Setting Up A Degree Wheel And Finding True Top Dead Center (TDC)
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- čas přidán 8. 07. 2024
- Information about degree wheels. What their purpose is, choosing a degree wheel, and how to setup a degree wheel on true top dead center (TDC) using a piston stop.
This video should be useful for most single cylinder engines. Even on a multi-cylinder engine, the technique is the same, but you would generally be setting up the degree wheel using the #1 cylinder.
Printable Degree Wheel
49ccscoot.proboards.com/thread...
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#DegreeWheel #EngineBuilding #Blueprinting - Auta a dopravní prostředky
Wow this was the simplest video of how to find the true dead center an engine. So easy for anyone to master this explanation.
Nice demonstration of TDC. A very critical point, especially for larger engines, is to ensure that the piston is very snug up against the piston stop. This removes any tolerance (space) in the piston pin & connecting rod that will alter your readings. I speak from experience here. It’s tempting to just “kiss” the piston stop to avoid leaving a mark in the piston. If you do this, like I did, your TDC reading will not be accurate by 1-2°. If you are concerned about putting a mark in the top of the piston, tape a flat piece of metal on top of the piston where the stop makes contact. Do not use something soft like a vacuum cap on the piston stop. Anything soft will compress and screw up your readings. Don’t slam the piston into the stop, of course, but when you make initial contact with the stop, place a little pressure on the breaker bar to ensure the piston is tight up against the stop. Do this clock and counter clockwise and you will get accurate readings like Brent did.
That CD idea is genius!
Excellent Video Sir, I will be using this procedure to reassure my 4 stroke 912 rotax non certified ultralight aircraft engine did not knock itself out of "Sync" by a propeller strike, as it has a press on crank journals. ty so much!! 100-100 perfect explanation,and detail. best video on Utube!!
Easiest and best explained method I've seen yet
best explaination ive seen, thank you
very helpful, thank you!
Thank you for making this video!
Of all the videos about tdc this one is the best explained with a piston stop good job
Thank you!
My new favourite channel. The description is truely a tour de force.
Thanks for sharing pal
Tom
Sydney Australia.
Great explanation, thank you
Excellent demonstration/instruction
Well explained!
Excellent job of explaining.
Thank you.
Well presented.
Great video, easy to follow. Thanks for sharing.
Well explained and demonstrated. Very useful thanks
very well done
Hi Brent. Another great and informative video... I also just watched your video on calculating compression ratios... A lot of that info was above my pay grade and I will probably never do those calculations but I feel like it was good for me to know what is involved... Where did you learn so much about engines??? You are the smartest guy that I have found on CZcams.I learn something new every time I watch one of your Videos... Thanks for sharing your knowledge...
If I'm the smartest guy you've found on CZcams, we've got a problem. lol There are some really intelligent and talented people here. I've learned by doing and by reading mostly, with some guidance from friends on the forum when needed.
great explaination. Thanks helpfull
Amazing video.. so very well explained.. bravo mate.. thank you very very much for this.👌👌👌👌
Great teaching. 👍🏾
Very neat...thank you.
Many thank's
Excellent explanation brother
Thank u, excellent video
this is so much helpfull thanks
Correct, i like it
Great video
excellent
brilliant videos dude! thanks heaps :-D
Thanks. Glad if they help!
Brilliant movie, at last I understand.
My friend asked me what is 15 ° I do not understand I'm Vietnamese but you answered my questions thanks
Excellent video sir, fans from ph
Love it, when you said "Stick that on CD"
Why? Because CDs used to exist? lol Good luck sticking it onto a Spotify.
@@49ccscoot I love how you used commonly available material like CD to make a background instead some premium metal disc.
@@49ccscoot I am sorry , My whole point was to appreciate your work. :)
@@Sam-to1zg No worries. I didn't even think they were easy to get today, but I see them for $15 for 100. That's a lot of degree wheels. Still, they aren't lying around everyone's home like they were 10 years ago.
If you could drill it right in the center, you could probably get creative and use thick plastic plates that are $1-2 each and just upscale when printing to have a super cheap wheel.
Great video. Finally helped me understand.
👍👍👍👍
This is a timely video for me. We have two 139QMB scooters. One was always a bit slower than the other. While installing a big bore kit on the slow one, I realized that the cam gear holes did not line up parallel with the cylinder head when the flywheel indicated TDC. I took the head off to verify that the flywheel was made properly and it did seem to accurately point to TDC. So I'm assuming the cam was installed one tooth off from the factory.
1) Could being one tooth off account for the scooter's lethargy?
2) Have you ever heard of them coming screwed up from the factory like that?
Simultaneously fixing the timing and jumping up to 81.3cc should provide nearly limitless fun! Just waiting on jets in the mail.
