking "cogged" teeth is on the inside; closer to the center of the crank.
Your breakdown "free" mileage statistic is amazing! 2011 must have been a good year in Scooter manufacturing land! This Peace scooter is a 2014 with 11K and change on the clock.
One can see in the very good photos of the crankgear sprockets on Ebay, that one of those gears is TALLER than the other. Hard to tell if they have the same amount of teeth, but it looks like they might, and I count 17 as well like you did...so, there must be 34 Teeth on a standard camshaft sprocket.

https://www.ebay.com/itm/A12-Camshaf...1alXGR&vxp=mtr

The above link illustrates the 150cc cam sprocket. Believe you'll find the teeth on it, are like the more pointed ones on the crankshaft sprocket (outer ones).

As far as the missing, backfire, etc....sounds like intermittent electrical problem. Have you looked at the spark plug wire and tightness of the boot. Might even unscrew the boot, snip 1/4" off the wire, and screw the boot back on nice and tight.

It could be something else altogether.....just think I'd check a bunch of other things for misfire/backfire condition, before splitting the case.

Hi rks That was my thought as well, that the crank sprocket would be like the sprocket on the cam; with the more pointed teeth. The miss could be electrical. I am using new CDI, COIL, PLUG. It is somewhat strange because if you keep feathering the throttle on it, eventually it clears up and can run WOT or near WOT with no miss. I have not been able to pinpoint the problem (fuel delivery or electrical) as the engine has been doing this ever since I got it running. It was starting right up but with a noticeable miss at idle and at mid throttle, it would bog (not die), and miss. It did not backfire until I installed a new performance muffler here recently. I have checked the tightness of the coil wire and plug boot. I will unscrew it and check it again however.
Carb is new and clean, stator is new, coil and plug cap are new. Plug is new. Head gasket is new. Cylinder gasket is also new. So, I am currently stumped as to what the CAUSE is...but you may be right about the intermittent electrical problem. ALL THE Ground wires I have found are tight, clean, and secure. Any other ideas??
As far as electrical problems go, there WAS no voltage to the fuel enricher (when running), or the horn. I do not think the enricher is really needed down here, and I have plugged off the enricher port on the carb.

UPDATE Still fighting a miss on the engine. Checking into a valve gap issue as well. Will close up the gaps and keep informed. Any other ideas (besides a badly worn chain) let me know.
Closing up the valve clearances produced no difference. A badly worn timing chain can negatively affect timing. The backfire I am getting could be due to a retarded spark I presume and that is definitely a possibility on this engine.

Just thinking out loud here.....you said, "Carb is new and clean, stator is new, coil and plug cap are new. Plug is new. Head gasket is new. Cylinder gasket is also new".....how about the pickup coil, it's gap, and it's wiring harness....also check the pins in the connecter.

Because you stated the enricher had no juice with engine running, and the ignition, like the enricher, is AC powered... I keep thinking your problem is electrical.

But then again, bogging at higher throttle settings is a classic sign of too much fuel/not enough air. The carb you put on it isn't one of the high performance, 26mm or larger, is it?

Hello again Mr. rks Well sir, not a high performance carb. The pickup module came new with the stator. I air-gapped it at .010". The pins in the connector for it seem fine. It seems to produce a yellow spark, but it IS consistent tested outside the engine. I advanced the timing some yesterday (to where the T on the flywheel lines up even with the crankcase indicator). I had it set a mark or two BEFORE the T (to the left) on the flywheel previously. The intake valve was too tight though and it ran the same. The way the old chain lays on the cam sprocket tells me it may be quite worn. There are gaps and it does NOT completely seat on the sprocket. It has always been that way since I started working on it. I didn't wish to do a complete disassembly. I am considering installing a new chain (which may CURE the problem), as I have tried everything else.
I am NOW getting current to the enricher and I checked it on the scooter running before installing it. I have a new one and an older one. They both work. I also have the horn working now. Whether or not it is sufficiently charging I have yet to check. It was not before and I am on my second Rectifier/Regulator.
Since it was backfiring thru the muffler, I figured the timing must be retarded. The thing is CLOSE to where it needs to be but may never be able to achieve correct timing with a worn chain. The NEW chain tensioner looks like it is extended pretty much ALL the way out too. There is a very pronounced DIP IN the top part of the chain where the tensioner is pushing it down.
Does anyone KNOW on a GY6 150cc engine how much a NEW tensioner would extend with a used (good condition) or even a NEW chain? That would definitely clarify the chain condition. Parts on the chains do wear and they can be become elongated by a substantial amount.

I think I'd be looking for a donor scooter. I wound up with three 150 GY6's and a 50 cc GY6. You might even consider a whole new engine if you intend to do some serious riding. Otherwise you might as well tear this one down and do some careful measuring of parts and put everything back to factory standards. But I'm looking at new GY6's long case advertised for 235.95 with free shipping and no tax.

Hello Roscoe That is definitely sage advice. Do you care to relate the mechanical issues with the scoots you just mentioned? I want it to run properly and probably give it to my Grandson so he will have transpo without costing his folks anything. He seems interested in it, but his mom is having second ideas about him on a 2 wheeler. He isn't going to be a baby forever though!
I have seen that price for a new GY6 150 as well and the 50cc units are NOT that much cheaper.

50 and 150 GY6s won't interchange. Some have put 150s on a 50cc frame but it involves some welding and wiring. One of the 150s I have starts, runs and rides, and the 50cc now 81.3cc also does. So I've got a couple of 150s that I've never messed with. I kind of intended to get one of those engines running and put it on the 50cc but did the big bore kit instead. I like riding the little scooter, it's my favorite. What I found with the older scooter that had set for a long time was they required a lot of attention to get them dependable..... and then you better know how to repair them. For me it's a hobby and something fun to do but for a kid needing basic reliable transportation they would be a challenge.

OK, I had installed a new timing chain. Now the new tensioner extends very little and tightens it up; whereas on the old chain and new tensioner it was fully extended. What a difference! Tensioner and chain seem to be working correctly. However; I am still seemingly fighting timing isssues. Advancing it did NOT seem to cure the backfiring and engine miss. It starts right up though so I presume it is close or? I guess I will try DIFFERENT timing positions till maybe I hit upon the correct setup.

Scooter Update: To answer rks's earlier inquiry; after some research... yes I installed a 26mm carb on it and am using the stock airbox. I also installed a cheap high performance muffler on it, because the stock one had fallen apart. I am using a standard NGK spark plug, not the Iridium model. Engine running, but still missing. Plug inspection not showing black like when I first started repairs, shows common brown, but getting backfiring and hesitant throttle. The auto enricher is connected and now working as well. Any ideas?