250ES Refresh hit a wall...

[Airmapper]

I've been doing a bunch of things at once, and apparently I did one of them wrong.

On my 250ES I can't get it to hit a lick. No inclination or offering to fire.

The biggest contributing issues I think apply is I have rebuilt the carburetor, and replaced the timing chain.

While I feel stupid at the moment, I'm not a noob to small engines, I just feel I either misunderstood the service manual somewhere, or made some dumb mistake.

Best I can tell the root problem is there does not seem to be any fuel entering the combustion chamber. I sprayed a little Kroil in the chamber to keep it lubed while I turned it over setting timing, the plug still smells like that stuff, not fuel. I wonder if that might not be interfering, but I didn't put that much in there, and surely if fuel were entering the chamber it would ignite regardless, Kroil is mildly flammable itself, and should allow the gas to ignite.

I think I have spark, the plug fires outside, who knows what it's doing inside. (It is new.)

I have a compression stroke, and I am getting puffs out the exhaust. Apparently the timing is close enough that it is pumping air, although if it's pulling from the intake or not I guess might be the big question.

On the timing chain, I could not get the timing marks to align perfectly with the head. By that I mean a few degrees, not way off. I was within one chain link, slipping the chain just made it slightly off in the other direction.

I set the valve lifter clearance. But after cranking on it some it loosened up dramatically. I set the flywheel back to the timing mark and re-set clearance to .003", didn't change anything.

So basically I am not entirely sure where to look first, by all accounts everything "should" be good. I've never messed with a timing chain before, and wonder if I did not goof something up there. At the same time, timing a little off shouldn't prevent it from at least trying to hit, backfiring, or some sign of life. As for the carb, it's not my first carb rebuild. I've rebuilt everything from 4 barrel automotive carbs to lawn mowers, and I rebuilt a 250SX carb not a month ago so I was familiar with it already. I have a hard time believing I goofed it up so bad it won't run, but who knows.

Another thing worth mentioning is I have some kind of issue with my fuel tank petcock. But it's issue is sending fuel even when it's off, so I don't think there is any lack of fuel to the carb. I drain the bowl and it has gas in it, so it appears to be getting fuel (i.e. the needle valve isn't stuck.)

I'd appreciate any ideas at this point. I don't feel like tearing it down to the timing chain again if I'm really not sure that is it.

[DohcBikes]

You said that after cranking the valve lash loosened dramatically. This is not common.

Are you sure that you are setting the valve lash at top dead center on the compression stroke...

[Airmapper]

You said that after cranking the valve lash loosened dramatically. This is not common.

Are you sure that you are setting the valve lash at top dead center on the compression stroke...

I'm fairly confident it was. Setting up the timing chain the instructions were to place the camshaft in lobes down, and once I got the head cover back on, I set the valve lash while it was in that same position, and I checked the timing mark several times during that process to make sure the flywheel had not moved. Later, after several attempts to start, I opened the lifter covers to observe the cycles, I seen that clearance was greater. To reset it, I used the timing mark, and seen it was after the exhaust/intake cycles.

I believe I used the correct mark on the flywheel as well. There is another set of marks I found, but only one with a "T" stamped by it.

[prometheus]

If you think its possibly a fuel issue try starting fluid. Give it a little squirt and if you get it to fire a few times then you know you have a carb issue. If it still wont fire I would check compression to see if valves are tight. If good compression and still no fire your timing is off. Way off. Might be firing on exhaust stroke.

[Airmapper]

Thanks, I had to pick up a can of the stuff. Gave that a try and got mixed results. It will putter a bit but something just doesn't seem right about it. No regular rhythm to it. I get a few muffled hits, nothing, then a few more.

I don't feel like it is sucking from the intake at all, I cracked open the intake hose and I can't feel any suction when I hit the starter.

I don't have a real compression tester, but sticking my finger over the spark plug hole, I can turn it to the compression stroke and it doesn't have enough pressure to push air around my finger. I don't know if that is normal or not, but it seems like there should be more pressure there.

I've about convinced myself to go ahead and take the valve cover back off and look over the timing marks again.

[DohcBikes]

I'm fairly confident it was. Setting up the timing chain the instructions were to place the camshaft in lobes down, and once I got the head cover back on, I set the valve lash while it was in that same position, and I checked the timing mark several times during that process to make sure the flywheel had not moved. Later, after several attempts to start, I opened the lifter covers to observe the cycles, I seen that clearance was greater. To reset it, I used the timing mark, and seen it was after the exhaust/intake cycles.

I believe I used the correct mark on the flywheel as well. There is another set of marks I found, but only one with a "T" stamped by it.

This sounds very iffy. I can tell you this: cam timing is not something you can or should be "fairly certain" of, it is a mechanical procedure that has no margin for uncertainty.

I can also tell you this: if the lash increased significantly after turning the engine over, you didn't do it right.