Thank you very, very much for your channel and all of its content. My GY6 experience would have been greatly diminished had this content not been here.
+smith jones My first Chinese 4T had a flywheel 21 degrees off of TDC. It messes up how you set the cam timing and the ignition timing. It was a total dog before I found that out and changed it. It can also put you at risk of piston and valve contact and subsequent damage.
In the late 90s I had a Dodge Stratus that came from factory with the with the cam timing two teeth off it never had any real power until about 4 years later it blew a head gasket when I rolled the engine to top dead center before pulling in the head I went to Mark everything or at least confirm that the marks were there and found one cam was two teeth off. When I put it back together I lined it up with the factory marks and that car engine came to lifethey had more power than it did the day we drove it off the lot.
Great video.Any chance you could show us the process of finding the LCA as I have a 4 valve head on a pitbike that needs to be set to 100 degrees.Because I don't have a cam card I got no idea how many degrees the cam is set to.Hope this makes sense
This engine is in a scooter waiting to be sold so I don't wish to tear it down and my other 4T is a project scoot that I don't want to tear apart yet either, so it would be a long time before I did that. Sorry. If you google finding lobe centerline angle, a lot of info will come up. Most info that you find is for automotive engines, but it's the same process. Sorry I can't' be of better assistance ATM.
I know how to use pressure gauges, but I don't know if PSI can convert to a compression ratio, so I ask you, please let me know thank you.
I love the bolt mark you now got on your piston! If that piston does break, that will be the reason!
i saw these degree wheels in videos but did not know how they are used. thanks!. i would very much like to know how they are used for multi-cylinder engines like inline to v-types.
Nice vid. Im now getting hook with 2t motors and i want to understand how timing works. In this vid you talked about tdc. If i get the tdc, do i need to get ex and in timing or getting the tdc will cover both?
TDC is just the top of the stroke. If you're trying to find port durations, you will do that after you've got the degree wheel zeroed on TDC. Some people just 0 the wheel as a port is beginning to open and then read degrees of rotation till it closes. I prefer finding TDC and then checking port timing.
👍👍👍👍👍
Great video and explanations but It would have been much better if this war demonstrated on an engine where the timing is off of indicated markings
Visually TDC markings on my engine seems to be ok. But just how much degrees off is to be concerned with?
A few degrees is probably alright. Not good, but not so likely to cause big problems. I had an old Chinese scooter that was over 20 degrees off and it ran poorly. I put a BBK on it and all sorts of parts and it wouldn't pass 35MPH till I found the improperly made flywheel and replaced it. It also had more issues with P2V clearance than it should. Some engines could have serious interference issues by that point and fail quickly.
for example in open 30 degrees in close 70 degrees and 30 + 70 + 180 = 280: 2 = 140-30 = 110 so 110 it is the right time to install the camshaft. Am I wrong? Please let me know
I just bought an aerox, once you go 2 stroke you can't go back to 4, just that kick in the pants when you hit powerband on a 2 , you just miss so much riding a 4 banger. just gonna put a mild taiwanese 70 kit in this one (the one in it, the PO busted one of the studs off of the cylinder, I kinda wondered why it wouldnt run properly at low revs) so I have to replace it, and buy another one to put a polini 94cc full house kit in. You can buy them cheap as chips here, especially unlicensed ones, and everything is still available for them on the web. nothing beats having that storage area under the seat for around town.
+shoominati23 I have nothing against 4Ts, but it does feel like something is missing if you're used to piped 2Ts. It's kinda nice to get great gas mileage on the 4Ts though, and IMO all engines can be fun to experiment with.
yeah. I'm older than you probably think , and I get hassled by my friends for riding scooters, even though do I own bigger motorbikes too. But you just can't beat the practicality around the city! And they are surprisingly quick with something like a cheaper midrace 70 kit, a yasuni c16 , variator weights and a gear up kit. and FUN!
THE ONLY RELEVANT INFORMATION TO MY SEARCH ANYWHERE ON THE INTERNET! Jesus! Thanks for taking the time to create this video. I'd like to confirm where in the range of 12 degree to 15 degree my stock ignition actually is on my 08 2t zuma (I heard it can range). Do I use the center of one the stock stator bolt locations in my case as a reference point for zero and then count the amount of degree marks I find that to be away from TDC, to find BTDC?
The easiest way to figure out where your ignition is actually firing is to use a timing light. That will tell you when the spark really happens, vs trying to figure it out based on when the reluctor passes the pickup and having to know if it's the leading or trailing edge of the reluctor to be most concerned with. For that, you just need to find TDC and make a mark on the flywheel and a pointer that points directly to that mark at exactly TDC. Use an adjustable timing light and adjust till the mark and the pointer align and the light will tell you what the timing is.
