Valve adjustment on 49cc 139QMB

[scootnewb]

Ok, i think I know the reason. Now I got to wrench on it.

Ok, this is how the cam was at TDC BDC before I rebuilt the top end.



Now this is how it is.

Here is the flywheel with the T mark lined up with the pointer on engine case.



This is how the cam sits with the flywheel in that postition.







It looks like one link off.

So gotta make sure to get that correct before installing the BBK and mark the chain and flywheel with a marker.

[scootnewb]

Ok. I have a plan.


I know these posts are needy as f$%k but I don't want to damage it (anymore than I already may have). 

0. Remove spark plug
1. Rotate the flywheel until the ‘T’ mark is lined up with the indicator on the engine case

2. Remove valve cover.
3. Mark this chain link

4. Loosen the 2 bolts on the chain tensioner
5. Remove the 4 bolts that hold the head on.
6. Remove chain
7. Rotate the cam a little bit counter clockwise
8. Line up the large hole in the cam with marked chain link
9. Put it back together
10.Adjust valve clearance
11. Put back valve cover

Then test it out before I attempt the bbk install.




Does that sound right?

[greginisn]

Don't be afraid of seeming needy. If you don't know something there is usually at least someone that can provide a good & useful answer.

I had intended to post a reply earlier but messed up and my reply ended up in that giant bit bucket at the end of the internet somewhere.  Forget the actual numbers get yourself a wallboard screw with a square drive head that head will fit your valve adjusters. Snug up the adjustment screw very lightly then back it out either 1/4 turn or 1/3 turn. what ever works for you. It may click a bit but that won't hurt anything. I'm using the back off 1/3 turn setting but your scooter's needs might be different.

Anyway good luck with your valve setting and what a great find you made discovering the cam had been chained up a tooth or so off.  


Greg

Re that screw: it's the one that uses the #2 square drive bit. Common as dirt.

[scootnewb]

Apr 26, 2018 22:05:42 GMT -5 greginisn said:

Don't be afraid of seeming needy. If you don't know something there is usually at least someone that can provide a good & useful answer.

I had intended to post a reply earlier but messed up and my reply ended up in that giant bit bucket at the end of the internet somewhere.  Forget the actual numbers get yourself a wallboard screw with a square drive head that head will fit your valve adjusters. Snug up the adjustment screw very lightly then back it out either 1/4 turn or 1/3 turn. what ever works for you. It may click a bit but that won't hurt anything. I'm using the back off 1/3 turn setting but your scooter's needs might be different.

Anyway good luck with your valve setting and what a great find you made discovering the cam had been chained up a tooth or so off.  


Greg

Re that screw: it's the one that uses the #2 square drive bit. Common as dirt.

Thanks.

I will try that. I have one of those special valve tools with the square bit. If the valves aren't damaged from the cam / timing fiasco I have a hunch the standard clearance will be fine. I'm thinking I mistook the piston hitting the valves, (from the wonky cam / timing chain setting), as valve clatter.

The good news is I have another head with pre-installed valves I can slap on.

Do you know if the cam being off by one tooth could've caused any serious damage? 

[greginisn]

I'll go out on the limb here and say No, you probably haven't messed anything up. The reason being is the valves have been have been closed or nearly closed for quite some time while the piston is rising, relatively speaking, so the piston should not have made any contact with the valves. 

But this is assuming that you were only off by a gear tooth or so. A gross installation error in the valve timing could cause some serious damage tho.  Also with gross error the engine wouldn't start.



Good luck with this. 


Greg 

[scootnewb]

Yes! This is great news. 

I wonder though, is there something that keeps the chain on the correct teeth on the other end? i mean I'm pretty sure I kept some tension on the chain while rebuilding the top end as I thought to myself, "What if it falls off the teeth inside the case?"

I am pulling an all nighter. It's supposed to rain tomorrow afternoon so I plan on starting this as soon as the sun comes up. 