[Dustin87R]

Does the ES have a compression release that works off of the cam? When I adjusted the valves on my 400 I turned the engine clockwise after I passed TDC and it caused the valve clearance to change on the exhaust valve once the engine reached 1200 rpm.

[6speedthumper]

You did put the timing chain tensioner back in, and correctly, right? Are you sure you ordered/received the correct timing chain? It could be a link, or two, too long. You did tighten down all of the rocker box/valve cover bolts, right?

You set the valve lash then it loosened up after only cranking the engine. Was the adjuster and it's lock nut loose? Or, was it the clearance that was excessive? It could be as simple as the timing jumped. Or, it could be worse and you bent a valve. Both will cause little to no compression, and no intake vacuum, like you are experiencing. Also, if you bent a valve the valve lash clearance will have likely increased because the valve is either not quite closed, or stuck totally open.

You're going to have to dig deeper and investigate everything you did.

[Airmapper]

The last few posts rolled in while I was actually working on it, I just got in from the garage.

Yes, tensioner has been in and properly wound back so it can recoil and self adjust.

Timing chain is a D.I.D SCA-0412A SV, purchased off ebay, it has a sticker on the box listing for a ATC250ES and TRX250, for what little to nothing that is worth. I cannot find an application cross reference that lists a D.I.D part # for the ATC250ES.

The chain is tight and well within tensioner range of movement. No play in it at all. For all I can tell by appearance it is correct. The timing marks return to their positions every revolution.

Valve cover bolts were all tightened before setting the valve lash. Adjuster and lock nut were not loose.

I took it apart again this evening and went over it all again. I reset the chain. I found the timing mark, made darn sure it had a "T" (Apparently there is an "F" mark as well.) I only moved it a link or two but when I was done, I was confident I had everything as it should be, checked everything twice, and all that. I thought possibly I had used the wrong mark last time, who knows, but this time it all lined up very nicely and the timing marks were all perfect to where they should be, not even slightly off.

Set the valve lash and after one or two revolutions reset to the "T" mark, lash had very slightly tightened. I re-set it again.

After all that, it still won't hit a lick.....

[83ATC185]

You say you had the top end off, possibly broke a ring somehow? If everything else checks out its got to be a bent valve or broken ring, or maybe the ring gaps all got lined up when you put it back together. I'm not sure that would actually keep it from starting though...

[Airmapper]

You say you had the top end off, possibly broke a ring somehow? If everything else checks out its got to be a bent valve or broken ring, or maybe the ring gaps all got lined up when you put it back together. I'm not sure that would actually keep it from starting though...

Deepest I went is the valve cover, I haven't removed anything under that. Not to say that isn't the issue, but it's not one I've had until now, considering it ran when I parked it.

I tried to work on it some more a little while ago. The valve adjusters are loose again. The adjusters themselves are tight. I can't explain this, I know it's not right, but I can't figure out what in the heck could cause this to correct it. I set them on the "T" mark with the cam lobes down, compression stroke, but they just won't seem to hold an adjustment.

I'm with you though, why won't it start? Even if it's set up wrong, it should putter, sputter, backfire, or something, but it won't even offer to fire.

Edit to add:

I just removed the intake. It's blowing air out when I crank it. Whatever is causing that has to be my problem. I can see the lifter moving the intake valve spring. I first noticed it as I laid a screwdriver on top the airbox, and seen it hopping when I cranked the engine.

[83ATC185]

hhhmm did you take the cam sprocket off? Could it have gotten replaced 180 degrees out? You do say lobes down though, which is correct at TDC. Even with the valves off a little bit, it should still run, even if it does sound terrible.I honestly have no idea, I'm leaning toward timing though since that's the only thing that's changed. You might try taking the adjuster off and making sure its not sticking/hanging up somewhere.

[atc007]

Intake valve is your problem,Why?? We may never know lol. But you need to get your intake valve seated . Tear the head off

[6speedthumper]

You keep saying "lobes down", are you using the timing marks on the cam gear?????? There are two lines, one on each side of the bolt, and they get lined up with the plain of the cylinder head (parallel to the mating surface of where the valve cover mates with the head). Those marks have to be as such when the crank marks are lined up.

[Airmapper]

Intake valve is your problem,Why?? We may never know lol. But you need to get your intake valve seated . Tear the head off

I may have to, wasn't really wanting to go there, but I do want this thing to run after I spent this much money on it thus far. I think I may do a bit more testing to see what compression is doing, if I can find a tester.

You keep saying "lobes down", are you using the timing marks on the cam gear?????? There are two lines, one on each side of the bolt, and they get lined up with the plain of the cylinder head (parallel to the mating surface of where the valve cover mates with the head). Those marks have to be as such when the crank marks are lined up.

Yes I'm using timing marks. I say lobes down to try to make sure you guys know I didn't put it on 180 degrees out.