03-27-2013, 10:12 PM #1
Broken rocker arm and who knows what else
So I'm trying to finish up my 04 rxp build that I've been taking my sweet time on. Slow91 head job with ferrea valves,ported head and ex mani, Riva springs which turned out very nice. Started messing with cam timing today after I was sure I had dead on from the beginning but I was getting very low compression numbers so I was trying to find the sweet spot with cam gear and compression. Yes I have cam and crank locking tools and had this thing running on the stand, but compression was low (90 retarded, 110 advanced, had 130+ stock before build). Anyway, was getting really close and moved 1 more tooth and something really bad happened. Was cranking and got no compression and before I could let off heard a "pop". Somehow wound up damn near 180 off on timing and snapped #2 exhaust rocker in two. The chain or gear slipped a whole bunch and still not sure what happened.
So the question is, can you tell without pulling the head if I managed to mess up a valve or 12? All retainers and springs appear to be the same height, nothing looks out of whack. Was not running at the time, only cranking.
03-27-2013, 10:31 PM #2
Well first things first sorry for your mishaps. When your playing with timming theres only a slot on the cam gear to advance or retard if you are jumping teeth to adjust timming your asking for trouble. Easiest way is to take the cam gear while both cam and crank are locked and get it as close to center as possible with the slots as well as the lines and lock your three bolts down. From there you loosen your cam gear and rotate crank accordingly to achieve retard or advance. You never want to crank your motor to check compression until you get it established correctly. Now moving on I would start by verifying crank position and cam position locked and then proceed to line up sprocket with 1503 marks parrell with head and center the three slots as best as possible. Easy way to check for a damaged valve is pull the rocker arm assembly and put your compression tester in and if you have a air compressor pump air into it don't go crazy just enough to give you a idea if you damaged a valve you will know. I would probably recommend if already to have intake and exhaust off makes things easier to work with
03-27-2013, 10:55 PM #3
Thanks shrabber, never thought about a leakdown test. Was too busy beating my head on the wall. I had it set up what I thought was perfect with everything locked down and slots centered on holes with 1503 marks parallel to the head, but compression numbers were way off. 110 fully adavanced even with cold motor and new valves seemed way low
03-27-2013, 11:00 PM #4
Do not pay attention to compression until you run the motor. Things have to seat oil needs to come up and coat the rings well etc give it time compression will come up you have plenty of time to play with timming. The important thing to look for is consistent across cylinders you don't want 115 135 105 is you had 115 115 115 button her up and break her in then recheck compression dollars to donuts it will increase on its own
03-27-2013, 11:08 PM #5
Yeah let it run in ...
I did a comp test when built with 5 min run time and got 130 on all 3 ...
After 4 hrs or riding , it jumped to 145, 142 ,145 ....
03-27-2013, 11:12 PM #6
It was within 5% across all three I will give it that. I guess I might have been overthinking matters and couldn't leave well enough alone even though I knew better. Lesson learned, now I just hope damage is minimal
03-27-2013, 11:14 PM #7
Was the bottom end fresh or just the head?
03-27-2013, 11:19 PM #8
03-27-2013, 11:24 PM #9
Your comp should not of been that low then as your rings are already set.
What kind of comp did you have prior?
Still better to get accurate readings with warm motor.
03-27-2013, 11:43 PM #10
Cold motor before mods were 130 to 135. After was 90 retarded to 110 advanced. Started advancing cam sprocket a tooth at time and it got worse so I started from scratch and went the other way and got to 120. Next tooth and and everything went to hell. Stopped there and pulled rocker shaft to see what was going on and noticed the broken rocker and my marks on sprocket and chain were at least 10 teeth off.
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