ATC200 1984 Refuses to Start, Low Compression

[dwheeler23]

After months of this baby sitting and replacing everything imaginable electrical it still will not start.

Just did top end new gaskets, piston, rings, camshaft
NEW: pulse generator, extra CDI, air filter, Spark plug, Ignition Coil, Stator Coil
Rebored cylinder
Adjusted valves slightly so not ticking but not sure if correct

Result:
Compression still @ 30psi will not start does not even sound like there is spark but
electrical meter testing seems fine

Valves the issues??? Timing???

[Gabriel]

If you have the right size piston and rings in a freshly bored cylinder then your issue is most likely a valve. Valves are pretty cheap. I've replaced (and lapped in) them in every rebuild I have done so far. You could have the perfect ring gap and the highest compression piston imaginable and if the valves aren't sealing....it's crapola.
It's sounds insulting but it's been done MANY times...you sure the right size piston and rings are in there? If so, pull that head and rework it, then a new base and head gasket.

[knappyfeet]

Let's forget about anything electrical and deal with the 30 psi compression.

Gabriel is correct....it's probably valves. I would say do the oil trick to see if it's valves or rings but since it's 30 psi it needs to come apart anyways so focus on the head and valves. Put gas in the valve area and see if any seeps through. Make sure valves don't look pitted in the seat area. Also make sure cam timing is correct. Do it slow and methodically so nothing gets overlooked.

You got this...just take your time. Good luck

[Gabriel]

Anality during assembly prevents feeling like an azz when it won't start.

[dwheeler23]

Thanks for the input definetly right size piston and gaskets, The valves was literally my last thought since it was the only thing i did not service. Let me pull it apart AGAIN and take a look they looked fine to me but idk anymore.

For cam timing the timing chain mark and upper cam sprocket have to be aligned correct?

[Gabriel]

For cam timing the timing chain mark and upper cam sprocket have to be aligned correct?

Sort of. Those marks line up more than once in 4 cycles.

Rotate the engine to top dead center, make sure the flywheel mark is aligned. THEN move the cam to install the sprocket with those marks aligned.
Getting that wrong; Best case scenario, it don't run.....worst case you crater a piston into a valve. That will suck very much bad.

[roguemode]

Tell me how you set the valve clearance.

"not ticking" well... they should 'tick' actually.

It sounds like you have no lash. A valve is staying open slightly.

[roguemode]

If you want solid help, give full sentence replies and be detailed, or this will get out of hand quickly and it will never run...

Also one more question.

How many 4 stroke topends have you rebuilt?

[dwheeler23]

Alright. Have not rebuilt any top ends ever 100% new to this. Sorry, Im trying my best to rely information without dragging on with everything i have already done. Im pulling the motor off now and going to check everything over again. By setting the valve clearance i used the valve adjuster tool and tightened it slightly so it barely has clearance(so shaking it a bit it does not tick), maybe a valve is staying closed or that is too tight. Its tough to get a feeler gauge in there and im pretty sure all my other timing is set properly and will be when i reassemble

[roguemode]

Pictures of your cam timing would be helpful. Pictures of everything always helps with diagnosis. Even if it's "just a 200 motor", it puts us there with you and makes it so much easier.

There are some people that can set valve clearances by feel, but they have a lot of experience.

You generally have to bend the end of your feeler gauges to get accurate readings on these engines. As you said, there's not much room.

Just some info while it's in my brain. Your engine has to be at TDC on the compression stroke to set the valve clearance. As you turn the flywheel, watch the intake rocker arm go down, come back up, and just as it gets to the point of rest, start watching your timing marks. It has a tendency to want to keep rolling past tdc on the "T" mark, so be mindful. Don't rotate 4 strokes backwards. If you roll past TDC, you need to keep going back around until you reach it again. Sometimes friction resistance on the flywheel is a good way to keep it from rolling over.

[roguemode]

PS those valve adjuster tools suck. It is very easy to unknowingly over tighten an adjuster if you don't have much experience, and that makes it so a valve stays open. If you have no ticking when you grab the rocker and move it, then you have zero lash, and that is bad.

[roguemode]

Also do not pour oil into your cylinder because if you just honed the barrel for new rings you don't wanna do that. The very last thing you want is excess oil in your cylinder the first time it starts. The rings will never, ever seal.

