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Post by wilyhammers on Jul 5, 2018 17:42:43 GMT -5
So as you might see in my other post I successfully installed a 47mm big bore kit on my TaoTao ATM50 139QMB scooter, working perfectly except for a throttle issue at start.
I had ordered a new camshaft and it came and I decided to install it in my working scooter (WHHYY)
I forgot to put a screwdriver to lock the flywheel at TDC, so there was a lot of drift.
After realizing this, I don't know how much drift so I just put the flywheel at TDC and set the new camshaft in the right position with the small holes at the sides and the big hole directly up.
Unfortunately after putting it back together, the start sounded like it had no compression. I thought about it for a sec and opened it back up, realizing it has TWO TDCs, on different strokes. So I figured I had gotten the wrong one, so I reset it for the other TDC. I don't know how to tell which is the right TDC.
Back together, it's still got no compression. It's hot AF so I think it'll be a few days before I can get back to it.
Any guesses if I ruined my piston or any guesses on what I've done wrong? I'm kicking myself for getting it running fast and hard then screwing it up with an unnecessary camshaft 'upgrade'
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Post by scooterted on Jul 5, 2018 18:37:52 GMT -5
Either TDC will work.
Did you reset your valve lash?
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Post by acvw74 on Jul 5, 2018 18:45:26 GMT -5
Why do we do these things when it is HOT as HELL in the garage?
Question...Were the valve clearances good after installing the new cam?
If all else fails...put the old cam back in and see if it goes back to "normal"
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Post by wilyhammers on Jul 7, 2018 17:12:07 GMT -5
I'm actually working on the sidewalk - I decided against dragging it up 3 flights of stairs to my AC'd condo. So I took the head off, verified TDC at the head itself, double checked everything, readjusted the camshaft offset, checked the valve clearances, and nothing. I'm not sure it's a compression problem - there is definitely some compression. The starting just sounds weird to me. I can't place it, it sounds like something is missing. Can anyone tell what sounds wrong here? photos.app.goo.gl/BaHbuZD3HJAXnbDD9 |
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Post by scooterted on Jul 7, 2018 17:22:26 GMT -5
Def sounds weird. Just for fun did you try the stock cam?
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PirateLabs
Scoot Enthusiast
Posts: 296
Location: Bowling Green, KY
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Post by PirateLabs on Jul 7, 2018 18:28:36 GMT -5
I'm actually working on the sidewalk - I decided against dragging it up 3 flights of stairs to my AC'd condo. So I took the head off, verified TDC at the head itself, double checked everything, readjusted the camshaft offset, checked the valve clearances, and nothing. I'm not sure it's a compression problem - there is definitely some compression. The starting just sounds weird to me. I can't place it, it sounds like something is missing. Can anyone tell what sounds wrong here? photos.app.goo.gl/BaHbuZD3HJAXnbDD9You said: "There is definitely some compression". What does that mean? 80 psi is "some compression". 100 psi is too but, an engine like this will not even start if not quite a bit higher than that so, it is important to know just how much. It does not sound like it is turning freely like 0 compression, I agree with that...but...I think you need to check it to get a figure that might help your diagnosis. Or, as has been suggested here above, install the old cam and if it still runs great like before...this will tell you something. If not, then there is another issue. I don't mean to sound obvious but when trouble shooting...you have to proceed in some sort of logical manner or you do not learn much. It ran on the old cam, does not run on the new one. To eliminate the new cam you need to swap it back to the old one. I think you have checked a lot of other things it could have been if installed incorrectly so...go back to basics. I am trying to be helpful but, if it were me, I would not want to hear that I had to swap cams yet again. Maybe someone else will have something better...this is all I have. Good luck, Bill |
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Post by humanshield on Jul 7, 2018 21:42:42 GMT -5
I had ordered a new camshaft and it came and I decided to install it in my working scooter (WHHYY) You need give people ALL the information so they can help you.
What cam? Stock? A9?
How much compression? Like PL said above, it matters. HF has a cheap compression tool that works.
A cam could lower your compression. Maybe you bought or received the wrong cam. Try to give more specifics when asking for technical help.
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Post by GrumpyUnk on Jul 8, 2018 11:32:38 GMT -5
If the valves were damaged(bent) due to contact with the piston, you would have little compression if any.
You may be one of the 'lucky' people who have their T mark at the wrong spot. I know not which/when those products are, but verifying ACTUAL physical TDC of the piston when at the mark would be a good first step.
If you remove the cylinder head again, do check that the mark is properly made on the flywheel.
All that aside, if you take it apart, set the old and new cams side-by-side. Adjust the sprockets so they are parallel in their position. Inspect the position of the cam lobes to be sure they are similar. They should BOTH be pointing in the same direction when the sprockets are aligned. One cam should likely have 'fatter' cam lobes that will start to open and close the valves a bit earlier and later due to shape. BUT, they should both be peaked at about the same spot.
