[fsuroxu]

I just got my 2003 300ex a few weeks ago. When I got it the valves were rattling pretty loud so I took it to a local shop to have the valves adjusted. Got it back home and it was running fine but the valves were still making a lot of noise. I did the research and decided to try it myself. No problem but same amount of noise. The thing is, I went to the woods for about a 30 minute ride with no problems, came home and decided about an hour later to go back out to the woods. Got on the bike, started right up but died after about 5 seconds. Tried to start again and it gave me trouble, got it started and went to take off, bike died as soon as I touched the gas. Took the carb off and the pilot was slightly clogged so I cleaned it. Started the bike up and it died again. Now it will only try to start or start for about a second then die. It is getting gas and good spark. The valves seem to be adjusted right .005 on the intake side and .004 on the exhaust. What are some things that could be wrong?

 

[Helmut]

If you're absolutely sure that the carb is clean and isn't the problem and if you have a good spark, maybe the timing chain is stretched and it jumped time. A lot of times the timing chain can be stretched and it will be noisy and can be mistaken for the valves rattling. Just a thought.

 

[94300ex]

yeah sounds like it jumped time.

 

[TRX2fiveO]

Valves are adjusted wrong. .004 on both intake and exhaust. rotate the engine and allign the hash mark above the "T" with the cover notch and feel of the exhaust valve if they are tight rotate it around 180 and feel of them again if they are loose or more loose that is TDC adjust them there. do this while the engine is cold by the way.

 

[fsuroxu]

I am going to get a new timing chain an see if that fixes it. Even if the valves are +.001 on the intake side it should still run. It won't start at all now. By the way, I just got done boiling the carb in lemon juice, so I know it's clean. Thanks for the replies .

 

[TRX2fiveO]

I know you have probably alreay done this but remove the airfilter and try to start it. Also before you go yanking out the timing chain. when you remove the rocker cover assembly reset the timing and check it there are two "-" on the back side of the cam gear they should allign with the top of the heads edge where the rocker cover meets with it. and the lobes will be facing towards the bottom of the head around 4 o'clock and 8 o'clock.

 

[fsuroxu]

I already tried it without the filter, no good. I am a very visual person, I have the manual. Are there any pics of the timing settings in there? If you have pics that would be awesome. Thanks for your help. Also, I have heard that the timing chain tension-er can go bad. How can I check it or should I just replace it?

 

[Helmut]

I already tried it without the filter, no good. I am a very visual person, I have the manual. Are there any pics of the timing settings in there? If you have pics that would bee awesome. Thanks for your help.

If you have the factory service manual, you can go to the section about the head/valves and look under "installing camshaft" and it will show the timing marks.

 

[TRX2fiveO]

do you have the actual Honda service manual or the Clymer manual? Im pretty sure the Honda manual has the pics I have
I looked in my 250X manual which is the same and it does. my 300ex manual is on my laptop but it's dead right now. sorry

If you look on the front of the cam you will see a punch mark above one of the bolts that is supposed to be at the top.

 

[jg85838583]

ok. sounds good, I will check the timing tomorrow and post what i find. Thanks for your help.

 

[fsuroxu]

That last message ^^^^^ is from me I was at a buddy's house on his account.

 

[TRX2fiveO]

What have you found out bro?

 

[fsuroxu]

I got the rocker cover off today and the end of the intake side rocker arm that rides on the cam lobe is completely shot. The cam lobe looks ok but the cam gear marks do not line up at TDC. I haven't gotten the tension-er off yet to take a look at it but the timing chain feels real tight. I just wonder what could have caused it to jump time. Like I said, I just got it so I don't know if this problem has occurred before but there are scar marks on the dowel pin that holds the intake rocker shaft in place. I am assuming work has been done to it before. I think I am going to reset the timing and replace the intake rocker arm and the tension-er and see what happens. I can get the parts on e-bay for about $60 so it is not that expensive. If you know of anything else I should check, please let me know. Thanks again.

 

[TRX2fiveO]

I can't imagine anyone replacing the cam and not the rocker if it bad. can you post up some pics? when you pulled the cover what was the location of the cam lobes? Just for couriosity

 

[fsuroxu]

I don't remember where the lobes were but one timing mark on the cam sprocket was at about 11 o'clock. How will I know if the tension-er is good or not. I am thinking that the cam is original to the quad. I just don't know if maybe someone had a rocker arm issue before and maybe just changed the rocker and nothing else, not really solving the problem. I will try to post some pics of the cam sprocket in position at TDC, the rocker arm in question, and the cam lobes. It will be tomorrow when it is daylight though. You have been a great help brother, I really appreciate it.

 

[TRX2fiveO]

if you have the rocker cover off it sounds like you are on exhaust stroke the lobes should be pointing downward like 5 o'clock and 8 o'clock when you are TDC on compression stroke. the "-" marks on the back will be straight inline with the head and the dimple mark on the front will be pointing up. I know I covered thzat, I'm just reitterating. I'm glad to help out just keep us posted with the findings.

 

[fsuroxu]

Ok. I know i am on the compression stroke because I took the spark plug out and held my finger over the hole to make sure. Turning the crank counter-clockwise just past when I felt pressure from the cylinder, I started looking for the mark on the flywheel. Found the "T" mark and stopped there. At this point, the cam sprocket bolts are at 11 o'clock and 5 o'clock. Are the marks right next to the bolts? Those were the only marks I saw. I hope I am doing this right. Thanks again. By the way, can I shine a light in the plug hole and see the piston at TDC? I ask this because I can't check it right now due to it being dark. Thanks again!

 

[Helmut]

When it's in time, the two flat marks (-) should be level with the top edge of the head and the bolts should be straight up and down, one on bottom and one on top. The flat marks (-) are 90 degrees from the bolts. If you don't see the marks, look on the backside of the cam gear.

By the way, can I shine a light in the plug hole and see the piston at TDC?

You should be able to see it, but if you can't, you can stick a drinking straw down through the sparkplug hole and let it sit on top of the piston and you can see it raise up and stop when you move the piston.

 

[jkhuntin]

If he went counter-clockwise from first feel of pressure wouldn't that have put him back on the exhaust stroke. Shouldn't he have continued clockwise to the T mark for TDC on the compression stroke, or am I incorrect? This is as much for my knowledge as anything.

 

[Helmut]

If he went counter-clockwise from first feel of pressure wouldn't that have put him back on the exhaust stroke. Shouldn't he have continued clockwise to the T mark for TDC on the compression stroke, or am I incorrect? This is as much for my knowledge as anything.

Not if he was turning it counterclockwise to begin with. If he was turning it clockwise to begin with and then turned it back counterclockwise when he felt pressure, it might.