300EX Timing Problems

[Rusty91o]

I'm trying to get the timing correct on my 97 300EX, but I can't seem to get it. I got it at TDC, and matched the cam timing chain, and the timing sprocket up correctly and I still don't get anything. At one point I got it to run, it was a little off, but it ran. I ended up getting backfire through the carb, so I shut it off. I adjusted it, and I can't get it to start again. Also what do the marks on the flywheel mean? there are 2 notches right next to each other. Another notch that has an F, and the last one (where TDC is supposed to be) is a T. But what do the other mean. There are also the same markings on the opposite site as well. I'm guessing for the different strokes. Please somebody help me out with this.:(

[Sjorge450R]

okay do this.

take the valve cover off. But the flywheel on the T, then try to wiggle the rockers. if the dont wiggle then you are at the top of th exhaust stroke. Rotate the fly wheel all the way around until you get back to the T. the rockers will wiggle. then look to see if the sprocket marks are parallel to the head. If they arent, ubolt the sprocket and move it so that they are. Also make sure that the cam lobes are facing down. Also use some blue lock tite on the sprocket bolts. then put everything together and try it.

steve

[Rusty91o]

Thanks alot! I'm going to try that.

[Sjorge450R]

Originally posted by Rusty91o
Thanks alot! I'm going to try that.

no problem.Let me know how you end up

[bwamos]

Also with the tensioner disengaged make sure there is no slack on the exhaust side (front) of the cam chain. All the slack should be on the intake/tensioner side. Common mistake.. can throw you off a couple teeth.

My 300ex just has the || & |T marks. You align the | next the the T with the notch in the hole. Then on the cam sprocket, you should have 3 notches. The 2 opposite each other should be aligned with the gasket mating surface of the head. The 3rd pointing up. But, if the cam was put on the sprocket backwards, the lobes will be facing up, not down. You may want to unbolt it and put it back on the right way for future sanity. Lobes should be downward. Perpendicular cam mark should be opposite the lobes.

[Rusty91o]

IDK guys. I'm doing everything right, but it's still not starting. It started before so I know the carb is good, and It looks fine too. Everytime I go back in after trying it, the timing sprocket os still matched up. And I still have very string spark. Is there anything else I could be missing? Or is there something that can still cause it to not run?

[Rusty91o]

I'm still having problems. Is it possible that the flywheel is off, causing it to spark at the wrong time?

[Sjorge450R]

Originally posted by Rusty91o
I'm still having problems. Is it possible that the flywheel is off, causing it to spark at the wrong time?

no that can only be put on one way. Are you getting spark at all. Is the motor cranking?

Take the spark plug out then put it in the plug boot, touch it to the frame and hit the starter button. See if it sparks.... Then we will go from there.

[Rusty91o]

I have done that. I have a very strong fat spark., and there is no damage to the spark plug, or wiring.

[Sjorge450R]

Originally posted by Rusty91o
I have done that. I have a very strong fat spark., and there is no damage to the spark plug, or wiring.

so whats it doing when you try to start it?

[Rusty91o]

When everything is set correctly, I'll crank it, and it will just crank. That's it. The "run" switch is on and functional. However. If I set the timing to a completely different setting I might get backfire out the carb.

[Rusty91o]

Is it possible that the valve clearances are off? Someone said to me that if something with the valves is even slightly off it may not start. But how would that explain it starting before? And Just yesterday I also went through the entire fuel system, and cleaned the crap out of it just for good measure. And still nothing. I'd take it too a shop and have it all done and not worry about it. But money is tight. :(

[Sjorge450R]

yeah your problem seems wierd. Make sure your jets are clean in the carb. they could be clogged. Take the carb off and push the throttle to see if it shoots gas out. dont look into the carb when you do it becaue it comes flying out. (i got it in the eye once or twice. I never learn....lol) The valve clearances shouldnt matter. But if its not a gas problem, it is definetly a electrical problem. Check the connection of the wires on the clutch cover.

[300ex_#387]

Might want to look over your harness. Could be a bad ground, coroded wire, or you might hav shorted out a wire.

[Sjorge450R]

Originally posted by 300ex_#387
Might want to look over your harness. Could be a bad ground, coroded wire, or you might hav shorted out a wire.

well hes getting spark so hes getting a good ground. I think its more along the lines of a unplugged wire somewhere.

[Rusty91o]

Ok this is good news to me. If it's not the valves I should be able to find the problem. I eliminated the fuel system except the carb which I am going to clean out now. I will then look over the entire electrical system, for anything I see suspicious/wrong. Thanks, I'll let you know what happens. :cool:

[300ex_#387]

Down by your brake pedal there are 2 wires. They are covered by a plate. Make sure that those 2 are still plugged in.

[Sjorge450R]

Originally posted by 300ex_#387
Down by your brake pedal there are 2 wires. They are covered by a plate. Make sure that those 2 are still plugged in.
yeah those are the two I was refering to on the clutch side. They will cause the quad not to start. The one has a R or a N on it. The N goes towards the front. If they are installed backwards, you will hit the reverese limiter in drive....lol.

[250X_project]

Well, if you feel it may be the valves- adjust them. .004 on each. Also if you have good compression, fuel air mix, and a healthy spark.....timing is all that is left. If you cam/valve timing is right, you may be on to something when you previously asked about your flywheel throwing off the ignition timing. Yes, the flywheel goes on one way, and one way only, but the flywheel key is a sacrificial part, meaning it is purposely made to break. This saves your flywheel and crank(hopefully anyway).

