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Discussion Starter · #1 · (Edited)
What's up fellas!!!! New to the site here! I've done tons of research on it but can't find anything with my exact problem. Its a 03 400ex bone stock engine, no lid, 165 main and stock pilot and full DG exhaust. My issue is when the engine is cold, after the engine starts the decompression will "stick" and tick like hell for about 15 seconds. The whole time the exhaust note sounds like a Subaru and it will shut off!!!! The only way to get it to release is to give it a couple of light revs and it will "click" once and go to sounding normal. If I let it go back to idle it will engage again. The only way to keep this from happening is to turn the idle up to about 2000 until the engine is warm. Which is rather anoying! I've adjusted the valves at least 6 times and diffrent clearances but no diffrence. Other than that the thing runs like a top and has no problem pulling the tires in 4th for a nice calming stand up wheelie!!

I have contemplated taking the decomp off but I see mixed feed back about the cam, some say the hole in the can needs to be welded and some say it doesn't! Or just buy a stage 1 hot can and say to hell with it all :).

Anyways any feedback is appreciated whether it is helpful or not...thanks!!!
 

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Is the pin and spring in the head under the decompressor? I'm guessing the motor has been worked on and the "shade-tree" mechanic that did the work may have lost the parts or could not figure out where they went and left them out. If you put in a HOT CAM, the decompressor and the setting pin are removed. Another solution is to remove the decompressor from the stock cam.

Check it out and let me know if I am right
 

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Check the valve clearance. Be sure the engine is on TDC of the compression stroke. Note the excerpt in the service manual -

"NOTE: If all the valves are closed except the RH exhaust valve, this may indicate a jammed decompressor unit. A jammed decompressor will also cause a steady ticking sound when the engine is running. To release the decompressor, move the wrench fitted to the crankshaft bolt quickly back and forth. The quick changes in crankshaft direction should release the decompressor from the valve."

If this in not the source of noise, check the cam chain. With the engine on TDC of the compression stroke, remove the cam chain tensioner from the back of the cylinder (before removing the tensioner, remove the bolt and sealing o-ring from the center of the unit) - note how far the tensioner pushes itself away from the cylinder. If the distance is 1/4 inch or less, remove the tensioner assy. Use a small screwdriver (turning clockwise) to retract the tensioner plunger by turning the screw inside the tensioner that the bolt and o-ring hides. If the plunger extends itself freely when the screwdriver is removed (or simply released), then the tensioner is working properly. If the tensioner is working properly and the distance the tensioner pushed out of the cylinder is 1/4 inch or less, replace the cam chain.

There are other reasons for the noise, but short of an engine tear-down and inspection of all the parts, the ones I have described are the most common.
 

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Discussion Starter · #5 ·
Thank you for the reply. I have checked and reset the valve lash multiple times to no avail. I checked the chain and tensioner last week when I replaced the clutch. The tensioner was at least 3/8 from touching the cylinder after it had already contacted the chain guide. The noise seems to only happen when the oil is cold and thick after about 10 minutes of riding it goes away. All rockers and can lobes looked good when I had the rocker box off a month or so ago and it has only been ridden once since then.
 

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Did you retract the cam chain tensioner when you installed it and then let it take up the slack?

Are you using premium grade fuel from a brand name retailer?

At 3/8 inch, I would judge the cam chain worn out and install a new one.

When you refer to the oil as thick, what grade of oil are you using and is it approved for use in motorcycles?
 

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Discussion Starter · #7 ·
Tensioner retracts and springs back out as it should. And when I say thick I mean the engine and oil is cold. And yes I run 10w40 during the winter and 20w50 during the summer and yes motorcycle oil designed for wet clutch systems. Both different viscositys make no change in the noise or how it acts. I know its not the timing chain because that's not going to make it act funny like it does.
 

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Sorry, the videos did not help

Glad to hear that you know about the JASO standard

Personally, I run 10W40 petroleum in one machine and 15W50 full synthetic in another year round - always use 93 BP fuel

My last guess is a scored piston - my son scored a piston by running too hard when cold - it started "ticking" and he just could not put up with it - a new piston and rings, hone the cylinder and it was like new again, but that does not explain the sudden engine stop.

Again, personally, I have my idle set at about 2000 rpm - it prevents stalling during sudden deceleration for turns or stops and makes restarting a hot motor easier - right or wrong, it's just my way of doing things

Anyone else on here got any suggestions?
 

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Discussion Starter · #11 ·
I have heard of using full synthetic in these bikes but have read some mixed opinions about it. What brand of synthetic do you use?

As far as a damaged piston I guess that is possible. Only smokes way up in the rpms and runs extremely strong for a stock internal 400ex. It shows no sign of getting better or worse its more of an annoyance to me. And to answer your question I run 93 in mine.

I usually turn the idle up when I first start it, ride for about 10 or 15 mins and then turn it back down. After it gets hot it starts with barely a touch of the button.
 

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You could try replacing the spring or plunger, but it definitely sounds like a decompression issue.

It is possible to press it off of the stock cam, but I would just install a stage 1 hotcam and call it a day. It will wake the quad up a bit and won't lose any reliability.
 
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