[dwheeler23]

Okay thanks for the input i will upload some photos. I know im not that experienced with these small motors thats why its quite frustrating when i think im doing everything correct but there is definitely some major thing i am missing. Either my valves are in bad condition.... My timing is super off from the valve clearance ( or would the timing chain slipping off mess that up? ).... or there's some crack or something somewhere im not noticing which i highly doubt. I grabbed this thing on craigslist for cheap to try and get it running again but my little knowledge has made it cost me more than it probably should to even get it running. When i first got it it would roll start down the hill but run awfully and not idle well never really got to really ride it, eventually didnt start back up one day at all so thats why i went through the electrical system first thinking it was spark related.

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[dwheeler23]

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[roguemode]

Probably needed a carb clean. Lol.

Post pictures of your cam timing.

Your valve clearance has nothing to do with mechanical or spark timing.

You shouldn't be taking it all apart again you should just be checking the valve clearance at this point.

[roguemode]

257640Hopefully you got the head gasket surface a lot cleaner than that before you assembled it. I'll wait for all your pics I guess

[roguemode]

P.S. Your exhaust valve looks trashed, corroded, pitted and possible has been damaged.

Whatever you are scratching around with please stop. Aluminum is soft

[dwheeler23]

i was double checking if the valve seats or springs had any major damage but i will upload that next. What would that consist of a picture of the cam & sprocket?

[dwheeler23]

All that material is stuck i cant get it off without scratching it. Yes i need to be careful with the aluminum i tried my best . I might also be able to find a spare running motor from my buddy as a last option but id rather not

[roguemode]

Show the position of the cam when the flywheel timing is at "T" on the compression stroke.

[roguemode]

All that material is stuck i cant get it off without scratching it. Yes i need to be careful with the aluminum i tried my best . I might also be able to find a spare running motor from my buddy as a last option but id rather notYes you can, and if you didn't get it off, it is not going to seal.

What you need, is a mechanic.

What you might try, if you want to keep going, is to buy a carbide gasket scraper. That residue has to be gone. Now, as a tech, I am concerned with a lot of other things.

Do you have the factory service manual, or are you just winging it?

[roguemode]

Also I want to say that if you want to be the one to make this engine run, you can do it.

Yes your exhaust valve looks to be trash. If it is already disassembled again, you should just take the head apart, send it for service, and buy new valves.

[dwheeler23]

I do have the factory service manual online and thats like a 160$ service correct? I got the cylinder rebored + piston kit for around that price. The spare running motor might cost me only 100$ so idk what is my best move. I have a metal gasket scraper, razors, and plastic scrapers and after scraping forever while doing the piston installation lots of left over gasket material were on still edges. Maybe my headgasket is not sealing nicely but such low compression 15-30psi i feel like its something else . The gasket you see pictures is almost burned in. Il send over cam timing pics a little later i have to step out for a bit. Once i adjust the valve clearance again and reassemble does the motor have to be fully connected to the carb & drive chain to test compression properly?

[Gabriel]

Gasket scraping absolutely sucks. I've been known to get mad and use my die grinder with a wire brush. You can remove aluminum with one so it's really a bad idea. You have to REALLY watch what you're doing. When I do, I color all bare metal with a sharpie as a witness mark to make sure I don't go over it again.

[twomanytoys]

Put the spark plug in the head to plug hole, fill the cavity where the valves are with fuel...see how quick it drains out past the valves...it should not drain. If it does your valves/seats need refreshed.

Also you gotta get all that old gasket off carefully...you need to be sealed perfectly!

[roguemode]

I do have the factory service manual online and thats like a 160$ service correct? I got the cylinder rebored + piston kit for around that price. The spare running motor might cost me only 100$ so idk what is my best move. I have a metal gasket scraper, razors, and plastic scrapers and after scraping forever while doing the piston installation lots of left over gasket material were on still edges. Maybe my headgasket is not sealing nicely but such low compression 15-30psi i feel like its something else . The gasket you see pictures is almost burned in. Il send over cam timing pics a little later i have to step out for a bit. Once i adjust the valve clearance again and reassemble does the motor have to be fully connected to the carb & drive chain to test compression properly?No the compression can be checked with no carb on. Yes I know the gasket seems burned on, I have rebuilt, maybe 100 or more of these engines.

