I've got a 97 900rr that i had the head ported and decked.. I've got some adjustable cam gears to make up the difference for the extra chain slack, and I was wondering if any one had some good specs for in and ex cam open and closing degree.. any info, or a place i could find some would be great..
900RR cam timing
1 - 14 of 14 Posts
Joined
·
32,034 Posts
If the cams are stock '97's set them up to the specs in the manual.
You don't usually need to adjust cam timing just from milling the head - a worn chain will put the timing out further.
You can remove any chain slack simply by fitting a new chain.
I took 0.55mm off my GSXR750 and 1mm off one of my cars with no cam timing adjustment. How much was taken off yours?
"Decking" nowadays seems to just mean machining it flat again so it's probably just 0.10mm or so.
For '96-98 stock appears to be (all at 1mm lift):
IN opens at 15 BTDC and closes at 35 ABDC.
EX opens at 39 BBDC and closes at 11 ATDC.
Unless it's a late Cali model which has different cam specs.
IN opens at 0B TDC and closes at 37 ABDC.
EX opens at 40 BBDC and closes at 0 ATDC.
cbr900racer77 is probably the best guy to talk to but I'd be surprised if he runs stock cams.
Honda Motorcycles - FireBlades.org - View Profile: cbr900racer77
Joined
·
554 Posts
All I could find at the moment was for 92-96 RR's. Were the newer ones different? Specs for those are intake...open 18btc, close 37abc. exhaust...open 39bbc, close 18atc. Lobe centers for both is 100. I've been up almost 20 hours straight. I'll try and find newer model specs in morning. Those were 49 state cams. You do have stock cams, right?
Joined
·
32,034 Posts
There's the man himself
Joined
·
554 Posts
What are these "stock cams" you speak of?:idunno: LOL. Bladeracer took care of everything I would've said. (He's more knowledgeable than me, trust me). Did you ever answer him as to how much was taken off? I had 15 thousandths taken off head once and tried to run some Web cams with stock pistons. Didn't work too well. I got lucky and heard tapping noise on startup. The valves were barely making an impression in the oil residue on top of pistons. Another thousandth or so and it would've gotten ugly. Normally I clay an engine I think will be close but was lazy on that one.
Joined
·
32,034 Posts
How much more lift did they have over OEM or was it more due to them being open for longer?
Joined
·
554 Posts
It was a little of both. Stockers were 322 lift/235 duration, Webs I had in there were 352 lift/262 duration. Stock pistons need a little more valve pocket. I'm going off some bad memory here, but if I remember right I took one layer off head gasket and had 50/80 piston to valve clearance with the JE pistons with same cam.
Joined
·
554 Posts
Did you clay it? What was your piston/valve clearance if checked? I'm no pro by any means but I know there has to be people out there that have gone closer than 50/80. My buddy was 47 thous on intake side and bike actually ran better with the 50. Guess cam/compression/head and all that have to be in sync. I'd KILL for an apprenticeship at an actual "builder" shop for a few years.
Joined
·
554 Posts
.018..that's 2 layer gasket, right? Is this your 900 or 600 (or did you say and my old butt just missed it lol). Not too familiar with the 6. If it's the 9, stock head gasket is right at 30 thou. So you basically lost 22 thous. You should be safe. I have a bare block (893) that's been decked 25 thous. Previous owner said it ran like a raped ape (and I believe him). I can't give the thing away, (it's for sale $200) nobody wants cheap horsepower.
Joined
·
554 Posts
The 919 stuff isn't too hard to find. All I have (or had) is 893 stuff. I've sold everything but that block and a few internals. I have a complete (disassembled) 93 that I bought last year and haven't gone and gotten yet (no room). Only space I had left is occupied with the Blackbird motor swap project.
1 - 14 of 14 Posts
Join the discussion
Join now to ask and comment!