Intake valves slightly open on 4 stroke Yamaha 15...normal??

[JonnyPartTime]

Hi guys,

Just wanted to start by saying thanks to everyone for all of the great advice that I've gotten so far. I've been through hell and high water with my 2000 Yammy F15ESHY lately and I think I've almost got it fixed. However, when I went to rebolt my cylinder head back on after replacing the head gasket, I noticed that both of my intake valves are remaining slightly open when they're supposed to be closed. Is this normal? I just wanted to check before I put everything back together. Thanks!!

 

[99yam40]

Re: Intake valves slightly open on 4 stroke Yamaha 15...normal??

are they bent or is the cam holding them open?

 

[JonnyPartTime]

Re: Intake valves slightly open on 4 stroke Yamaha 15...normal??

Hi again, 99yam40.

They're both equally open. I considered that they might be bent but I wanted to check if this was normal before I started pulling them apart. The cam appears to be holding them open but I can't be sure. is there anyway to check?

 

[99yam40]

Re: Intake valves slightly open on 4 stroke Yamaha 15...normal??

do you have the service manual for that motor?
Probably need it to make sure you take it apart and put it back together properly.

Not sure what you mean by valves being open when they should be closed,
It never closes the intake valves?
Are the valves adjustable or do they have any slack when cam is at the point they should be closed?

how did you check compression if valves did not close?

Some motors will bend valves if cam timing is out of adjustment and turned

 

[JonnyPartTime]

Re: Intake valves slightly open on 4 stroke Yamaha 15...normal??

I have the manual and I've been following it.

I mean that the intake valves never completely shut in the closed position, I'm able to actually see a crescent of light coming through. The valves close, but there is still a tiny gap between the head and the intake valve at the intake valve's 3 o'clock position, if you're looking at the inside of the head. The valves are adjustable but they don't seem to close any further when I adjust them. I've heard of the intake valves remaining slightly open on the Briggs and Stratton motors for their "easy start" feature, so I wasn't sure if the same went for this motor also.

I checked the compression before I discovered this new and exciting issue, and even though it seemed low, I still didn't think to look at the valves. I just happened to notice it as I was about to reassemble the motor.

 

[99yam40]

Re: Intake valves slightly open on 4 stroke Yamaha 15...normal??

I never heard of any 4 stroke motor not closing the valves completely, the compression would not be able to build up and the valves and seats would burn up from the burning gases blowing back through if it would fire at all

 

[JonnyPartTime]

Re: Intake valves slightly open on 4 stroke Yamaha 15...normal??

I figured this much. I either foresee a valve job...or me reading this thing its last rights and pushing it off a bridge Thanks again yam, you've been a huge help.