Pondering engine TIMING?????
 

OK I've been running this way for about 4 months now. It always starts like a fine tuned race car first click every time. POWER.......... well as far as I can tell is not lacking....I'm running a slight bit rich...mechanically everything is how it should be ...,BUT......

Timing mark is aligned, but cam is way out. piston is top dead center verified with head off and (the straw method) Exhast and intakes are at specs ,,,, plus or minus a thousand for the high compression head and all....

My main question is should I leave all alone and where is is , or set cam to proper position....I including pictures....

So it starts great, runs great, and has good power, and you want to mess with it? lol

On a serious note, are you checking the cam timing on the proper stroke?

lid
 

yes i am sure its proper. the main reason i ask or bring it up, is because i started to get a valve tap only at low acceleration, the tap goes away once it reaches about 2100 rpm...it reminds me of an old v8 fuel knock . lol...ohh is there a cam chain check?

that cam timing looks way off but, ur saying its running well then I don't know what to say.

yes it runs great minus the valve chatter at low rpm under load.... well what about timming chain are there any specs you know about....

I think if it's off you need to fix it.

did u change the chain?

No I never changed it. Just wondering about the valve chatter at low rpm under load...something is wearing if I'm getting a valve chatter....

is chain tensioner maxed out and any looseness to the chain?

If it's only making noise under load it sounds like detonation. [pinging]

A loose cam chain will usually make noise at a certain rpm or on deceleration. Usually caused by a bad cam chain tensioner.

I'll check tensioner after work today...to me it sounds mostly like a detonation tap...i have a slight rotational play in can ir moves I would have to guess a 16th inch (without measuring it). What cause the detonation ping....

A picture can at times be deceiving. Your marks on the cam look to be way off but the angle at which the picture was taken can add deception. I have run into this many times when installing a cam to where it will be off one way so I will try to move the cam in line but it will be off the opposite way by the same amount. In these cases the cam cannot be centered so you end up a half tooth advanced or a half tooth retarded. In this case of only a half tooth off you will want to err to the advanced side. The reason for this is simple, since these engines are masses produced many times tdc is close and not exact. The only way to find true tdc is with a degree wheel and piston stop. I will say 80% of these engines are 1/2-1 degrees off true tdc from the factory. Being off 1/2 tooth as described earlier is no big deal. What concerns me is as you described sounds like a ping which is left alone will eventually burn valves and melt the piston. If you would like you can give me a call 662-301-1563 and we can try to figure this out.

I'll give you a shout tomm around 5pm...ok I checked tensioner and it is still good...before I call you im going to pull valve train and inspect...but I went through my build notes and found out I did move advance timing to compensate for the large flat stainless valve and titanium springs, also have forged high compression piston..with out advancing the timing i would burn up starter clutches...with timing in proper position it would always starting like you had a slightly dead battery. So I do believe timing is good, and the tap under load only during acceleration... Still has me stumped. Its like if you in a vehicle and in second gear and going to slow when you hit gas and you hear the valves chiming....

mike is that a stock camshaft ?

Have you tried running hi octane fuel and see if that quiets the chatter?

Jman, I am running a A-9 cam...I want to get a12 soon to see the difference.

Xlint, I have not tried high-test yet. I will give it a try this weekend, waiting on new belt...

High compression with low octane makes detonation more likely.

Well Ill try 93 octane...still waiting on belt....

im pretty sure you have the camshaft in backwards meaning 180 degrees out, when I put the A style camshafts in I put them in with the 2 holes lining up with the top of the head and the label of whatever a9,a10,a11,a12 facing upward not hidden in the head.

Yes I know what your saying about the number and the A-9 is on top and two little holes parallel with the head...i just took pic of how many teeth I was off
..but its not off, well maybe a little. Talked with Tom last night and we figured we will wait until I run high test and double check if I'm running to rich...Belt will hopefully be in today so If it comes in today ill run it up....

Problem found
 

OK found problem! https://youtu.be/hugzPHazALY

Sounds like the chain is off the crank sprocket and on the oil slinger.

Yeah maybe but what's weird is if I spin it toward it will rotate fine.
So if its off will it do that even run...but either way I believe I have to spilt case
Thanks tom

like tom said I bet the chain is on the wrong sprocket inside the case.

Well I pull it apart and take a look.thanks all and maybe ill get to do a ride or bash one of the days...

No need to split case. You will just need to remove the head and MAYBE the cylinder, (can't remember) and use a long screwdriver or stick to put the chain back on the sprocket.

Pay close attention to the chain guide (broke tabs/"ears") and chain tensioner. (make sure it isn't maxed out trying to tighten the chain) If anything looks funky, replace them.

How did this thing run at all? lol

Ur guess is good as mine I can go to garage right now and it will fire right up...you can even check with timing light spot on...but she you put load on it that's when it would act weird...just shear luck I caught it...

Weird!

The sprocket and oil sling are right next to each other. The slinger looks just like the sprocket with as many teeth. The difference is the slinger teeth are blunt to where the chain will fit and even turn cam until a load is placed upon it. Now it is also possible you have a split sprocket to where it is now totally slipping but from the sound of your video it appears to sound just like the chain slipping on the slinger. Anyway you will need to pull the head and cylinder and using a small bright light, look into the case and inspect.

