250sx Head Noise

[mike84bigred]

I took my 250sx apart today because there was some chattering going on in the head. I thought it may be the clearances. I took the valve covers off and noticed the lifters rock side to side slightly. Could that be the noise i'm hearing? What do you guys think I should do about it?

Anyone ever buy that plastic gas tank for these off ebay? Any good?

[TeamGeek6]

Rocker to shaft clearance should only be 5-10 thousandths (?) and they should slide sideways a little, but not rock. If they are loose sideways (rotate, not slide) then the rockers and shafts are hosed. Otherwise just valve clearances (rocker to valve stem) are too loose. Ive found that old Honda engines tend to lose valve clearances when hot, so set them cold and check them hot. Too tight when hot = burnt valve. Might be a stretched cam chain it the valve clearances are OK.

[ThreeKing]

I have a lot of noise in mine. Pretty sure it's a worn exhaust valve guide. How do I know? I took my motor apart to work on the cases and put a new exhaust valve in. The valve had a loose fit when assembled but I thought it would be OK anyway. Big mistake, the motor has a loud clattering sound when running. I tried several lash adjustments but still noisy.

[benb1984]

my 87 250 es makes the same top end noise, it first started about a month after i got it, and sounds like a big slap or something hitting somthing.. it sounds like its dying slowly to be blunt... once its running for 5 mins it will idel with out the noise, so it only dose it when its cold, it has got worse but i am not game to pull it apart, i have a spare engine so wen it dies ill take it to the shop, its not worth much anymore, its been tourtured by me, belted with that lumpy, bent in the ditch, barrel rolled several times down the dirt road, good times..... its just a bush basher now, but the noise sux, i have the pdf service manual, but it dosnt help me much with this, as i am not a mechanical person... ask my poor car... anyway....... any help with my noise would be great, im thinking coz it only dose it when its cold it could be easy for some one to identify?
do yours do it hot?
or only cold?

i found that if u have a holy exhaust the noise dosnt sound so bad... and keep heaps of oil up to it... coz if its something grinding,, oil will help that tiny bit

ben.



"GET STUFFED" LOVE AUSTRALIA

[mike84bigred]

Mine seems to quite itself out a bit when its been running. I guess i'll just do the clearances, put some AMS synthetic oil in it and have a blast. My buddys 250 Big Red and 200s make a similar noise and still run strong. Time to put it back together and have some fun. You guys got anything on that palstic gas tank?

[mike84bigred]

Well did some work on it today. Chaged the oil, oil filter, gas filter, air filter. I am almost postive its the cam chain making the noise. It pretty much doesen't make any noise when its warm but really bad when its cold. The chain tensoner on those motors aren't adjustable, correct? Had the best ride of my life on it tho..

[Dirtcrasher]

It's an automatic tensioner. Probably worn chain and guides. I'd change the 2 guides and the chain, usually the sprockets are fine. A worn chain gets pretty noisy...

[Danold]

many of the problems here sound like cam chain noise. my old bigred made same noise and the tensioner was out of adjustment. ended up putting a hole in the piston with the exhaust valve. so with my advise just get a new cam chain. It is 2nd bigest noise maker in th 250 motor(other than the valves). Dennis Kirk even sells Silent Series cam chains for the 250 for pretty cheap.

[benb1984]

does anyone wanna go into any detail on exactly how to change it? i imagine youd take the top off the motor, would it be clearly visible at that time if it was the chain or not? and same with the valves.. is there any way to just check them with out a week of pulling the whole motor apart?

[Dirtcrasher]

does anyone wanna go into any detail on exactly how to change it? i imagine youd take the top off the motor, would it be clearly visible at that time if it was the chain or not? and same with the valves.. is there any way to just check them with out a week of pulling the whole motor apart?

YES, BUY A F!#$! MANUAL Imagining is not a good thing.

It is quite involved to change the timing chain on an SX. Quite a few things have to come off in the right cover too. Your most likely not gonna see or feel chain stretch. But you will find the guides worn down.

[mike84bigred]

Well this blows. Just got the thing. Was not planning on a rebuild. Couple of questions. Do you have to pull the motor? Can I change it without taking the head off, clutch off?

[Dirtcrasher]

Got that manual on the way right bud??


Motor stays in bike.

Yes the clutch has to come off, and valve cover and oil pump and centrifugal clutch and a bunch of other crap. Didn't you here the noise when you bought it?? You did start by adjusting the valves, right?

[mike84bigred]

Valves yes. I heard the noise when I bought the machine but I thought I could just tighten the chain tensioner. This the only machine I have ever owned that is not adjutable. I have other concerns though. See my new thread.