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-   -   1990 xt 600 won’t start (https://www.horizonsunlimited.com/hubb/yamaha-tech/1990-xt-600-won-t-102684)

Wheelie 9 Mar 2022 11:23

Quote:

Originally Posted by njenduro (Post 627109)
I did look at the video for the adjustment , maybe it’s that cdi box. The bike was running and stalled and then it doesn’t start back fire like it ran out of gas and that’s it. Now the neutral safety switch if that was bad it would not turn over correct. Thanks for all the help.

You say you don't have a spark. It could be the CDI - I've had this happen on a different bike, given the same symptoms.

I agree with the comments regarding valves. To me it sounds like you have an electrical problem - not fuel, air or compression.

You can probably rule out the ignition switch as it is turning over, as well as the starter relay, etc.

If you can set the kill switch to off and that also cuts out the starter switch (won't turn over), then you can probably also rule out the kill switch (some bikes don't have the starter and kill switch connected). If the engine still churns with the kill switch off, then it is worth checking the switch.

I don't see how the neutral switch has anything bro do with this. If anything but giving you a N light on the dash, it could on your bike be wired to prevent you from being able to run the starter in gear. As you say, it churns. Ergo, not at fault.

I've had spark plugs leads fail in several machines before, and sometimes in the middle. But if you've measured the continuity, and you have good contact, you should have seen a spark. You can probably rule this one out.

Your guess that it could be the CDI is a pretty good one I think. In fact, I think it is the most likely culprit from the intel you've gathered so far.

If you have a fuel problem, it is gunk or the pump... as you have ruled out the carburettor. However, it is unusual that you get a 100% blockage over night. Usually you will have a trickle of fuel, which will at minimum let the bike sputter for a few seconds after having rested for a while. Anyhow, testing if fuel is getting to the cylinder, and working yourself backwards, is usually quite simple.

njenduro 10 Mar 2022 21:18

Does anybody know of a coil that I can use temporarily just to see if I can get a bike to start because the coil is going to be coming in at the end of the month I’d rather check for something now just in case if it’s not it I can start doing more testing somewhere else like the CDI thanks again

njenduro 11 Mar 2022 22:40

Checking again, I checked the coil to the spark plug cap and got 23 ohms on the 200k scale. Does that seem off? thanks.

xtrock 12 Mar 2022 13:00

Quote:

Originally Posted by njenduro (Post 627178)
Checking again, I checked the coil to the spark plug cap and got 23 ohms on the 200k scale. Does that seem off? thanks.

You have manual and it says spark plug cap 10k ohm at 20degree C, coil -+ 3,4-4, 6 ohm, sec coil - coil + lead on plug lead 10,4-15, 6k ohm.

njenduro 16 Mar 2022 20:19

Check the valves intake and exhaust they were tight at tdc. They seemed real tight by means the could not even get the feeler gauge on them. So adjusted valves still no start. Any other suggestions

xtrock 16 Mar 2022 23:00

Quote:

Originally Posted by njenduro (Post 627275)
Check the valves intake and exhaust they were tight at tdc. They seemed real tight by means the could not even get the feeler gauge on them. So adjusted valves still no start. Any other suggestions

Sound to me like you have adjustet on wrong top dead center, just not possible that bike was running if valves didnt open before. Never adjust before you can get feeler gauge down!

njenduro 16 Mar 2022 23:36

There were 2 marks as I was turning the nut, then the 3 rd mark, I even checked the piston for tdc and then the mark was right on the notch.

njenduro 16 Mar 2022 23:45

I did watch that video and had the same marks mine looked like l-l then l which I lined up to the notch the last mark. I did check the piston and it was up to the top. When I checked the intake it was very tight with the feeler gauge so loosen up and adjusted same with exhaust valves adjusted. I don’t remember when the last time the valves were adjusted that is why I tried that too.

xtrock 16 Mar 2022 23:52

Quote:

Originally Posted by njenduro (Post 627278)
I did watch that video and had the same marks mine looked like l-l then l which I lined up to the notch the last mark. I did check the piston and it was up to the top. When I checked the intake it was very tight with the feeler gauge so loosen up and adjusted same with exhaust valves adjusted. I don’t remember when the last time the valves were adjusted that is why I tried that too.

360 degree again and it would be correct, If all was closed. I dont know, first you write couldnt get feeler gauge in and now it was tight? Did you use correct blade thickness?

njenduro 17 Mar 2022 00:18

I am sorry for being confusing. What I did first was put everything at tdc and I checked the intake valves first and I noticed that the feeler gauge was to tight ( using the spec from manual)and I could not get it in there so I tried the exhaust same even with a smaller size. So what I did was tried the piston up and down and got that at the top and I did notice that the mark on the inspection cover was right on. So still noticed that the gauge was way to tight to even get in there. So I adjusted per the manual.

Bobmech 17 Mar 2022 21:09

You could be 360 degrees out on the crankshaft?
The easy way to check the camshaft is in the correct position to adjust the valves, is to rotate crankshaft to the point where the exhaust rocker has is just finishing closing and the inlet rocker is just starting to open, then rotate the crankshaft 360 degrees. It is now at the top of the compression stroke and the valves can be adjusted.

Bob

njenduro 18 Mar 2022 02:44

Quote:

Originally Posted by Bobmech (Post 627289)
You could be 360 degrees out on the crankshaft?
The easy way to check the camshaft is in the correct position to adjust the valves, is to rotate crankshaft to the point where the exhaust rocker has is just finishing closing and the inlet rocker is just starting to open, then rotate the crankshaft 360 degrees. It is now at the top of the compression stroke and the valves can be adjusted.

Bob

How does this happen ? I just lost you. Also if I go to tdc why can’t I just adjust them also how do you know this happens

Bobmech 18 Mar 2022 22:15

For every 2 rotations of the crankshaft the camshaft does 1 rotation.
You must adjust the valves at TDC on the compression stroke(when the valves are closed), not TDC when the valves are in overlap(not fully closed).
The compression stroke occurs every 2 crankshaft rotations.
You can google "4-stroke cycle" for more info.

Bob
Certified Mechanic for 30 years

njenduro 19 Mar 2022 13:18

Your right on that. The manual said turn the crank counterclockwise till the t Is aligned and adjust. If so how do I know if it is on the compression stroke. Also is it on the compression stoke on the intake or exhaust valves. Thanks for your help

xtrock 19 Mar 2022 15:07

Quote:

Originally Posted by njenduro (Post 627328)
Your right on that. The manual said turn the crank counterclockwise till the t Is aligned and adjust. If so how do I know if it is on the compression stroke. Also is it on the compression stoke on the intake or exhaust valves. Thanks for your help

Its like i told you in the beginning, if you cant get feeler gauge in you are on wrong turn of tdc, if you had gap its ok, NEVER adjust if there is no gap!Look inside you will see different position of camshaft.


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