Why is it important to understand top dead center vs. overlap on a 4-stroke? #DOHC #how2wrench

I gotta find tdc on a 1984 bmw m10 4 cylinder. Hope I can do it correctly. This engine is a landmark for bmw

take a peak at the aprilia rsv4 engine... :/ pretty cool

I got a fairly new carbureted 250cc dirt bike I have a question riding the bike for a little bit and I wondered if the valves were a little too tight so I loosened the intake valve just a smitch because there was Zero play there any movement at top dead center I loosened it less than a quarter of a turn tightened it down made sure everything was top dead center I didn't have a gapping tool bought by hand felt normal now would that have anything to do with running hot cherry head pipe

Great explanantion that other videos try to explain but not as well or incorrectly

Don't forget to teach you need 1.21 gigawatts into the flex capacitor.

What an amazing tool to visualize the full cycle and TDC! So I’m trying to decipher if when you are at TDC on compression stroke, should the timing gear marks/dots be lined up/facing each other and the distributor be pointing to cylinder 1? I’m in the middle of replacing my gears and chain on my 4.2 l on my 89 YJ. I had replaced the old distributor a while back with and HEI system and wonder if we put it in 180 when we did it. Is that possible, would it even run? Right now when I have the timing gear marks lined up facing each other, at what I think is TDC compression stroke, the distributor is pointing 180 away from cylinder 1 (don’t remember what cylinder it is). I would love to see all four of the components tied together, TDC/compression stroke, timing gear marks,and distributor angle, that would be awesome. Hope you still check this video and reply to questions.😊

What an education! I always assumed that both valves would be fully closed every time the piston goes to TDC.

damn this was so so helpful! cant wait to try this in the morning.

Always look for de butterfly positsion of the cam lobs.😊

Here’s my question.

What would I notice if I adjusted my valves on the wrong stroke?
How would the engine run?
Would I notice a compression loss if I did a compression check?
Would the engine run at all?
Would I hear a lot of valve chatter?

I just went through this with my sons atv, it needed the valves adjusted, had 2 different people do them and both times it was ting tinging. I finally wrapped my headed around what was going on and did it myself. I’ve been a 2 stroke my whole life.

i just rebuilt my motor and didn’t know about this. i put every rocker arm on “tdc” and torqued them accordingly. would that cause cylinder 1 intake and exhaust valves not to work ?

Hi sir. Which way do you turn the flywheel?

Mate, absolutely awesome, very easy to understand with the cutaway engine. The explanation with the intake valve opening and closing with the next revolution always being at TDC in invaluable. Cheers mate, great video. 👍👍

So say you put an engine back together and it has overlap. Will it blow the rings out at high RPM? What kind of damage can it do?

Very great video. As an ex mechanic here in Australia myself not once I have been taught this. Thanks mate and G’day from Australia.

Love the perfect placement of the bright red cart in the back to match the exhaust port diagram in red. :-}

This video is worth it’s weight in gold!!! You’ve got an awesome channel and I’m sure you’ve helped thousands of people sharing your knowledge! I really appreciate your channel. Do you have a Patreon account?

when installing the rockerboxes what is the best way to set the engine on B cirkel or Top Dead Center ??

What's the best way to tell if you're at top dead center on the compression stroke if the cams are already out I've got a 2017 yfz450r I'm redoing the top end for the first time by reading the service manual. My new cams will be in this week and I'm going to try to get it all back together

Yes overlap is caused by error in the valve clearance that is why we need to test the shims and made sure it is not too tight and not too loose.

Roger that 👍

my crankshaft pully has grad. marks an tdc stapped in it a timming light will tell where it firing exactly if need to correct just turn dist. slowly the tighten i set mine at 4 deg, before tdc

when that eng is running use a timming light to see exactly where it firing in relation to arrow twist dist. to slight errors retighten dist. simple

to find compression stroke on a Harley Davidson just pull out spark plugs and look into front cylinder for the intake valve coming down and then when it starts to go up to close as you turn the rear wheel CCW on a stand look at the window for the timing mark to come around and look in the service book for a pic of what it may look like not all Harleys have the same marking...

Thanks man I forgot about over lap.

Can you check valve lash when cam is facing upwards and inward instead of outward? Basically as long as the valve is closed? Thanks just curious

Hello; would be really good to explain how to find lobe center (degreeing a camshaft) with that cutaway engine.
Nobody; and I mean nobody explained the technique right for an student or a rookie. Always says something like "put TDC; rotate engine the way it rotates; stop when the valve is open ...etc" Do not working regarding understanding
Thanks

Sir can you tell on which strock the valve clearance should be made...

Fortunately on my honda cb125f it's really obvious when you have free play or not.

Very nice your video bro, can i reuse your video?

So what if you did a rebuild and new timing chain and the crank has got turned a bunch to (making sure everything was moving smoothly and waiting for parts) but just can’t seem to get it right first time it was sucking in the exhaust weird second time lapped valves better and would only run on the gas I put down the plug hole third time was really sucking through the carburetor but wouldn’t even run with gas down the plug hole and every time the valves had a different clearance but cdi doesn’t know tdc from overlap friggn so weird but I’ve been in this engine a lot and this is a first

Hello sir very nic sir ... Sir i want your hellp .. for surching job .. for this work. ... Sir plz hello mee .

Thank you!

👍👍

now i see why my valves were tight even with top dead set i didnt spin it over twice

I have a v6 3.0 vze with 2 cams and the timing belt seems to have slipped. the crankshaft goes to TDC (piston 1)and so does the Drivers side cam but the passenger cam hops right past TDC by 9 teeth. What happened? Do I need to crack the plugs to get it to TDC on that side?

Hi Shane. Forgot to ask. Is it doing damage or putting the timing out if I turn the flywheel backwards please ? G

Hi from the U.K. Shane. The only other thing I would find useful from this video is a close up of the action between the lobes and valves. The stills were good but I think It would register with me more in slow motion. Mainly because I'm old with poor sight and slow on the uptake. Lol. I have an OHV/OHC 125 single bore Chinese bike. Poor compression and burning oil. Lapped the valves/seats and put a new piston and rings in. By the way I have the engine out of frame in house. Highest compression reading so far has been 91 but have lost that since moving sprocket around to try and improve the figure. No timing marks anywhere on the camshaft. There are two lines on the sprocket but don't know if they should be horizontal or vertical to the body. If I set the lobes upward at TDC so both valves are open will that take care of the overlap please ? Thanks. G

I'm more confused than before, I actually don't know what you are talking about ... :D

This is why two strokes are where it's at

Great video, was having trouble finding tdc on my ktm. Now I thoroughly understand what I'm doing. Thanks for the knowledge

I just set the valve clearance on a raptor. Does not start. I think i woked the overlap. 🙈

Great video you can think you machine is out of time but its just not on compression stroke

Awesome video well explained and with the engine displaying its function it was easy to understand

I have a dirtbike and I am having issues starting it head was sent to machine shop and cylinder so everything is precise. I have assembled it and I have too much compression. I’m wondering if this can be issue. I can’t think of anything else. I have marks where they should be but if I turn fly wheel again and I find the line a second round the lives point down and the cams marks are not aligned with head. Is it this what you described?

روعه

just rebuilding xt 225 yamaha i forgot to ,mark the keyed drive cogs , how do i fix it to the correct place so the timing for the valves is correct as its rotation needs to be real accurate or it collides

Wish I had a teacher to show me the things I had to learn the hard way...