1st- run a compression test. 170-199PSI, with stock 9.4:1 compression. If it is okay, than your valves are fine. Now go to the flywheel. After that, w/o seeing it for myself I don't really have much of an idea. The wiring may be an issue, yet you are said to be getting a good spark.... Good luck! ;)

Let us know what you find!!!!

[Rusty91o]

Ok last night I completely cleaned out the carb. The carb was in great shape, and was all clean. All the jets are good and functional, and floats are working properly. So the entire fuel system is out of the problem. The two wires on the right side case are also in and installed correctly. I also gave all the wiring a good look over and it all looks good. I'm going to have to aquire the tools to do a compression test. Also, If the flywheel key was borken, would I be able to tell? Because when I manually crank it to find TDC, everything seems to work fine and I don't hear anything wrong, or feel anything wrong.

[250X_project]

In your case, being you have removed the cam and re-timed it the only way to tell if you have a broken key is to take the cover off and unbolt the flywheel and take a look.

You'll need a 12mm adapter for the tester. I don't know what stores you have near you, but Adcanced Auto is where I got mine. I like it very well. ;)

[Rusty91o]

Ok. For the tester, I also have an Advanced Auto near me, that's good, I can go and get one. How much was it?

[250X_project]

Okay good. I love Advanced. It was just under $43 after tax, I believe. The one kit comes with 4 different sizes. I can do an XR80, my wheeler, my sled, and more. (10mm, 12mm, 14mm, 18mm.) Very easy to use. I am pleased with it. Good luck, and let us know.

[250X_project]

Actually, What did you do to need to re-time it? Did you put piston and rings in? If there is new rings and gaskets than the valves are the only thing to hinder your compression. If you can correctly time this engine, adjusting the valves is relatively easy. Just a thought... ;)

[Rusty91o]

No I didn't put a piston or rings in it. And I don't really need anything specific to time it aside from some tools. How do you adjust the valves?

[250X_project]

Okay, but why did you have to re-time the engine?

To adjust the valves.... rotate the engine to TDC(must be correctly timed) then take off the valve covers on the top of the engine. Loosen the lock nut, tighten push rod down to .004 with a feeler gauge, then hold this clearance as you tighten the lock nut. Check clearances when tightened. Repeat this for each of the 4 valves.

[Rusty91o]

The entire head had to be taken off. So the timing chain, and camshaft had to come off also. That's why it had to be timed. I thought of something just now. My new head might be off of a 250ex. Even though they are the same thing, is it instead possible that they have different valve clearances and such? Which would cause it not to run?

[Rusty91o]

Ok guys. I checked the valve clearance, and it is all set. This time I set up a timing light to it. Accoring to it, It is sparking right when it should be. I don't know what else to do. I think I'm going to have to just bring it to the dealer.

[250X_project]

I'm not sure a 250EX head would fit onto that. A 250X head would and would be exactly the same, causing no problems. Now how new is this "new" head? Maybe your valves are not lapped well and not sealing correctly, loosing compression. Will it pop start?

If the ignition timing is Definitely dead on, than your key is fine....

The bottom line is, that a compression reading would help greatly to rule different subjects out. ;) I wish you the best of luck...

[250X_project]

And it won't hurt anything to explain more on why the head was removed! :D You could have mashed the valves for all I know, getting metal in the engine, eating the rings and lowering compression... :eek2:

[Rusty91o]

The head had to be taken off to put the new one on, because the old one had a bent valve because the piston hit it. There doesn't appear to be anything in the cylinder, and the oil looked good good too when I drained it. I gues the only thing left that I need to check is the compression, with the tester.

[250X_project]

Okay, that is what I would do next.

Now being that one of the valves dropped... Was it because the keepers were bad, high RPM, or are you running a high lift cam with stock springs.. or just worn springs? And only ONE valve hit? Did the "new" head come with new springs?

Sorry just trying to paint a picture here... ;) I wish you the best of luck! :D Keep me posted on progress.

[Rusty91o]

I have no idea about how it happened. I got the quad this way a month ago. The fact that it didn't work was the only way I was able to get it. Only one valve was bent, and the valve guide cracked. So I got a used, but working head off of somebody else. It was pulled off of a working quad. The keepers are on good. And the head came with springs.

[250X_project]

Okay, I remember your previous post. Sorry I just like to know all I can. I would go for a compression test, if it has fuel and spark, and correct timing. That's all that is left. ;)

[Rusty91o]

Yeah I just need to get the tester. Maybe I can borrow the one from work. Because that has to be it. We've ruled out every thing else. I'll bet I'm losing compression out of the valves or something.

[Sjorge450R]

Originally posted by Rusty91o
Yeah I just need to get the tester. Maybe I can borrow the one from work. Because that has to be it. We've ruled out every thing else. I'll bet I'm losing compression out of the valves or something.

yes that is a possibility.

[not2hi]

Are you sure the other valve wasn't bent as well?

If you have the head off, you can do a leak test, at least until you get a comp test done.

The same thing happened to ours...turns out both valves were bent (ever so slightly), and then even with new valves, it took a good bit of valve grinding to get them to seat on the old head properly.

[Rusty91o]

I'm not using the same head though. I got a new one on there. I should do the leak test as well. I need to get a good solvent. Since that might tell me right off the bat how I'm losing compression.

[not2hi]

I just used kerosene.

[250X_project]

That's a great idea. I'm sorry I didn't think of it already. Good thinking. :D

[Rusty91o]

It said in my Manual to use Kerosene. I just need to go and get some.