Ok all. Before I Break engine down I figured ill inspect...ok I used my optic snake cam and the chain is on..and i do believe that the chain is just way to loose...i see chain tensioner pushing down micarta guide and still looking at it you can see top part of chain hanging as you spin it... It stays loose the hole time...if anyone has a pic of the lower gear that could help...thanks all

The timing chains come in different sizes (number of links)

Did you or anyone else replace the chain when maybe doing an engine upgrade?

When I went with my stroker (2.2mm) crank, the chain was too tight. So I needed a longer chain because of the taller cylinder. I then had a chain that was too loose and gave me a similar problem.

I never replaced chain...it was stock from original. But who knows what was done before me lol. All I know its been running great for about a year and then one day when i was out in the mud for an hour or so I start to get the valve chatter...or detonation/ pre-ignition what ever and now its all gone down hill lol...i should of left it alone untill it blew up lol
..so my plan is to remove ok chain and put new chain in. I'm going to do a redneck way of changing the chain I'm not splitting case yet. If it solves the problem then ill split case and go through rebuild...

The chain might just be worn out. Whenever I do a build I always replace the chain.

Right, chain may have stretched.

Does the chain tensioner work properly by chance?

Yes I do believe it is stretched...and i am pretty sure the tensioner is good plus I have a spare one....you can see tensioner pushing and holding the guide down...

Is it maxxed out? (tensioner) Or does it have more room to go?

go back to simple analysis ... if your rotate the flywheel backwards and cam gear isn't moving at all like in your video, its got a sprocket issue. Shouldn't be any way the chain has as much stretch in it to take up the amount you turned the flywheel. whether the drive sprocket is split or worn in one direction on the inside bore, mostly stripped of teeth, or the timing gear is slipping on the cam (dk if that's possibly) there's something wrong at that level. Not saying the chain isn't stretched as well, but that's a lot of rotation!

Somethng is wrong with this picture. Thete is no way you are going to rotate that crank shaft as we saw in the vid with the chain slipping, and hen right after be able to fire that baby up. If you were able to (which I would not attempt by the way) you needed to have played the powerball. I am curious as to the final outcome on this so I am subscribing!

Lmao today I'm not working, played hookie, so I will turn flywheel in video backward untill all lines back up and fire it up run it and show you and then shut it down and rotate backwards untill it slips....i just decided to build the other engine though,but in doing so is going to require me to look into the motor that is currently on my buggy. Either way we will figure it out...

Yes if you get it lined up...I meant if you rotated it, let it slip, and didn't line it back up.

Does the motor have a lot of time on it?

The other thing I am wondering is when you put the tensioner back on, did you reset the tension? I could see failing to do so causing excessive pressure on the chain and that causing excessive wear on the chain forcing it to stretch. My experience is that the chains holds up rather well.

Timing
 

Ohh I would never start if tming is out!!! AnfLways reset tensioner. And shoot that motor could have a million miles on it ...I know it has a lot of me beating the crap out of it.I'm uploading video now.

Did you try rotating the engine the other direction? I noticed when checking the valves on my grandsons mini 110cc atv that the cam only rotated in one direction. Believe it was counter clockwise. If I turned it the other direction, the valves wouldn't go up and down at all. When I looked closer at the flywheel I noticed it had an arrow pointing counter clockwise.

I should say the cam only turned when I rotated the motor counter clockwise. If I turned it the other direction, the cam didn't move....exactly like in your video.

Taloth. I never seen or heard of that..that would be like it siting on a one way bearing but it still would screw timing all up..it a fixed sprocket on crank and a semi fixed gear on top...only if as others have said that the sprocket be broke can it happen or chain being over over over over stretched.but I guess anything is possible..

Well when I disassemble the engine and start rebuild..ill will take pics and all and post it...does anyone know the exact amount a stock gy6 timing chain should be...
I might even turn my blue buggy into a 4wd hammerhead..picked up older king quad...so there is alot of planning I need to do but working 6 days a week 10-12 hours a day I just dont have enough freaking time...

Camshaft is connected to the crank via the timing chain. The flywheel is connected to the crank via woodruf key. So turning flywheel in either direction will turn the crank thus turn the camshaft.

Chain results
 

OK pulled Chan and found that the chain is just wore out and is binding on links, which is causing the sprocket to jump off or skip on lower sprocket.

I'm going to go and button it back up and see how she runs...

OK took it for a short run its back to normal minus I don't like the cam I'm using...gonna go back to a-9...

What cam did you use?

The A9 is a more top end cam. Most guys seem to like the lower range cams on these buggies.

I'm running an A12 now with good results. Although, I do want to try the A11 again as I liked it in my other engine combination too.

Umm dont know what actual cam it is.. It came out of howit motor...i know the lobes are shorter by 10 or 15 thousand, I think. I'll measure today when i swap back out...and with this cam in I can not even get close to redline. I run about 100 yards and rpm and speed still climbing slowly...

glad to hear you got it back up and running. I have used both the a-11 camshaft and the a-12 camshaft and have been pleased with both. I might try a a-9 in the future just to see the differences but have to finish the other mods first.