Here is a link for head service by someone that i have used with perfect results. To have the head completely disassembled, seats cut with a 5 angle serdi, surface shaved flat, reassembled and sent back to you it's about 80 bucks, plus parts, which you should buy and send with. I know it says crf50 head for the auction bu the service and price is exactly the same for any 2 valve air cooled head, just send him a note with your head. https://www.ebay.com/itm/HONDA-CRF50-SERDI-VALVE-JOB-CRF-50-XR-50-XR50/252779530407?hash=item3adad588a7:g:XyYAAMXQHDlRcL9 r

Then you have to put it together correctly.

[roguemode]

Here is their website, and their email address is there. I dealt with them through ebay.

http://www.zforcemotorsports.com/

[dwheeler23]

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Im 99% sure i got the cam timing correct. Valve timing im a little confused on am i adjusting it at "T" when the piston is at the Top nearest the spark plug hole or the bottom.

When aligning "T" and the 0 on the cam sprocket with the Top Notch, the piston is at the top nearest spark plug as seen in the picture and the both intake and exhaust arms/valve adjusters jiggle a little since i probably loosened them too much if anything (P.S. the exhaust valve adjuster is tighter to adjust compared to the intake). Still got 30 psi compression on ressembly.


Sorry if thats confusing maybe im not adjusting the valves on the right stroke. I feel like i adjusted them on both and still nothing. Also just cracked my pulsegen base ugh frustrating

[roguemode]

In that picture, I think your cam timing is one tooth off.

Thank you for the pics, in this fashion you will find your way to the end. Only way to fail is to give up. It may cost a little more but you are paying for experience and knowledge.

[roguemode]

So, retard the cam sprocket one tooth and show the results. Be mindful that I told you the exhaust valve looks trashed. Also, if you put it back together with that gasket residue still on the head, then you aren't listening, you just want it done. Building engines is not about wanting it done it's about doing something yourself and doing it right until it is done. You don't seem like the type thats late for a race so what's the hurry? Your tools look hard and sharp. If you are cussing, scratching and scraping, this is not the hobby for you. Nothing in this field works if you are impatient.

[twomanytoys]

So did you test the valves for leaking? I feel like your fighting this LOL.

[dwheeler23]

i will retard the timing and see could one notch affect it so drastically??

The valves look bad yeah and the gaskets are not perfect but would that keep the compression soo low?
Does pouring a bit of gas in the valve area to check for leaks work i saw someone mention that above

To be honest im trying my best to understand how all this works so a future project might come easier, and i am being as gentle as i can but a slight overtighten and it snaps. Ive taken it apart like 5 times now so at least that is a bit easier but i feel like there's some major component im messing up i feel like even if my gaskets were crap i would get a better reading than 30.

[dwheeler23]

So did you test the valves for leaking? I feel like your fighting this LOL.

Next move. Pour gas up top and check for leaks below??

[roguemode]

i will retard the timing and see could one notch affect it so drastically??Yes.


The valves look bad yeah and the gaskets are not perfect but would that keep the compression soo low? Yes.


Does pouring a bit of gas in the valve area to check for leaks work i saw someone mention that aboveYes, but you already know you have leaks. If you set it all up right and it still doesnt build compression, this gas trick is a novelty. Your top is leaking. There, now you know.


To be honest im trying my best to understand how all this works so a future project might come easier, and i am being as gentle as i can but a slight overtighten and it snaps.Welcome to it! Tight is tight and old metal thats been hott a lot of times is brittle. That's what working on old bikes is man.


Ive taken it apart like 5 times now so at least that is a bit easier but i feel like there's some major component im messing up i feel like even if my gaskets were crap i would get a better reading than 30.Nope. If theres no seal theres no pressure build, simple as that.

[roguemode]

So did you test the valves for leaking? I feel like your fighting this LOL.Take a look at the pics bro. Dont get wrapped up on this stupid test, there's a lot more wrong here than a backyard leak test will reveal. At least 6 things that have been done wrong already. The head is leaking, and there's things that are obvious that he hasnt addressed yet.

Stop looking for a simple answer. The fact is that this project is far from done because of the urge to hurry.

[roguemode]

How hard are your tires when they have 30psi in them?... You want that motor to have well over 100psi in it, imagine how tight metal has to fit against metal to hold that kind of pressure. It has to be right.