49ccscoot.proboards.com/thread/15348/checking-ignition-timing-light
+90GTVert Do you teach that method of fire?
+90GTVert I hear you say and I know this teaching is correct
Thaks to u people turn into mechanics and some breakanics lol.
Great video thanks for sharing.
You ask what is 15 ° I do not understand very well I'm Vietnamese butt you answer my question thank you for answering my question
top
I hope you reply and thank you
I've found that it's both easier* and more accurate** to simply measure DURATION and divide it by 2, to get your #'s...
*easier because you don't even need to find TDC, heck I made my last wheel a 'fixed' wheel so it only counts degrees it doesn't tell me "relative to TDC" but I don't need that because I simply check duration from when exhaust closes before TDC on piston's way up, to where it cracks open on the way down.
**more accurate because you're measuring a distance on the wheel 2X as long, but the wheel's precision is fixed....so you're getting a sharper reading when you get duration and divide by 2, than simply measuring from TDC w/ a properly zero'd wheel!
Would love your thoughts on this, I mean I *know* it works (as I, of course, do multiple checks and they are consistent as can be), and I can't "fault it", but am surprised it's not the norm simply because it forces a 2X larger measurement using the same wheel IE same margin of error on a 2X larger distance, automatically a tighter reading for true timing #'s!
A lot of people do prefer that method. I don't know that it's actually more accurate. I've tried both ways and got the same numbers. If you check the open and close points and make sure they match up, it has been accurate for me as far as I can tell. The main thing for me is to take your time with the process, however you prefer and to try to be consistent with how you're measuring.
Dang ol' tell ya 'hwhat man!
Dammit Bobby.
Great video as always even though I've watched it more than a few times. You didn't state if you need to put pressure on your piston stop tool like if it was torqued down so there's no deviation with TDC. Oh one thing what size were your spacers in know it will very with each engine.
The piston stop needs to be tightened so it doesn't move. You shouldn't put much pressure at all on it to stop the piston. I don't recall what spacers for the one shown. The stuff that comes with the Summit kit works on lots of things.
a dial indicator would be much faster to check tdc and if your timing marks are correct .
sir....will i get a wrong reading if the dial indiactor is not aligned with valve retainer when measuring duration??please reply
You can. Do a search for "dial indicator cosine error". There are videos explaining it and demonstrating it.
90GTVert ..that means dial should be align whether you are measuring duration or lift ....right??
Yes.
could you use indicator to find tdc, and then just set degree wheel on zero ? thanks
czcams.com/video/TKTNKGCeOkc/video.html
I have a question my friend when you have the calculated done on how much degree is going to be how I know if I have to add or minus before or after tdc
You move whichever way evens it up. So in the vid I needed 15 degrees and had 12 and 18. So I'd either subtract 3 from 18 or add 3 to 12.
How deep I have to screw the piston stopper, because if I screw to much is going to be off timing or the point of a tru tdc is trying to up the piston much I can at the tdc?
@@3030rey Only far enough to stop the piston before TDC.
Did the timing Mark at the flywheel match at the end ?
I believe it was just barely off of true TDC. I expect to see them correct in some applications, but cheap Chinese scooters are pretty commonly a little off. I had one that was nearly 30 degrees off IIRC.
You can indicate how the camshaft is calculated
Q. How much depth does your piston stop, have to be the lil screw in the middle?
It shouldn't have to go too deep. 1/4" will cover most. Some don't even need anything there and a piston will contact a flat stop.
90GTVert thanks Mr. This was good teaching.
Thank you. Glad to help.
I really wish you showed your flywheel so we could see if it was off! :)
This one was just slightly off, which I think I said in the video. I have had one that was over 20 degrees off in the past from the factory on a 139QMB. That can cause serious issues.
How do you correct it!?
I replaced the flywheel, since it was machined wrong. Before the replacement came, I installed the flywheel without the woodruff key and clocked it using a degree wheel. It wouldn't be a bad idea to try to lap the flywheel to the crank with valve grinding compound if one were to use a flywheel without the key. It's also possible that the crank could be machined wrong, and again not using the key could fix that at least till a replacement was found.
How about when checking valve clearance?
Checking piston to valve clearance or valve lash? If it's a lash setting, you don't normally need to go as far as a degree wheel. For P2V clearance, I have a few videos about that.
P2V Info : czcams.com/video/oZghWIpqquc/video.html
P2V Clay Method : czcams.com/video/4_ZdcAE67L0/video.html
P2V Dial Indicator/Feelers : czcams.com/video/sLe6-AgbtlA/video.html
Also : Valve lash : czcams.com/video/s0K-ytyjOFg/video.html
I can ask you this. Can PSI convert the compression ratio? Please let me know thank you very much
PSI/pressure can't convert to a compression ratio accurately that I know of. You may get close if you know the dynamic compression ratio. A google search will bring up formulas.
