350x head questions

[Dirty200]

started smoking a little so before it got out of hand I wanted to get in and fix it.. the piston and jug walls seem to be in good shape, you can still see the milling marks, no scratches or scoring. the two exhaust valves are pretty burned up, lots of black soot. to me that seems like a valve seal/valve seating issue. ive read things on here about the valve guides getting worn out, is there any way to measure that? also im missing the pin that holds in the decomp release, if anyone knows what size that little pin is... thanks

[Dirtcrasher]

There is a spec for that I'm sure. I remove the valve springs and make sure the valve travels smooth but not much side to side play.

If your cylinder and rings are that nice, it's most likely the valve seals. But, your correct, you can replace the valve seals but a sloppy valve guide will wear out the new seal in time.

Out of all the 350X heads I've dealt with, I haven't found bad valve guides yet.

I have that pin in my shop, I can get you the OD and OAL if you shovel the snow out from it :D

[Dirty200]

haha just pm me the address ill bring a shovel... if you ever make it in there and remember, please do shoot me those dimensions

[Dirtcrasher]

I WILL forget :lol: PM me so it stares back at me, then I'll remember.

Snows all cleared, just busy day!!

[yaegerb]

started smoking a little so before it got out of hand I wanted to get in and fix it.. the piston and jug walls seem to be in good shape, you can still see the milling marks, no scratches or scoring. the two exhaust valves are pretty burned up, lots of black soot. to me that seems like a valve seal/valve seating issue. ive read things on here about the valve guides getting worn out, is there any way to measure that? also im missing the pin that holds in the decomp release, if anyone knows what size that little pin is... thanks

Just because it looks good doesn't mean it is. Need a dial bore gauge to ensure it's in spec or send it to a shop and have them spec it against the manuals tolerances.

Too late now, but in the future if it's smoking take a static compression test. Then put a tablesspoon of oil in the sparkplug hole. If compression increases its rings, if it doesn't it's valves.

[axeman24]

Just because it looks good doesn't mean it is. Need a dial bore gauge to ensure it's in spec or send it to a shop and have them spec it against the manuals tolerances.

Too late now, but in the future if it's smoking take a static compression test. Then put a tablesspoon of oil in the sparkplug hole. If compression increases its rings, if it doesn't it's valves.

man I love that test so the oil will make the rings seal better to the cylinder (if the rings are bad)

[yaegerb]

man I love that test so the oil will make the rings seal better to the cylinder (if the rings are bad)

That is correct.

[Dirtcrasher]

That pin is M5 x 28MM long. I'd I'd wager it's hard as a rock!!

[barnett468]

man I love that test so the oil will make the rings seal better to the cylinder (if the rings are bad)

Only a little . A typical increase is only around 4-7 lbs, and unless you have a very high quality gauge and perform the test the exact same way both wet and dry, the results can be inaccurate . You are also best off using heavier straight weight oil like 40w for the test because the thinner oils will pass through the gap or other worn areas in the rings more easily which will reduce the sealing effect and thereby reduce the amount of compression increase you might get compared to using heavier/thicker oil.


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