[dwheeler23]

Okay i hear you. Let me get back to you after one more tear down and see if i can do it up properly. Just trying everything alright

[twomanytoys]

Take a look at the pics bro. Dont get wrapped up on this stupid test, there's a lot more wrong here than a backyard leak test will reveal. At least 6 things that have been done wrong already. The head is leaking, and there's things that are obvious that he hasnt addressed yet.

Stop looking for a simple answer. The fact is that this project is far from done because of the urge to hurry.


LOL ok Ill leave you 2 to it!
I cant tell if his piston is the right size...but I can tell his valves are toast if gas drains through them like a pasta strainer! LOLOL


Fyi,,,take head off...turn upside down...fill the round cavity up and see how fast it drains off past valves...any thin liquid will do. Gas is handy ususally.
If it drains off at all...you need a valve job.
And yes...chunks of gasket holding your parts apart is a bad thing.

[roguemode]

If it drains off at all...you need a valve job.
Or you have a little carbon on a valve, or weak springs, or several other things

[twomanytoys]

Or you have a little carbon on a valve, or weak springs, or several other things

You like to argue dont ya? Just trying to help the poor guy figure out why he only has 30psi of compression.
Maybe you should go help him in person since your such the expert and dont want anyone else to help him LOLOL

[roguemode]

You like to argue dont ya? Just trying to help the poor guy figure out why he only has 30psi of compression.
Maybe you should go help him in person since your such the expert and dont want anyone else to help him LOLOL

I don't want to waste my time so I want him to listen to me instead of someone that is hyperfocused on a test that won't matter at all.

[twomanytoys]

I don't want to waste my time so I want him to listen to me instead of someone that is hyperfocused on a test that won't matter at all.


Ummm this is an open forum...not a personal chat room. LOLOL
Obviously your new to the internet...
Im done wasting my time here. You and your proven results :lol: are on your own.

[dwheeler23]

Alright guys no need to bicker i appreciate everyone's advice lets just get this trailprotrailprotrailprotrailprotrailpro running. Cant even go riding someone stole my 250 raptor off my property while on vacation so this is my only hope right now and im determined.

So. After scraping EVERY piece of gasket i could get i think the gaskets are good and cleaned.
I made sure piston rings are 120 degrees apart, checked dowels + O rings, and TDC cam timing and valve adjustment perfectly imo.

Tested the upside down valve leak trick with rubbing alcohol and after trying it twice im pretty sure theres no leak. Going to triple check with a towel underneath or something.

After assembling up to the pulse generator cover im still getting 30 psi! Maybe 40 but definitely still to low to operate. Got to be something else major
A weak valve spring seems possible when i crank the recoil i hear a woosh of air go out the exhaust area.

P.S. I also have untouched new valve spring seals that came with the top end gaskets kit could that be a cause? As i mentioned the valve springs is the one area i have not really touched yet i would need a compressor or whatever tool necessary and a bit of a walkthrough to service them or just send them in. Would putting another set of used valves + springs work off a running trike or whats my options.

Another thing that came with the top end kit was a metal ring somewhat larger than the thrust washer behind the cam sprocket no idea where it would go/replace.

I feel like im close but dont want to get excited yet. IT HAS TO BE VALVE RELATED RIGHT??
Will upload BEFORE & AFTER photos soon
The Serdi valve servicing needs like 5-6 weeks DAMN

[dwheeler23]

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[dwheeler23]

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[dwheeler23]

After getting some Hondabond for the valve gasket and even ordering a new head with valves off ebay supposedly off a running ATC, im still getting similar compression maybe 40-50 now but still 30. Im stumped the timing chain is definitely in place the valve clearance is minimal as it should be. All gasket material is off WHAT ELSE COULD POSSIBLY BE WRONG ...

[twomanytoys]

Damn dude...you sure your testing gauge is good LOL:D

[dwheeler23]

its like a Innova 20$ off amazon seems fine. Has a button to release the air and get a reading. Lots of air coming through the spark plug hole maybe more than before. I dont see any cracks in the motor like i really have no idea whats left to check. The manual says faulty decompressor lever how can i troubleshoot that cause it seems fine but i dont know the cable thats supposed togo the starter is missing but i test it with the lever pulled and not .

I feel stupid at this point lol

[twomanytoys]

You tried that gauge on any other motors?

[83ATC185]

How does pulling the recoil feel with a spark plug in it? If it gives much resistance at all it has to be higher than 30, something bad bad has to be wrong for it to be that low, that motor would basically free wheel.