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1982 TT250 will not start

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Hi,

I am in the process of a complete rebuild. I have tore down and rebuilt engine. Set valve clearance .007mm intake and .013mm exhaust. New spark plug with strong blue spark. Compression is approx. 150. Carb is clean and rebuilt. Petcock good. New fuel filter. 

All timing marks were set to spec during rebuild. At one point I thought I might be out 180 degrees, so I adjusted that. Made no difference so switched it back. 

Checked resistance on pickup coil and source coil. All within spec +/- 10%  

This thing will not fire.

Have spent 2 days rechecking everything over and over. I have spayed starter in plug hole and into intake and does not even try to start. When trying to kick it, almost always damn near breaks my ankle. 

Any ideas would be greatly appreciated at this point. 

Edited by ddiggerr

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Well I just spent another 2 hours this morning going over everything again. I did notice the decompression cable is no longer working. I am thinking this is why it is such a bear to kick over lately. 

Everything is where it should be except still no gas getting to plug. It is as dry as it was coming out of package before I installed it. Could this be a carb issue?

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More time wasted. I have 3 CDIs for this bike and three ignition coils. I had them all tested yesterday and all are good. I opened engine up again to make sure everything lines up (timing) at TDC of compression stroke. Valves are in spec. Carb is clean inside and out. 

Spark has been confirmed with plug against motor as well as with plug in while using spark tester. Nice blue spark either way. Kill switch works as it should. 

Compression is still there. 

My question now is, if one of the valves were not seated fully, would this result in not firing? When I turn magneto slowly through its motions I can hear air blowing out somewhere during compression. But I am getting 150 psi when its on tester.

Anyone have any ideas yet? I am almost out of hair to pull

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You make no mention of the spark plug being wet with fuel

If your valves were leaking, you'd have no compression.

Most common no start is a clogged pilot jet. Did you install a new one? Is the fuel also new?

 

Moved to the Vintage section

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3 minutes ago, William1 said:

You make no mention of the spark plug being wet with fuel

If your valves were leaking, you'd have no compression.

Most common no start is a clogged pilot jet. Did you install a new one? Is the fuel also new?

 

Moved to the Vintage section

Spark plug seems to always be dry after kicking for a bit. New gas in tank. Previous owner installed new carb kit. I tore down carb and checked everything. Cleaned everything twice and put back together. 

It wont even fire with a shot of gas or starting fluid directly in the cylinder. 

I am baffled as to why

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Dry plug means it is not getting fuel.

Many 'aftermarket' carb kits are trouble.

Engines need compression(which you have) fuel, and spark (which you have.

I'd chase down why the plug comes out dry and triple check cam timing. I'd also confirm the pulse trigger coil is installed EXACTLY per the manual and ditto with the stator. If it is firing at the wrong time, it will not run.

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1 hour ago, William1 said:

Dry plug means it is not getting fuel.

Many 'aftermarket' carb kits are trouble.

Engines need compression(which you have) fuel, and spark (which you have.

I'd chase down why the plug comes out dry and triple check cam timing. I'd also confirm the pulse trigger coil is installed EXACTLY per the manual and ditto with the stator. If it is firing at the wrong time, it will not run.

I am beginning to think that it is firing at the wrong time. Will dig deeper

 

Update: figured I was out 180 degrees. Flipped it around. Put a small squirt of fuel into intake (carb is off) and kicked it over.

It fired. Literally. A ball of flames came out the intake. Gave it another kick and samething. It sputtered and backfired out intake. 

Im done for the day. 

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A 4S engine with an ignition pulser at the crank is known as a wasted spark engine. That means it fires once just after compression (the power stroke) and again (the wasted spark) during the exhaust stroke.

So... if you set the cam timing to the correct mark on the flywheel (there are typically several marks, one for ignition, one for cam timing and another for TDC) with the cam(s) at the correct spot, then the engine is correct. You could remove the cam chain, rotate the engine one full revolution, reattach the cams it it would still be correct. The relationship between cams and piston does not occur until the cams are connected.

Being you have a hint of life, I'd wager your cam timing is off a little (most common error). Quadruple check you are using the correct mark at the crank and the cam sprocket(s). Also if that is absolutely perfect, recheck the pulser location in relation to the flywheel.

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3 hours ago, oldnbold said:

Is your idle speed adjuster open too far?

I dont have carb on. I sprayed some fuel directly into intake. 

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So I played around with it a little more. In the pictures this is as close to being lined up as it gets for cam timing. One tooth either way does not line up on the mark.

When I spray some fluid into intake it ignites and shoots flames back out but never actually runs. If i squirt some gas into intake it does absolutely nothing. 

I also included a picture of the cam chain tensioner. It is practically all the way in before it starts poking out. Is this normal?

Also, the pulse coil is set as low as it will go. I cannot get it any lower than 0.10mm

PicsArt_03-28-06.28.31.jpg

20170328_182320.jpg

Edited by ddiggerr

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Well after sitting here scratching my head I decided to rotate flywheel slowly to see if there was something else going on. 

As it started on the compression stroke, I could hear air escaping all the way up to TDC. I am thinking this is the cause of my no fire. 

I dont hear anything from either valve during the compression stroke. Possibly leaking past my rings. No idea and hate the thought of pulling motor again. 

 

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8 minutes ago, William1 said:

Do a leak down test. you are wasting a lot of time guessing.

Yup. Thats what I was thinking. Will have to wait till next week now. Gone for a few days. 

Thanks

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The fact that the cam timing marks won't line up and the tensioner is screwed right in is a real good clue the cam-chain is toast. There is no other good reason for the timing marks not to be right on.

I'm not sure if that's the only problem, but it is a problem....

patuca

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  There is a chance that the cam chain is not on the crankshaft sprocket.

  If that is the case the cam chain adjuster will be as yours is and each time you kick it the timing will move slightly and the engine will not start.

  Sooner than later you will bend the valves.

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