@@49ccscoot yes thank you very much
@@49ccscootI didn't find it, estimated how many psi was equal to the compression ratio
@@longtattat3865 It's in here : en.wikipedia.org/wiki/Compression_ratio
If i use higher cc example honda wave dash 110cc .i use different wheel or same????
Im from philipines 😁😁
Really interesring how to used a degree wheel how about the 4 stroke cams how to get using degree wheel
czcams.com/video/kLLMWsF3FXk/video.html
What for full dome piston?
I'm not sure exactly what you're asking.
Hi; why the wheel says "intake open BTDC" AFTER the TDC mark actually? I mean if you rotate the crankshaft CW; BEFORE would be at the left hand of the TDC mark viewing the wheel as you rotate it...
If you're rotating it clockwise, the BTDC does come before the TDC mark.
@@49ccscoot I have 2 slots in the crankshaft flywheel. One is TDC the other is for 38ºBTDC (for the timing) when I put the degree wheel and rotate CW, the 38º mark is find at the left of the TDC not at the right like in that wheel
@@TheReverb1 There are engines that rotate counterclockwise. You can tell for sure by watching what the intake and exhaust valves do. If you can see/feel the piston, you can be sure which is TDC so the lines shouldn't get confused.
@@49ccscoot I know that; also my engine rotates CW as mentioned, In any case if you rotate the wheel in the same motion than the crank; CW for example; the BTDC should be at the left of the TDC mark not at the right like that wheel
Bro.. Cant download tht wheel degree sticker link u uploaded ...
www.49ccscoot.com/Gaskets/49ccScoot2TDegreeWheel.pdf
@@49ccscoot tq bro..
You sound like the guy from Ferris Buellers.
Can someone explain how he knew exactly how much depth he needed to screw down his screw on this home made head stud bolt plate ?
It doesn't have to be exact, and generally the engine setups that I'm messing with will either function with just a flat plate or with very little of the bolt protruding downward.
Saly the link to the degree wheel doesn´t work anymore...
I just checked and it all works for me. If you can't get it to work, there are plenty online for free.
That's odd. I'll try again. Thanks for your reply :)
The link on the forum no longer exists it seems.
I just checked all links on the page that is linked in the description and they are all active, as is the description link. Give it another try. The servers do have errors periodically so maybe it will work this time.
I paid more attention this time. Looks like it's a permission issue through not being signed up.
Oops, there was an error!
You do not have permission to access this thread.
@@Alan_Hans__ Registration is free. No BS.
Small roundness of large roundness gives us more accuracy?
Large wheels will give you a greater degree of accuracy.
+90GTVert yes thank you
+90GTVert Is there any formula for calculating the lobe angle?
@@longtat6587 google "lobe separation angle calculator"
+90GTVert What is that application called?
You can give a formula for calculating the camshaft and placing the camshaft in the calculated formula
What are you looking for? Degreeing a cam?
+90GTVert Yeah, how to put the camshaft to fit
+90GTVert I think you know how and I ask
+90GTVert Are there formula equations for the angle of the camshaft sir?
@@longtat6587 Search for "how to degree a camshaft" here. Good vids will come up. If you're working on a scooter like me, the issue is that we don't usually get cam cards or any specs to go by like you do for cars and motorcycles with cams from major brands. Most specs that I've seen on cams for a GY6 or 139QMB are useless.
What about intake center line
czcams.com/video/kLLMWsF3FXk/video.html
@@49ccscoot nice thanks
Couldn't you use a plunger indicator or finger indicator to find absolute true TDC?
I've got a video about that as well : czcams.com/video/TKTNKGCeOkc/video.html
Damn so the marking on the magnet is not always right?
It's usually correct or close, but at least with Chinese scooters, it's possible that the timing marks are way off.
The cam valves set how new to fit them always confused me
This list of words gave me a headache. What in the fuck are you trying to say?
The bigger your disk, the higher the accuracy, right?
Correct.
@@49ccscoot thanhk you
Your link doesn't work.
Still works fine for me.
It says, "Oops! There was an error.
You do not have permission to access this thread."
Oh, gotta register to see some parts of the forum. It's free and it removes some ads.
That piston stop is a horrible idea because you would always be stopping the piston somewhere before top dead center leaving you a few degrees off when you need to be between 34-36 degrees. Just take the spark plug out and use a plastic pen. Stick the blunt end of the pen in the hole. Look to see when it is in between rising and falling. Or better yet, use a compression gauge.
I hope you will respond
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Oh, you may have to be a member. It's free.
Wow, way to overcomplicate a simple process!