Hello all,

I'm curious to know if anyone else has came across a problem such as this...
I'm having a very technical issue with my beloved machine. I have ran out of adjustment on several of my intake valves.

I've had (3) 1990 cbr1000FL's over the years totaling well over 500k miles, I've been through this process several times and have never had this type of issue.

This particular machine is relatively young, sporting about 40k miles. After a very fresh and spot on adjustment I would get about 8,000 miles before several of the valves would tighten up so badly they would keep the valve open, consequently the engine will not fire when cold and overall its a performance issue and a compression loss. SO NOW, I've been through this nonsense like 5 times with this bike, WAAAAY more than necessary in this short of time!!

THIS IS THE ISSUE: I'm adjusting, and adjusting, and adjusting to keep this POS running. All the while adjusting in one direction each time, loosening. At its current state, its has 3 or 4 primarily intake valves that are bottomed out on their adjustment range and the rocker pads are still dragging on the cam lobe and holding the valve open.

please give me the benefit of the doubt. It is not bad torque, stripped threads, or bent cam shaft. Something is happening, and I'm not sure what!

My best guess is... this hunk of **** was built on a Friday, and the adjuster socket "which" I believe is pressed into the cylinder head is pulling out of its position. However, I have attempted to "reseat" said socket by strategically pounding on the head of the adjustment screw with a hammer. I've set enough **** in my day to know that sucker is seated. Or at least I think it is!
besides, if you disassemble the entire shootin match the adjustment screw gently pulls right out of the socket. So I'm not sure how the hell the socket would "pull" out of the cylinder head anyway???.

I'm looking for very experienced technical advice as I've thought though most of the obvious. Nothing is broken, bent, or worn out to the best of my knowledge.

I'm at the point where I'm about to swap out the head. HOWEVER, I still wont know what's happening inside this motor. That is my primarily purpose of this thread.

I ride hard, but I'm older now and have "beaten" my other machines more and just as much. I have never had so much valve adjust trouble EVER!!

ANY educated advice is highly appreciated, thank you in advance.

Kind Regards,
Paul

 

Sounds like the valves are sinking into the seat or the seat is sinking into the head. You should be able to measure the height of the valve and compare it to spec or at least compare it with a good one.

 

interesting.....I have never considered this. Is this something that happens often out in the world of these machines? What does this mean? The cylinder head casting is junk?
I don't currently have the bike apart, so I cant verify that. However, that does make probable sense. I have never heard of such an issue. Please tell me more
thank you very much!

 

My disclaimer is that I have never had a 1000f apart, but I have had hundreds of motors apart over my years as a professional.

What happens is the seat gets pounded into the casting, the seat just comes apart, or the valve gets worn or burned and ride further in the seat. All of which will increase the stem height causing the clearance to get tight. As it continues to do it's thing, it will keep getting tighter. Since you have it apart, you should be able to see if the top of the stem and compare it to the height of the others.

 

I hear ya! I'm totally picking up what your putting down sounds to me like this is VERY likely what is happening. My question now is WHY? The bike is still young, and if well cared for can crush 100k no problem. What gives? bad egg?

I really appreciate your time buddy!! seriously this makes perfect sense.

Is this seriously just a wear issue? or do you think I have a jetting issue that's causing excessive heat? to the best of my knowledge the bike is bone stock, however I'm in Las Vegas and cruise primarily at 2,300 feet above sea level. if anything, I would say it runs slightly on the richer side. however id totally like to hear your thoughts!

thank you 74 Demon

 

Lean mixture or bad timing can cause burned valves.So can running with them tight. Bad castings, cracks, bad seats, bad valves, as well as abuse can cause issues. Sometimes the why can't be explained....

Usually burned valves are exhaust valves as they are the ones that are open when the combustion gasses are hottest.
Can you do a leakdown test?