New rebuild gone bad

[greco400]

hey, this is not my quad a buddie of mine, we rebuilt it with new piston and rings, with new vavle seals and all the gaskets well it went pretty fast we got the piston in with the cylinder the cylinder was fine still had the pattern in side ( what happen befor it smoke real bad, we looked the oil ring was shot) well we put it back together started right up then the vavles started taping realy bad, we even adjusted them while running, nuthing helped just got louder, well he took it for a ride then he was riding and then all of a sudden it started pouring out smoke, took it back to the shop and we heard a noise like the rod was hitting something. i personaly think its the timing chain, i was wondering what you guys thought it was?

sorry for long post
thanks

[Bill Fuller]

Could someone please explain to me how you adjust the valves while the motor is running:confused: Did you put the decompressor pin back in?

[markk]

I also dont think its possible to adjust valves while its running, Did it drop a valve into the cylinder?

and like bill said.


If your running a stock cam, adjust your intake to .004
exhaust to .005

If your running a hotcams, ajust your intake to .005
exhaust to .006


Also to adjust the valves u need to have the motor on TDC Top dead center. I beleive its the 2nd or 3rd mark on the Flywheel, it will say T!

[greco400]

Yes you are able to adjust your vavles while its running ( my dad owns a auto shop and does it every day and has a top alcohol dragster but there are clips that you put on the vavles so oil doesn't squirt everywhere but i think that is for Car's

I don't know what happen i think its the cam chain slapping but i will have to check it out

[markk]

Originally posted by greco400
Yes you are able to adjust your vavles while its running ( my dad owns a auto shop and does it every day and has a top alcohol dragster but there are clips that you put on the vavles so oil doesn't squirt everywhere but i think that is for Car's

I don't know what happen i think its the cam chain slapping but i will have to check it out



NO REALLY your not able to adjust valves on a 400ex while the motor is running.

Im not gona argue with you about your father knowing or not, Because i know what your talking about with a chevy motor. But a GM motor isn't the same as a honda!

Now u can adjust the valves on a Small Block or Big Block GM motor while they run, But u tighted them untill they dont rattle, and then back them off a little bit. And then i beleive chrystlers are slef adjusting. But a 400ex u need to take off both caps on the left side cover, Turn the motor over untill u find TDC (top-dead-center) and then adjust your vavles then! also make sure you dont over tighten the valve cover caps:macho

[jak1389]

not that this has anything to do with the vavles but when you guys put in the new piston and rings did you hone the cylinder?

[markk]

I dont think they did, He mintioned that it still had the marks in the cylinder from the original bore job. But i was thinking about my buddies 416 he build, His buddie put the oil filter in bacwards, and it scortched the intire top end, ANd it sounded ungodly.

Also when a time chain tensioner goes it it makes hoible racket. I had to replaced mine about 4-5months ago.

[400exredrider]

sounds exactly what happend when my 416 dropped a valve,,, put a hole in the piston, ruined the ported head, 2300 dollars later its running again.:( good luck

[mills_racing]

what about the wrist pin? could you have put it in wrong? or maybe its wore out if u didnt relplace it...just one of a million that could cause one to tick.

[greco400]

Yes markk you are 100% correct but, we could not get the vavles do stop tapping and this way we got it to stop. We put everything in it the right way if you have a droped vavle would it still run?

[Bill Fuller]

WHAT ABOUT THE DECOMPRESSOR PIN?The motor will continue to tap if you are running a cam with a decompressor.The pin sits in the cam bed,directly under the decompressor lobes.If you are running an aftermarket cam then nevermind.















I would still like to see someone adjust the valves while the motor is running.:ermm:

[44oEX]

yeah me to, since the motor has to be cold and at top dead center to adjust the valves.

if you adjusted them when it was running well your just dumb and that is you problem.

[slamdak8782]

if you can adjust them running your hands must move real fast have you been practicin lol jk any ways sounds very possible that the timing gear was out and that could scorch the top end real quick. I really dont see the engine blowing up from not honing but its possible. You guys should have measured the piston to wall clearance between .002 and .004 I just had mine done. Also the reason you cant adjust them running is because the adjusters are moving up and down
You have to set it at tdc top dead center on the intake stroke Intake valves are the bigger ones. Find tdc by taking the plug out of the bottom of the engine to make sure the T is lined up, t is for time. At TDC the valves have 0 pressure on them because they are closed. Go from there but if it was knocking you guys shouldnt have rode it bearing failure can occur in less than 30 seconds run time my prognosis is get the right info next time. You will find very valuable info in a clymer manual