[britboy]

Hi guys,im doing the valve clearances on my mc19. did the shims & came apart ok. can get cams back in ok but engine just locks solid when try to crank it over by hand. cams are in same as they came out. thinking it could be the cam grearing? really not sure what could be wrong. thanks

 

[Pygmygod]

Are you making sure that you're turning it over the right direction? (Turn engine toward front of bike I believe is the usual way they go)

They don't have a cam-chain do they?

Once you had the camshafts removed you didn't turn the engine crank over?

Made sure any cam journal guides didn't fall out and into the engine? (Those round locator things which line up the head and the cam journal together before you screw them in.)

Made sure you don't have any parts left over on the bench?

 

[britboy]

yeh clockwise,its like a brickwall after bout quarter of a turn. no cam chain on these,gear driven. cranks fine with the cams,nice free.
didn't have anything left over & was really careful nothing fell in the engine. I'm thinking there might be something wrong with the gearing,might pull that out tomorrow for a look

 

[britboy]

cranks fine without the cams sorry

 

[Pygmygod]

With the 4-cylinders you have to turn then measure the valve clearance, then turn and measure next valve clearance, yea? (Or similar)

Did you make sure that it all went back in at the right amount of 'turns' to where it's supposed to be once you finished checking 4th cylinder valve clearances? Or after the cams were removed did you start turning the engine around a few times without the cams in??

(I'm a bit more familiar with 1-cylinder dirtbikes sorry.)

 

[generator]

Hi guys,im doing the valve clearances on my mc19. did the shims & came apart ok. can get cams back in ok but engine just locks solid when try to crank it over by hand. cams are in same as they came out. thinking it could be the cam grearing? really not sure what could be wrong. thanks

I hope you put the cam caps back on the same way they came out , they are NOT reversible (turned around) I find it easier to line the marks up when they face the outer edges of the head.
Have you had the gear cassette out (under the cam gears) ? have you removed & replaced the head bolts that are located under the cassette (there is no need to, but all headbolts EXCEPT the two head bolts under the cassette use copper washers under their heads, if copper washers are used under these bolts, the cam gears will hit them, )
Study the cam gear marks (scribed lines) make sure you are aligning the intake mark on the intake, and vise versa on the exhaust

 

[britboy]

thanks guys,turned out to be a couple of sticky valves. obviously hasn't been well serviced before I got it. all good now

 

[generator]

thanks guys,turned out to be a couple of sticky valves. obviously hasn't been well serviced before I got it. all good now

Sticky valves + collision with pistons = bent valve stem.
Re check valve clearances, if you have upset a valve, the clearance will have increased.:icon_cussing:

 

[motthomas]

There are no such thing as sticky valves. If a valve is not returning to seated postion under spring load when hand cranking the engine then there is something wrong that needs seeing to BEFORE you attempt to start the engine. These engines have 3-3.3mm valve-to-piston clearance at TDC so if a valve is staying open enough to contact the piston and stop the engine from turning then its open a lot.

The most likely culprit as Tiny said is bent valve. If I were you, I would have a very good look for more evidence and prepare to pull the head and remove the affected valve.

 

[britboy]

put a bore camera down there & valve seems to opening & closing fine. clearance was way out on the one though

 

[generator]

put a bore camera down there & valve seems to opening & closing fine. clearance was way out on the one though

Do a leakdown test, that'll tell you more

 

[ErickCBRrrMC22]

gracias chicos, resultaron ser un par de válvulas pegajosas. obviamente no ha sido bien reparado antes de que lo consiguiera. todo bien ahora
[/COTIZAR]como que válvulas pegajosas , que quiere decir eso?