Replacing the old cam and checking it for compression would be a good check on the quality/usefulness of the 'new' performance cam. Could be defective out of the box.
tom
Added: TDC is TDC is TDC. The cam determines actual function, compression or exhaust when the piston is at TDC. I think the cam sprocket can be installed 'upside down', with the single hole at the crankcase end with no effect as it WILL be there at the next TDC, either exhausting or compressing...
tom
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Post by wilyhammers on Jul 9, 2018 11:29:50 GMT -5
If the valves were damaged(bent) due to contact with the piston, you would have little compression if any. You may be one of the 'lucky' people who have their T mark at the wrong spot. I know not which/when those products are, but verifying ACTUAL physical TDC of the piston when at the mark would be a good first step. If you remove the cylinder head again, do check that the mark is properly made on the flywheel. All that aside, if you take it apart, set the old and new cams side-by-side. Adjust the sprockets so they are parallel in their position. Inspect the position of the cam lobes to be sure they are similar. They should BOTH be pointing in the same direction when the sprockets are aligned. One cam should likely have 'fatter' cam lobes that will start to open and close the valves a bit earlier and later due to shape. BUT, they should both be peaked at about the same spot. Replacing the old cam and checking it for compression would be a good check on the quality/usefulness of the 'new' performance cam. Could be defective out of the box. tom Added: TDC is TDC is TDC. The cam determines actual function, compression or exhaust when the piston is at TDC. I think the cam sprocket can be installed 'upside down', with the single hole at the crankcase end with no effect as it WILL be there at the next TDC, either exhausting or compressing... tom I've got a compression tester on the way to give a final answer on that one. I should have included more information this: I went from the stock camshaft to an A9 camshaft. When taking apart the engine again, I did verify that the TDC marking did line up with true piston TDC. I didn't see any visible damage to anything. I compared the profiles of the original and A9 camshaft. They were pretty damn close, I think the closing side of the lobe apex looked a teeny bit steeper but it was hard to tell. I put the A9 back in there because it looked so identical to the original, and I was checking for damage and for true TDC, and thinking I may have been one tooth off on my camshaft chain. However I did find that the turnover noise sounds exactly the same when put back together. The plan is to go check for spark today, check compression tomorrow, and go from there. Sounds like putting the original camshaft in again would be the next step. |
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Post by acvw74 on Jul 9, 2018 13:45:19 GMT -5
If you pull the head off...Hold the head in your hand and pour some carb cleaner (or oil) in the combustion chamber and see if it holds the liquid...just to make sure you haven't burned a valve.
I noticed you didn't have the cooling tins on the engine...was that just for diagnosis? If you ran it that way very long, you might be loosing compression past the rings.
Keep the data coming...there is an answer to this problem.
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Post by GrumpyUnk on Jul 10, 2018 11:02:22 GMT -5
If the shrouds were left off.... curtains for the piston rings, and possibly the piston and cylinder. The rings will start to get too hot, have more friction, and finally get stuck to the lands. I have one that was run that way... for a while ... until the lands broke, and the cylinder wall got scored... and the compression ratio approached 1. It would not start, and measuring compression was a problem as it did not read on a new gauge. Old gauge read below 50psi. You need the shrouds. Anyone telling you different knows nothing of manufacturing economics. Every penny, or even half-penny spent in product is scrutinized. If a washer is not needed, absolutely, there will be no washer, no part number, no stock shelf space used, no re-order, no person checking or program doing same, and the money spent for those things, and the washer in question, would stay in the makers pocket. Profit. Shrouds retail for ~$20 a set if you are a searcher. That's a LOT of pennies, even at the factory price of $2 per set.(made up, but I bet not more)
tom
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Post by wilyhammers on Jul 11, 2018 10:19:01 GMT -5
Updates and answers:
I did a spark test, looks good.
I definitely have not been running the engine without the shrouds - they are off since I am constantly taking the engine apart.
I pulled the head again, put some oil in there and it kept it fine. However, with the orientation of the engine it's only trying to go through the bottom. I replaced the original camshaft, adjusted valves again, still the same problems.
The compression tester is here but not the right adapters. I should get those tomorrow so I can see where the compression is. Still nothing looks wrong visually and I can't detect any compression leaks. I'm a bit perplexed.
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Post by diynuke on Jul 11, 2018 12:51:10 GMT -5
I'm actually working on the sidewalk - I decided against dragging it up 3 flights of stairs to my AC'd condo. So I took the head off, verified TDC at the head itself, double checked everything, readjusted the camshaft offset, checked the valve clearances, and nothing. I'm not sure it's a compression problem - there is definitely some compression. The starting just sounds weird to me. I can't place it, it sounds like something is missing. Can anyone tell what sounds wrong here? photos.app.goo.gl/BaHbuZD3HJAXnbDD9That sounds like no compression at all.. And it kind of sounds like the piston rings are all stuck xD |
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Post by acvw74 on Jul 11, 2018 21:12:12 GMT -5
Tonight was the first time I was able to hear the your video - It truly sounds like zero compression.
A crude compression check...put your finger over the sparkplug hole and turn the engine over by hand.
IF there isn't any compression...start working your way down:
Pull the valve cover off and turn the engine over several times...make sure the valves are cycling.
If the valves are cycling...you are going to have to pull the head off...to check the valves put the head in your hand with the combustion side up and pour some oil in see if it leaks our (don't forget to put the plug back in)
Is the head gasket in good condition?
Check the cylinder - quick check on the ring by putting a little oil in the cylinder and see if it holds.
Good luck!
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Post by wilyhammers on Jul 12, 2018 16:39:53 GMT -5
Absolutely zero compression. I will pull the head off and take a look at everything tomorrow on a workbench.
I was trying to think how my initial actions could have resulted in this. It seems clear to me now that it's likely got bent valves due to my camshaft being synced wrong. I think I'll be ordering a new head
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