[GrumpyUnk]

Unless the marks are incorrect on the flywheel(some have been reported, I know nothing more than that), that seems correct to me.
When you re-assembled, you did retract the chain tension gizmo before inserting it with the spring? The ones I've seen have a 'latch' that holds the tensioner roller and shaft back until it is inserted into the bore, then the spring, then the hollowed bolt. If you remove the cam/rocker cover, can you rotate the camshaft back and forth at all? If you can, then there's slack in the chain.
Just listened, and that seems to me to be valve lash clatter or tapping. I think I would remove the cover, rotate to TDC, walk the crankshaft around 720 degrees, slowly, watching the cam and followers.
You should be able to discern the four strokes by watching intake open & close, compression, (TDC), firing, exhaust valve open and close, intake valve open, intake, and back to the bottom to start the compression stroke.
As you 'walk' through the four strokes of the piston, valve movement and cam rotation, you should be able to put your hands on the rocker arms/followers, and check for 'tappy' clearance. If there's more clearance than specifiec at ANY position, then something is wrong with the setup, or the technique. Maximum clearance should be taken with the follower on the base of the cam lobe, whic is totally visible if you look.
If you have noise, you have clearance, unless the sprocket is loose on the cam or ???
tom

[GrumpyUnk]

You can be off more than one tooth and will likely avoid valve-piston interference. If you had the two connect, you would know it as you'd lose compression real quickly.
I would remove the tensioner when trying to re-time the cam. The chain rides on a sprocket on the crankshaft at the other end. The ratio of the sprockets is 2:1. Two turns of the crankshaft will cause one turn of the camshaft. The individual links are not special in any way. The only time links are 'special' is when the cam does not have keyways for timing, and you have to space the cam based on counting links. Paint marks on the links helps. The one I am slightly familiar with is the DOHC Duratec 3.0 or the other similar Ford products.
I would do the inspection/observance of valve operation I noted just previously, and try slipping the feeler gauge at 1/4 or 1/8 turn intervals. Use a size gauge LARGER than what you set them at, and you should find the place in rotation where they have more clearance. I have one PDF that indicates the cam sprocket should be 90 degrees CW from what is shown above(big hole top/two holes parallel). I discounted it, but maybe should not have. Dunno for sure. Do the check, and you should find somewhere that has clattery clearance. Adjust as desired. I think .002" and .003" are good... but you choose your own numbers as there are a lot of differing opinions/specifications that different manufacturers suggest/specify. I just don't know. Don't want clatter(will cause follower wear) and don't want too tight(will cause burned valve damage). Just give it up, you can't win... (laugh)
tom

[scootnewb]

I removed the chain tensioner, marked the right link and lined up the cam at the crack of dawn.

It is definitely 2:1 and now the large hole at the top of the cam is correct when the flywheel is aligned with the 'T'



But then this ... 49ccscoot.proboards.com/thread/21261/guys-got-cam-chain-misaligned

[diynuke]

Apr 26, 2018 16:24:20 GMT -5 diynuke said:

Apr 26, 2018 13:48:19 GMT -5 scootnewb said:

Well, I've tried them all and I am still getting clatter. I guess I might be doing something wrong but it seems pretty straight forward. Set to TDC, use feeler gauge before and after tightening the nut. Make sure there is a little drag but not real resistance.

I've gone from 005 004 003 002 0015.

I still get this.



But I think I got that idle problem sorted fam. XD

I also popped on the Uniflow so I will need to change the  jets but I don't even want to start on that until I can solve this ticking problem. 

I am kind of frustrated because i don't really know what I am doing and I think perhaps the piston is making contact with the valves. 

Watch out that you don't tilt the feeller gauge.   and it almost kind of sounds like there is play in the bearings of the cam.
mine also has some valve noise so i will try a tighter gap.   now i have 0.10mm in   0.15mm out
however no more wear on anything after 19.000km (always have been that gap)

Okay I've gone to a tighter gap and it rattle's allot less while still having the same compression (145psi)
exhaust a smidge tighter than before (because of the heat i don't want it to be too tight and risk burning a valve/having bad compression Which will result in terrible hot starting) and the inlet allot tighter so that i could barely feel it moving

[diynuke]

By the way the most annoying thing of removing the head is the camshaft so if that it already out/loose why not take a peak under the head?
you can hand tighten the head bolts but torque wrench is preferred ;D and well you can easyly see if there is damage. however i don't think that's the problem.

