Spark but no fire.

I've got the engine re-assembled after putting in a new piston and cylinder. I set the timing as per the manual. Turned it by hand first to make sure it's ok.

When I crank the engine to start it, it spins, but won't fire. I pulled the plug (many times now) and checked that there IS indeed spark. But it won't run. What's odd is that it won't run on starting fluid either. I thought maybe it was flooded, so I let it air out overnight, and still nothing. There's not even a pop of puff from it trying to start. I figure that with starting fluid, even if the timing was off, there would be a pop or something.

Could it be that there's just not *enough* spark? I assume I have the engine together correctly, because the only way to get the timing off would be to have the cam 180 degrees out, and by then they'd hit the piston. No?

Edited by yellowdatsun

You need to triple check your cam timing. One tooth off will yield a no-fire situation.

Make sure you are looking directly across the top of the engine from the side when checking the timing marks on the cam sprocket and holder. Also verify that you've lined up properly on TDC before you check the cam timing.


Edited by JimDettman

I triple checked everything before I tightened the cam sprocket bolts. But I pulled the cam cover off just to be sure, and here's what I've me it looks spot on.



Kinda hard to see the arrow on the head, but you can see the side of it through the sprocket hole, which is darn near exactly where the line on the sprocket is. If it was a tooth off it would be way further out than that.

Edited by yellowdatsun

Don't rely on the mark from the right side case.

On the left side ignition cover, remove the plug using a 6mm Allen.

Line up the second timing mark ( the TDC mark) with the cut in the threads.

That is the most accurate way to do it.

Pffft, so looking into the flywheel hole, when everything else is at TDC, there are no marks all. How could the transmission side crank bolt be so far off?

I'll adjust things and we'll see what happens.

True what doc said . there is a T and a F mark on the flywheel. sometimes its hard to see them with the oil on it. Also cam lobes should be facing the rear and slightly up @ TDC

Edited by StonedInNy

Ok, so here's the flywheel side, now lined up:


But when you line up this side, you can't even see the crank bolt dimple on the other side. What the heck? I could see if they were a little off, but that would be WAY off.

FWIW, I've seen comments about which mark to use on the crank bolt, because apparently there's supposed to be two. Mine doesn't have two, only the one pictured in the previous post. I've spun the engine around a few times in search of the second, but it doesn't exist.

Edited by yellowdatsun

It's like there's a half-tooth discrepancy when aligning the flywheel and the cam sprocket. One tooth on the cam in one direction and it's too far advanced, and one tooth in the other direction and it's too far retarded. Which way should I error? If I have the flywheel lined up on the left mark, where should the cam be? Above the arrow, or below?

I assume the left flywheel mark is TDC, and the right is fire. Correct?

--EDIT: OK, so turns out right mark is TDC. Found that in the Clymer manual that everybody hates. The factory manual sucks with it's timing information. Let me try this again and see if things will line up now.

Edited by yellowdatsun

We have ignition! Works wonders when you have the right information. With the flywheel set on the mark to the right, and the cam set correctly, it fired instantly. Still have no idea what the deal is with the right side crank markings though, but they're obviously wrong.

Edited by yellowdatsun

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