But for a last resort looking will never hurt.

[scootnewb]

Thanks.

I plan on removing the head tomorrow if the weather is good. I watched another video of a tao tao which had a similar noise. It turned out to be a broken valve spring so I have some new valves and springs coming Tues. In the comments section of that video, someone said the hose from the valve cover to the PAIR system came off and caused a similar noise. When I redid the top end I removed the PAIR system but I didn't use a block off plate. Instead I left the hose connected to the valve cover, cut it real short and put a bolt in the end with some clamps around it. Hopefully it is just that. I will try making a proper block off plate. I also have a new head from a bad BBK I can put on to test too. Ultimately I wanted to use the stock head as I hear that is better for compression and this weekend I plan on installing a good BBK. Fingers crossed

[scootnewb]

Apr 26, 2018 16:24:20 GMT -5 diynuke said:

Watch out that you don't tilt the feeller gauge.   and it almost kind of sounds like there is play in the bearings of the cam.
mine also has some valve noise so i will try a tighter gap.   now i have 0.10mm in   0.15mm out
however no more wear on anything after 19.000km (always have been that gap)

I must have missed your first reply. I was frantically posting and looking for answers.

Hopefully it's not play in the crank bearing. I was pretty good about the feeler gauge but I'll double check the clearance and make sure I'm not tilting it. Before I redid the top-end it didn't sound like that. I figure if the piston was hitting the valves because the cam was one tooth off then it shouldn't be hitting after correcting the cam and the noise should be gone.  It looks like there'll be some sun in the AM tomorrow so I'll remove the head and look for signs of contact. If it's all good, I'll put on a different head that doesn't have a pathway for the pairing system and see what happens. 

[scootnewb]

Apr 27, 2018 10:41:44 GMT -5 GrumpyUnk said:

Unless the marks are incorrect on the flywheel(some have been reported, I know nothing more than that), that seems correct to me.
When you re-assembled, you did retract the chain tension gizmo before inserting it with the spring? The ones I've seen have a 'latch' that holds the tensioner roller and shaft back until it is inserted into the bore, then the spring, then the hollowed bolt. If you remove the cam/rocker cover, can you rotate the camshaft back and forth at all? If you can, then there's slack in the chain.
Just listened, and that seems to me to be valve lash clatter or tapping. I think I would remove the cover, rotate to TDC, walk the crankshaft around 720 degrees, slowly, watching the cam and followers.
You should be able to discern the four strokes by watching intake open & close, compression, (TDC), firing, exhaust valve open and close, intake valve open, intake, and back to the bottom to start the compression stroke.
As you 'walk' through the four strokes of the piston, valve movement and cam rotation, you should be able to put your hands on the rocker arms/followers, and check for 'tappy' clearance. If there's more clearance than specifiec at ANY position, then something is wrong with the setup, or the technique. Maximum clearance should be taken with the follower on the base of the cam lobe, whic is totally visible if you look.
If you have noise, you have clearance, unless the sprocket is loose on the cam or
tom

Thanks for all your detailed posts. I missed a few posts while I was frantic .. running in and out, googling, posting.. etc etc

I did retract the tensioner before inserting it.

"You should be able to discern the four strokes by watching intake open & close, compression"

I am set to head out there in an hour or so and I'll definitely check this out.

"You can be off more than one tooth and will likely avoid valve-piston interference. If you had the two connect, you would know it as you'd lose compression real quickly."

Good, that was worrying me.

I am going to put on a new head today (hopefully) and will be able to check the piston head for signs of contact.

I'll be sure to post updates.

[scootnewb]

Well the good news is the piston had no signs of damage or anything indicating it was making contact with the valves.





But not sure if that is right all oily like that.

Anyway, checked the spacers, put on the gasket




Got the head on




Then...I crushed the rocker arm assembly. The new torque wrench did not work properly. It is set to 14 foot pounds. I have since tried it on other bolts and lug nuts on my car and it doesn't fucking release. I can't believe it.




New rockers coming tomorrow. Well this is a learning experience. I should always test my torque wrench. But I should have known I was going way beyond the 14 foot pounds just by the feel.